519108 - layout.css.dpi=0 no longer uses system DPI value if system DPI < 96

Status: VERIFIED FIXED

(Core :: Graphics, defect)

Description

[Elmar Ludwig]

Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.9.3a1pre) Gecko/20090927 Minefield/3.7a1pre ID:20090927032050

The platform patch for bug 449283 removed the special handling for layout.css.dpi=0 and made it equivalent to layout.css.dpi=-1, which forces the system DPI to be at least 96. This causes a regression in font sizes for me.

I have set layout.css.dpi=0 in about:config to use the X server's native DPI setting (85x86 dots per inch on my display). On a current trunk build, text with a CSS font-size of 10pt is rendered at a size of 13.33px (this can be verified using the "Computed Style" in the DOM inspector panel), which is equivalent to 10pt at 96 dpi or 11.3pt at 85 dpi. Thus, all fonts using pt sizing appear ~13% too big.

Setting layout.css.dpi to 85 still renders fonts at the correct size (for my display). I can attach a testcase and/or screenshots if needed.

Comment 1

[Mark Finkle (:mfinkle) (use needinfo?)]

Testcases and a screenshot would be great

Comment 2

[Elmar Ludwig]

Attachment: testcase using different font sizes

Comment 3

[Elmar Ludwig]

Attachment: rendering on 2009-09-22-03 trunk build

testcase rendering at 85 DPI (system setting), 2009-09-22-03 trunk build

10.0pt should be same size as 11.8px  (ok)
11.2pt should be same size as 13.33px (ok)

Comment 4

[Elmar Ludwig]

Attachment: rendering on 2009-09-23-03 trunk build

testcase rendering at 85 DPI (system setting), 2009-09-23-03 trunk build

10.0pt should be same size as 11.8px  (not ok)
11.2pt should be same size as 13.33px (not ok)

Note that all fonts sized in "pt" as well as the UI fonts (menu and toolbar) are rendered larger than in the 2009-09-22-03 build.

Comment 5

[Mark Finkle (:mfinkle) (use needinfo?)]

should be fixed by bug 531289 on mozilla-192 and trunk