[GSOC] Tiled Rendering, ahunt, Weekly Report 01 / WK22

Dear All,

The last 2-3 weeks I've been working on the following:

* Pushing the tiled rendering api out via LibLO:
** Initially by painting to an X11 "context" (I.e. the 5+ handles that 
SystemGraphicsData contains
    on Linux).
*** Was quite horrible, and not at all cross platform. Also results in a 
background window being
      shown as we have to use one of the X11 backends for this (and 
they all show a full
      window for the SalFrame which every document creates...).
** Ported to using bitmap buffer rendering (i.e. using the svp backend), 
and simply returning
   a pointer to the basebmp BitmapDevice internal buffer.
** Further modified to allow feeding in an arbitrary buffer (going via 
vcl VirtualDevice->
    svp SvpSalVirtualDevice -> basebmp BitmapDevice) -- this is a 
little finicky as the buffer
    is liable to be ignored if the VirtualDevice's size is changed at 
any point -- but seems to
    work fine for now.
** Also added support for setting top-to-bottom rendering direction (svp 
assumes that the
    buffers should be painted bottom-to-top, gtk the opposite -- we can 
now set this freely,
    saving us direct buffer manipulation).

* Moved bitcount->colourspace mapping into a central place for svp, 
implemented overriding
  of the defaults. (Previously there was a hardcoded assumption that 
BGR (or ABGR) was used
 for 24 (or 32 bit) colours. In our case we need RGB(A) for use in gtk 
(and similarly for qt AFAICS).)
** We just use 32 bit for now as that already has RGBA/ARGB/ABGR/BGRA 
implementation, we could
     quite easily allow the RGB/BGR choice for 24 bit too AFAICS (and 
allow arbitrary choie via the
     libLO API if appropriate).
** The alpha channel doesn't actually work -- for now I have to manually 
overwrite it in the tiled
     rendering app to make the document visible -- still need to dig 
into this in more detail.

* Miscellaneous reading around calc wrt. where tiled rendering should 
happen.
* Miscellaneous digging around vcl.

Current work is happening on feature/gtkbmptiledviewer, the app is under 
instdir/program/gtktiledviewer.
(The feature/gtktiledviewer branch is the X11 rendering early version of 
things.)

(Unfortunately I'm still in the middle of uni. projects for another 1.5 
weeks so not fully free yet...)

Cheers,

    Andrzej