Make impBufferDevice faster again

When the Primitives for the Glow-Effects were added
(modified ShadowPrimitive2D, SoftEdgePrimitive2D and
GlowPrimitive2D) a modified version of impBufferDevice
was created and used. That lowered the speed for
drawing objects with transparence by about factor 2.5
and was unfortunately not only done for these
Primitives, but for transprent objects in general.

For the mentioned factor refer to:
Patch to demonstrate former and now repaint differences
https://gerrit.libreoffice.org/c/core/+/129301

After having reworked those Primitives to use another
mechanism and being decomposed so they will work in all
now and future renderers, it is possible to go back to
that easier and faster method to render Transparency.

For extended information, please take a look at the
added comments, mainly in vclhelperbufferdevice.hxx

Identified a still bad behaviour when objects use a
TransparenceGradient. Corrected that and added (at
this opportunity) a method 'createAlphaMask' along
with 'convertToBitmapEx' which is now used in the
GlowPrimitive2D & ShadowPrimitive2D which only need
the AlphaMask to do their job anyways (I had commented
there that thjis is possible before). That will
be faster for visualizing those Primitives.

Change-Id: Ieac880384de26960c2c4b8740a1dee1e15d7ac9e
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/140022
Tested-by: Jenkins
Reviewed-by: Armin Le Grand <Armin.Le.Grand@me.com>

0 files changed, 0 insertions, 0 deletions