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Bug 598482 part 21 - Update the invalidation setup comment. r=roc

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This commit is contained in:
Markus Stange 2011-12-23 22:52:25 -05:00
parent 2d49769823
commit 0438c4de66
1 changed files with 7 additions and 14 deletions
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21
view/src/nsViewManager.h
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@ -53,32 +53,25 @@
/**
Invalidation model:
1) Callers call into the view manager and ask it to update a view.
1) Callers call into the view manager and ask it to invalidate a view.
2) The view manager finds the "right" widget for the view, henceforth called
the root widget.
3) The view manager traverses descendants of the root widget and for each
one that needs invalidation either
one that needs invalidation stores the rect to invalidate on the widget's
view (batching).
a) Calls Invalidate() on the widget (no batching)
or
b) Stores the rect to invalidate on the widget's view (batching)
// XXXbz we want to change this a bit. See bug 243726
4) When batching, the call to end the batch either processes the pending
Invalidate() calls on the widgets or posts an event to do so.
4) The dirty region is flushed to the right widget when
ProcessPendingUpdates is called from the RefreshDriver.
It's important to note that widgets associated to views outside this view
manager can end up being invalidated during step 3. Therefore, the end of a
view update batch really needs to traverse the entire view tree, to ensure
that those invalidates happen.
To cope with this, invalidate event processing and view update batch
handling should only happen on the root viewmanager. This means the root
view manager is the only thing keeping track of mUpdateCnt. As a result,
Composite() calls should also be forwarded to the root view manager.
To cope with this, invalidation processing and should only happen on the
root viewmanager.
*/
class nsViewManager : public nsIViewManager {