GIFImageDecoder.cpp (not used by Safari, but used by various other WebKit ports) has a bug I introduced several weeks ago which causes it to mis-decode transparent sections of interlaced GIFs, by not overwriting earlier rows' opaque pixels with later rows' transparent ones. It's not too tricky to fix this. Patch coming shortly.
Created attachment 17978 [details] patch v1 Sometimes we need to overwrite our buffer with transparent pixels, and sometimes we need to not do it. This lets the GIFImageReader code tell us which one is the case.
*** Bug 16504 has been marked as a duplicate of this bug. ***
Comment on attachment 17978 [details] patch v1 I did notice this regression. Patch looks sane, but haven't had the opportunity to review it closely yet and it does break the GTK+ build at least: g++ -c -pipe -D_REENTRANT -I/usr/include -Wall -W -Wcast-align -Wchar-subscripts -Wformat-security -Wmissing-format-attribute -Wpointer-arith -Wwrite-strings -Wno-format-y2k -Wno-unused-parameter -Wundef -fno-exceptions -fno-rtti -Wreturn-type -fno-strict-aliasing -O2 -I/usr/include/cairo -I/usr/include/freetype2 -I/usr/include/libpng12 -I/usr/include/cairo -I/usr/include/freetype2 -I/usr/include/libpng12 -I/usr/include/gtk-2.0 -I/usr/lib/gtk-2.0/include -I/usr/include/atk-1.0 -I/usr/include/cairo -I/usr/include/pango-1.0 -I/usr/include/glib-2.0 -I/usr/lib/glib-2.0/include -I/usr/include/freetype2 -I/usr/include/libpng12 -pthread -I/usr/include/glib-2.0 -I/usr/lib/glib-2.0/include -I/usr/include/libxml2 -I/usr/include/libxml2 -fvisibility=hidden -fvisibility-inlines-hidden -fPIC -DQT_SHARED -DBUILDING_CAIRO__=1 -DBUILDING_GTK__=1 -DUSE_SYSTEM_MALLOC -DNDEBUG -DHAVE_STDINT_H -DBUILD_WEBKIT -DENABLE_DATABASE=1 -DENABLE_ICONDATABASE=1 -DENABLE_XPATH=1 -DENABLE_XSLT=1 -DENABLE_SVG=0 -DENABLE_VIDEO=0 -DWTF_CHANGES=1 -DBUILDING_GTK__ -I/usr/share/qt4/mkspecs/linux-g++ -I../../../WebCore -I../../../../WebKit -I../../../WebCore/platform/gtk -I../../../WebCore/platform/network/curl -I../../../WebCore/platform/graphics/cairo -I/home/alp/Projects/webkit/ngit/WebKit/WebCore/loader/gtk -I../../../WebCore/page/gtk -I../../../WebKit/gtk/WebView -I../../../WebKit/gtk/WebCoreSupport -I../../../JavaScriptCore -I../../../JavaScriptCore/kjs -I../../../JavaScriptCore/bindings -I../../../JavaScriptCore/bindings/c -I../../../JavaScriptCore/wtf -I../../../JavaScriptCore/ForwardingHeaders -I../../../WebCore -I../../../WebCore/ForwardingHeaders -I../../../WebCore/platform -I../../../WebCore/platform/network -I../../../WebCore/platform/graphics -I../../../WebCore/loader -I../../../WebCore/page -I../../../WebCore/css -I../../../WebCore/dom -I../../../WebCore/bridge -I../../../WebCore/editing -I../../../WebCore/rendering -I../../../WebCore/history -I../../../WebCore/xml -I../../../WebCore/html -Itmp -Itmp -I../../../JavaScriptCore -I../../../JavaScriptCore/kjs -I../../../JavaScriptCore/bindings -I../../../JavaScriptCore/bindings/c -I../../../JavaScriptCore/wtf -I../../../JavaScriptCore/pcre -I../JavaScriptCore/kjs/tmp -I../../../WebCore/platform/gtk -I../../../WebCore/platform/graphics/gtk -I../../../WebCore/platform/graphics/cairo -I../../../WebCore/svg/graphics/cairo -I../../../WebCore/platform/network/curl -I../../../WebCore/platform/image-decoders -I../../../WebCore/platform/image-decoders/bmp -I../../../WebCore/platform/image-decoders/gif -I../../../WebCore/platform/image-decoders/ico -I../../../WebCore/platform/image-decoders/jpeg -I../../../WebCore/platform/image-decoders/png -I../../../WebCore/platform/image-decoders/xbm -I/home/alp/Projects/webkit/ngit/WebKit/WebCore/loader/gtk -I../../../WebCore/page/gtk -I../../../WebKit/gtk/WebCoreSupport -I../../../WebKit/gtk/WebView -I../../../WebCore -I../../../WebCore/ForwardingHeaders -I../../../../WebKit -I../../../JavaScriptCore/kjs -I../../../JavaScriptCore/bindings -I../../../JavaScriptCore/wtf -I../../../WebCore/platform -I../../../WebCore/platform/network -I../../../WebCore/platform/graphics -I../../../WebCore/svg/graphics -I../../../WebCore/svg/graphics/filters -I../../../WebCore/platform/sql -I../../../WebCore/platform/text -I../../../WebCore/storage -I../../../WebCore/loader -I../../../WebCore/loader/icon -I../../../WebCore/css -I../../../WebCore/dom -I../../../WebCore/page -I../../../WebCore/bridge -I../../../WebCore/editing -I../../../WebCore/rendering -I../../../WebCore/history -I../../../WebCore/xml -I../../../WebCore/html -I../../../WebCore/bindings/js -I../../../WebCore/svg -I../../../WebCore/platform/image-decoders -I/usr/X11R6/include -I../../../WebCore -I. -o tmp/GIFImageDecoder.o ../../../WebCore/platform/image-decoders/gif/GIFImageDecoder.cpp ../../../WebCore/platform/image-decoders/gif/GIFImageDecoder.cpp: In member function ‘virtual WebCore::RGBA32Buffer* WebCore::GIFImageDecoder::frameBufferAtIndex(size_t)’: ../../../WebCore/platform/image-decoders/gif/GIFImageDecoder.cpp:161: warning: comparison between signed and unsigned integer expressions ../../../WebCore/platform/image-decoders/gif/GIFImageDecoder.cpp: In member function ‘void WebCore::GIFImageDecoder::haveDecodedRow(unsigned int, unsigned char*, unsigned char*, unsigned int, unsigned int, bool)’: ../../../WebCore/platform/image-decoders/gif/GIFImageDecoder.cpp:329: error: no matching function for call to ‘WebCore::RGBA32Buffer::setRGBA(unsigned int*&, int, int, int, int)’ ../../../WebCore/platform/image-decoders/ImageDecoder.h:73: note: candidates are: static void WebCore::RGBA32Buffer::setRGBA(unsigned int&, unsigned int, unsigned int, unsigned int, unsigned int) make: *** [tmp/GIFImageDecoder.o] Error 1
*** Bug 16340 has been marked as a duplicate of this bug. ***
Created attachment 18015 [details] patch v2 Fix stupid typo in patch v1. I left off a *.
Comment on attachment 18015 [details] patch v2 r=me Thanks Peter!
Landed in r28925.