Layout has been using imgIContainer::IsOpaque to determine if the image will draw opaquely to all pixels it covers, and doing culling based on this.
However imgIContainer::IsOpaque doesn't guarantee anything. It only describes if the image, when in a decoded state, has all opaque pixels. So if the image doesn't have fully decoded frames around (because they got discarded) it may not draw opaquely to all of its pixels.
So we create a new function that first checks if there is a fully decoded frame.
Previously we weren't sending scroll position updates with origin nsGkAtoms::restore
over to the APZ at all, on the assumption that they should never clobber an APZ
scroll offset. However, there are scenarios where that is not true.
In particular, during a frame reconstruction, a layers update may be sent to the
compositor between the time a scrollframe has RestoreState() called on it, and
the time the scrollframe has ScrollToRestoredPosition() called on it. The layers
update that happens during this interval (correctly) sends a scroll position of
(0,0), and forces the APZ to scroll to that position. This is necessary to
prevent APZ from remaining at an invalid scroll offset while the frame is still
being rebuilt.
However, once ScrollToRestoredPosition() is called and the old scroll offset is
restored, that restored scroll position needs to get sent to the APZ in order to
have it properly restore to the original scroll position. In order to do this,
the main thread must flag the metrics with a scroll offset update. Since the user
may have scrolled concurrently in the compositor from the (0,0) position, we also
need to check for that case in the APZ code and avoid restoring the scroll
position. This is equivalent to the corresponding main-thread code in
ScrollToRestoredPosition().
MozReview-Commit-ID: LxRapVSrsJ3
The patch is generated from following command:
rgrep -l unused.h|xargs sed -i -e s,mozilla/unused.h,mozilla/Unused.h,
MozReview-Commit-ID: AtLcWApZfES
--HG--
rename : mfbt/unused.h => mfbt/Unused.h
Layout has been using imgIContainer::IsOpaque to determine if the image will draw opaquely to all pixels it covers, and doing culling based on this.
However imgIContainer::IsOpaque doesn't guarantee anything. It only describes if the image, when in a decoded state, has all opaque pixels. So if the image doesn't have fully decoded frames around (because they got discarded) it may not draw opaquely to all of its pixels.
So we create a new function that first checks if there is a fully decoded frame.
I'm not convinced that we can actually get regular content
<_moz_generated_content_before> elements in here, since it's only if
CompareTreePosition returned 0 that we look at the element name,
but might be best to make this test stronger in any case.
MozReview-Commit-ID: 8CgxcU9AbDA
--HG--
extra : rebase_source : 4a47ed62895d83f720ec7ccfde253e2c1945b34f
This patch makes GetBounds(), GetScreenBounds() and GetClientBounds() more
obviously infallible, like existing functions such as GetNaturalBounds() and
GetClientSize(). This results in clearer behaviour in nsCocoaWindow.mm if
Objective C exceptions occur. Along the way, the patch removes some useless
failure checks for these functions.
The patch also removes the NS_IMETHOD from GetRestoredBounds and makes that
function MOZ_MUST_USE.
Structs in our style system use an arena-style allocation system,
managed by the presshell to which they belong. All of the relevant
overloads that forward allocation requests to the presshell declare
themselves as CPP_THROW_NEW, which indicates that they do not throw
exceptions. The C++ specification states that operator new overloads
that declare themselves to not throw exceptions require a null check on
their return value. However, the relevant presshell allocation method,
AllocateByObjectID, is infallible and will never return a null pointer.
The callers of all of these methods are therefore doing useless
(compiler-generated) null checks. Let's get rid of those useless checks
by removing the CPP_THROW_NEW annotations. This change declares these
methods will return non-null pointers and throw exceptions in case of
errors--but as we don't use exceptions, and AllocateByObjectID will
abort on OOM, everything works out OK.
