mirror of
https://gitlab.gnome.org/GNOME/gtk.git
synced 2024-11-17 23:10:22 +00:00
70 lines
2.5 KiB
Plaintext
70 lines
2.5 KiB
Plaintext
|
Things to care about when using/programing for GTK+
|
||
|
|
===================================================
|
||
|
|
|
||
|
|
This file is meant to collect some frequently triggered failures when
|
||
|
|
programming for/with Gtk, having the spirit of a developers FAQ.
|
||
|
|
It is also the correct place to list up things that programmers should
|
||
|
|
care about in general.
|
||
|
|
|
||
|
|
In the hope that this text might be usefull to someone,
|
||
|
|
|
||
|
|
- Tim Janik <timj@gimp.org>
|
||
|
|
1998/02/11
|
||
|
|
|
||
|
|
|
||
|
|
Automatic destruction of widgets on removal from parent
|
||
|
|
-------------------------------------------------------
|
||
|
|
|
||
|
|
This is a reference counting issue, you would want to refer
|
||
|
|
to refcounting.txt on it.
|
||
|
|
|
||
|
|
|
||
|
|
What are all the widget flags about?
|
||
|
|
------------------------------------
|
||
|
|
|
||
|
|
Refer to the file widget_system.txt which covers widget flags and the
|
||
|
|
resulting invariants in a detailed way.
|
||
|
|
|
||
|
|
|
||
|
|
GdkWindow pointers may be NULL in GdkEvents
|
||
|
|
-------------------------------------------
|
||
|
|
|
||
|
|
The notification nature of the signal mechanism might cause events to
|
||
|
|
be emitted that have their GdkWindow pointer set to NULL.
|
||
|
|
This is due to the fact that certain events need to be emitted after the
|
||
|
|
real GdkWindow of a widget is not any longer pertinent.
|
||
|
|
It's up to the signal handling function (application) to check for the
|
||
|
|
window field of the event structure to be != NULL, if it is going to
|
||
|
|
perform any operations through Gdk calls on it.
|
||
|
|
Events that a likely to trigger a missing check for the window pointer
|
||
|
|
currently are (and correspond to the trailing signals):
|
||
|
|
|
||
|
|
GDK_SELECTION_CLEAR GtkWidget::selection_clear_event
|
||
|
|
GDK_FOCUS_CHANGE GtkWidget::focus_in_event
|
||
|
|
GtkWidget::focus_out_event
|
||
|
|
|
||
|
|
Events that are asured to have a valid GdkEvent.any.window field are
|
||
|
|
|
||
|
|
GDK_EXPOSE GtkWidget::expose_event
|
||
|
|
|
||
|
|
|
||
|
|
gtk_widget_ref() vs. gtk_object_ref()
|
||
|
|
-------------------------------------
|
||
|
|
|
||
|
|
The widget referencing functions gtk_widget_ref() and gtk_widget_unref()
|
||
|
|
are currently just wrappers about the corresponding referencing functions
|
||
|
|
for objects. Still you should use the widget referencing functions if you
|
||
|
|
are sure the referenced object is of type GTK_WIDGET_TYPE.
|
||
|
|
|
||
|
|
|
||
|
|
Writing Gdk functions
|
||
|
|
---------------------
|
||
|
|
|
||
|
|
When writing Gdk functions that operate on GdkWindow structures in any
|
||
|
|
maeningfull sense, that is casting to a GdkWindowPrivate structure for
|
||
|
|
access to fields other then GdkWindow.user_data, the programmer is
|
||
|
|
recommended to check for the GdkWindowPrivate.destroyed field to be ==
|
||
|
|
FALSE, especially if the GdkWindowPrivate.xwindow field is used.
|
||
|
|
Silent abortion of the Gdk function is the correct behaviour if this
|
||
|
|
condition isn't met.
|