[Okular-devel] Redrawing the screen due to optional content group changes

[Jeremy Maitin-Shepard]

On Sat, Jul 18, 2015 at 7:27 AM, Albert Astals Cid <aacid at kde.org> wrote:

> El Divendres, 17 de juliol de 2015, a les 12:52:30, Jeremy Maitin-Shepard
> va
> escriure:
> > Forwarding to the list, since I sent my original reply incorrectly...
> >
> > On Fri, Jul 17, 2015 at 12:51 PM, Jeremy Maitin-Shepard <
> jeremy at jeremyms.com
> > > wrote:
> > >
> > > On Thu, Jul 16, 2015 at 3:16 PM, Albert Astals Cid <aacid at kde.org>
> wrote:
> > > [snip]
> > >
> > >> > Any advice about how to deal with this redraw problem?
> > >>
> > >> Trigger the redraw yourself? See Saheeb's branch for optinal content
> > >> (origin/gsoc2015_layer_feature), I'd say it probably makes sense for
> you
> > >> to
> > >> base your work on his branch.
> > >
> > > Thanks, I'll take a look.
>


I see that the gsoc2015_layer_feature branch just triggers a redraw of
every page in the document any time there is any change to optional content
group visibility.  Merging my changes on top of this branch indeed makes
the animation kind of work.  However, there are some serious performance
issues.  Redrawing the whole document for each frame of the animation kills
performance if there are many pages.  To avoid this though would seem to
require poppler providing an interface for determining which pages are
affected by each optional content group.  (This is needed for a proper
implementation of the Javascript OCG interface anyway.)  Alternatively a
hack might be to redraw only the current page; not sure how this would
interoperate with the layer panel.

Even in single page documents, though, redrawing the whole page is often
too slow to achieve reasonable frame rate.  Somehow acrobat reader is
significantly faster.  It would be nice if there were a way to prerender
each optional content group individually so that toggling the visibility
wouldn't require rerendering.
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