[LyX/master] Update PAINTING_ANALYSIS

[Jean-Marc Lasgouttes]

commit a23522073c8bb2cd06ddc7cc564e9c78f868a86d
Author: Jean-Marc Lasgouttes 
Date:   Mon Nov 20 17:24:09 2023 +0100

Update PAINTING_ANALYSIS
---
 development/PAINTING_ANALYSIS | 62 +--
 1 file changed, 42 insertions(+), 20 deletions(-)

diff --git a/development/PAINTING_ANALYSIS b/development/PAINTING_ANALYSIS
index a506371965..438d7ca9c3 100644
--- a/development/PAINTING_ANALYSIS
+++ b/development/PAINTING_ANALYSIS
@@ -3,7 +3,7 @@ Understanding the painting process
 
 This file tries to describe the state of the metrics/painting
 mechanism, and identify the improvements that could be made. The first
-section can be read alone, although the context for them is really
+sections can be read alone, although the context for them is really
 given in the following ones.
 
 Please keep this file up to date as the code evolves!!!
@@ -20,9 +20,10 @@ following section. Some actions are proposed.
 
 ** SinglePar update
 
-This flag only has an effect in the current BufferView and at
-top-level, but I think it is useful in other views too. Doing this
-will require some work on the update pipeline, though.
+This flag only has an effect in the current BufferView, but I think it
+is useful in other views too. Doing this will require some work on the
+update pipeline, though.
+
 
 ** Buffer::change issues
 
@@ -53,17 +54,16 @@ The global idea would be to extend FitCursor to cover also 
horizontal
 cursor.
 
 
-* Clean-up of drawing code
+* TODO Clean-up of drawing code
 
 ** Set Row::changed() in a finer way
 
 *** singleParUpdate
 
 When the height of the current paragraph changes, there is no need for
-a full screen update. Only the rows after the current one need to have
-their position recomputed.
+a full screen update (at top level, at least). Only the rows after the
+current one need to have their position recomputed.
 
-This is also true when scrolling (how to do that?)
 
 *** redoParagraph
 
@@ -71,13 +71,16 @@ It should be possible to check whether the new row is the 
same as the
 old one and keep its changed() status in this case. This would reduce
 a lot the amount of stuff to redraw.
 
+
 ** Put labels and friends in the Row as elements
 
 It should not be necessary to access the Paragraph object to draw.
 Adding the static elements to Row is a lot of work, but worth it IMO.
 
+
 ** When a paragraph ends with a newline, compute correctly the height of the 
extra row.
 
+
 ** Merging bv::updateMetrics and tm::metrics
 
 While the full metrics computation tries hard to limit the number of
@@ -89,6 +92,12 @@ insets. We should re-use the bv::updateMetrics logic:
 
 The difficulty for a tall table cell for example, is that it may be
 necessary to break the whole contents to know the width of the cell.
+Also, the anchor is relative to the outer paragraph, which means that
+for a very long inset it is necessary to rebreak until the contents
+that needs to be shown (to compute the heights).
+
+All in all, this is difficult to get right. This is less important now
+that SinglePar updates work in nested insets.
 
 
 * Description of current drawing mechanism
@@ -99,10 +108,12 @@ There are three parts to drawing the work area:
 
  + the metrics phase computes the size of insets and breaks the
paragraphs into rows. It stores the dimension of insets (both
-   normal and math) in bv::coordCache.
+   normal and math) in bv::coordCache and the vertical position of the
+   top-level paragraphs.
 
  + the nodraw drawing phase paints the screen (see below) with a null
-   painter. The only useful effect is to store the inset positions.
+   painter. The only useful effect is to store the positions of
+   visible insets.
 
  + an update() signal is sent. This in turn will trigger a paint
event, and the actual screen painting will happen then.
@@ -115,18 +126,18 @@ whether this is correct.
 
 Depending on the Update::flags passed to the method, it sets an update
 strategy in (NoScreenUpdate, SingleParUpdate, FullScreenUpdate,
-DecorationUpdate). It triggers a recomputation of the metrics when either:
+DecorationUpdate). It triggers a call to updateMetrics when either:
 
  + Update::Force has been specified
  + Update::FitCursor has been specified and there is a need to scroll
the display.
  + Update::SinglePar has been specified and the current paragraph has
-   not changed height.
+   changed height.
 
 If a computation of metrics has taken place, Force is removed from the
 flags and ForceDraw is added instead.
 
-It is OK to call processUpateFlags several times before an update. In
+It is OK to call processUpdateFlags several times before an update. In
 this case, the effects are cumulative. processUpdateFlags executes the
 metrics-related actions, but defers the actual drawing to the next
 paint event.
@@ -137,21 +148,32 @@ update flag is Update::None.
 
 ** Metrics computation (and nodraw drawing phase)
 
-This is triggered by bv::updateMetrics, which calls 

[LyX/master] Update PAINTING_ANALYSIS and add a new task

[Jean-Marc Lasgouttes]

commit 095c390fe2d7c983ccb0228d73c09b8da58bc206
Author: Jean-Marc Lasgouttes 
Date:   Wed May 11 14:16:08 2016 +0200

Update PAINTING_ANALYSIS and add a new task

diff --git a/development/PAINTING_ANALYSIS b/development/PAINTING_ANALYSIS
index acb033d..78719f5 100644
--- a/development/PAINTING_ANALYSIS
+++ b/development/PAINTING_ANALYSIS
@@ -58,15 +58,14 @@ The global idea would be to extend FitCursor to cover also 
horizontal
 cursor.
 
 
-* Proposals
-
-
 * Clean-up of drawing code
 
 The goal is to make painting with drawing disable fast enough that it
 can be used after every metrics computation. Then we can separate real
 drawing from metrics.
 
+Other changes are only clean-ups.
+
 ** DONE RowPainter
 
 Inset position is set in paintInset, paintOnlyInsets, and paintText.
@@ -114,29 +113,14 @@ topBottomSpace parameter should be removed after that.
 
The helper version should return a Row::Element instead of an InsetTable.
 
-** TODO make Inset::display() more useful
+** Do not make RowPainter operations update x_
 
-[This has been started in the features/betterbreak branch. Time will
-tell whether it really helps. The question in particular is the
-handling of separator insets]
+It is better to make them const and update x_ separately.
 
-Extending the DisplayType enum would allow to remove special cases
-from the code.
-
-The enumeration could be like
-: Inline = 0
-: BreakBefore = 1 // break row before this inset
-: BreakAfter = 2 // break row after this inset
-: CanBreakAfter = 4 // optionally break row after this inset
-: AlignLeft = 8
-: AlignRight = 16
-: NoBoundary = 32 // do not allow cursor to go at the end of the row
-: //before display inset
-: Display = BreakBefore|BreakAfter
-
-A display equation would be Display, other could be Display|AlignLeft
-BreakAfter can be used by Newline or separator insets
-CanBreakAfter can be used by the optional hyphen InsetSpecialChar.
+Then it will be possible to reorder the painting of the different
+elements. In particular, if text is painted last, it will be more
+visible in the presence of underlines (foreign language, change
+tracking, spell check).
 
 ** Set inset position during metrics phase
 
@@ -222,12 +206,8 @@ update flag is Update::None.
 ** Metrics computation
 
 This is triggered by bv::updateMetrics, which calls tm::redoParagraph for
-  + all visible paragraphs
-  + paragraph above the screen (up to one page)
-  + paragraphs below the screen (up to one page again)
-
-The paragraphs outside of the screen are required to make PageUp/Down
-work.
+all visible paragraphs. Paragraphs above or below the screen (needed
+for page up/down) and computed as needed.
 
 tm::redoParagraph will call Inset::metrics for each inset. In the case
 of text insets, this will invoke recursively tm::metrics, which redoes

[LyX/master] Update PAINTING_ANALYSIS

[Jean-Marc Lasgouttes]

commit 78eaf8333bacec8d735eae06c0745163d06a5122
Author: Jean-Marc Lasgouttes 
Date:   Sat Mar 5 00:09:34 2016 +0100

Update PAINTING_ANALYSIS

Some things were wrong, and some new ideas are added (some are done in
this branch already).

diff --git a/development/PAINTING_ANALYSIS b/development/PAINTING_ANALYSIS
index d1da54b..4934c5e 100644
--- a/development/PAINTING_ANALYSIS
+++ b/development/PAINTING_ANALYSIS
@@ -60,13 +60,75 @@ cursor.
 
 * Proposals
 
-** set inset position during metrics phase
+* Clean-up of drawing code
 
-This implies to set inset positions relative to outer inset during
-metrics phase and then in a second loop to descend into insets and
-update positions correctly.
+The goal is to make painting with drawing disable fast enough that it
+can be used after every metrics computation. Then we can separate real
+drawing from metrics.
 
-Effect: avoid going through the painter machinery when it is not necessary.
+** DONE RowPainter
+
+Inset position is set in paintInset, paintOnlyInsets, and paintText.
+This should be done only once in paintInset
+
+** DONE TextMetrics::drawParagraph
+
+We can really simplify the code when drawing is disabled only
+paintInset needs to be called.
+ + do right at the start when drawing is already disabled
+ + do it in the loop for rows that are not visible on screen.
+
+The only thing we want to do here is to set inset positions (for
+text). The other insets still use the painter with drawing disabled.
+
+** Painter::text
+
+We cannot remove (or make private) the version that uses a
+FontInfo because it is used by PainterInfo::draw. Document this and
+remove unused arguments rtl and double spacing. This would become a 
specialized helper.
+Proposed solution: keep the existing function, but private and without
+optional arguments.
+
+Avoid to return (and thus compute) the width of strings?
+ + used by InsetSpecialChar (fixable)
+ + used by textDecoration() in text(): more difficult to fix
+
+Idea: add a version of text where wordspacing and textwidth (giving
+the width of strings) are required parameters and remove optional
+version.
+
+==> more versions, no optional parameters.
+
+** Set inset position during metrics phase
+
+In order to do that, a no-paint drawing will be initiated after every
+redoParagraph. This code path will need to be made as fast as possible.
+
+Effect: avoid depending on actual drawing having taken place. In turn,
+it will allow to do drawing on paint events, like any reasonable
+application would do.
+
+** Cleanup after complete metrics
+   Then the following can be done:
+   + remove hack in InsetMathNest::drawSelection
+   + remove painting when not inside in drawParagraph
+   + remove Cursor::inCoordCache?
+
+** Use Row for MathData
+
+It may not be so difficult. Implement x2pos and pos2x from
+the TM:cursorX and TM::getPosNearX, and use them for both text and
+math.
+
+Will the strings display OK if drawing string-wise?
+
+Then it would be possible to streamline drawing with disabled painter.
+
+** Paint directly to screen
+
+Instead of using an intermediary pixmap. I have no idea of how
+difficult it will prove.
+One benefit will be that subpixel aliasing will work again (#9972)
 
 ** Merging bv::updateMetrics and tm::metrics
 
@@ -75,16 +137,10 @@ 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. 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.
+ + Main InsetText should not be special.
 
-There was a proposal to always compute _all_ rows, but this may become
-expensive for large files. This would though help scrolling.
+The difficuly for a tall table cell for example, is that it may be
+necessary to break the whole contents to know the width of the cell.
 
 
 * Description of current drawing mechanism

[LyX/master] Update PAINTING_ANALYSIS

[Jean-Marc Lasgouttes]

commit 47c0b3cc052ece15dea5289b683bc57bb9cfc01a
Author: Jean-Marc Lasgouttes 
Date:   Mon May 30 14:54:20 2016 +0200

Update PAINTING_ANALYSIS

Remove all the tasks that have been performed.

diff --git a/development/PAINTING_ANALYSIS b/development/PAINTING_ANALYSIS
index e1b0b64..3ddfc74 100644
--- a/development/PAINTING_ANALYSIS
+++ b/development/PAINTING_ANALYSIS
@@ -66,62 +66,11 @@ drawing from metrics.
 
 Other changes are only clean-ups.
 
-** DONE RowPainter
-
-Inset position is set in paintInset, paintOnlyInsets, and paintText.
-This should be done only once in paintInset
-
-** DONE TextMetrics::drawParagraph
-
-We can really simplify the code when drawing is disabled only
-paintInset needs to be called.
- + do right at the start when drawing is already disabled
- + do it in the loop for rows that are not visible on screen.
-
-The only thing we want to do here is to set inset positions (for
-text). The other insets still use the painter with drawing disabled.
-
-** DONE Painter::text
-
-We cannot remove (or make private) the version that uses a
-FontInfo because it is used by PainterInfo::draw. Document this and
-remove unused arguments rtl and double spacing. This would become a 
specialized helper.
-Proposed solution: keep the existing function, but private and without
-optional arguments.
-
-Avoid to return (and thus compute) the width of strings?
- + used by InsetSpecialChar (fixable)
- + used by textDecoration() in text(): more difficult to fix
-
-Idea: add a version of text where wordspacing and textwidth (giving
-the width of strings) are required parameters and remove optional
-version.
-
-==> more versions, no optional parameters.
-
-** DONE When a document ends with a newline, add the bottom margin anyway
-
-The code that tests for a newline was added at 6bb98d07 in 2007.
-
 ** When a paragraph ends with a newline, compute correctly the height of the 
extra row.
 ** Rewrite TextMetrics::editXY, checkInsetHit using row information 
(getPosNearX)?
 
The helper version should return a Row::Element instead of an InsetTable.
 
-** DONE Do not make RowPainter operations update x_
-
-It is better to make them const and update x_ separately.
-
-** DONE remove pit argument to breakRow
-
-There are probably other places where the pit is not needed anymore:
-computeRowMetrics, labelFill, setRowHeight, isLastRow, isFirstRow
-
-** DONE Split setRowHeight to separate the computation of space above/below 
paragraph
-
-This allows to remove the topBottomSpace parameter. The spacing is
-computed in redoParagraph, where it feels more natural.
-
 ** Remember rtl status in the row object
 
 This will avoid to pass a Paragraph object to methods that do not need it.