gre-ilya/fltk
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

Update Fl_Widget_Tracker docs with better example code.

Browse Source 
git-svn-id: file:///fltk/svn/fltk/branches/branch-1.4@12344 ea41ed52-d2ee-0310-a9c1-e6b18d33e121
This commit is contained in:
Albrecht Schlosser 2017-07-20 15:06:11 +00:00
parent 94c9d70f7c
commit db1f29fdb5
1 changed files with 16 additions and 14 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

30
FL/Fl.H
View File

@ -1319,39 +1319,41 @@ public:
This class should be used to control safe widget deletion.
You can use an Fl_Widget_Tracker object to watch another widget, if you
need to know, if this widget has been deleted during a callback.
need to know whether this widget has been deleted during a callback.
This simplifies the use of the "safe widget deletion" methods
Fl::watch_widget_pointer() and Fl::release_widget_pointer() and
makes their use more reliable, because the destructor autmatically
makes their use more reliable, because the destructor automatically
releases the widget pointer from the widget watch list.
It is intended to be used as an automatic (local/stack) variable,
such that the automatic destructor is called when the object's
Fl_Widget_Tracker is intended to be used as an automatic (local/stack)
variable, such that its destructor is called when the object's
scope is left. This ensures that no stale widget pointers are
left in the widget watch list (see example below).
You can also create Fl_Widget_Tracker objects with \c new, but then it
is your responsibility to delete the object (and thus remove the
widget pointer from the watch list) when it is not needed any more.
widget pointer from the watch list) when it is no longer needed.
Example:
\code
int MyClass::handle (int event) {
int MyClass::handle (int event) {
if (...) {
Fl_Widget_Tracker wp(this); // watch myself
do_callback(); // call the callback
if (...) {
Fl_Widget_Tracker wp(this); // watch myself
do_callback(); // call the callback
if (wp.deleted()) return 1; // exit, if deleted
if (wp.deleted()) return 1; // exit, if deleted
// Now we are sure that the widget has not been deleted.
// It is safe to access the widget
// Now we are sure that the widget has not been deleted,
// and it is safe to access the widget:
clear_changed(); // access the widget
}
box(FL_FLAT_BOX);
color(FL_WHITE);
redraw();
}
}
\endcode
*/