on-mouse-in

Arguments: dialog-item

Returns the value of the on-mouse-in event handler for the argument control. The value of the on-mouse-in property should be a function object or a function name (a symbol naming a function). This function is called when the mouse cursor is moved into the control's rectangular area. on-mouse-in may be nil if no function need be run.

If an on-mouse-in function is supplied, it should take three arguments, which are (1) the control, (2) the mouse-button-state at the time the mouse moved into the control, and (3) the window that the mouse was most recently in. The return value does not matter.

Many functions take a mouse-button-state argument. This argument is a single integer that tells what combination of mouse buttons and shift keys when the message that is being handled occurred. Each mouse button or shift key is represented by a constant that has a single bit flagged, and so bit tests on the button-state argument can be used to tell whether particular mouse buttons or shift keys were down. The particular constants are left-mouse-button, middle-mouse-button, right-mouse-button, first-x-button (see *ignore-mouse-x-buttons*), second-x-button (see *ignore-mouse-x-buttons*), shift-key, control-key, and alt-key.

See also on-mouse-out.

See cg-events.htm for information about event handling in Common Graphics.

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Created 2019.8.20.