Hi All,
Status for the last week
* Started Working on Calc Tiled Rendering
** Getting some output to be shown was deceptively simple.
** Even images seem to be shown, however only as an outline
(i.e. not showing the content) -- the same thing seems to
be happening in Calc (where you need to touch/move/otherwise
manipulate the document before the image itself is shown, so
AFAICS not a tiled rendering specific bug).
** However scaling / matching document coordinates is tricky
(and is what I've spent most of the week working on).
***: For document "size" we currently grab the area containing
cells with data, which is then the suggested minimum area that
should be rendered.
**** Client can request that additional are (with empty cells) be rendered,
allowing for an infinitely expanding document as in calc.
**** However this area (or the way we currently determine it) doesn't
take into account images (and presumably other objects) that aren't
within a cell, and also cells that are merely formatted but
don't have data.
(I.e. will still need some improvement to be truly useful).
***: Scaling is also wrong, it turns out we have a bunch of rounding
errors being
propagated due to repeated scaling, which means that when you
request
a tile nominally covering the whole document you would get
something like
in calc_scalewrong.png (attached).
(Ignore the image being cut for now, see above)
****: For some reason calc does most of its drawing in pixel mapped
mode, rather
than in document dimensions, i.e. it handles all the scaling
itself, rather than using
the virtual device scaling. This results in multiple
multiplications with some fairly
small fractions, with errors creeping in that way.
****: Managed to fix this (for the cell outlines only for now, cell
contents/images
still to be done), by rewriting the painting to only use the
virtual devices built
in scaling (whereas currently the scaling is passed into the
ViewData, which multiplies
the desired scale by the screen PPT[XY], which is where most of
the error occurs).
See calc_tiled.png for this (I've changed zoom-levels just to
make scaling issues more
apparent, this can be tweaked easily in the gtktiledviewer
sources).
****: However using this means that Calc (non-tiled rendering mode) will
also be affected,
see calc_broken.png.
****: Still thinking about the best way to proceed, some options would be:
1) Have tiled-rendering conditions throughout the code to use
the correct scaling
only then (probably a huge nightmare to maintain).
2) Rewrite all of the frontend code to get rid of the internal
scaling, instead relying on
the virtualdevice scaling (better for maintenance, but
potential for bugs in the short term).
This probably shouldn't be too tricky, but will touch quite
a bit of code.
3) Combination of the above: work on the tiled rendering only
for now, rewrite the frontend
later to use the tiled output + use the tiled dimensions
for the rest of the UI (i.e. the column/
row bars), and finally scrap the old code.
****: We could potentially just ignore these scaling issues, but for
tiled rendering I suspect
it's crucial that coordinates stay in the same place since we
might be grabbing the same content
rendered at multiple zoom levels etc., and the document
potentially moving around at different
scaling levels would look quite glitchy I suspect.
* Some more LOK work:
** glib inspired class/object splitting.
** Since we're now breaking ABI anyway, got rid of the annoying
double initialisation.
Cheers,
Andrzej
Attachment:
calc_broken.png
Description: PNG image
Attachment:
calc_tiled.png
Description: PNG image
Attachment:
calc_scalewrong.png
Description: PNG image
