Bug 135419 – Black canvas when using RTL/webGL on Google Maps

• Component: WebGL
• Status: RESOLVED INVALID

[Michael Davidson]

When launching in RTL languages, the WebGL canvas is always black. This doesn't happen for our 2D canvas rendering, and doesn't happen in LTR languages.

Compare:

http://google.com/maps?force=webgl&hl=ar   (RTL, WebGL, bad)
http://google.com/maps?force=webgl&hl=en  (LTR, WebGL, looks good!)
http://google.com/maps?force=canvas&hl=at (RTL, Canvas2D, good)

[Brent Fulgham]

What operating system version are you running when you encounter this? Is it a shipping Mavericks version, or the developer seed for the upcoming OS?

[Alex Christensen]

I think this is a problem in your content.  Switching the user agent to Google Chrome -- Mac makes it no longer happen.
I see the map for a moment, then it smoothly fades to black.  I'm not familiar with the inner workings of Google Maps.  Do you have any idea what would cause this?

[Michael Davidson]

My OS: 10.9.4
Retina MBP
GPU:  NVIDIA GeForce GT 650M 1024 MB

Alex, the initial map you see is image tags showing raster content. The WebGL context never shows content, it's always black.

[Michael Davidson]

Nightly version: Version 7.0.5 (9537.77.4, r171650)

[Brent Fulgham]

Seems to be limited to Retina hardware.

[Michael Davidson]

A clue:

In non-Safari high DPI browsers, we scale the canvas using style.width/style.height. If you emulate the Chrome UA, you'll see that it does render, but not with correct crisp text.

In Safari, we scale using a webkit-transform of scale(.5, .5), which yields sharp text in LTR languages but a black canvas in RTL languages.

[Michael Davidson]

This is a bug in the maps code. We're not setting the origin of the transform in RTL languages.