User Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_10_1) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/41.0.2272.118 Safari/537.36 Steps to reproduce: Open this fiddle with FireFox 37.0.1 on Windows 8.1 (all other platforms I could check did not show the problem): https://jsfiddle.net/aahb1z7L/6/ Actual results: compositing operations seem to be ignored or work only partially when a clipping area has been defined Expected results: compositing operations should work, within the clipping area, as with all other configurations tested.

[Tracking Requested - why for this release]: Regressed since Firefox37 Pushlog: https://hg.mozilla.org/integration/mozilla-inbound/pushloghtml?fromchange=badfce143136&tochange=74852f33ad9c Suspect: Bug 1082827 Set gfx.canvas.azure.backends = direct2d,skia,cairo in preferences helps

Could you attach about:support graphics section for the configuration that fails?

about:support graphics section that problem happens Graphics -------- Adapter Description: AMD Radeon HD 6450 Adapter Drivers: aticfx64 aticfx64 aticfx64 aticfx32 aticfx32 aticfx32 atiumd64 atidxx64 atidxx64 atiumdag atidxx32 atidxx32 atiumdva atiumd6a atitmm64 Adapter RAM: 1024 Asynchronous Pan/Zoom: none ClearType Parameters: Gamma: 2200 Pixel Structure: R ClearType Level: 100 Enhanced Contrast: 200 Device ID: 0x6779 Direct2D Enabled: true DirectWrite Enabled: true (6.2.9200.16571) Driver Date: 11-20-2014 Driver Version: 14.501.1003.0 GPU #2 Active: false GPU Accelerated Windows: 1/1 Direct3D 11 (OMTC) Subsys ID: 23111787 Vendor ID: 0x1002 WebGL Renderer: Google Inc. -- ANGLE (AMD Radeon HD 6450 Direct3D11 vs_5_0 ps_5_0) windowLayerManagerRemote: true AzureCanvasBackend: direct2d 1.1 AzureContentBackend: direct2d 1.1 AzureFallbackCanvasBackend: cairo AzureSkiaAccelerated: 0

Of course, I tested this with newly created profile. https://hg.mozilla.org/mozilla-central/rev/2c9708e6b54d Mozilla/5.0 (Windows NT 6.1; WOW64; rv:40.0) Gecko/20100101 Firefox/40.0 ID:20150413030203

Untracking since bug 1151821 is already tracked.