StackOverflow2013

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copied!<p>I discovered that if we observe <code>color</code> keypath of <code>NSColorPanel</code> we get called one extra time on mouse up events. This allows us to ignore action messages from <code>NSColorWell</code> when the left mouse button is down and to get the final color from keypath observer.</p> <p>In this application delegate example code <code>colorChanged:</code> is a <code>NSColorWell</code> action method.</p> <pre><code>void* const ColorPanelColorContext = (void*)1001; @interface AppDelegate() @property (weak) NSColorWell *updatingColorWell; @end @implementation AppDelegate - (void)applicationDidFinishLaunching:(NSNotification *)notification { NSColorPanel *colorPanel = [NSColorPanel sharedColorPanel]; [colorPanel addObserver:self forKeyPath:@"color" options:0 context:ColorPanelColorContext]; } - (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context { if (context == ColorPanelColorContext) { if (![self isLeftMouseButtonDown]) { if (self.updatingColorWell) { NSColorWell *colorWell = self.updatingColorWell; [colorWell sendAction:[colorWell action] to:[colorWell target]]; } self.updatingColorWell = nil; } } } - (IBAction)colorChanged:(id)sender { if ([self isLeftMouseButtonDown]) { self.updatingColorWell = sender; } else { NSColorWell *colorWell = sender; [self updateFinalColor:[colorWell color]]; self.updatingColorWell = nil; } } - (void)updateFinalColor:(NSColor*)color { // Do something with the final color... } - (BOOL)isLeftMouseButtonDown { return ([NSEvent pressedMouseButtons] & 1) == 1; } @end </code></pre>

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