https://bugs.documentfoundation.org/show_bug.cgi?id=101162
--- Comment #6 from Clemens Eisserer <linuxhi...@gmail.com> ---
Hi Tomaz,
> Linux OpenGL backend doesn't have glyph caching so it is currently slow and
> implementing
> that is not that trivial (mainly rendering glyph to texture with FT is
> missing) but not too hard either,
> I just don't have the time to implement that.
Thanks for your answer, this also explains why I see most time spent
in various types of memcpy when working with spreadsheets containing a
lot of text. When I tried to run earlier versions of the OpenGL backend on my
Intel-HD (OpenGL-2.1) I also saw a lot of shader recalculations and
other performance problems reported by the intel driver (with
INTEL_DEBUG=perf).
This makes me wonder ... would it make sense to apply for
Google-Summer-of-Code with the intention of bringing the OpenGL
backend on Linux to a production-ready state (so that it can be
enabled on linux by default), by:
* Implement the missing glyph-cache
- including subpixel antialiasing (requires GL_NV_texture_barrier or
readback for proper blending)
* Test and tune for various driver/hw combinations out there (r600,
radeonsi, nouveau, nvidia proprietary, i965) and
- resolve bottlenecks (shader recompilations, other expensive state changes,
texture upload)
- extend the white/black lists
- profile typical API interations between LibreOffice and VCL and
tune the backend so that common cases hit driver fast paths.
- extend the use of shaders where approriate
LibreOffice always had a rather sluggsih UI on Linux especially when
working with documents that contain images, so it would be great if
that could be finally solved.
I know layering a typical immediate-drawing-API on top of OpenGL won't
magically make everything super-fast, but I hope it will improve the
average feel and responsiveness.
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