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Bug 1201401 - Work around a crash in CVCGDisplayLink::getDisplayTimes. r=spohl

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Differential Revision: https://phabricator.services.mozilla.com/D45426

--HG--
extra : moz-landing-system : lando
This commit is contained in:
Steven Michaud 2019-09-11 16:49:45 +00:00
parent 84b7cdad58
commit a57ff23303
1 changed files with 17 additions and 29 deletions
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46
gfx/thebes/gfxPlatformMac.cpp
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@ -387,40 +387,28 @@ class OSXVsyncSource final : public VsyncSource {
return;
}
// Workaround for bug 1201401: CGDisplayIDToOpenGLDisplayMask() is a
// documented method with undocumented behavior -- it returns '0' as an
// error condition. Through at least macOS Catalina, Apple relies on
// this behavior in the CoreVideo framework to indicate that a given
// display is (temporarily) invalid (kCVReturnInvalidDisplay). But a
// method called (indirectly) from CVDisplayLinkCreateWithCGDisplays()
// ignores this error return (again indirectly), eventually leading to
// crashes in CVCGDisplayLink::getDisplayTimes(). The workaround is to
// call CGDisplayIDToOpenGLDisplayMask() ourselves, and do an early
// return if it returns '0' (that is, if a succeeding call to
// CVDisplayLinkCreateWithCGDisplays() would trigger Apple's bug and
// lead to a crash). It also makes sense to return early if
// CGGetActiveDisplayList() fails or there are no active displays.
const UInt32 kMaxDisplays = 256;
uint32_t displayCount;
CGDirectDisplayID displays[kMaxDisplays];
if ((CGGetActiveDisplayList(kMaxDisplays, displays, &displayCount) !=
kCGErrorSuccess) ||
(displayCount == 0)) {
return;
}
for (uint32_t i = 0; i < displayCount; ++i) {
if (CGDisplayIDToOpenGLDisplayMask(displays[i]) == 0) {
return;
}
}
// Create a display link capable of being used with all active displays
// TODO: See if we need to create an active DisplayLink for each monitor
// in multi-monitor situations. According to the docs, it is compatible
// with all displays running on the computer But if we have different
// monitors at different display rates, we may hit issues.
if (CVDisplayLinkCreateWithCGDisplays(
displays, displayCount, &mDisplayLink) != kCVReturnSuccess) {
CVReturn retval = CVDisplayLinkCreateWithActiveCGDisplays(&mDisplayLink);
// Workaround for bug 1201401: CVDisplayLinkCreateWithCGDisplays()
// (called by CVDisplayLinkCreateWithActiveCGDisplays()) sometimes
// creates a CVDisplayLinkRef with an uninitialized (nulled) internal
// pointer. If we continue to use this CVDisplayLinkRef, we will
// eventually crash in CVCGDisplayLink::getDisplayTimes(), where the
// internal pointer is dereferenced. Fortunately, when this happens
// another internal variable is also left uninitialized (zeroed),
// which is accessible via CVDisplayLinkGetCurrentCGDisplay(). In
// normal conditions the current display is never zero.
if ((retval == kCVReturnSuccess) &&
(CVDisplayLinkGetCurrentCGDisplay(mDisplayLink) == 0)) {
retval = kCVReturnInvalidDisplay;
}
if (retval != kCVReturnSuccess) {
NS_WARNING(
"Could not create a display link with all active displays. "
"Retrying");