lyx_mirror/00README_STR_METRICS_BRANCH

This branch is where I (jmarc) try to implement string_wise metrics
computation. This is done through a series of cleanups. The expected
speed improvement will only be visible at the end of the road: indeed
for now we intend to keep unchanged behavior for testing purposes.

What is done:
* Make TextMetrics methods operate on Row objects: breakRow and
  setRowHeight instead of rowBreakPoint and rowHeight.

* change breakRow operation to operate on text strings on which
  metrics are computed. The list of elements is stored in the row object
  in visual ordering, not logical.

* re-implement cursorX using row elements

* re-implement getColumnNearX using row elements (boundary is not
  considered yet).

* Implement proper string metrics computation (with cache), when
  lyxrc.force_paint_single_char is false. In this case, remove also
  useless workarounds which disable kerning and ligatures.

Next steps:

* get rid of old code of cursorX and getColumnNearX (which have been
  kept for comparison purpose, guarded with KEEP_OLD_METRICS_CODE).

* re-implement row painting using row elements (can it be done?)

* profile and see how performance can be improved.

* Document the code

Difference in behavior
* end of paragraph markers metrics are computed with the font of the
  actual text, not default font. This will be extended to the other
  methods.

* When cursor is after a LtR separator just before a RtL chunk, the
  cursor posiiton is computed better with the new code.

Other differences that should be considered as bugs
* words longer than the screen are no monger broken at an arbitrary
  point. This is a problem for languages like chinese that do not use
  separators.

* Boundary is not taken in account properly in getColumnNearX
Add a readme file describing the state of the branch 2013-06-18 08:18:32 +00:00			`This branch is where I (jmarc) try to implement string_wise metrics`
			`computation. This is done through a series of cleanups. The expected`
			`speed improvement will only be visible at the end of the road: indeed`
			`for now we intend to keep unchanged behavior for testing purposes.`

			`What is done:`
			`* Make TextMetrics methods operate on Row objects: breakRow and`
Implement real string width computation Important features: * widths are cached in a map * old behavior is still used when lyxrc.force_paint_single_char is true. 2013-06-25 06:18:25 +00:00			`setRowHeight instead of rowBreakPoint and rowHeight.`

Add a readme file describing the state of the branch 2013-06-18 08:18:32 +00:00			`* change breakRow operation to operate on text strings on which`
Store in the Row object the list of elements it contains * Row now contains a vector of Elements * replace Row::dump by a proper << operator * the width is updated as elements are added * breakRow is reimplmented to use this infrastructure 2013-06-25 12:57:09 +00:00			`metrics are computed. The list of elements is stored in the row object`
Implement proper handling of RtL in Rows Now the row elements are sorted according to RtL/LtR. Some additional cleanup. 2013-07-16 22:59:34 +00:00			`in visual ordering, not logical.`
Implement real string width computation Important features: * widths are cached in a map * old behavior is still used when lyxrc.force_paint_single_char is true. 2013-06-25 06:18:25 +00:00
Convert cursorX() and computeRowMetrics() to the new scheme * convert cursorX to new scheme; old computation is still there for the sake of comparison. * use Row to compute separator width in computeRowMetrics; again, the old code is retained for now. * Get rid of rowWidth() 2013-07-17 22:25:08 +00:00			`* re-implement cursorX using row elements`

Re-implement getColumNearX using row elements The code is now so much shorter that it is scary... Expect that further changes will be necessary Cursor boundary is not handled yet. 2013-07-21 18:22:32 +00:00			`* re-implement getColumnNearX using row elements (boundary is not`
			`considered yet).`

Implement real string width computation Important features: * widths are cached in a map * old behavior is still used when lyxrc.force_paint_single_char is true. 2013-06-25 06:18:25 +00:00			`* Implement proper string metrics computation (with cache), when`
Re-implement getColumNearX using row elements The code is now so much shorter that it is scary... Expect that further changes will be necessary Cursor boundary is not handled yet. 2013-07-21 18:22:32 +00:00			`lyxrc.force_paint_single_char is false. In this case, remove also`
			`useless workarounds which disable kerning and ligatures.`
Add a readme file describing the state of the branch 2013-06-18 08:18:32 +00:00
			`Next steps:`
Implement real string width computation Important features: * widths are cached in a map * old behavior is still used when lyxrc.force_paint_single_char is true. 2013-06-25 06:18:25 +00:00
Convert cursorX() and computeRowMetrics() to the new scheme * convert cursorX to new scheme; old computation is still there for the sake of comparison. * use Row to compute separator width in computeRowMetrics; again, the old code is retained for now. * Get rid of rowWidth() 2013-07-17 22:25:08 +00:00			`* get rid of old code of cursorX and getColumnNearX (which have been`
Re-implement getColumNearX using row elements The code is now so much shorter that it is scary... Expect that further changes will be necessary Cursor boundary is not handled yet. 2013-07-21 18:22:32 +00:00			`kept for comparison purpose, guarded with KEEP_OLD_METRICS_CODE).`
Implement real string width computation Important features: * widths are cached in a map * old behavior is still used when lyxrc.force_paint_single_char is true. 2013-06-25 06:18:25 +00:00
			`* re-implement row painting using row elements (can it be done?)`

Add a readme file describing the state of the branch 2013-06-18 08:18:32 +00:00			`* profile and see how performance can be improved.`

Convert cursorX() and computeRowMetrics() to the new scheme * convert cursorX to new scheme; old computation is still there for the sake of comparison. * use Row to compute separator width in computeRowMetrics; again, the old code is retained for now. * Get rid of rowWidth() 2013-07-17 22:25:08 +00:00			`* Document the code`

Add a readme file describing the state of the branch 2013-06-18 08:18:32 +00:00			`Difference in behavior`
			`* end of paragraph markers metrics are computed with the font of the`
Implement proper handling of RtL in Rows Now the row elements are sorted according to RtL/LtR. Some additional cleanup. 2013-07-16 22:59:34 +00:00			`actual text, not default font. This will be extended to the other`
			`methods.`
Add a readme file describing the state of the branch 2013-06-18 08:18:32 +00:00
Convert cursorX() and computeRowMetrics() to the new scheme * convert cursorX to new scheme; old computation is still there for the sake of comparison. * use Row to compute separator width in computeRowMetrics; again, the old code is retained for now. * Get rid of rowWidth() 2013-07-17 22:25:08 +00:00			`* When cursor is after a LtR separator just before a RtL chunk, the`
			`cursor posiiton is computed better with the new code.`

Store in the Row object the list of elements it contains * Row now contains a vector of Elements * replace Row::dump by a proper << operator * the width is updated as elements are added * breakRow is reimplmented to use this infrastructure 2013-06-25 12:57:09 +00:00			`Other differences that should be considered as bugs`
Implement proper handling of RtL in Rows Now the row elements are sorted according to RtL/LtR. Some additional cleanup. 2013-07-16 22:59:34 +00:00			`* words longer than the screen are no monger broken at an arbitrary`
			`point. This is a problem for languages like chinese that do not use`
			`separators.`
Re-implement getColumNearX using row elements The code is now so much shorter that it is scary... Expect that further changes will be necessary Cursor boundary is not handled yet. 2013-07-21 18:22:32 +00:00
			`* Boundary is not taken in account properly in getColumnNearX`