The distancefield cache did not clear the textures before using
them. Hence, random values could leak through in the edges of the
distancefields, leading to random pixels at the edges of the rendered
glyphs.
This issue was rarely visible before, because of the way the glyphs
were stacked on the textures. That stacking was changed as a result of
7190aa26f6, which made the issue happen
more often, so it was detected by lancelot.
Change-Id: Ibe7a20dd7ba557ab92966e714c25a100e218ed24
Reviewed-by: Yoann Lopes <yoann.lopes@qt.io>
ff645deb25