608633 - Canvas strokeText produces artifacts when clipping

Status: RESOLVED DUPLICATE of bug 499628

(Core :: Graphics: Canvas2D, defect)

Description

[Daniel Baulig]

User-Agent:       Mozilla/5.0 (Windows; U; Windows NT 6.1; de; rv:1.9.2.12) Gecko/20101026 Firefox/3.6.12
Build Identifier: Mozilla/5.0 (Windows; U; Windows NT 6.1; de; rv:1.9.2.12) Gecko/20101026 Firefox/3.6.12

When I use strokText subsequntial calls to clip will cause the clipped area to be stroked, additionally to be clipped. The clipped area will get a border, as if I stroked after building the path. You can see the effect in my linked application prototype.
When the page is loaded everything should work fine by default. If you move the viewport to Europe you will see some small numbers, which are drawn using fillText. Because I want a border around the text I added a strokeText infront of the fillText and suddenly the bug appeared. You can switch the strokeText on with the checkbox to the right. I tested if bug appears in Chrome, but it does not. When you move the zone highlighting the old position is removed using clipping, aswell as when you click on one of the units, it will be removed using clipping. As you can see the border will appear around the clipped area.

Reproducible: Always

Steps to Reproduce:
1. Load the demonstration application (URL)
2. Check the checkbox
3. Produce clipped repaints by moving the highlight with your mouse around
Actual Results:  
Clipped areas will have a border as if stroked. If you change the stroke color (strokeStyle), the color of the border will suite the changed strokeStyle.

Expected Results:  
It should not be any different than when the checkbox is not checked, except, of course, the numbers that are drawn using strokeText should have a small black border ;)

See Details.
The part of the code of concern: http://gist.github.com/657213
Search for this.stroke, which is the strokeText toggle.

Comment 1

[(mostly gone) XtC4UaLL [:xtc4uall]]

Is this related to Bug 499628?

Comment 2

[Daniel Baulig]

I am pretty sure this is a duplicate. Please flag it as such. I searched the bug database for related bugs, but wasn't able to find that one. Propably because when I started writing the bug report I wasn't aware of that actually clip is what produces the artifacts and as such I didn't contain it in my search phrase.