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Update file from Abdel's comments and some of my own thinking

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This commit is contained in:
Jean-Marc Lasgouttes 2015-10-04 00:03:46 +02:00
parent 7ef19902ea
commit c4da9b9e37
1 changed files with 33 additions and 22 deletions
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55
development/PAINTING_ANALYSIS
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@ -18,14 +18,6 @@ tm::TextMetrics
These questions are consequences of the description made in the
following section. Some actions are proposed.
** Inset cache
Why do we store inset dimensions both in bv::coordCache and in
pm::insetDimension? The later one is bad when same
buffer is shown in different views.
I propose to get rid of pm::insetDimension.
** SinglePar update
The flag Update::SinglePar is set in many places but never acted on.
@ -38,12 +30,6 @@ SingleParUpdate shall be removed.
Moreover, I fail to see (yet) where the 'single' part of the program
is acted on.
** Two phase drawing
Why is it necessary to set the inset positions in the drawing phase?
It seems to me that everything can be done in the metrics phase (at
least for non-math insets).
** Buffer::change issues
When calling Buffer::changed outside of bv::processUpdateFlags,
@ -54,24 +40,49 @@ a good value? NoScreenUpdate?
On a related note, what is the semantics of a call to
Buffer::changed(false)? What does the caller mean?
** Metrics outside of visible area
Why is it required to compute metrics on page above and below the
visible area? Couldn't this be done on demand? I suspect this could be
made transparent by doing it in the proper metrics-fetching method.
** What happens with FitCursor when the cursor is already OK?
In this case, we invoke Buffer::change(false) with drawing disabled,
which means that the paint machinery is invoked to update inset
positions. Why is this necessary at all?
positions.
Actually, this was added as part of the horizontal scrolling GSoC
work. We need to investigate how costly this is.
* Proposals
** get rid of pm::insetDimension.
The information contained there is already in bv::coordCache.
Effect: only code simplification.
** set inset position during metrics phase
This implies to set inset positions relative to outer isnet during
metrics phase and then in a second loop to descend into insets and
update positions correctly.
Effect: avoid going through the painter machinery when it is not necessary.
** Merging bv::updateMetrics and tm::metrics
While the full metrics computation tries hard to limit the number of
paragraphs that are rebroken, the version that is used for inner inset
does not try any such optimization. This can be very bad for very tall
insets. How difficult would it be to re-use the bv::updateMetrics logic?
insets. We should re-use the bv::updateMetrics logic:
+ transfer all the logic of bv::updateMetrics to tm.
+ Main InsetText should not be special.
** Metrics outside of visible area
Currently metrics are computed for current visible paet of text, the
page above and the page below. It should be possible to compute hidden
rows ony on demand, although it might be a bit slow.
There was a proposal to always compute _all_ rows, but this may become
expensive for large files. This would though help scrolling.
* Two phase drawing