Bug 89285 – Disappearing polyline

• Component: SVG
• Status: RESOLVED FIXED

In developing an SVG using US Census TIGER data, I found my polylines disappearing in Chrome 19. Attached is a small sample of the dataset that causes the polyline to disappear. The sample comes from the line used to draw Calhoun County, Iowa. The attached sample works as expected (line appears) in IE9, FF13, and O12.

If the user zooms out three to four times, the line magically appears. No amount of zooming in can cause the line to appear. In the attached sample, removing "-94.846508,42.560022" causes the line to reappear without changing zoom.

I'm not familiar enough with the WebKit SVG engine to know what is causing this failure, but it makes it impossible to use US Census TIGER data when all the polylines keep disappearing. Somehow, that one coordinate is causing the engine to error when drawing.

Created attachment 147968 [details]
Disappearing polyline bug example / testcase

Created attachment 147969 [details]
Disappearing polyline bug example / testcase (with the error)

Created attachment 147970 [details]
Larger example

This attachment contains the entire county's dataset. If the user zooms in once or twice, more polylines disappear. If the user zooms out 3 or 4 times, the missing polylines appear.

Created attachment 148222 [details]
X-Large example (map of Iowa)

Instead of using polylines, polygons are used in this example. Same problems.

Again, this example works perfectly in IE9, FF13, and O12. In Google, the user has to zoom out twice to get most of the county polygons to show. The user has to zoom out another two times to get the state outline to appear. At maximum zoom out, some counties are still not drawn.

[Nikolas Zimmermann]

(In reply to comment #4)
> Created an attachment (id=148222) [details]
> X-Large example (map of Iowa)
> 
> Instead of using polylines, polygons are used in this example. Same problems.
> 
> Again, this example works perfectly in IE9, FF13, and O12. In Google, the user has to zoom out twice to get most of the county polygons to show. The user has to zoom out another two times to get the state outline to appear. At maximum zoom out, some counties are still not drawn.

Are you testing this on Windows? I've checked your examples with WebKit/trunk on Mac, and they look exactly like in FF/O - seems like a non-Mac only issue. Can you confirm this?

I do not have access to a Mac to test this. I am testing this on Win7.

I double-checked to make sure it wasn't an extension causing the error, but it occurs in incognito mode and I don't have any extension enabled incognito.

Same results in incognito Chrome on Vista. Using release channel.

[Nikolas Zimmermann]

(In reply to comment #8)
> Same results in incognito Chrome on Vista. Using release channel.

Can you upload a screenshot on how it looks like on Windows (on default zooming, and when zoom in/out).  It seems this bug is windows specific.

Created attachment 148941 [details]
Screenshot of "X-Large example (map of Iowa)", default zoom

Because the testcase is a very small line, resulting in a blank screenshot at default zoom and appearing after zooming out, I'm using the "x-large example (map of Iowa)" for the screenshots - it better demonstrates the problem. 3 files will be submitted. The first is at default zoom, the second will be zoomed out twice, the third will be zoomed out 4 times. In the 2nd example, most of the missing polygons appear. In the 4th example, the polygon of the state finally appears, but a few counties (noted by the thinner lines, particularly in the east) are still missing.

Created attachment 148942 [details]
Screenshot of "X-Large example (map of Iowa)", zoomed out twice

Created attachment 148943 [details]
Screenshot of "X-Large example (map of Iowa)", zoomed out 4 times

[Philip Rogers]

(In reply to comment #8)
> Same results in incognito Chrome on Vista. Using release channel.

I wonder if this has been fixed in more recent versions? I could not reproduce on the latest builds with Linux.

Do you mind trying to reproduce in Chrome beta? I think the next version (20) is due out sometime very soon.

Tried it in Chrome Canary. Everything worked. Must be fixed in a later build.

[Philip Rogers]

Cool, glad to hear it's now fixed :)