Cocoa Internals/Input

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Revision as of 04:32, 18 July 2018 by Skalogryz (talk | contribs) (initial mouse event handling description)
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Mouse

The biggest difference between Apple and LCL ideology is the way of handling MouseMove events.

According to Apple - mouse events are easily to flood the event queue and thus are disabled by default, unless a use presses and hold the button.

Apple provides a special NSWindow mode to allow MouseMove events to come through even with buttons unreleased. However, such MouseMove events would be reported to the focused controls (aka FirstResponder), rather than the control immediately under the cursor.

(MouseDown, MouseUp events are reported directly to the control under the cursor, similar to LCL).

Because of that, Widgetset mouse event processing routine first checks, if cursor is actually above the focused control, and if it's not, it would let Cocoa propagate the mouse event, down (from child to parent) the controls hierarchy.

Such propagation happens, when NSView inherited mouseMove event is called.

If the actual control is found, the propagation of the event is stopped.