Resending to the list.
On Feb 18, 2013, at 2:50 AM, iain <i...@sleepfive.com> wrote:
>
>
> On Mon, Feb 18, 2013 at 7:17 PM, Kyle Sluder <k...@ksluder.com> wrote:
>> On Sun, Feb 17, 2013, at 11:46 PM, iain wrote:
>> > I'll give this a go, does -setFrameSize just deal with the visible
>> > portion
>> > when inside an NSScrollView/NSClipView? If so, thank you, that's great.
>>
>> No. You're missing my point.
>>
>> You have -viewWillDraw, an override point at which you know your view
>> will draw. You don't need to track your visible rect. You will only be
>> asked to draw rects that intersect with your visible rect[1]. Just query
>> -getRectsBeingDrawn:count: from within -drawRect, and render your
>> waveform for those rects.
>
> Well, that's essentially what I'm doing, by only drawing in the dirtyRect
> (yeah, I know that's just one big union of the results of getRectsBeingDrawn,
> but "essentially").
Right, but you're missing the crucial step of caching this drawing.
I'm obviously not being clear. Here's some pseudocode:
- setFrameSize:(NSSize)size {
[super setFrameSize:size];
[self discardEntireWaveformCache];
}
- setNeedsDisplayInRect:(NSRect)rect {
[super setNeedsDisplayInRect:rect];
[self invalidateWaveformCacheForReft:rect];
}
- viewWillDraw {
if ([self waveformCacheDiscarded]) {
[self allocateWaveformCacheOfSize:self.bounds.size];
}
for (NSRect rect in [self getRectsBeingDrawn]) {
if (!([self waveformCacheIsValidForRect:rect])) {
[self cacheWaveformForRect:rect];
}
}
}
- drawRect:(NSRect)unused {
for (NSRect rect in [self getRectsBeingDrawn]) {
[self drawWaveformCacheForRect:rect];
}
}
Implementation of the waveform cache, as well as more sophisticated techniques
like background rendering the waveform cache are left as exercises to the
reader.
--Kyle Sluder
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