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Update the painting process documentation
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@ -67,31 +67,11 @@ drawing from metrics.
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Other changes are only clean-ups.
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** When a paragraph ends with a newline, compute correctly the height of the extra row.
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** Rewrite TextMetrics::editXY, checkInsetHit using row information (getPosNearX)?
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The helper version should return a Row::Element instead of an InsetTable.
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** Set inset position during metrics phase
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In order to do that, a no-paint drawing will be initiated after every
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redoParagraph. This code path will need to be made as fast as possible.
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Effect: avoid depending on actual drawing having taken place. In turn,
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it will allow to do drawing on paint events, like any reasonable
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application would do.
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** Cleanup after complete metrics
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Then the following can be done:
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+ remove hack in InsetMathNest::drawSelection
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+ remove painting when not inside in drawParagraph
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+ remove Cursor::inCoordCache?
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** Paint directly to screen
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Instead of using an intermediary pixmap. I have no idea of how
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difficult it will prove.
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One benefit will be that subpixel aliasing will work again (#9972)
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** Merging bv::updateMetrics and tm::metrics
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While the full metrics computation tries hard to limit the number of
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@ -107,19 +87,19 @@ necessary to break the whole contents to know the width of the cell.
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* Description of current drawing mechanism
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** Two stage drawing
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** Three-stage drawing
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There are two parts to drawing the work area:
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There are three parts to drawing the work area:
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+ the metrics phase computes the size of insets and breaks the
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paragraphs into rows. It stores the dimension of insets (both
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normal and math) in bv::coordCache.
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+ the drawing phase draws the contents and caches the inset
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positions. Since the caching of positions is useful in itself,
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there is a provision for drawing "without" drawing when the only
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thing we want is to cache inset positions
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(Painter::setDrawingEnabled).
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+ the nodraw drawing phase paints the screen (see below) with a null
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painter. The only useful effect is to store the inset positions.
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+ an update() signal is sent. This in turn will trigger a paint
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event, and the actual screen painting will happen then.
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The machinery is controlled via bv::processUpdateFlags. This method is
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called at the end of bv::mouseEventDispatch and in
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@ -145,7 +125,7 @@ update flag is Update::None.
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** Metrics computation
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This is triggered by bv::updateMetrics, which calls tm::redoParagraph for
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all visible paragraphs. Paragraphs above or below the screen (needed
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all visible paragraphs. Some Paragraphs above or below the screen (needed
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for page up/down) and computed as needed.
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tm::redoParagraph will call Inset::metrics for each inset. In the case
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@ -155,8 +135,9 @@ all the paragraphs of the inset.
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** Drawing the work area.
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This is done in bv::draw. This method is triggered mainly by
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Buffer::changed, which draws all the work areas that show the given buffer.
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This is done in bv::draw. This method is triggered by a paint event,
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mainly called through Buffer::changed, which draws all the work areas
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that show the given buffer.
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Note that, When Buffer::changed is called outside of
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bv::processUpdateFlags, it is not clear whether the update strategy
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@ -186,3 +167,6 @@ The action depends on the update strategy:
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+ SingleParUpdate: only tries to repaint current paragraph in a way
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that is not yet very clear to me.
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BufferView::draw can also be called with a null painter from
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BufferView::updateMetrics().
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