Open Bug 1079716 Opened 8 years ago Updated 2 months ago

Incorrect subpixel font rendering with ClearType


(Core :: Graphics, defect)

32 Branch
Windows 7





(Reporter: mark, Unassigned)



(5 files)

Attached file
User Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:32.0) Gecko/20100101 Firefox/32.0
Build ID: 20140923175406

Steps to reproduce:

I created an HTML pull-down menu using LIs. See reduced testcase attached to this bug. STR are on Windows 7, Firefox-release, AMD video hardware, Platform update installed (DirectWrite 6.2.9200.16492).

1. Make sure HWA is on and you're using ClearType
2. Move the mouse over the different items in the menu to open items and sub-menus

Actual results:

Subpixel font rendering is often bolder/blurry greyscale (should not be used) and flips between ClearType and Greyscale randomly as different items are hovered over.

The effect is clearest with light text on dark backgrounds.

Expected results:

Font rendering should always be ClearType
I verified with HWA off in Windows XP in a VM (blocked graphics adapter) with just cleartype enabled, and the same thing happens there, so it's not HWA related.

That's on the cairo back-end without hardware accelerated windows.

Adapter Description	VMware SVGA II
Adapter Drivers	vmx_fb
Adapter RAM	Unknown
Device ID	0x0405
Direct2D Enabled	Blocked for your graphics card because of unresolved driver issues.
DirectWrite Enabled	false (
Driver Date	7-1-2011
Driver Version
GPU #2 Active	false
GPU Accelerated Windows	0/1 Basic Blocked for your graphics card because of unresolved driver issues.
Vendor ID	0x15ad
WebGL Renderer	Blocked for your graphics card because of unresolved driver issues.
windowLayerManagerRemote	false
AzureCanvasBackend	skia
AzureContentBackend	cairo
AzureFallbackCanvasBackend	cairo
Summary: Incorrect subpixel font rendering with HWA+ClearType → Incorrect subpixel font rendering with ClearType
Attached file menustyle.css
Attached file menu.html
Could you attach a screenshot of the rendering on your machine, please. (at the highest zoom if possible)
Flags: needinfo?(mark)
This screenshot (400%) is taken on Windows 7 with cleartype and direct2d enabled. it shows cleartype and greyscale mixed. Moving the mouse over other selections will kind of randomly switch the rendering between the two.
Same menu on Windows XP, hardware acceleration disabled (blocked driver), cairo back-end.

Looking at it close up, I noticed that what is pure grey on direct2d, seems to be a mix of cleartype and grey here. The cleartype settings on this setup are not really tuned so looks a little funky.

The mix is odd...  is the subpixel rendering applied twice on the same glyphs?
Flags: needinfo?(mark)
Severity: normal → S3
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