Section: Graphics Software (1)
Updated: 9th August 2017
xzgv - picture viewer for X, with thumbnail-based file selector
(NB: This man page is automagically generated from xzgv's
texinfo file, and so may look a bit odd.
We apologise for the inconvenience. :-))
xzgv is a picture viewer for X, with a thumbnail-based file selector.
The thumbnails used (thumbnails being small `preview' versions of the
pictures) are compatible with xv, zgv, and the Gimp. The kinds of
pictures xzgv allows to be viewed are raster-format pictures (sometimes
called `bitmaps' and/or `pixmaps'); things like GIF files, JPEG files,
PNG files, and so on.
Most of the time, you will probably want to use xzgv's file selector
(see The File Selector) to pick which file(s) to view. This is what
appears on the left-hand side of the window when you start xzgv as just
`xzgv' (see Options). It displays a list of
subdirectories and picture files in the current directory, along with
small `thumbnail' versions of the pictures if they exist. (If no
thumbnails appear in a given directory, or if they are missing for some
files, you can create/update them by pressing `u'. See Updating
When you've picked a file to view, you can view it by clicking on it, or
pressing `Enter'. This reads the picture and displays
it in the right-hand part of the window, the viewer (see The
Viewer). You can then move around the picture (if it is larger than
will fit) by dragging it with the mouse, or using the scrollbars, or the
cursor keys. You can then select another image with the file selector
(though you need to press `Esc' or `Tab' first if using the
keyboard), or you can quit xzgv by pressing `q'.
While xzgv works much like any other X program, and is certainly
mouse-friendly :-), it's also designed to be keyboard-friendly.
Everything in xzgv can be done entirely from the keyboard. Much of this
keyboard support works like the original zgv (a similar console-based
picture viewer for Linux).
This overview is, as you might expect, only the very simplest of
introductions to what xzgv can do, and describes only a very basic use of
xzgv. xzgv can do a lot more; read on to find out what.
xzgv was primarily written by Russell Marks, also the author of this
manual. It is maintained by Reuben Thomas, who ported it to Gtk+ 2.
Costa Sapuntzakis contributed code for much faster JPEG thumbnail
generation (to zgv, which I adapted for xzgv).
The directory/file icons used were loosely based on gmc's
dir-close.xpm. I think Tuomas Kuosmanen was responsible for
that, judging from the change log.
`mkinstalldirs' is straight from the `texinfo' package, and
was written by Noah Friedman. (This is also used during installation.)
Huge thanks go to the many people responsible for GTK+, without which
xzgv would almost certainly not have happened. (But no thanks for
Electric Eyes, which was nearly nice enough for me not to bother with
xzgv at all! :-))
getopt*.[ch] are from the GNU libc.
Normally you'd invoke xzgv as plain `xzgv
' (perhaps via a window
manager menu, or GNOME/KDE menu, etc.). However, you can directly
specify files to view, or a start directory, on the command-line. In
addition, there are various options.
(If you're new to xzgv, you should probably skip the rest of this section
for now and come back to it later.)
The general format of the xzgv command-line goes roughly like this:
xzgv [options] [dir | file ...]
Two types of options are supported --- the traditional Unix
single-letter options, and GNU-style long options. Most options can be
used in either way, and both forms are listed in the table below.
Note that all options are processed after any configuration file(s).
Config file settings are just like the long-option names below minus the
`--' (see Configuring xzgv), though a few command-line options
are not permitted as config file settings (e.g. `help'), and vice
Here's what the options do:
Automatically hide selector when a picture is selected, allowing the
viewer to use the whole window.
Enable libjpeg `fancy upsampling'. xzgv defaults to using the faster
method; as the libjpeg documentation puts it, ``The visual impact of the
sloppier method is often very small.''
(Note that this is normally enabled; use
`--delete-single-prompt=off' to disable it.) If disabled,
xzgv will immediately delete a file when told to, without prompting for
confirmation. (It's `single' because deleting multiple files at
once will be supported in future, and that will have a separate prompt
Use dithering in 15/16-bit, whatever the default setting is.
See Viewer Options, for a discussion of benefits/drawbacks. You can
also use `--dither-hicol=off' to disable this.
In JPEG files, use Exif orientation tags (inserted by e.g. digital
cameras) to correct image orientation before display. See Viewer
Options, for details.
When doing a recursive thumbnail update, don't read existing thumbnails
before updating. This is pretty much obsolete as of xzgv 0.7, as the
speed increase is now negligible. But, it may still be useful if you
want to update a huge number of small directories for which few
if any updates are needed.
Run fullscreen, using the entire screen for xzgv's window, without even
any window-manager decorations (window frame, title bar, etc.) if
Set the xzgv window's geometry (position and/or size) to geom. The
geometry string should be in the usual X format, with the extension that
positions/sizes may have a `%' suffix meaning that they are treated
as percentages of the screen width/height. The default geometry is
For those unfamiliar with the way `geometry' works, here's a brief
description of the syntax. It's `WxH', or `+X+Y', or
`WxH+X+Y', where `W' is width, `H' height, `X' the x
position, and `Y' the y position. The first form specifies only the
size, the second only the position --- the `WxH+X+Y' form specifies
Now, the `+X+Y' bit normally specifies where the top-left of the
window is. But you can use `-' instead of `+' for the x and/or
y position, in which case it specifies the gap between the right/bottom
of the window and the right/bottom of the screen. (Note, however, that
any window frame your window manager adds to the window is disregarded
in this calculation, so you may need to experiment somewhat to get the
desired position.) You can also use negative numbers with both `+'
and `-' --- so `+-50+0' puts the window partly off the left of
the screen, and `+0--50' puts it partly off the bottom of the
screen --- but this is of questionable value. :-)
Finally, as mentioned above, xzgv extends this syntax by allowing you to
use `%' to specify percentages of the screen width/height rather
than pixels, e.g. `50%x30%-30%-20%'. It also allows you to use real
numbers such as `12.34', which can be useful with `%'.
Display a list of options and a terse description of what the options
Set the boundary numpix after which images are considered `big',
and are no longer rendered all-at-once (which gives much nicer
scrolling, but is harder on memory and can be slow for big images) but
are instead rendered piece-by-piece. Units are number of pixels in image
(i.e. width times height), and the default is 2000000 pixels.
Shows only directories and image file types in the selector, identified
by their extensions.
Interpolate between the picture's pixels when scaling up
(see Scaling). This usually looks nicer, but it's rather slow.
If enabled, control-clicking on the viewer scales only the X axis. (The
default is to scale only the Y axis.)
(Note that this is normally enabled; use `--revert-orient=off' to
disable it.) If disabled, orientation (flip/mirror/rotate) state
is retained between pictures (see Viewer Options).
(Note that this is normally enabled; use `--revert-scale=off' to
disable it.) If disabled, scaling is retained between pictures
(see Viewer Options).
Set the default/initial size of the selector in pixels. The normal
setting is 200.
Show names of currently-tagged files on exiting xzgv. (They're listed to
stdout, one per line.) This can be useful when you want to select
multiple files graphically and work on them with something else.
Show on the status bar when thumbnails are being read. The status bar
must be enabled for these messages to be visible, of course. :-)
For the first directory shown, skip the cursor past .. (the
parent dir). This can be useful when you'd like to immediately use space
to `page' through the dir.
Set the initial sorting order used in the selector. Possible settings
are `name', `ext', `size', and `date' (or
`time'); only the first char of the setting
(`n'/`e'/`s'/`d'/`t') need be given. The
default is name order.
Set the timestamp type to use when using time/date sorting order.
Possible settings are `mtime' (default), `ctime', and `atime'; only the
first char of the setting (`m'/`c'/`a') need be given.
Show a status bar below the selector; this, for example, says when a
picture is being read.
Use rows a third the normal height in the selector. This can be very
useful on lower-resolution screens, or if you're really interested in
filenames, not thumbnails.
Show version number.
Show version number of GTK+ xzgv is using.
Fit picture to viewer window, whatever its actual size (see Zoom
When in zoom mode, only reduce pictures to fit; i.e. make big
pictures viewable all-at-once while leaving small picures intact.
When in zoom mode, adjust only the most proportional dimension to fit,
and allow scrolling on the other dimension; i.e. like a fit page width
option in PDF readers, but not limited to horizontal adjusting.
If started with `xzgv files', xzgv hides the file selector
and treats the file or files as if they were the sole contents of a
directory. (It also automatically loads the first file.) As such, you
can use the Next Image and Previous Image commands to navigate between
the images, or do Exit to Selector and use the selector directly.
If started with `xzgv start-dir', xzgv starts up as usual,
but with the selector starting on the directory specified (rather than
the current directory).
Settings which are either on or off (boolean) are, as you might expect,
enabled by using e.g. `-z' or `--zoom'. However, there's an
alternative long-option form for setting these, resembling how they're
set in config files --- the syntax is `--option=state', where
state is `on'/`y'/`yes'/`1' to enable the
option, or `off'/`n'/`no'/`0' to disable it. The
most useful thing about this is that it allows you to disable options
which were previously enabled, by using e.g. `--zoom=off'.
(Readers used to the way GNU-style long options work should note that,
since this `on'/`off'/etc. arg is optional, you can't use the
`--option arg' form in this case; it must be `--option=arg'
for it to work.)
A NOTE ON NOTATION
Much of this manual is taken up by a description of xzgv's various
commands in its file selector and viewer. Most of these are available
both from the keyboard, and from popup menus. (A popup menu appears when
you press `F10
' or `Menu
', or right-click on the selector or the
viewer; each has its own menu.) So in the manual, you will often see
things rather like this:
`Selector menu, Menu the item is in, Menu item
Description of what the key/menu item does.
Sometimes the key given has a `(Selector)' or `(Viewer)' suffix;
this is because some keypresses in xzgv are specific to the selector or
the viewer, and won't work unless the relevant part of xzgv has the
THE FILE SELECTOR
Usually, on starting up xzgv, you'll want to use the file selector ---
the list of files on the left. (The other subwindow (on the right) is
the viewer.) The selector lets you pick files to view (among other
things). It lists the subdirectories and picture files in the current
directory, along with small `thumbnail' versions of the pictures if they
THE SELECTOR MENU
Almost all selector commands are available from the selector's pop-up
menu, which appears when you right-click anywhere on the selector. (You
can also press `F10
' or `Menu
' to bring up the menu, but as
there are keyboard shortcuts for just about everything in xzgv, this
isn't often that useful. :-))
Usually, it doesn't matter where on the selector you right-click.
However, a few commands on the File menu operate on a single
file, the one selected by the keyboard cursor. A problem when using the
mouse, you might think --- but when you right-click on the selector, as
well as popping up the menu, xzgv moves this cursor to the file you
right-clicked on (if any). (You can see this by the way a hollow box is
drawn around the file.) So to use e.g. Details on the File
menu, you need to right-click on the file you want details on.
Both the selector and viewer have `Help' menus, most items of which
refer you to this manual:
`Selector menu, Help, Contents
`Viewer menu, Help, Contents
View the manual's overall contents.
`Selector menu, Help, The File Selector
View the manual's section on the file selector.
`Viewer menu, Help, The Viewer
View the manual's section on the viewer.
`Selector menu, Help, Index
`Viewer menu, Help, Index
View the manual's concept index.
`Selector menu, Help, About
`Viewer menu, Help, About
Give some brief information about xzgv, including the version number and
Currently, the way xzgv lets you read the manual is a bit crude; it runs
the `info' program (see Top in the info-stnd info file) in an `xterm'.
You can exit xzgv either by using one of two exit keypresses, or by
selecting the appropriate option from the selector's popup menu:
`Selector menu, Exit xzgv
(There's also an exit option on the selector's File menu
(`Selector menu, File, Exit'), as `Exit' is generally on any File
(This section is deliberately early on in the manual, as thumbnails are
probably the most important feature of the file selector, so it's best
that you know how to create/update them sooner rather than later.)
Thumbnails are small versions of the pictures they represent, and are
displayed by the file selector if they exist. xzgv uses xv-compatible
thumbnails --- if you create thumbnails with xv they will work with xzgv,
and vice versa. xzgv's thumbnails are also compatible with the Gimp, and
If no thumbnail exists for a file, a small `document' icon appears
instead (similar to the `folder' icon used for directories).
While thumbnails can be made relatively quickly, it's by no means an
instant process. For this reason, thumbnails have to be created in
advance, and are stored as files in their own right in a subdirectory
xzgv never creates/updates thumbnails without you telling it to. So, if
you enter a directory where the picture files don't have any thumbnails,
or where the thumbnails seem to be out of date, you should press
`u', or select Update Thumbnails from the selector's menu.
(Even if the thumbnails can't be written (say, if you don't have
permission to write them), the selector will still show the updated
thumbnails until you leave the directory.)
Alternatively, you can create/update thumbnails for the current
directory and all subdirectories by using `Alt-u' or Recursive
Update. But be warned that a recursive update can take some time!
`Selector menu, Update Thumbnails
Create thumbnails for any files which don't have them, and update
thumbnails which are older than the corresponding file. While this is
going on, a window appears showing how far through the process xzgv is.
While the update is in progress, you can abort it by clicking on the
Cancel button, or pressing `Esc' or `Enter', or by
clicking the delete-window button (if your window manager provides one)
on the title bar. xzgv will stop once it has finished the thumbnail it
is currently working on (if any).
`Selector menu, Recursive Update
Create/update thumbnails for all files in the current directory and all
subdirectories. This can take some time, so you are prompted to confirm
you really want to do this (see Dialog Boxes). Progress is indicated
in much the same way as for a normal update, but only for the directory
currently being updated --- the overall progress is not indicated, other
than by the current dir being (as ever) displayed in the main window's
title. You can abort a recursive thumbnail update in the same ways as
for a normal update (see above).
By default, xzgv behaves a little oddly when doing a recursive update,
to give some consistency with the normal update. See Thumbnail
Issues, for details.
Dealing with thumbnails can be `interesting' at times, and there are a
few ways this influences things:
xzgv doesn't read the thumbnails in a directory all at once. Instead, it
just reads the directory contents, then starts up what is effectively a
kind of background task to read in the thumbnails. So xzgv may not be
quite as responsive as usual for a short time after entering a directory
with many thumbnails (say, a few hundred) --- but on the other hand, at
least it is responding. :-)
The `background task' makes a special effort to show thumbnails for the
files currently visible in the selector first, no matter how much you
move around the list, but it reads them all in eventually.
The thumbnails used in xzgv require 256 colours to display. This can be
a problem if you're running X in 256 colours or less as, even if you're
running an 8-bit (256 colour) server, there will almost inevitably be
fewer colours available. Currently, xzgv just uses whatever gdk
reports as the closest match to each individual colour used in
thumbnails. This gives a tolerable result on 8-bit servers, assuming
gdk was able to allocate a large number of colours; however, it gives
terrible results if it couldn't, or if running on 4-bit or 1-bit
servers. Sorry about this --- it should be fixed in future (either by
using gdk to draw the thumbnail pixmaps, or by dithering them `by
hand' to suit the colours available).
Finally, when doing a recursive thumbnail update, xzgv (by default)
reads existing thumbnails in a directory before updating any. Or rather,
it reads thumbnails for those files currently visible in the selector.
This can slow things down very slightly, but keeps the `look and feel'
consistent with the normal update. (Still, you can disable this with the
`--fast-recursive-update' command-line option (see Invoking
xzgv) or equivalent config file entry (see Configuring xzgv).)
SELECTOR LAYOUT AND RESIZING
The file selector is simply a list of subdirectories and filenames,
along with any thumbnails that exist for them. The list is normally in
asciibetical order (but you can change this; see Changing the Sorting
). Names of directories are shown first, and they are shown in
order at the beginning of the list, before all the picture files. Long
filenames may not fit in the visible part of the file selector display;
if so, there will be a horizontal scrollbar you can use to see the rest
of the name(s) (you can use cursor left/right to do this from the
The list is very often larger than can fit on the screen at once. If
this is the case, only part is shown at a time, but you can move around
the list using the (vertical) scrollbar, or with cursor up/down and the
If you find the selector window to be too small vertically, and would
like to see more files at once, you can start xzgv fullscreen by using
the -f option (see Options), and/or use `thin rows'
mode (see File Selector Options).
If you find the selector too small (or too big) horizontally, you can
change this by moving the splitter line's `handle' (a small square
button between the selector and viewer, near the bottom of the window),
which changes the relative sizes of the selector and viewer. You can
move it by dragging it with the mouse, or with these keys:
Move the window split left.
Move the window split left more slowly.
Move the window split right.
Move the window split right more slowly.
Reset the window split to its default position.
You can also set the initial/default size of the selector --- in effect,
the position of the window split --- using `--selector-width'
(see Options) or the config file option `selector-width'.
MOVING AROUND THE LIST
This section is mainly for those of us more inclined to the keyboard
side of the force. :-) Mouse-happy types can freely skip it.
When the selector has the keyboard focus, the cursor (or in GTK+ jargon,
the `focus row') is normally shown as a hollow box around one of the
list's rows. This serves the following functions:
It selects a file for view commands to operate on.
It determines which part of the list is shown, as the part of the list
shown onscreen always contains the cursor (unless you move around using
There are several commands for moving the cursor. In summary, most
`special' keys like the cursors do what you'd imagine they do, but in
Move the cursor back roughly a page.
Move the cursor forward roughly a page.
Move the cursor to the start of the list.
Move the cursor to the end of the list.
Move the cursor to the first filename starting with the next key
pressed, which would generally be a letter or number. Case is
significant; `a' and `A' are different. If no key is pressed
within 2 seconds, the command is cancelled.
If no files start with the specified character, it moves to the first
file which starts with a later char (in asciibetical order). If there
are none for which this is the case, it moves to the last file ---
unless there are no files (just directories), in which case it has no
VIEWING A FILE
To view a file from the selector, you can click on it, or press
' after moving the cursor to the relevant file,
or right-click on the file and choose `File' then `Open'.
`Selector menu, File, Open
View the chosen picture file, or if a subdirectory is chosen, make that
the current directory.
See The Viewer
, for details of how the viewer works.
If xzgv has a serious problem reading a file, it will give an error.
Errors are shown in dialogs which appear in the middle of the screen ---
they stay there until you click Ok
(or press `Enter
xzgv also uses similar dialog boxes for other things:
Getting confirmation that you want to do something. `Enter' or
`y' picks `yes'; `Esc' or `n' picks no. (Again, you can
click on the relevant button with the mouse to do the same.)
Showing progress when updating a thumbnail. This is a slightly unusual
dialog, in that it automatically disappears when the update is complete.
However, it does provide a Cancel button which you can click to
abort the update (pressing `Enter' or `Esc' does the same).
Reading a directory name. Here you should type the directory name then
click Ok (or press `Enter'), or click Cancel (or press
`Esc') to abort. The text-input `widget' used allows a certain
amount of editing, including these keys:
Move the cursor left. (A vertical bar shows the cursor position.)
Move the cursor right.
Move the cursor to the start of the line.
Move the cursor to the end of the line.
Delete char to the left of the cursor. (Note that `Backspace' is
(usually) the key above the main `Enter' key; it is often labelled
simply as an arrow.)
Delete the char the cursor is on.
You can also set the X selection (by selecting text with the mouse, or
holding `Shift' while moving the cursor) to allow pasting text into
other programs, and you can cut/copy/paste text in the usual ways:
You can paste text from (some) other programs using the latter command,
CLOSING A FILE
Usually, when you view a file, the viewer subwindow keeps displaying it
until you view a different file. However, if you `close' the file, the
viewer stops displaying the file and returns to its initial state.
`Selector menu, File, Close
`Close' the currently-viewed file, clearing the viewer subwindow.
The listing the selector gives for a file is pretty sparse --- just the
filename and (if the file has one) the accompanying thumbnail. While
this does keep things simple, you sometimes want to know how much space
a file takes up, when it was last modified, the dimensions of the image,
that kind of thing. So, you can show details of a single file using the
`file details' command:
`Selector menu, File, Details
Show various details about the file pointed to by the keyboard cursor.
See The Selector Menu, for how to choose the file details are given
for when using the mouse. (Basically, you right-click on the file when
popping up the menu.)
Most of the details shown come from the OS (by using the `stat(2)'
system call), and should always be available unless you have limited
permissions for the directory the file is in. The file dimensions
(width/height), however, come from the file's thumbnail. If it doesn't
have one, or if it's unreadable, or if it has one and it's readable but
it doesn't mention the original image's width/height, then the
Details from thumbnail area is greyed out.
(In explanation of the latter point --- pre-5.0 versions of zgv did not
generate width/height comments in thumbnails, so zgv users in particular
may find the width/height details missing. (xzgv has always been ok,
though, it's just zgv which had this problem.) Worse yet, versions 5.0
and 5.1 generated them with incorrect sizes for most JPEGs. To fix
either problem for a given directory, do `rm -fr .xvpics' in that
dir from a shell prompt and recreate the thumbnails with zgv 5.2 or
later, or xzgv/xv/Gimp.)
The file selector is not restricted to working on one file at a time.
You can `tag' as many (or as few) files as you wish, and certain
commands described in this section will act on them.
Initially, all files are untagged, and the filenames usually appear in
black (though this depends on the GTK+ theme you're using). Tagged files
appear in red.
Tag and Untag Commands
There are several ways to tag or untag files. The keyboard-based ones
which work on individual files (also available on the Tagging
menu) move the cursor down one row afterwards, to make tagging or
untagging multiple files easier.
To tag or untag a single file with the mouse, control-click (i.e. hold
down the control key and click) on the relevant filename or thumbnail in
the selector. It's true that you could use Tag and/or
Untag on the Tagging menu (see The Selector Menu, for
how to choose the file tagged/untagged when doing it this way), but this
is usually much less convenient than using control-click. (The menu
entries for those are really just for completeness.)
There is also a command available in the viewer to tag the
currently-viewed file. See Changing Picture, for details.
`Selector menu, Tagging, Tag
`Selector menu, Tagging, Untag
`Selector menu, Tagging, Tag All
Tag all files.
`Selector menu, Tagging, Untag All
Untag all files.
`Selector menu, Tagging, Toggle All
Toggle all tags. This inverts the tagged state, so that all previously
tagged files become untagged, and all previously untagged files become
Currently there is no way to toggle a (single) file's tag state from the
Moving Between Tagged Files
These commands let you search for (move to) the next or previous tagged
file (if any). Note that `next' and `previous' here are relative to the
keyboard cursor's position; if you use these from the menu, be careful
to right-click on the file you want to start the search from.
`Selector menu, Tagging, Next Tagged
Move to next tagged file in dir.
`Selector menu, Tagging, Previous Tagged
Move to previous tagged file in dir.
Equivalent commands are also available in the viewer (see Changing
You can copy or move tagged files to a directory you specify. If no
files are tagged, xzgv copies/moves the file the cursor is currently on
--- unless the cursor is on a subdirectory, in which case it gives an
`Selector menu, File, Copy
Copy tagged files (or the current file) to a given directory. xzgv asks
for the destination directory using a dialog (see Dialog Boxes) and
copies the files there. If it comes to copy a file but there is an
existing file in the dir with the same name, the file is not copied and
nor are any of the remaining files.
`Selector menu, File, Move
Move tagged files (or the current file) similarly.
RENAMING A FILE
As well as copying/moving files, you can rename them:
`Selector menu, File, Rename file
Rename the current file or directory --- xzgv will refuse to overwrite
any existing files/directories. The new name must remain in the current
directory. (See Copying/Moving Files, for how to move a file to a
different directory (albeit keeping the same name).) See The Selector
Menu, for how to choose the file renamed when using the mouse.
(Basically, you right-click on the file when popping up the menu.)
I know `Ctrl-n' isn't the most mnemonic keypress possible for
`rename', but all the good ones were taken. :-/
DELETING A FILE
Deleting a file is pretty straightforward:
`Selector menu, File, Delete file
Delete the file pointed to by the keyboard cursor (and any accompanying
thumbnail). See The Selector Menu, for how to choose the file deleted
when using the mouse. (Basically, you right-click on the file when
popping up the menu.)
Note that only one file is deleted (hence `Delete file'); there is
currently no way to delete all tagged files.
The easiest way to change the current directory in xzgv is usually to
click on a directory entry in the file list (or move the cursor to it
and press `Enter
'). Selecting the `..
moves to the parent directory of the current one.
There is an alternative though:
(Note that the key for this command is shift-`g', not `g'.)
`Selector menu, Directory, Change
Go to a specified directory. xzgv asks for the destination directory
using a dialog box which you should type the dir's name into
(see Dialog Boxes), and moves to that directory if it exists.
RESCANNING THE DIRECTORY
Normally, xzgv reads a directory once (on starting up, or when a new
directory is selected). So if the contents of the directory are changed
by another program, this is not automatically reflected. You can,
however, explicitly tell xzgv to `rescan' the directory (reread the
contents), which will update xzgv's notion of what's in it:
`Selector menu, Directory, Rescan
Rescan the current directory.
CHANGING THE SORTING ORDER
Normally, the files are listed in asciibetical order by name. However,
you can instead have the file list sorted by size, last-modified
date/time, or by `extension' (the file type).
(Only the order of files can be altered; directories are always listed
first, and always in name order.)
`Selector menu, Directory, Sort by Name
Sort by name. This is the default.
`Selector menu, Directory, Sort by Extension
Sort by extension.
`Selector menu, Directory, Sort by Size
Sort by size. The biggest files are listed last.
`Selector menu, Directory, Sort by Time & Date
Sort by time/date. The newest files are listed last.
You can set the default sort order via the command-line (see Invoking
xzgv) or a config file (see Configuring xzgv).
There are three possible timestamps you can use for the `Time & Date'
`Selector menu, Directory, Time & Date Type, Modification Time (mtime)
Use the last-modified time (`mtime'). This is the default.
`Selector menu, Directory, Time & Date Type, Attribute Change Time (ctime)
Use the last-attribute-change time (`ctime'). Note that this is
not always the time the file was created, which it's sometimes
mistaken for; for example, moving a file with `mv' will usually
change the ctime.
`Selector menu, Directory, Time & Date Type, Access Time (atime)
Use the last-accessed time (`mtime'). The selector order is not
automatically updated when xzgv reads files, since this would probably
be annoying; do a manual rescan if need be.
FILE SELECTOR OPTIONS
Various aspects of the file selector's behaviour can be configured while
xzgv is running, by using these toggle commands (which enable the feature
if it was previously disabled, and vice versa).
These settings can also be altered using command-line options
(see Options) and/or config file settings (see Configuring
`Selector menu, Options, Auto Hide
Toggle the auto-hiding of the selector when a picture is viewed (off by
default). This is handy for small screens/windows, or for old-time zgv
users who just dig that groovy modal interface, er, man. :-)
`Selector menu, Options, Status Bar
Toggle status bar at the bottom of the selector (off by default). This
displays messages in certain circumstances --- normally, it just says
when a picture is being read.
`Selector menu, Options, Thumbnail Msgs
Toggle reading-thumbnails messages (default is off), only visible if the
status bar is enabled. These messages make it clear when all thumbnails
have been read, but having something flash up every time you change
directory is generally just annoying.
`Selector menu, Options, Thin Rows
Toggle `thin rows' mode (off by default), in which thumbnails are shown
at a third their normal size so that many more files can be shown at
once. (The odd keyboard shortcut for this is inherited from zgv's
`visual' mode toggle, which had a roughly similar effect.)
`Selector menu, Directory, Images Only
Toggle the option to show only directories and image files in the
selector (off by default). This is handy in directories where images
and other file types are intermingled and you want to avoid the
`Couldn't load image' error on those other files. Images are identified
by their extensions.
Once you've selected a file to view, it's shown in the viewer (the
right-hand part of xzgv's window). This section describes what you can
do while viewing the picture.
Like the selector, the viewer has its own menu --- right-click anywhere
on the viewer (or press `F10' or `Menu') to show it --- and a
similar help menu (see The Selector Menu).
EXITING THE VIEWER
When using the mouse to control xzgv, it doesn't matter whether the
selector or the viewer has keyboard focus --- mouse operations transcend
such petty boundaries. :-) But keyboard control is (of necessity)
effectively modal, and so you need to `exit' the viewer in order to have
keyboard control over the selector again. You also need to exit the
viewer if you've enabled auto-hide mode.
Exiting the viewer is simple:
`Viewer menu, Exit to Selector
Exit the viewer. This also returns the selector to its former size, if
it was previously `hidden'.
Another way of exiting the viewer is to middle-click on it, but this
mouse-only approach is really only of use when the selector is `hidden'.
A picture may well be too large to fit entirely in the viewer window.
There are two main things which can help you see more of the picture at
Make the xzgv window larger. You could `maximize' it with your window
manager, or you could start xzgv with a larger window using
`--geometry' or fullscreen mode (see Options). The
fullscreen mode gives xzgv the maximum window size possible, but needs
co-operation from your window manager (and alas, many are not as willing
as one might like) --- in some cases you may even find `--geometry
100%x100%' to be more effective.
Hide the selector. To do this, either use auto-hide mode (see File
Selector Options), or hide the selector explicitly (see Hiding the
But of course, these are only partial solutions to the problem; there
will inevitably always be pictures larger than your screen can show at
once. In general, then, there are two ways to see the whole of the
Scrolling is the default approach to handling big pictures in xzgv. When
the viewer is started up, the top-left of the picture is shown --- you
can either drag the picture around with the mouse (i.e. click and hold
the button down, then move the mouse around), or use the scrollbars, or
use the cursor keys (and others) to move around the rest of the picture:
Move up 100 pixels. `Ctrl-Cursor Up' and `k' both move up 10
Move down 100 pixels. `Ctrl-Cursor Down' and `j' both move down
Move left 100 pixels. `Ctrl-Cursor Left' and `h' both move left
Move right 100 pixels. `Ctrl-Cursor Right' and `l' both move
right 10 pixels.
Move up (nearly) the window height. (It moves by 90% of the height.)
Move down (nearly) the window height.
Move left (nearly) a window-length. (It moves by 90% of it.)
Move right (nearly) a window-length.
Move to the top-left of the picture.
Move to the bottom-right of the picture.
An alternative way of viewing the whole picture, one which lets you see
the picture onscreen all at once no matter how big (or small) it is, is
Zoom mode's name derives from the idea of `zooming' a small file up to
fit the window. But in reality, it is more often used to reduce a large
file to fit.
Zoom mode is not the default, and has to be enabled. Once enabled, it
stays on until you turn it off again (or until you enable scaling, or
select Normal (see Scaling)).
`Viewer menu, Options, Zoom (fit to window)
Toggle zoom mode.
`Viewer menu, Options, When Zooming Reduce Only
When in zoom mode, only reduce pictures to fit. This can be
useful when going through a lot of unpredictably-sized pictures, as it
means that you can see all of a big picture easily without also meaning
that tiny little icons assume a scale of Biblical proportions. :-)
`Viewer menu, Options, When Zooming Panorama
When in zoom mode, resize to make the most proportional dimension fit and
allow scrolling on the other dimension. This can be useful when viewing
iamges that do not adjust nicely to the window size but you want to see them
as big as possible while using the most space available. The cause for this
function was to better read comics, so you can guess it works like a
`fit page width' option, but is not limited to horizontal adjustment.
The way zoom mode reduces a file to fit the window is (relatively) quick
but harsh, and may make the picture look a bit ugly. In future there may
be a smoothing option like zgv's vkludge, but for now I'm afraid
the fairly crude resize is all that's available.
There is in fact an alternative to zoom mode, as you can scale down an
image instead. This is generally only useful for very large images,
however; zoom mode tends to be the Right Thing for the most part.
You can scale a picture --- this makes it appear larger (or smaller)
onscreen. xzgv acts much as if the scaled picture were the real picture;
for example, the cursor keys scroll around in steps of 100 scaled
pixels, even if this means moving a fraction of a pixel (or many pixels)
in the original picture (and similarly for movement with the mouse).
The main limitation of scaling (other than how much it slows things down
:-), at least when scaling up) is that you can only scale by integer
values, so you can only make each pixel in the image twice as wide/high,
or three times as wide/high, or four times, and so on.
(It may seem odd saying e.g. `twice as wide/high' rather than `twice the
size', but technically `twice the size' would be referring to scaling up
the width (and height) by about 1.414...)
Normally, xzgv does no scaling, which could be considered a ratio of 1:1.
Scaling up increases that ratio. How it is increased depends on which
option/key you use:
`Viewer menu, Scaling, Double Scaling
Increase the ratio by doubling it --- this leads to ratios of 2:1, 4:1,
`Viewer menu, Scaling, Add 1 to Scaling
Increase the ratio by adding one --- leads to ratios of 2:1, 3:1,
There are similar commands to decrease the ratio:
`Viewer menu, Scaling, Halve Scaling
Decrease the ratio by halving it.
`Viewer menu, Scaling, Sub 1 from Scaling
Decrease the ratio by subtracting one.
Usually the double/halve scalings are more useful.
Note that you can also double/halve the scaling by using
shift-left-click on the viewer to double, and shift-right-click to
halve. This still changes scale `around' the middle of the window though
(rather than around the point clicked on, as you might expect), which is
a little strange and may possibly be changed in future.
When you scale `below' 1:1, the above commands lead to ratios of (e.g.)
1:2, 1:4, 1:8, etc. --- that is, the ratios work the same way, but the
other way around. This gives you an increasingly small image.
The scaling ratio is never decreased below 1:32. It is also never
increased beyond the point where the overall image size would exceed
32767x32767 --- this limit is due to the combination of X's limit on
window sizes, and the implementation used by xzgv for scaling.
One problem with scaling up, given the way it's currently implemented,
is that it's not well-suited to dithered display --- so if you're
running on an 8-bit server, dragging the image around slowly when using
scaling (especially scaling with interpolation) may result in some
nasty, streaky, undithered-looking parts of the picture. :-(
You can undo the effect of scaling (up or down) at any time:
`Viewer menu, Scaling, Normal
Resume `normal' display --- disables scaling mode, and also zoom mode.
Normally, scaling up works by simply making the pixels into larger and
larger squares (in effect), which remain the same colour. However, you
can enable a feature called `interpolation' which smoothly graduates the
colour change between the top-left corners of each pixel. This is
very slow, but looks nice.
`Viewer menu, Options, Interpolate when Scaling
Toggle interpolation in scaling mode.
(If you like the appearance of scaling with interpolation, you may also
be interested in a program I wrote called pnminterp, which can
scale up a PGM or PPM file while applying this effect. These days it's
part of the netpbm package.)
Scaling down, however, is implemented a bit like a special-case zoom
mode, and currently there are no ways of making that look nicer. :-/
xzgv normally `reverts' scaling (returning the scale to 1:1) back to
normal when you view a new picture. However, it's possible to disable
this behaviour (see Viewer Options).
There is also support for an alternative form of scaling --- decoupled,
or axis-specific, scaling. When you scale in this way, only one axis of
the image is scaled at once. For example, you might choose to
effectively double the height of an image (with the width left
unchanged). Indeed, this sort of scaling is useful for temporarily
correcting pictures intended for display using pixels twice as wide or
high as normal.
`Viewer menu, Scaling, X Only, Double Scaling
Increase the (x axis) ratio by doubling it.
`Viewer menu, Scaling, X Only, Halve Scaling
Decrease the (x axis) ratio by halving it.
`Viewer menu, Scaling, X Only, Add 1 to Scaling
Increase the (x axis) ratio by adding one.
`Viewer menu, Scaling, X Only, Sub 1 from Scaling
Decrease the (x axis) ratio by subtracting one.
`Viewer menu, Scaling, Y Only, Double Scaling
Increase the (y axis) ratio by doubling it.
`Viewer menu, Scaling, Y Only, Halve Scaling
Decrease the (y axis) ratio by halving it.
`Viewer menu, Scaling, Y Only, Add 1 to Scaling
Increase the (y axis) ratio by adding one.
`Viewer menu, Scaling, Y Only, Sub 1 from Scaling
Decrease the (y axis) ratio by subtracting one.
There are also mouse shortcuts for scaling up/down a single axis;
control-left-click scales up, and control-right-click scales down. By
default this acts on the y axis, but the active axis can be toggled with
`Alt-c', or by toggling the `Ctl+Click Scales X Axis' option
(see Viewer Options).
Interpolation is not currently supported in situations where the x
scaling does not match the y scaling.
MIRROR AND ROTATE
Sometimes when viewing a picture you will want to flip it horizontally
or vertically, or rotate it:
`Viewer menu, Orientation, Mirror (horiz)
`Mirror' the picture (flip it horizontally).
`Viewer menu, Orientation, Flip (vert)
`Flip' the picture (flip it vertically).
`Viewer menu, Orientation, Rotate Right
Rotate the picture 90 degrees clockwise.
`Viewer menu, Orientation, Rotate Left
Rotate the picture 90 degrees anti-clockwise. (Any US readers surprised
and/or annoyed by my not saying `counter-clockwise' will realise why the
menus say rotate right/left. :-))
`Viewer menu, Orientation, Normal
Restore the picture orientation to normal. This undoes the effect of any
mirrors, flips, and/or rotations.
xzgv normally `reverts' the picture orientation (the way the picture has
been transformed by mirror/flip/rotate) back to normal when you view a
new picture. However, it's possible to disable this (see Viewer
Options), so that any new pictures are mirrored, flipped, and/or
rotated in the same way.
It's possible to go directly to the previous or next file (or tagged
file) in the directory, or to tag a file, without having to pick the
file from the file selector by hand. These commands are particularly
useful when using xzgv from the keyboard, but there's also a notable
mouse shortcut for moving to the next image.
`Viewer menu, Next Image
Move to next file in dir, and view it. You can also click on the
picture/viewer to do this. (If you find this interferes with dragging
the picture around (though it shouldn't), or just don't like it, it can
be disabled (see Config Variables).)
`Viewer menu, Previous Image
Move to previous file in dir, and view it.
`Viewer menu, Tagging, Tag then Next
Tag current file, then move to next file in dir and view it.
`Viewer menu, Tagging, Next Tagged
Move to next tagged file in dir, and view it.
`Viewer menu, Tagging, Previous Tagged
Move to previous tagged file in dir, and view it.
HIDING THE SELECTOR
When running on small screens, or in a small window, it can get a bit
annoying to lose viewer space by having the selector constantly
displayed when you don't actually need it. The usual solution to this
problem is to enable auto-hide mode. But what if some pictures you're
viewing are small and some large? It can sometimes be nearly as annoying
having the selector hidden to `make room for' a small picture which
didn't need it. So for that reason, or perhaps if you just don't like
auto-hide mode :-), you may prefer to leave auto-hide off and explicitly
hide the selector when necessary:
`Viewer menu, Window, Hide Selector
Hide the selector. (This is actually a toggle, of sorts; `hide selector'
when it's already hidden unhides it.)
You can also hide or unhide the selector by middle-clicking on the
Generally it's easy enough to use your window manager to change windows
etc., but when running fullscreen this can sometimes be a little
problematic. For this reason, xzgv has built-in support for `iconifying'
`Viewer menu, Window, Minimize
Minimize the xzgv window.
As with the selector, various options can be disabled/enabled which
relate to the viewer.
These settings can also be altered using command-line options
(see Options) and/or config file settings (see Configuring
`Viewer menu, Options, Zoom (fit to window)
Toggle zoom mode, discussed in more detail elsewhere (see Zoom Mode).
`Viewer menu, Options, When Zooming Reduce Only
Toggle reduce-only in zoom mode, also covered elsewhere (see Zoom
`Viewer menu, Options, When Zooming Panorama
Toggle panorama view in zoom mode, also covered elsewhere (see Zoom
`Viewer menu, Options, Interpolate when Scaling
Toggle interpolation when a picture is being scaled-up. Again, this has
already been mentioned (see Scaling).
`Viewer menu, Options, Ctl+Click Scales X Axis
Toggle the axis scaled when you control-click (or control-right-click)
on the image. The default is to scale the y axis.
`Viewer menu, Options, Dither in 15 & 16-bit
Toggle dithering in 15/16-bit modes. This increases the apparent colour
depth making gradations look much better, but it's slower than
undithered rendering, and can (in 16-bit) slightly distort a picture's
colour balance. (The `F' key was chosen for this as the dither
toggle is functionally similar to zgv's `fakecols' toggle.)
`Viewer menu, Options, Revert Scaling For New Pic
Normally xzgv returns the scaling back down to 1 (normal) when a new
picture is selected. By disabling this, you can retain scaling across
picture selection. (There is currently no keyboard shortcut for this
fairly-seldom-changed option --- to toggle it from the keyboard, you
should use the popup menu (press `F10'), and select the menu item.)
`Viewer menu, Options, Revert Orient. For New Pic
Similarly, xzgv returns to the picture's true orientation (not mirrored,
rotated, etc.) on selecting a new picture. Disabling this option means
that any mirrors/flips/rotates applied persist across multiple images.
(No keyboard shortcut --- see above.)
`Viewer menu, Options, Use Exif Orientation
Toggle support for Exif orientation. Devices which create JPEG files
in the Exif format (e.g. many digital cameras) may add an orientation
tag to the file, which says how the camera was being held when the
picture was taken. When this tag is present, xzgv can adjust the image
to compensate for a camera being held on its side. (This isn't done by
default as it misrepresents the true image, which could be confusing
if you don't know why it's happening.) Enabling this option may be
useful if you take pictures with your camera on its side, but don't
want to have to rotate the pictures before being able to view them
properly. Of course, for this to work your camera has to be inserting
the orientation tag in the first place --- but it can't hurt to try it
and see. (No keyboard shortcut --- see above.)
Picture files are stored in a variety of different forms, or `file
formats'. xzgv, via gdk, supports many.
FILE TYPE IDENTIFICATION
The format a file is in is identified by its content. The file-reading
code relies on libgdk to determine the file type and read the file
correctly; generally this uses the format's `magic number' to determine
file type --- e.g. a JPEG/JFIF file starts with the (hex) bytes `FF
'. So if you start xzgv with xzgv foo
, and foo is in a
supported format (such as JPEG), the format will be figured out and the
file loaded even though the `extension' is absent.
Many aspects of the way xzgv works can be modified by using a
A configuration file lets you alter aspects of xzgv's behaviour. xzgv
supports two possible config files --- a system-wide one,
; and one for each user in their home directory,
. Both are optional. If $HOME/.xzgvrc
it is used instead of /etc/xzgv.conf
Before describing the format of config files, it may help to give an
# Sample xzgv config file
# Comment lines begin with `#' and are ignored,
# as are blank lines.
# make pics fit window
# hog the screen :-)
It is a line-based format. Each line (or rather, each line which is not
a comment line and is not blank) assigns a value to a single predefined
`variable'. xzgv has many such variables it lets you modify in this way.
For example, the fullscreen option above controls whether or not
xzgv tries to use the whole screen for its window. If it is given the
value `on'/`y'/`yes'/`1' it does; if
`off'/`n'/`no'/`0', it doesn't. Most variables are
of this yes-or-no `boolean' type.
Since the variables set in a config file have a direct effect on how xzgv
works, it can be easier to simply call them `settings'. Indeed, such
terminology is used on occasion in this documentation.
CONFIG VARIABLE TYPES
There are various types of variable:
Boolean. These are on-or-off, yes-or-no variables. Most of xzgv's config
file variables are of this type.
Integer. These are whole numbers. The meaning of the
number depends on what the variable is used for.
Geometry. This window size-and/or-position specification format is only
used for the `geometry' setting. See Options, for a
description of how this type works.
Currently, most configuration variables (settings) in xzgv can also be
set by command-line options; indeed, the name of the setting in all such
cases is identical
to that for the long version of the option
'). As such, they're documented
in the section which discusses command-line options and the like
However, there are some settings only available in the config file:
This is enabled by default, allowing you to click on the viewer to skip
to the next image. If disabled, clicking on the viewer does nothing.
Here I (RJM) attempt to explain why I did things the way I did. This is
presented in a question-and-answer format of sorts.
WHY YET ANOTHER VIEWER?
Previously, this section concentrated on xv; that may have made sense
when I originally wrote it, and still makes a certain limited amount of
sense for zgv, but for xzgv it was looking increasingly dated. And so
here I am writing an update. :-)
I originally wrote xzgv as I simply wasn't happy with the viewers for X
that I was aware of at the time (mid-1999). At the time of writing (late
2000), other key things about xzgv are becoming apparent, partly through
responses I've been getting to it:
It's `fast'. No, it doesn't do any particular operation faster than
other viewers as far as I know (well, maybe thumbnail updates :-));
rather, the interface tries not to get in your way. Click on a filename,
and the picture appears. No multiplicity of toolbars or windows, it's
As with zgv, it tries to do one thing well, viewing pictures. It isn't
perfect in this regard, I'll admit, but at least it stays well clear of
It's, er, quite a lot like zgv. Some of us old fogies like this. :-)
I won't pretend xzgv is The Ultimate Viewer For Everyone. Some people
will prefer other approaches, or just simply prefer other viewers. (Some
people may even still use xv, ghod forbid.) There are a few viewers
which you may like to try if you don't think much of xzgv:
gqview. This seems to be well-regarded. I find it a bit gimmicky and
kitchen-sink-ish; not quite as `pure' or focused as xzgv, IMHO. I think
more people use it than xzgv though.
xli. I'm not sure if this is maintained these days, but it's not too bad
a viewer. No thumbnails or file selector though. (These days I mostly
use this for setting the root window pixmap, something I don't
think belongs in a viewer, but which xli does happen to be quite good
qiv. If I read between the lines correctly, this is essentially a modern
replacement for xli.
gtksee. I've not tried this, but I think the idea is that it's an ACDSee
clone, and there seem to be an awful lot of people who want a clone of
that. Which is their problem. :^)
Electric Eyes. To be honest, I think this has been outclassed by other
viewers these days, which shows how far we've come.
Ah, you say, what of xv? Well, we've emphatically reached the
point where no-one need use xv any more. Anyone using xv these days
really should drop that pile of ill-conceived non-Free crap and use one
of the better viewers now available. It's that simple.
WHY NO IMAGE-EDITING CAPABILITIES?
It's a fscking viewer
, dammit. If you want xv you know where to
(OTOH, if you want a decent image editor, use the Gimp.)
WHY A TEXINFO MANUAL?
For years, I maintained a conventional `man page' for zgv (which xzgv
was loosely based on). But over time, I realised just how impossibly
confusing the zgv man page had become.
So I wanted to rewrite zgv's documentation in a more sensible way, in
some other format than a man page. I wanted an established,
well-supported format with structure and cross-referencing. I felt this
made it a choice between HTML and texinfo. HTML seemed to me to be a
moving target like no other, and not as well supported on text-only
terminals as Info (and thus texinfo). (This latter point is admittedly
not too relevant as far as xzgv is concerned.) When I noticed that a
converter existed to convert texinfo to HTML in any case, the case was
closed. xzgv's documentation was then based on zgv's --- the
documentation is probably more similar than the programs are. :-)
Don't get me wrong --- I like man pages. And even with the excellent
Texinfo documentation and Emacs' very helpful Texinfo mode, writing
texinfo is hardly easy. (Without Texinfo mode's node- and menu-update
commands, I personally would find it near-impossible!) But big man pages
just aren't that good for reference, and this is made worse by the
relative lack of structure.
WHY ONE-SPACE SENTENCE ENDS?
The conventional way to write texinfo is to follow each sentence with
two spaces after the dot (or whatever ends the sentence). Many people
normally write this way in a non-texinfo context too. But a sizeable
proportion of people normally write text with only one space after the
dot --- and I'm one of them.
The Texinfo documentation gives the impression that two-space
must be used; it says ``it is important to put two spaces at the
end of sentences in Texinfo documents.'' But the only circumstance in
which spacing from the texinfo file is preserved at all (in any sense
other than `there is a space here') is when the texinfo is converted to
Info format. So, in fact, the decision to use two-space depends on how
the author wants Info output to appear --- this is a subjective decision
which should be entirely down to the preference of the author,
despite the Texinfo documentation's attempt to make two-space sound like
an objective you-must-do-this kind of thing.
You might wonder what the problem with using one-space is, then. Well,
`makeinfo' has to reformat paragraphs, and whenever it needs to insert
space at (what appears to it to be) the end of a sentence, it inserts
two spaces. This behaviour cannot be altered, unlike in Emacs
(sentence-end-double-space; see Fill Commands in the emacs info file) and GNU fmt (-u; see fmt
invocation in the textutils info file). Also, attempting to `fix'
the output Info with sed doesn't work properly because the `tags' used
to find nodes quickly are then incorrect. These could of course also be
fixed, but this would involve a lot more work than a simple sed
So realistically, anyone who writes texinfo with one-space has to put up
with the occasional two-space sentence end being inserted into their
text --- worse still, the current `makeinfo' formatting algorithm seems
to insert two spaces even after abbreviations (such as `e.g.' and
`etc.'), which breaks even two-space texinfo. (This is particularly
ironic, by the way, since two-space partisans' main argument in favour
of the practice is often the way it makes it possible to tell the
difference between abbreviations and the end of a sentence.)
One last point may be worth noting; I am not the first person to write
texinfo files using one-space. At the time of writing, it is used in the
texinfo documentation for BFD, gdbm, GTK/GDK, (Linux) IPC, and viper,
and I expect there are instances I'm not aware of.
BUGS AND RESTRICTIONS
All (non-trivial) programs have bugs. Anyone who denies this...
clearly hasn't written too many programs.
is wrong. ;-)
It follows that xzgv, like everything else, always has some bugs.
Usually these are not too serious, or I'd have fixed them before
releasing xzgv. But either way, bugs and other problems with xzgv are
In zoom mode, it copes with resizing the window as a whole, but
when you change the size of the pane (apart from when
hiding/showing selector or resizing from keyboard, but that's only 'cos
I kludged it :-)).
When scaling up and dithering, you end up with a crappy-looking picture
if you drag the picture around slowly (since each exposed bit is
dithered independently, with no regard given to matching up to any
Scaling up is slow. Not sure if I can do much about this.
Using an alignment widget to centre the viewer window results in some
annoying `bounce' in certain resizing situations etc.
Thumbnails don't look so great in palette-based (e.g. 8-bit) modes.
When dragging an image around, if you quickly move the mouse pointer
over from the image area to the selector area, the image seems to `jump'
a little. I think this may have something to do with the paned window's
window-splitting bit, but I'm not sure. Also, it jumps when moving
across scrollbar sliders and the paned window splitter handle.
It doesn't apply any tranparency mask. The practical result of this
seems to be purple transparent bits in thumbnails and scaled-up images,
and black transparent bits elsewhere. This doesn't affect PNG files,
If a GIF file is corrupted in such a way that the decompressed image
has a larger number of pixels in it, the extra pixels will be ignored
and no error or warning will be generated.
If you look up `joe code' in a dictionary, right next to ``see zgv'' it
now says ``but for really in-depth insight into the joe code
nature, see xzgv''. :-)
Thumbnails are given an accurate width/height `IMGINFO' comment, but are
always claimed to be "RGB".
xzgv doesn't duplicate zgv's behaviour of generating thumbnails
under ~/.xvpics/_foo_bar_baz if it can't generate them in
/foo/bar/baz/.xvpics. I doubt anything else supported it, and it
complicated lots of things unnecessarily. This isn't particularly
suboptimal, but as an incompatibility with zgv it merits mention.
Only the first image of a multiple-image GIF is used. (These days,
multiple-image GIFs are usually animations.)
If you find xzgv does something wrong, which you suspect might be a fault
of some sort (a bug) in the program, it is best to report it as I may
not be aware of the problem. (But first, check it is not a `known bug'.
See Known Bugs
. It is not usually helpful to report a bug I already
It is important to include as much detail in a bug report as you can.
Here are some details you should include:
The version of xzgv you are running. `xzgv --version' reports this.
The versions of GTK+ you are using. `xzgv --version-gtk' reports
the GTK+ version being used by xzgv.
The bitdepth your X server is running in (common depths are 16-bit,
24-bit, and 32-bit). If you don't know what depth you're running in, try
A description of the bug --- what effects it has, the circumstances it
occurs in, and so on. Does it only happen for certain types of file?
Only when in 8-bit modes? Only when dithering is enabled? Even
`irrelevant' details can sometimes be useful.
Finally, if you are a programmer and believe you have managed to fix the
bug yourself, patches are gratefully accepted. :-) You should generate
the patch using `diff -c' or (preferably) `diff -u'.
Then, please file a bug report in the SourceForge bug tracker.
REPORTING DOCUMENTATION BUGS
Bugs in the documentation can sometimes cause as much trouble as bugs in
the program; if you notice a problem in the documentation, it's a good
idea to report it.
For reports of documentation bugs, you should include these details:
The version of xzgv the documentation is for.
If it is a problem in one specific section of the documentation, specify
which part it is (by this I mean the heading it comes under;
texinfophiles should read this as `the node name' :-)).
The format of the documentation you saw the problem in (e.g. info, man
A description of the problem.
See Reporting Bugs
, for details of where to send the bug report.
If you want to suggest a feature you'd like in xzgv, or a change to an
existing feature, contact me; see See Reporting Bugs
for the address.
Future changes etc. are listed in the TODO file.
Russell Marks <firstname.lastname@example.org
> and others;
see the section ACKNOWLEDGEMENTS