This information is worse than useless for "perlTk" users, but can of some help for people interested in using modified Tk source with "perlTk".
This document is under construction. The information is believed to be pertinent to the version of "portableTk" available when it was created. All the details are subject to change.
During bootstrap of the C glue code the "Xevent::?" codes and a handful of "Tk::Widget" and "Tk::Image" routines are defined. (Much more XSUBs are created from "Tk.xs" code.) The widget subcommands are glued to Perl basing on the list included from "pTk/Methods.def". In fact all the subcommands are glued to XSUBs that are related to the same C subroutine XStoWidget(), but have different data parts.
During the Perl code bootstrap the method "Tk::Widget::import" is called. This call requires all the code from particular widget packages.
Code from the widget packages calls an obscure command like
This command (actually Tk::Widget::WidgetClass()) creates three routines: Tk::Widget::Text(), Tk::Widget::isText(), and Tk::Text::isText(). The first one is basically "new" of "Tk::Text", the other two return constants. It also puts the class into depository.
The only remaining black magic is that the "Tk" initialization routine creates a lot of commands, but the subroutine for creation is usurped by portableTk and the commands are created in the package "Tk". They are associated to XSUBs that are related to one of three C subroutines XStoSubCmd(), XStoBind(), or XStoTk(), but have different data parts.
The result of the call is blessed into "Tk::MainWindow", as it should.
Now "Tk::Toplevel" @ISA "Tk::Widget", that in turn @ISA "Tk". So a call to "$top->wm('title','Text demo')" calls "Tk::wm", that is defined during call to Tk_CreateMainWindow(). As it is described above, the XSUB associated to XStoSubCmd() is called.
This C routine is defined in "tkGlue.c". It gets the data part of XSUB, creates a "SV" with the name of the command, and calls Call_Tk() with the XSUB data as the first argument, and with the name of XSUB stuffed into the Perl stack in the place there "tk" expects it. (In fact it can also reorder the arguments if it thinks it is what you want).
The latter procedure extracts name of "tk" procedure and "clientData" from the first argument and makes a call, using Perl stack as "argv" for the procedure. A lot of black magic is performed afterwards to convert result of the procedure to a Perl array return.
Tk::Text::new($top, background => $txtBg);
The package "Tk::Text" has no method "new", so the "Tk::Widget::new" is called. In turn it calls "Tk::Text->DoInit($top)", that is "Tk::Widget::DoInit(Tk::Text,$top)", that initializes the bindings if necessary. Then it creates the name for the widget of the form ".text0", and calls "Tk::text('.text0', background => $txtBg)" (note lowercase). The result of the call is blessed into "Tk::Text", and the method "bindtags" for this object is called.
Now the only thing to discuss is who defines the methods "text" and "bindtags". The answer is that they are defined in "tkWindow.c", and these commands are created in the package "Tk" in the same sweep that created the command "Tk::wm" discussed above.
So the the same C code that corresponds to the processing of corresponding TCL commands is called here as well (this time via "XStoTk" interface).
Ilya Zakharevich <email@example.com>