César Leonardo Blum Silveira wrote: > I have a few doubts about the way I code my GTK applications. One of > them is: Is it ok to use many global variables for the widgets? For > example, in a glade app where callbacks are of the form > > void callback(GtkWidget *widget) > > I can only have access to the widget that received the signal, but > what if I want to make it change a property of another widget? Should > I use a global variable or should I try getting the toplevel widget > and then decending to the "neighbour" widget I want to make changes > on?
Opinions about it certainly differ. Some people may prefer global variables for all important widgets for two reasons: 1. it's the very fastest way to get pointers to widgets, 2. it's okay for them to deal with large amounts of global vars (despite known problems that could result with them on larger scale applications). However, I think the majority of programmers prefers to avoid global variables whenever possible. Both for stylistic as well as for complexity reasons. Having to keep track of global variables for somee (or many) widgets is more difficult and error-prone than not needing to do so. With the exception of toplevel (or popup) windows I don't use any global vars to store pointers to widgets in them. Instead, during program execution I refer to widgets by name. The name property of widgets, if being used properly, is a wonderful and well readable way to refer to widgets. It's a glimpse of high-level (or scripting) language programming in C(++). This way you don't need to juggle with numerous global variables and their (possibly frequent) proper initialization (and deinitialization) at all. It's certainly a bit slower than directly accessing a global variable of which the memory address is directly known at execution time and doesn't need to be determined. However, the speed impact should be neglegible unless you plan to search for far more than some 1000s different widgets per second (or signal handler). Performance limitations of GTK+ applications are not caused by this sort of custom functions, anyway. Since this way of easy programming appears not to be supported officially by GTK+ I use my own simple function for this purpose: widget_find_by_name (), retrievable at http://www.spamkiller.bytechase.cx/democode/widget_find_by_name.c For instance, if you have a window named "W_Main" and a text field named "I_Value" in it then you can simply refer to the latter from within any callback by something like this: { GtkWidget *i_value = WFBN ("I_Value"); gtk_widget_do_this (i_value, ...); gtk_widget_do_that (i_value, ...); } For other windows you may (or may not) simply define similar macros like WFBN_WIN2 (...) for instance. BTW, the difference between my function and lookup_widget(), provided by Glade, is that my function is absolutely independent from Glade and doesn't need any further precautions like lookup_widget() does. It just suggests you to set the "name" property of widgets appropriately. _______________________________________________ gtk-app-devel-list mailing list gtk-app-devel-list@gnome.org http://mail.gnome.org/mailman/listinfo/gtk-app-devel-list
