Enhance documentation of event processing
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@ -259,6 +259,19 @@ public:
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your overridden method so that you don't short-circuit events that you
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your overridden method so that you don't short-circuit events that you
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don't handle. In this last case you should return the callee retval.
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don't handle. In this last case you should return the callee retval.
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One exception to the rule in the previous paragraph is if you really
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want to \e override the behavior of the base class. This requires
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knowledge of the details of the inherited class.
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In rare cases you may want to return 1 from your handle() method
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although you don't really handle the event. The effect would be to
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\e filter event processing, for instance if you want to dismiss
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non-numeric characters (keypresses) in a numeric input widget. You
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may "ring the bell" or show another visual indication or drop the
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event silently. In such a case you must not call the handle() method
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of the base class and tell FLTK that you \e consumed the event by
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returning 1 even if you didn't \e do anything with it.
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\param[in] event the kind of event received
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\param[in] event the kind of event received
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\retval 0 if the event was not used or understood
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\retval 0 if the event was not used or understood
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\retval 1 if the event was used and can be deleted
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\retval 1 if the event was used and can be deleted
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@ -17,7 +17,8 @@ display a value of some sort.
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A composite widget holds a list of child widgets and handles moving,
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A composite widget holds a list of child widgets and handles moving,
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sizing, showing, or hiding them as needed. Fl_Group is the main
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sizing, showing, or hiding them as needed. Fl_Group is the main
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composite widget class in FLTK, and all of the other composite widgets
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composite widget class in FLTK, and all of the other composite widgets
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(Fl_Pack, Fl_Scroll, Fl_Tabs, Fl_Tile, and Fl_Window) are subclasses of it.
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(Fl_Pack, Fl_Scroll, Fl_Tabs, Fl_Tile, Fl_Window, Fl_Flex, Fl_Grid, etc.)
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are subclasses of it.
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You can also subclass other existing widgets to provide a different
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You can also subclass other existing widgets to provide a different
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look or user-interface. For example, the button widgets are all
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look or user-interface. For example, the button widgets are all
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