Layout of CSS transformed text may be broken when zoom in

NEW
Unassigned

Status

()

4 years ago
4 years ago

People

(Reporter: duanyao.ustc, Unassigned)

Tracking

33 Branch
x86_64
Linux
Points:
---

Firefox Tracking Flags

(Not tracked)

Details

Attachments

(1 attachment)

(Reporter)

Description

4 years ago
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.
(Reporter)

Comment 1

4 years ago
Created attachment 8442747 [details]
transformed text zoom in example
(Reporter)

Updated

4 years ago
Component: Untriaged → Layout: Text
Product: Firefox → Core
(Reporter)

Comment 2

4 years ago
> 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.
(Reporter)

Comment 3

4 years ago
firefox 30-33 all have this problem.
Version: 32 Branch → 33 Branch
(Reporter)

Comment 4

4 years ago
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
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