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8649ac7fe6
* fix handling of boundary situations in Row::Elements::x2pos; * fix handling of boundary situations in TextMetrics::getColumnNearX; * make sure to always use Font::isVisibleRightToLeft instead of Font::isRightToLeft; * Improve debug messages.
68 lines
2.5 KiB
Plaintext
68 lines
2.5 KiB
Plaintext
This branch is where I (jmarc) try to implement string_wise metrics
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computation. This is done through a series of cleanups. The goal is to
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have both good metrics computation (and font with proper kerning and
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ligatures) and better performance than what we have with
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force_paint_single_char.
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Currently everything is supposed to work for LTR text, and RTL text
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should work too except possibly metrics with Arabic and Hebrew fonts.
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We'll see what to do after some feedback.
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What is done:
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* Make TextMetrics methods operate on Row objects: breakRow and
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setRowHeight instead of rowBreakPoint and rowHeight.
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* Change breakRow operation to operate on text strings on which
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metrics are computed. The list of elements is stored in the row
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object in visual ordering, not logical.
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* Re-implement cursorX and getColumnNearX using row elements.
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* Implement proper string metrics computation (with cache), when
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lyxrc.force_paint_single_char is false. In this case, remove also
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useless workarounds which disable kerning and ligatures.
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Next steps:
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* check what happens with arabic and/or hebrew text. There may be some
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problems related to compose characters. I suspect that some code is
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needed in FontMetrics::width.
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* Get rid of old code in cursorX and getColumnNearX; it has been
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kept for comparison purpose, guarded with KEEP_OLD_METRICS_CODE in
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order to check computations.
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* rename getColumnNearX to getPosNearX or x2pos (and change code
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accordingly). It does not make sense to return a position relative
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to the start of row, since nobody needs this.
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* Re-implement row painting using row elements. This is not difficult
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in principle, but the code is intricate and needs some careful
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analysis. First thing that needs to be done is to break row elements
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with the same criterions. Currently TextMetrics::breakRow does not
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consider on-the-fly spellchecking and selection changes, but it is
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not clear to me that it is required.
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* Profile and see how performance can be improved.
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Difference in behavior (aka bug fixes)
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* end of paragraph markers metrics are computed with the font of the
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actual text, not default font.
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* When cursor is after a LTR separator just before a RTL chunk, the
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cursor position is computed better with the new code.
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Other differences (aka real bugs)
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* there are still difference in what breaks words. In particular,
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RowPainter breaks strings at: selection end, spellchecking
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extremities.
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* when clicking in the right margin, GetColumnNearX does not return
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the same value as before.
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