Force instant re-display after scrollRectToVisible
Force instant re-display after scrollRectToVisible
- Subject: Force instant re-display after scrollRectToVisible
- From: Allan Odgaard <email@hidden>
- Date: Thu, 11 Mar 2004 06:22:55 +0100
I am drawing onto an NSView by first using cacheImageInRect: (to make a
backup of the the region I will draw on top), and then lockFocus, draw,
unlockFocus and flushWindow.
The view is embedded in a scroll view, and at times I need to scroll
before drawing, so what I wanted to do was something like this:
[win restoreCachedImage]; // remove old drawing
[view scrollRectToVisible:aRect]; // scroll view
[win disableFlushWindow]; // disable flushing
[view displayIfNeeded]; // redraw newly exposed regions
caused by scroll
[win enableFlushWindow]; // re-enaable flushing
[win cacheImageInRect:otherRect]; // backup the region we'll draw
onto
[view lockFocus];
...
[view unlockFocus];
[win flushWindow]; // flush window
Unfortunately it does not work as expected -- the problem is that after
scrollRectToVisible: there is no dirty region to redraw, since
scrolling has not taken place yet. So I end up drawing the new stuff in
the view before it scrolls, and then it will scroll afterwards.
Is there anyway to make the clipview/scrollview scroll instantly?
As a workaround I implemented my own scrollRectToVisible: by using
NSCopyBits(), translateOriginToPoint: and setNeedsDisplayInRect:. This
made the above work, but a new problem arose, namely that the
clipview/scrollview do not observe the changes made to my views bounds,
when using translateOriginToPoint:, so the scrollers do not update.
I have enabled that the view should post bounds-changed notifications
when using translateOriginToPoint: and I have also tried to send
reflectScrolledClipView: to the enclosing scroll view (after
translating the origin), but w/o luck.
I do not see any methods in NSClipView to inform it that I have
translated the origin of my view, is it at all possible to use this
method when under the control of a clipview/scrollview?
I guess my next workaround could be to replace the clipview used by the
scrollview (to make it react on the change in bounds, resulting from
the translating), but I wonder if I am not going down the wrong road
here? since it doesn't look trivial to make an IB created scrollview
use a different clipview, also, the documentation for some methods of
the scrollview class imply that the scrollview will check if it is
actually working with a real clipview, so it would seem that conforming
to the interface of a clipview is not enough, I would probably need to
subclass NSClipView (which I would like to avoid, so that the
superclass doesn't e.g. do work when receiving bound and/or frame
change notification (although I *might* be able to overwrite all
methods to avoid such things).
For the records, I am aware of the possibility to modify the view's
drawRect: implementation. Unfortunately this is not an option.
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