The text and the brush are the two properties of text items
that change dynamically. To avoid complexities concerning
redrawing, set them concurrently instead of in two separate
calls.
Since setting one of the properties requires a full redraw,
there is no performance advantage in setting them individually.
This fixes a theoretical bug: the colors of axis labels were not
updated appropriately. However, it seems like value-dependent
labels weren't used anyway.
Signed-off-by: Berthold Stoeger <bstoeger@mail.tuwien.ac.at>
04e0d96bae