Open Bug 1027580 Opened 10 years ago Updated 2 years ago

Layout of CSS transformed text may be broken when zoom in

Categories

(Core :: Layout: Text and Fonts, defect)

33 Branch
x86_64
Linux
defect

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()

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(Reporter: duanyao.ustc, Unassigned)

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(1 file)

User Agent: Mozilla/5.0 (X11; Linux x86_64; rv:32.0) Gecko/20100101 Firefox/32.0 (Beta/Release) Build ID: 20140608030203 Steps to reproduce: Open the attached htm file with firefox, zoom in to maximum ratio by ctr++. The text lines in this file are specified with large font-size, e.g. 896px (64*14px); and transformed back to normal size, e.g. transform:matrix(0.03125,0,0,0.03125,0,0) (1/64 = 0.03125). So, these lines should look exactly same as those with font-size:14px. Actual results: All the text lines should be rendered properly. Expected results: Characters in "[64x]ABCDEFGHIJK" and "[32x]ABCDEFGHIJK" lines are overlapping, and their border box's heights are smaller. While "[16x]ABCDEFGHIJK" and below are normal.
Component: Untriaged → Layout: Text
Product: Firefox → Core
> Actual results: > > All the text lines should be rendered properly. > > > Expected results: > > Characters in "[64x]ABCDEFGHIJK" and "[32x]ABCDEFGHIJK" lines are > overlapping, and their border box's heights are smaller. While > "[16x]ABCDEFGHIJK" and below are normal. Well, it should be: Actual results: Characters in "[64x]ABCDEFGHIJK" and "[32x]ABCDEFGHIJK" lines are overlapping, and their border box's heights are smaller. While "[16x]ABCDEFGHIJK" and below are normal. Expected results: All the text lines should be rendered properly.
firefox 30-33 all have this problem.
Version: 32 Branch → 33 Branch
Additional experiment shows that: 1. Non-identity CSS transform is required to trigger this bug. A matrix(0.9,0,0,0.9,0,0) is enough. Only a large font-size can't trigger this bug. 2. The font-size value matters, while scaling factor of transform doesn't. The threshold font-size to trigger this bug seems between 336~392px. The bigger the font-size is, the more the characters overlapping.
Confirmed in 33.0a1 (2014-07-14), Ubuntu 14.04
Status: UNCONFIRMED → NEW
Ever confirmed: true
Severity: normal → S3
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