551405 - mozTextAlongPath stops rotating along mozPathText

Status: RESOLVED WORKSFORME

(Core :: Graphics: Canvas2D, defect)

Description

[skierpage]

User-Agent:       Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.3a3pre) Gecko/20100309  Minefield/3.7a1pre
Build Identifier: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.3a3pre) Gecko/20100309  Minefield/3.7a1pre ID:20100309031021

http://blog.vlad1.com/2008/06/04/html-canvas-in-firefox-3/ has a screenshot of a canvas example "showing how text can be drawn along a path, which itself is generated by text".  When I view the example the letter glyphs follow the text outline but "soon after the beginning" they are all upright.

Reproducible: Always

Steps to Reproduce:
1. Visit http://people.mozilla.com/~vladimir/demos/canvas-text-path.html
2. Compare with screenshot in http://blog.vlad1.com/2008/06/04/html-canvas-in-firefox-3
Actual Results:  
The gray letters along the path are all upright, except the 'T' at the start ("The Internet is becoming..."), does match the path. (I'll attach screenshot.)

Expected Results:  
Letters rotate to match the path, e.g. around the 'o' and along the diagonal of 'z'.  See screenshot in Vladimir's blog.

In other path text examples from bug 339553 like wave text, the letters do rotate to match the angle of the path, hence I think it's some interaction between mozPathText and mozTextAlongPath.

If I change the mozPathText to "ozilla", the letters around the 'o' and part of the 'z' rotate correctly, but after that they're all upright.  Weird.  I tried specifying a different serif font, "FreeSerif", for the text path and got a few more rotated glyphs, but still mostly upright.

It could be something about the way fonts and font rendering on my Linux/Kubuntu 9.04 amd64 system is configured. `fc-match serif` returns 'DejaVuSerif.ttf: "DejaVu Serif" "Book"', which I do have installed. `ldd firefox-bin` reports in part,
  libpangoft2-1.0.so.0 => /usr/lib/libpangoft2-1.0.so.0 (0x00007f26a325b000)
  libfreetype.so.6 => /usr/lib/libfreetype.so.6 (0x00007f26a2fd6000)
  libfontconfig.so.1 => /usr/lib/libfontconfig.so.1 (0x00007f26a2da4000)

Comment 1

[skierpage]

Attachment: screenshot showing canvas-text-path.html bug

This is http://people.mozilla.com/~vladimir/demos/canvas-text-path.html with one letter removed from ctx.mozPathText(), note how glyphs stop rotating half-way around the 'z'.

Comment 2

[skierpage]

bug 518172 (moz-transform doesn't rotate individual characters) occurs in CSS not canvas, but results in a similar visual glitch.  So maybe this bug belongs in Core-Graphics also.

Comment 3

[Daniel Holbert [:dholbert]]

I can confirm this bug:
Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.9.3a3pre) Gecko/20100315 Minefield/3.7a3pre

I'd say this and bug 518172 are *related*, and may very well be the same root cause, but until that's definitively established, it's worth leaving them separate since the testcases are significantly different from each other.

Comment 4

[Daniel Holbert [:dholbert]]

(Having said that, Core-Graphics may very well be the right component for this.  Comment 3 was more in response to bug 518172 comment 12)

Comment 5

[skierpage]

Mr. Vukićević's sample now works for me, in
Mozilla/5.0 (X11; Linux x86_64; rv:2.0b7pre) Gecko/20101006 Firefox/4.0b7pre

Most likely the fix for bug 518172 , Disable the previous_scaled_font cache http://hg.mozilla.org/mozilla-central/rev/36f921c9692f , fixed this as well.
As I understand it, ideally there would be a reftest for this bug that now passes, so I am not changing the status to RESOLVED.

Comment 6

[Daniel Holbert [:dholbert]]

This is WFM now too.  Resolving as WORKSFORME with dependency on bug 518172.

Adding whiteboard note & "qawanted" label to hopefully get a reftest (per the last sentence of comment 5).

Comment 7

[Joshua Mitchell (Inactive)]

Issue is resolved - clearing old keywords - qa-wanted clean-up