[poppler] Differing number of items returned from get_text{, layout} for glyphs over page edge

[Germán Póo-Caamaño]

On Wed, 2013-12-04 at 10:53 -0300, Germán Póo-Caamaño wrote:
> On Wed, 2013-12-04 at 13:34 +0000, Peter Waller wrote:
> > On 28 November 2013 07:22, Germán Póo-Caamaño <gpoo at gnome.org> wrote:
> >         FWIW, I tried to use poppler_page_get_text_layout_for_area()
> >          for
> >         implementing the text annotation markup in glib (in the demo),
> >         but it is
> >         notoriously slower than the deprecated
> >         poppler_page_get_selection_region().
> >
> > What are your timings? I tested it and see that
> > poppler_page_get_text_layout_for_area and
> > poppler_page_get_text_for_area are ~30% slower for emptyish pages and
> > <~5% slower for more populated pages. Absolutely it is O(1ms) so
> > doesn't seem a concern to me, but I'm curious what problem you're
> > encountering.
> 
> For highlighting text interactively (or any other text markup), it calls
> poppler_page_get_text_layout_for_area every time the selection region
> changes. That is, to get the rectangles and set/update the annotation.
> 
> So, the delay is multiplied for the number of updates required.

To make it clear, see the following screencast:

http://calcifer.org/tmp/evince/poppler-get-rectangles-comparison.ogv

On the left, the one that uses poppler_page_get_selection_region() to
get the rectangles in the selection region, and to the right the one
that uses poppler_page_get_text_layout_for_area().

See how the highlight follows the cursor on the left one.  In the other
one, the interaction with the mouse finished (the cursor changes once
the button is released) and after some seconds, the computation ends and
the text markup is updated.

-- 
Germán Poo-Caamaño
http://calcifer.org/
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