589805 - Frequent first-chance exceptions in dwrite code

Status: NEW

(Core :: Graphics, defect)

Description

[Benjamin Smedberg]

Trying to debug bug 586909, I turned on all first-chance exceptions and I'm hitting one within the dwrite code:

 	KernelBase.dll!_RaiseException@16() 	
 	msvcrt.dll!__CxxThrowException@8() 	
 	DWrite.dll!FailAsExceptionPolicy<FileFormatException>::SafeIntOnOverflow() 	
 	DWrite.dll!CheckedPtr<unsigned char const ,FailAsExceptionPolicy<FileFormatException>,unsigned int>::ReadAt<LanguageFeatureList>() 	
 	DWrite.dll!DetermineSimpleGlyphsFromTable() 	
 	DWrite.dll!`anonymous namespace'::ReadGlyphCoverage() 	
 	DWrite.dll!FontFaceRegionBuilder::Impl::WriteRegionInternal() 	
 	DWrite.dll!FontFaceRegionBuilder::Impl::WriteRegion() 	
 	DWrite.dll!FontFaceElement::AddToCacheImpl() 	
 	DWrite.dll!CacheWriter::AddElement() 	
 	DWrite.dll!ClientSideCacheContext::ClientLookup() 	
 	DWrite.dll!ClientSideCacheContext::InitializeElementImpl() 	
 	DWrite.dll!DWriteFontFace::DWriteFontFace() 	
 	DWrite.dll!DWriteFontFace::CreateFromKey() 	
 	DWrite.dll!DWriteFont::CreateFontFace() 	
>	xul.dll!gfxDWriteFontEntry::CreateFontFace(aFontFace=0x00468f18, aSimulations=DWRITE_FONT_SIMULATIONS_NONE)  Line 317	C++
 	xul.dll!gfxDWriteFontEntry::ReadCMAP()  Line 268	C++
 	xul.dll!gfxFontEntry::TestCharacterMap(aCh=0x00002011)  Line 108	C++
 	xul.dll!gfxFontFamily::FindFontForChar(aMatchData=0x04468ff4)  Line 586	C++
 	xul.dll!gfxPlatformFontList::FindFontForCharProc(aKey={...}, aFamilyEntry={...}, userArg=0x00468ff4)  Line 400	C++
 	xul.dll!nsBaseHashtable<nsStringHashKey,nsFrameScriptExecutorJSObjectHolder *,nsFrameScriptExecutorJSObjectHolder *>::s_EnumStub(table=0x00860d30, hdr=0x051507bc, number=0x00000041, arg=0x00468fb0)  Line 364	C++
 	xul.dll!PL_DHashTableEnumerate(table=0x00860d30, etor=0x716aa58a, arg=0x00468fb0)  Line 754	C
 	xul.dll!nsBaseHashtable<nsStringHashKey,nsRefPtr<gfxFontFamily>,gfxFontFamily *>::Enumerate(enumFunc=0x00000000, userArg=0x00468ff4)  Line 239	C++
 	xul.dll!gfxPlatformFontList::FindFontForChar(aCh=0x00002011, aPrevFont=0x14185100)  Line 383	C++
 	xul.dll!gfxFontGroup::WhichSystemFontSupportsChar(aCh=0x00002011)  Line 2555	C++
 	xul.dll!gfxFontGroup::FindFontForChar(aCh=0x00469088, aPrevCh=0x00000000, aNextCh=0x00000003, aPrevMatchedFont=0x00000074) 	C++
 	xul.dll!gfxFontGroup::ComputeRanges(aRanges={...}, aString=0x71639d3e, begin=0x004690d8, end=0x00469372)  Line 2385	C++
 	xul.dll!gfxFont::InitTextRun(aContext=0x00000000, aTextRun=0x14185100, aString=0x004690e0, aRunStart=0x0000000c, aRunLength=0x00000001, aRunScript=0x80000003)  Line 1349	C++
 	xul.dll!gfxFontGroup::InitTextRun(aContext=, aTextRun=, aString=, aTotalLength=, aScriptRunStart=, aScriptRunEnd=, aRunScript=)  Line 2291	C++
 	xul.dll!gfxFontGroup::InitTextRun(aContext=0x13486ae0, aTextRun=0x13685100, aString=0x00469368, aLength=0x0000000d)  Line 2214	C++
 	xul.dll!gfxFontGroup::MakeTextRun(aString=0x00469368, aLength=0x0000000d, aParams=0x00469308, aFlags=0x01100101)  Line 2190	C++
 	xul.dll!TextRunWordCache::MakeTextRun(aText=0x0046ad08, aLength=0x0000000c, aFontGroup=0x141804a0, aParams=0x004699c4, aFlags=0x01100100)  Line 693	C++
 	xul.dll!MakeTextRun(aText=0x0046ad08, aLength=0x0000000c, aFontGroup=0x00000000, aParams=0x004699c4, aFlags=0x01100100)  Line 450	C++
 	xul.dll!BuildTextRunsScanner::BuildTextRunForFrames(aTextBuffer=0x0046ad20)  Line 1812	C++
 	xul.dll!BuildTextRunsScanner::FlushFrames(aFlushLineBreaks=0x00000001, aSuppressTrailingBreak=0x00000000)  Line 1243	C++
 	xul.dll!BuildTextRuns(aContext=, aForFrame=, aLineContainer=0x00000000, aForFrameLine=)  Line 1177	C++

The exception gets caught in DwriteFont::CreateFontFace, which fails correctly, but it seems to me that if we've called it once, we should stop trying.

The font is:
+		nsAString_internal	{mData=0x14248f48 "DejaVu Sans MonoBold" mLength=0x00000014 mFlags=0x00000005 }	nsAString_internal

Comment 1

[Jonathan Kew [:jfkthame]]

(Untested thoughts...)

It looks to me like gfxDWriteFontEntry::ReadCMAP() should be modified so that it always sets the mCmapInitialized flag to PR_TRUE, regardless of success; then gfxFontEntry::TestCharacterMap() won't keep trying to call it.

In this case, the character map will be left empty (and mHasCmapTable remains false), which should mean we won't actually end up using this font.