Tk_ImageChanged

Section: Tk Library Procedures (3)
Updated: 4.0
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NAME

Tk_ImageChanged - notify widgets that image needs to be redrawn

SYNOPSIS

#include <tk.h>

Tk_ImageChanged(imageMaster, x, y, width, height, imageWidth, imageHeight)

ARGUMENTS

Tk_ImageMaster imageMaster (in) Token for image, which was passed to image's createProc when the image was created.

int x (in) X-coordinate of upper-left corner of region that needs redisplay (measured from upper-left corner of image).

int y (in) Y-coordinate of upper-left corner of region that needs redisplay (measured from upper-left corner of image).

int width (in) Width of region that needs to be redrawn, in pixels.

int height (in) Height of region that needs to be redrawn, in pixels.

int imageWidth (in) Current width of image, in pixels.

int imageHeight (in) Current height of image, in pixels.

DESCRIPTION

An image manager calls Tk_ImageChanged for an image whenever anything happens that requires the image to be redrawn. As a result of calling Tk_ImageChanged, any widgets using the image are notified so that they can redisplay themselves appropriately. The imageMaster argument identifies the image, and x, y, width, and height specify a rectangular region within the image that needs to be redrawn. imageWidth and imageHeight specify the image's (new) size.

An image manager should call Tk_ImageChanged during its createProc to specify the image's initial size and to force redisplay if there are existing instances for the image. If any of the pixel values in the image should change later on, Tk_ImageChanged should be called again with x, y, width, and height values that cover all the pixels that changed. If the size of the image should change, then Tk_ImageChanged must be called to indicate the new size, even if no pixels need to be redisplayed.

KEYWORDS

images, redisplay, image size changes