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7734270163
Do not cut strings at separators in RowPainter when text is not justified. This speeds-up painting by reducing the number of strings to draw. Do also a modest cleanup of paintChar (remove dubious optimization).
104 lines
3.9 KiB
Plaintext
104 lines
3.9 KiB
Plaintext
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!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
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PLEASE DO NOT DO WORK ON TOP OF THIS BRANCH.
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I INTEND TO REWRITE HISTORY LATER!!!
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!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
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This branch is where I (jmarc) try to implement string-wise metrics
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computation. The goal is to have both good metrics computation (and
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font with proper kerning and ligatures) and better performance than
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what we have with force_paint_single_char. Moreover there has been
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some code factorization in TextMetrics, where the same row-breaking
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algorithm was basically implemented 3 times.
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Currently everything is supposed to work for both LTR and RTL text.
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When KEEP_OLD_METRICS_CODE is defined in TextMetrics.cpp, the new code
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is tested against the old one in getPosNearX and cursorX. This can be
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helpful when looking for discrepancies between the algorithms. Note
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that this only makes sense when force_paint_single_char=true, since
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this enforces char-by-char metrics computation.
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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 at strings level to compute
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metrics The list of elements is stored in the row object in visual
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ordering, not logical. This will eventually allow to get rid of the
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Bidi class.
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* rename getColumnNearX to getPosNearX (and change code accordingly).
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It does not make sense to return a position relative to the start of
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row, since nobody needs this.
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* Re-implement cursorX and getPosNearX 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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* when lyxrc.force_paint_single_char is false, draw also RtL text
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string-wise. This both speeds-up drawing and prepares for code
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removal, since we now rely on Qt to do things we use to do by
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ourselves (see isArabic* and isHebrew* code in Encodings.cpp).
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* Do not cut strings at separators in RowPainter when text is not
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justified. This speeds-up painting by reducing the number of strings
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to draw.
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Next steps:
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* get lots of testing.
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* Get rid of old code in cursorX and getPosNearX; 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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* Profile and see how performance can be improved.
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Steps for later (aka out of the scope of this branch):
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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. The first thing that needs to be done is to break row
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elements with the same criteria. Currently breakRow does not
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consider on-the-fly spell-checking and selection changes, but it is
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not clear to me that it is required. Moreover, this thing would only
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work if we are sure that the Row object is up-to-date when drawing
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happens. This depends on the update machinery.
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This would allow to get rid of the Bidi code.
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Known bugs:
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* When selecting text, the display seems to move around. This is
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because partly selected words are drawn in two parts, and in case
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like "ef|fort" or "V|AN", there are some ligature or kerning effects
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that change the display. I am not sure yet how to fix that.
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* there are other differences in what breaks words. In particular,
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RowPainter breaks strings at spell-checking extremities. This seems
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to be harmless.
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* when clicking in the right margin, getPosNearX does not return
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the same value as before. I am not sure whether this is important.
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Other differences 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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* in RtL paragraphs, the end-of-paragraph marker does not move the row
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to the right anymore (ticket #9040).
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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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