The text is not clear or sharp with APZ enabled




3 years ago
2 years ago


(Reporter: over68, Unassigned)



46 Branch
Windows 7

Firefox Tracking Flags

(Not tracked)




3 years ago
Steps to reproduce:

1. Disable hardware acceleration.
2. Restart Firefox.
3. Go to

Actual results:

The text is not clear or sharp with APZ enabled.

Flags: needinfo?(bugmail.mozilla)
This was an intentional choice. We don't support component alpha layers in BasicCompositor, so we had to choose between grayscale text antialiasing + nice APZ scrolling and subpixel text antialiasing + janky main thread scrolling, and we chose the former.

And with hardware acceleration you still get all of the good things.

We've thought about adding component alpha layer support to BasicCompositor, but it would be a bit of work and it's not clear whether it can perform well.
Flags: needinfo?(bugmail.mozilla)
Hi blinky,

I have tested your issue on latest FF release (45.0.2) and latest Nightly build and could not reproduce it. I have disabled HWA and restarted Firefox and there was no difference on how the text is rendered with APZ enabled or disabled.

Is this still reproducible on your end ? If yes, can you please retest this using latest FF release and latest Nightly build ( and report back the results ? When doing this, please use a new clean Firefox profile, maybe even safe mode, to eliminate custom settings as a possible cause (

Flags: needinfo?(over68)

Comment 4

3 years ago
Should disable the protection with the steps in comment 0 to reproduce this bug.

Flags: needinfo?(over68)
User Agent: Mozilla/5.0 (Windows NT 6.1; rv:45.0) Gecko/20100101 Firefox/45.0
Build ID: 20160407164938

I have tested your issue on latest FF release (45.0.2), latest Nightly build (20160417030601) and managed to reproduce it. I have followed the steps from comment 0 and I've disabled the protection on the website in order see any real difference between how the text is rendered. This is more easily noticeable on the latest Nightly(48.0a1) than on the latest release(45.0.2).
Ever confirmed: true

Comment 6

2 years ago
First, does forcing on DirectWrite fix this? Set the gfx.font_rendering.directwrite.force-enabled pref to true. I have found that this often improves text. I am curious if it would here, even on the Basic renderer. 

Second, I often actually intentionally remove RGB antialiasing for image work. I often find that I need to artificially sharpen the text. Is it possible that merely using a sharper greyscale antialiasing would fix the problem without needing component alpha?
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