KB2670838 and the font rendering issue in Firefox

KB2670838 and the font rendering issue in Firefox

Three months after installing KB2670838 and updating my graphics drivers from Catalyst Mobility 13.12 to 14.4 the font rendering issue popped up. Except I didn’t get issues with text rendered in pages, but in Firefox’s menu/tabs/titlebar itself.

Nobody would think an update installed that long ago could be the culprit. Everyone would think the newly installed driver is (and it definitely has something do to with the issue). But we all need the latest drivers for performance reasons.

Thankfully, I found both discussions in Mozilla’s forums and Microsoft’s forums pointing me in the right direction. I remember hitting this issue once before, but stupid me never considered writing it down. Not this time.

Microsoft’s notes on update KB2670838 brag about improving DirectSomething performance:

This update improves the range and performance of the following graphics and imaging components:

  • Direct2D
  • DirectWrite
  • Direct3D
  • Windows Imaging Component (WIC)
  • Windows Advanced Rasterization Platform (WARP)
  • Windows Animation Manager (WAM)
  • XPS Document API
  • H.264 Video Decoder
  • JPEG XR codec

Apparently they improve performance but reduce quality.


After uninstalling the update, rendering returned to normal.

Edit: The issue can also appear without the updated installed if you updated to Internet Explorer 10 or 11. The only solution then is to uninstall IE and return to IE 9.

Later Edit: KB3013455 appears to cause similar problems. Also, if you’ve messed up with Firefox’s configuration while trying to resolve this issue, make sure you did not set the layers.acceleration.disabled
variable to true as that will cause similar behaviour in Firefox 40 / ESR 38.2.

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