MouseEnter Control
-
I'm building a custom control and I want it to change borders when a MouseEnter events happens. a) Can I simply paint the border in the MouseEvent method? OR b) Must I set a flag and call Invalidate(), and wire OnPaint to draw the new/old border appropriately? If a) is ok, then how do I get a graphics instance in the MouseEnter event. Or, is b) the preferred method to do this? Thanks, -Luther
-
I'm building a custom control and I want it to change borders when a MouseEnter events happens. a) Can I simply paint the border in the MouseEvent method? OR b) Must I set a flag and call Invalidate(), and wire OnPaint to draw the new/old border appropriately? If a) is ok, then how do I get a graphics instance in the MouseEnter event. Or, is b) the preferred method to do this? Thanks, -Luther
Because there are several things that can happen while your mouse is moving or resting comfortably in the bounds of your control, it'd probably be best to set a flag (ex: set to
true) and callInvalidate()in the handler forMouseEnterevent, and to clear the flag (ex: set tofalse) in the handler for theMouseLeaveevent. Of course, your override forOnPaint(note, this is an override, not an event handler, which are typically wired for other controls - use overrides when possible to override functionality from the base class) should draw the border appropriately depending on the flag. The first method is possible (seeControl.CreateGraphics) but is too problematic sinceMouseEnteronly fires once. Your border would get painted, sure, but then any successive painting required won't repaint the border.-----BEGIN GEEK CODE BLOCK----- Version: 3.21 GCS/G/MU d- s: a- C++++ UL@ P++(+++) L+(--) E--- W+++ N++ o+ K? w++++ O- M(+) V? PS-- PE Y++ PGP++ t++@ 5 X+++ R+@ tv+ b(-)>b++ DI++++ D+ G e++>+++ h---* r+++ y+++ -----END GEEK CODE BLOCK-----
-
Because there are several things that can happen while your mouse is moving or resting comfortably in the bounds of your control, it'd probably be best to set a flag (ex: set to
true) and callInvalidate()in the handler forMouseEnterevent, and to clear the flag (ex: set tofalse) in the handler for theMouseLeaveevent. Of course, your override forOnPaint(note, this is an override, not an event handler, which are typically wired for other controls - use overrides when possible to override functionality from the base class) should draw the border appropriately depending on the flag. The first method is possible (seeControl.CreateGraphics) but is too problematic sinceMouseEnteronly fires once. Your border would get painted, sure, but then any successive painting required won't repaint the border.-----BEGIN GEEK CODE BLOCK----- Version: 3.21 GCS/G/MU d- s: a- C++++ UL@ P++(+++) L+(--) E--- W+++ N++ o+ K? w++++ O- M(+) V? PS-- PE Y++ PGP++ t++@ 5 X+++ R+@ tv+ b(-)>b++ DI++++ D+ G e++>+++ h---* r+++ y+++ -----END GEEK CODE BLOCK-----
The flag method works cleanly - I typically try to avoid saving and polling state like that ... but practically speaking, I assume it makes sense in this stateful, event driven world. I also appreciate your comment regarding overrides vs handlers. It wasn't concretely clear to me when to use which. I see that for every child control I add to a parent, I could add a handler. Self-documenting and a bit easier to organize. Whereas, the control's own painting naturally belongs in the override. Thanks! -Luther