Document the Qt5 default in RELEASE-NOTES

[lyx.git] / development / PAINTING_ANALYSIS

diff --git a/development/PAINTING_ANALYSIS b/development/PAINTING_ANALYSIS
index f734edb3b012aea63443808e1aa3fdbf4ecfdab7..32bc93a5ff94169747bb454efeae3c96f9571b34 100644 (file)
--- a/development/PAINTING_ANALYSIS
+++ b/development/PAINTING_ANALYSIS
@@ -60,11 +60,41 @@ cursor.
 
 * 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.
+** Make SinglePar update flag useful again. 
 
-Other changes are only clean-ups.
+The current code can be very expensive when moving cursor inside a
+huge table, for example. We should test the flag again, although this
+will probably lead to some glitches here and there.
+
+** 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.
+
+This is also true when scrolling (how to do that?)
+
+*** redoParagraph
+
+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.
+
+** Create a unique row by paragraph and break it afterwards
+
+This should be a performance gain (only if paragraph breaking still
+shows as expensive after the rest is done)
+
+** do not add the vertical margin of main text to first/last row
+
+Would make code cleaner. Probably no so difficult.
 
 ** When a paragraph ends with a newline, compute correctly the height of the extra row.
 ** Merging bv::updateMetrics and tm::metrics
@@ -76,7 +106,7 @@ insets. We should re-use the bv::updateMetrics logic:
  + transfer all the logic of bv::updateMetrics to tm.
  + Main InsetText should not be special.
 
-The difficuly for a tall table cell for example, is that it may be
+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.
 
 
@@ -113,11 +143,19 @@ DecorationUpdate). It triggers a recomputation of the metrics when either:
    existing metrics. Note that the Update::SinglePar flag is *never*
    taken into account.
 
+If a computation of metrics has taken place, Force is removed from the
+flags and ForceDraw is added instead.
+
+It is OK to call processUptateFlags several times before an update. In
+this case, the effects are cumulative.processUpdateFlags execute the
+metrics-related actions, but defers the actual drawing to the next
+paint event.
+
 The screen is drawn (with appropriate update strategy), except when
 update flag is Update::None.
 
 
-** Metrics computation
+** Metrics computation (and nodraw drawing phase)
 
 This is triggered by bv::updateMetrics, which calls tm::redoParagraph for
 all visible paragraphs. Some Paragraphs above or below the screen (needed
@@ -127,6 +165,9 @@ tm::redoParagraph will call Inset::metrics for each inset. In the case
 of text insets, this will invoke recursively tm::metrics, which redoes
 all the paragraphs of the inset.
 
+At the end of the function, bv::updatePosCache is called. It triggers
+a repaint of the document with a NullPainter (a painter that does
+nothing). This has the effect of caching all insets positions.
 
 ** Drawing the work area.