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Enhance documentation of event processing

This commit is contained in:
Albrecht Schlosser 2023-11-17 15:25:21 +01:00
parent c5ef206c57
commit 6f7e1f4fb7
2 changed files with 15 additions and 1 deletions
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13
FL/Fl_Widget.H
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@ -259,6 +259,19 @@ public:
your overridden method so that you don't short-circuit events that you your overridden method so that you don't short-circuit events that you
don't handle. In this last case you should return the callee retval. don't handle. In this last case you should return the callee retval.
One exception to the rule in the previous paragraph is if you really
want to \e override the behavior of the base class. This requires
knowledge of the details of the inherited class.
In rare cases you may want to return 1 from your handle() method
although you don't really handle the event. The effect would be to
\e filter event processing, for instance if you want to dismiss
non-numeric characters (keypresses) in a numeric input widget. You
may "ring the bell" or show another visual indication or drop the
event silently. In such a case you must not call the handle() method
of the base class and tell FLTK that you \e consumed the event by
returning 1 even if you didn't \e do anything with it.
\param[in] event the kind of event received \param[in] event the kind of event received
\retval 0 if the event was not used or understood \retval 0 if the event was not used or understood
\retval 1 if the event was used and can be deleted \retval 1 if the event was used and can be deleted

3
documentation/src/subclassing.dox
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@ -17,7 +17,8 @@ display a value of some sort.
A composite widget holds a list of child widgets and handles moving, A composite widget holds a list of child widgets and handles moving,
sizing, showing, or hiding them as needed. Fl_Group is the main sizing, showing, or hiding them as needed. Fl_Group is the main
composite widget class in FLTK, and all of the other composite widgets composite widget class in FLTK, and all of the other composite widgets
(Fl_Pack, Fl_Scroll, Fl_Tabs, Fl_Tile, and Fl_Window) are subclasses of it. (Fl_Pack, Fl_Scroll, Fl_Tabs, Fl_Tile, Fl_Window, Fl_Flex, Fl_Grid, etc.)
are subclasses of it.
You can also subclass other existing widgets to provide a different You can also subclass other existing widgets to provide a different
look or user-interface. For example, the button widgets are all look or user-interface. For example, the button widgets are all