1831298 - Incorrect spacing of transformed synthetic-bold glyphs in print/pdf output

Status: RESOLVED FIXED

(Core :: Printing: Output, defect)

Description

[Jonathan Kew [:jfkthame]]

Attachment: testcase - compare screen rendering with pdf output

In the course of investigating bug 1823888, I looked at the use of CalcXScale to adjust the synthetic-bold offset in gfxFont::PostShapingFixup, and concluded that it doesn't make sense there.

CalcXScale is used when drawing, to try and determine the appropriate device-pixel offset to use for multiple strikes, but has no relevance to the metrics used for shaping and measurement. We should simply be applying GetSyntheticBoldOffset() here, without further scaling.

The error can be seen with the attached testcase, which uses the Andika font with synthetic bold applied (and negative letter-spacing, which makes it easier to see the problem). View this testcase on macOS; then choose Print / Save to PDF, and view the resulting PDF file. Note the greatly increased glyph spacing in the PDF compared to the screen display (and print preview).

Comment 1

[Jonathan Kew [:jfkthame]]

Attachment: save-to-pdf output of the testcase, showing bad glyph spacing

Comment 2

[Jonathan Kew [:jfkthame]]

Attachment: save-to-pdf output with corrected glyph spacing

Comment 3

[Jonathan Kew [:jfkthame]]

Attachment: Bug 1831298 - Don't apply spurious scaling to the synthetic-bold advance adjustment when shaping text. r=dholbert

Comment 4

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/57b96b26ef76
Don't apply spurious scaling to the synthetic-bold advance adjustment when shaping text. r=dholbert,emilio

Comment 5

[Sandor Molnar[:smolnar]]

https://hg.mozilla.org/mozilla-central/rev/57b96b26ef76