The change to GetAfterFrameForContent prevents the reframe that is part
of the chain of events leading to this bug, and thus fixes the bug on
its own. The change to GetBeforeFrameForContent seems desirable for
symmetry.
Note that patch 6 also independently fixes the reported bug.
This probably needs somewhat careful review. We should examine:
(1) what the rules for calling nsLayoutUtils::GetBeforeFrame and
nsLayoutUtils::GetAfterFrame are, and whether both (or neither)
need to be patched.
(2) What the rules are for which frame the GenConProperty() lives on,
and whether we should adjust nsIFrame::GetGenConPseudos() to either
do something more intelligent, or assert about callers.
(We should probably clean up some of these things in a followup bug.)
Since the symptom of this bug is (once patch 4 is in the tree) only
causing extra reframes, it can only be tested using the new API (from
bug 1115691) for observing reframes. I confirmed that the test for this
bug fails without the patch and passes with the patch (as noted by the
removal of its todo annotation).
This patch fixes the assertion on layout/generic/crashtests/600100.xhtml,
though I haven't investigated why.
This makes APZ behave nicely with most uses of a css transform:scale.
Summary of changes:
- FrameMetrics::mCumulativeResolution now includes the css-driven resolution
in addition to the pres-shell resolution.
- Displayports are now stored in Screen pixels rather than Layer pixels.
This is what we want anyways (as we'd like the displayport size to remain
constant as a fraction of the screen size), but it was necessary to make
this change as part of this patch because continuing to store them in
Layer pixels in the presence of a css-driven resolution would have
required a bunch of infrastructure to implement correctly.
Remaining work:
- Layout painting a scrollable layer at a resolution different from the
scale induced by the css transform causes problems. These will go away
with bug 1076192.
- Different resolutions on the x and y axes are not supported. This is
tracked by bug 1039967.
This makes APZ behave nicely with most uses of a css transform:scale.
Summary of changes:
- FrameMetrics::mCumulativeResolution now includes the css-driven resolution
in addition to the pres-shell resolution.
- Displayports are now stored in Screen pixels rather than Layer pixels.
This is what we want anyways (as we'd like the displayport size to remain
constant as a fraction of the screen size), but it was necessary to make
this change as part of this patch because continuing to store them in
Layer pixels in the presence of a css-driven resolution would have
required a bunch of infrastructure to implement correctly.
Remaining work:
- Layout painting a scrollable layer at a resolution different from the
scale induced by the css transform causes problems. These will go away
with bug 1076192.
- Different resolutions on the x and y axes are not supported. This is
tracked by bug 1039967.
