In the current code (last time I looked anyway), if you load a long page like http://www.timecube.com and then pan down, the displayport starts out covering pixels above the top of the document and to the left. As you pan down, the size of rendered area increases as the displayport moves into defined pixels. A similar effect happens when panning horizontally.
Not using available displayport area in this manner is bad for several reasons
- (obviously) checkerboard earlier than should
- resizing gfx buffers is rather expensive
- happens on every page load, not in edge cases
We shouldn't ever set the displayport above or to the left of document <0, 0>.
The WIP patch in bug 624451 fixes this.
Sorry, same here, and stechz is working on it already.
One bug is enough
*** This bug has been marked as a duplicate of bug 624451 ***