622838 - Scaling retained layers when we don't want to be

Status: RESOLVED FIXED

(Core :: Graphics, defect)

Description

[Stuart Parmenter]

Take 2 phones side by side, one with GL enabled and one without.
In portrait mode, load http://news.google.com (the full version, not the mobile one), and make sure it is zoomed all the way out.

The text on the GL phone will be much more blurred, making it look like we are scaling the layer with bilinear filtering.  We shouldn't be actually scaling the retained buffer at all however.  We want to have as-crisp-as-possible text rendered at the right size, not scaled.

I'm assuming this is some kind of rounding bug, but is pretty important to fix for text readability.

Comment 1

[Chris Jones [:cjones] inactive; ni?/f?/r? if you need me]

Text is also obviously blurry with fennec-desktop+GL on http://timecube.com/, portrait or landscape.

Comment 2

[Chris Jones [:cjones] inactive; ni?/f?/r? if you need me]

Attachment: Use the right rect-rounding mode to avoid accidentally resampling resolution-scaled ThebesLayer textures

The problem here is that with certain resolution values, multiplying a rect by the resolution will give us very small rounding errors, like say 0.0001.  If the rounding error is to the low side, RoundOut() gives the correct result.  However, if the rounding error is on the high side, we get 1 more pixel than intended, and this causes unintended texture resampling.  Round() is what we want since these rects are all (supposed to be) pixel aligned.  My fault!

Comment 3

[Chris Jones [:cjones] inactive; ni?/f?/r? if you need me]

Attachment: Before

Comment 4

[Chris Jones [:cjones] inactive; ni?/f?/r? if you need me]

Attachment: After

Comment 5

[Jeff Muizelaar [:jrmuizel]]

http://hg.mozilla.org/mozilla-central/rev/aacbdfc1029e