StackOverflow2013

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PORedrawing NSCollectionView on Scroll Causes Breakup of Graphics
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copied!<p>I have a minor irritant in an <code>NSCollectionView</code> in which the <code>NSCollectionViewItem</code>'s break up visually when I scroll the window.</p> <p>The rate of breakup depends upon the rate of scrolling. For example, if I scroll slowly the breakup occurs more often. Fast scrolling less so. It appears that the problem is when the custom NSView of the <code>NSCollectionViewItem</code> I am using crosses the boundary of the viewable frame.</p> <p>My NSView (custom view of the <code>NSCollectionViewItem</code>) has a very simple drawing algorithm - nothing too complex.</p> <p>Essentially I create a frame within the dirtyRect of the drawRect method and create a few frames inside that:</p> <pre><code>-(void)drawRect:(NSRect)dirtyRect { NSRect mOuterFrame = NSMakeRect(dirtyRect.origin.x, dirtyRect.origin.y, 104, 94); NSRect mSelectedFrame = NSInsetRect(mOuterFrame, 2, 2); NSRect mRedFrame = NSInsetRect(mSelectedFrame, 2, 2); NSRect mInnerFrame = NSInsetRect(mRedFrame, 2, 2); NSBezierPath * mOuterFramePath = [NSBezierPath bezierPathWithRect:mOuterFrame]; NSBezierPath * mSelectedFramePath = [NSBezierPath bezierPathWithRect:mSelectedFrame]; NSBezierPath * mRedFramePath = [NSBezierPath bezierPathWithRect:mRedFrame]; NSBezierPath * mInnerFramePath = [NSBezierPath bezierPathWithRect:mInnerFrame]; [mainBackgroundColor set]; [mOuterFramePath fill]; if (selected) [[NSColor yellowColor] set]; else [mainBackgroundColor set]; [mSelectedFramePath fill]; if (isRedBorder) [[NSColor redColor] set]; else [mainBackgroundColor set]; [mRedFramePath fill]; [[NSColor blackColor] set]; [mInnerFramePath fill]; } </code></pre> <p>I have tried locking the focus and releasing before and after the code as well as setting the graphics context and restoring it - none of which seem to solve the problem.</p> <p>I am using Snow Leopard - not that I think that makes a difference.</p> <p><strong>Solution Update</strong></p> <p>For anyone interested here is the solution to the problem as recommended by NSResponder. I was creating the initial <code>mOuterFrame</code> based upon the <code>drawRect:</code> methods <code>dirtyRect</code> which, as pointed out, was the incorrect thing to do. A quick change from:</p> <pre><code>NSRect mOuterFrame = NSMakeRect(dirtyRect.origin.x, dirtyRect.origin.y, 104, 94); </code></pre> <p>To a 0 based origination point:</p> <pre><code>NSRect mOuterFrame = NSMakeRect(0, 0, 104, 94); </code></pre> <p>I also tweaked the efficiency of the code, being as I am using only rectangles, as suggested although the code change above was enough to resolve the problem in itself. I had to add a change to get a two pixel line. New method:</p> <pre><code>-(void)drawRect:(NSRect)dirtyRect { NSRect mOuterFrame = NSMakeRect(0, 0, 104, 94); NSRect mSelectedFrame = NSInsetRect(mOuterFrame, 2, 2); NSRect mRedFrame = NSInsetRect(mSelectedFrame, 2, 2); NSRect mInnerFrame = NSInsetRect(mRedFrame, 2, 2); [NSBezierPath setDefaultLineWidth:2.0]; [mainBackgroundColor set]; [NSBezierPath strokeRect:mOuterFrame]; if (selected) [[NSColor yellowColor] set]; else [mainBackgroundColor set]; [NSBezierPath strokeRect:mSelectedFrame]; if (isRedBorder) [[NSColor redColor] set]; else [mainBackgroundColor set]; [NSBezierPath strokeRect:mRedFrame]; [[NSColor blackColor] set]; [NSBezierPath strokeRect:mInnerFrame]; } </code></pre>

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