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This is handled by Qt now. Note that a small optimization (do not draw text that is to the left of WorkArea) is removed because it cannot be guaranteed to be exact anymore. It was probably not very useful anyway, and would become useless once the RowPainter is rewritten to use Row information. Update 00README_STR_METRICS_BRANCH.
85 lines
3.1 KiB
Plaintext
85 lines
3.1 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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The bugs fixed and caused by this branch are tracked at ticket #9003:
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http://www.lyx.org/trac/ticket/9003
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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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* Do not honor lyxrc.force_paint_single_char anymore. This is a
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workaround that is not necessary anymore.
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* Implement proper string metrics computation (with cache). Remove
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useless workarounds which disable kerning and ligatures.
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* Draw also RtL text string-wise. This speeds-up drawing.
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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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* Do not cut strings at selection boundary in RowPainter. This avoids
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ligature/kerning breaking in latin text, and bad rendering problems
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in Arabic.
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* Remove homebrew Arabic and Hebrew support from Encoding.cpp. We now
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rely on Qt to do handle complex scripts.
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Next steps:
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* Get rid of LyXRC::force_paint_single_char, which is not used anymore
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in the source.
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* Maybe get rid of LyXRC::rtl_support, which does not have a real use case.
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* Fix bugs uncovered by testing.
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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, but it is not clear to me that
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it is required. Moreover, this thing would only work if we are sure
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that the Row object is up-to-date when drawing happens. This depends
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on the update machinery.
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This would allow to get rid of the Bidi.cpp code.
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* Change Row object to operate only on integers and not doubles. Then,
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rewrite the computation of spacing in justified paragraphs so that
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strings can be drawn without cutting at separators. This will improve
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performance.
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