Tab stops by WilliamDGH · Pull Request #934 · linebender/parley

WilliamDGH · 2026-10-28T05:00:08Z

Implement tab stops, which fixes issue 302.

LLM Contributions:

LLM did the research on CSS Text 4 and Blink's Font::TabWidth.
LLM created an implementation plan, a reference implementation and all test files.
I wrote the implementation code by hand following that plan.

What is it

Preserved tabs (U+0009) now advance to the next tab stop, following CSS tab-size. A tab shapes to no glyphs and a zero advance like a newline. The line breaker computes its advance when it reaches it and stores it per line, and EffectiveSpacing adds it back on read, like justification.

parley_engine

Changed shaping so a tab cluster has no glyphs and a zero advance, like a newline, instead of whatever glyph the font maps U+0009 to. Its width is left to the layout engine.

parley

Added StyleProperty::TabSize(TabSize). TabSize { size, skip_threshold } holds two lengths in layout units, scaled like other lengths and passed from TextStyle through the resolved styles to layout::Style. size defaults to 0.0, so tabs take no space until a size is set. A tab whose next stop is closer than skip_threshold skips to the one after it (one stop at most); when unset, the threshold is half the root style's font size, resolved once from the style table's root entry.
Added layout::tab::tab_advance to compute the distance to the next tab stop.
Changed the line breaker to size each tab when it reaches it and record the advance per line in LayoutData::tab_advances (each LineData owns a range, like aligned_subtree_offsets). Tabs with no advance get no entry. Backtracking to an earlier break, revert_to and a new layout all truncate the table.
Added the line's justification and tab advances as fields of EffectiveSpacing, which adds a tab's recorded advance as its after gap on read, like justification (a binary search over the line's entries). Hanging whitespace, run and cluster advances, glyph positioning and hit testing all go through it.
Changed Spacing::gaps to give tabs no letter or word spacing of their own, as CSS puts that spacing into the tab size's unit rather than around the tab.
Changed GlyphRunIter to end a glyph run at a glyphless advance and shift the next run by it, and to count spacing gaps for glyphless atoms like the breaker does.
Changed ContentWidthsMeasurer to size tabs from each constraint's running width, tracking hanging whitespace per constraint, so it keeps matching the breaker.
Declared parley/src/tests/test_layout.rs in tests/mod.rs.

Changelog

Added

StyleProperty::TabSize: preserved tabs advance to tab stops following CSS tab-size, with a configurable skip threshold. Tabs take no space until a tab size is set.

Changed

parley_engine: tabs shape to no glyphs and a zero advance, like newlines.

parley_engine: check that marks and joiners after a tab leave it glyphless

nicoburns · 2026-10-28T13:44:07Z

Blitz WPT results are looking generally good (+69 -20). See DioxusLabs/blitz#1313.

Benchmark results are not so great (roughly +20% on line-breaking, and content widths, and +10% glyph iteration). I suspect we can do better than this.

phase	base	#934	Δ
build	~43.9	~44.4	~+1%
break+align	~1.99	~2.45	+23%
widths	~0.90	~0.95	+5%
widths spaced	~1.00	~1.19	+18%
glyph-iter	~1.94	~2.16	+11%

nicoburns · 2026-10-28T17:12:21Z

I haven't fully reviewed the changes yet, but DioxusLabs#96 has this down to closer to 2%.

@WilliamDGH feel free to incorporate any of those changes into your branch as you see fit. And also as a general point, I didn't have to do much more than point my agent at the PR and tell it to fix the regressions to get these results. Would recommend!

WilliamDGH · 2026-10-29T01:29:09Z

I haven't fully reviewed the changes yet, but DioxusLabs#96 has this down to closer to 2%.

@WilliamDGH feel free to incorporate any of those changes into your branch as you see fit. And also as a general point, I didn't have to do much more than point my agent at the PR and tell it to fix the regressions to get these results. Would recommend!

Thanks @nicoburns , I will take a look of that PR and try to fix the benchmark results.

…tabs

WilliamDGH · 2026-10-29T07:13:53Z

Added 3 commits that recover the regressions on text without tabs, based on DioxusLabs/parley#96 (thanks @nicoburns).

Ran Tango benchmark on my Mac and this is the results:

Group	before	now
Line Breaking (12 rows)	+6.5 .. +18.7	+0.1 .. +4.8
Content Widths uniform / mixed (18)	+7.0 .. +25.9	-8.5 .. +7.9 (latin 8000 mixed +5.7 / +7.9 in both runs)
Content Widths spacing (3)	+5.2 .. +15.7	+1.8 .. +7.2
Page Content Widths (3)	+13.8 .. +21.7	-4.9 .. +7.0
Page Break / Resize (6)	+9.7 .. +16.8	-0.7 .. +1.5
Glyph Runs + Page Glyph Runs (11)	-5.3 .. +9.2	-9.1 .. -0.6
Query Cursor line down + up (4), not touched	+2.4 .. +4.0	+2.7 .. +4.4
everything else	within ±2	within ±1.5

Full Tango output, this branch vs merge-base (102 rows, -t 2)

Default Style - arabic 20 characters               [   8.3 us ...   8.2 us ]      -0.49%
Default Style - latin 20 characters                [   3.8 us ...   3.9 us ]      +1.45%*
Default Style - japanese 20 characters             [   7.1 us ...   7.2 us ]      +1.11%*
Default Style - arabic 400 characters              [ 167.4 us ... 167.3 us ]      -0.06%
Default Style - latin 400 characters               [  54.9 us ...  55.0 us ]      +0.19%
Default Style - japanese 400 characters            [ 125.7 us ... 126.0 us ]      +0.26%
Default Style - arabic 8000 characters             [   3.4 ms ...   3.4 ms ]      +0.04%
Default Style - latin 8000 characters              [   1.1 ms ...   1.1 ms ]      +0.71%
Default Style - japanese 8000 characters           [   2.4 ms ...   2.4 ms ]      +0.12%
Styled - arabic 20 characters                      [   9.9 us ...   9.8 us ]      -0.68%
Styled - latin 20 characters                       [   5.4 us ...   5.4 us ]      -0.12%
Styled - japanese 20 characters                    [   8.1 us ...   8.1 us ]      -0.10%
Styled - arabic 400 characters                     [ 183.3 us ... 181.2 us ]      -1.15%*
Styled - latin 400 characters                      [  70.0 us ...  70.2 us ]      +0.29%
Styled - japanese 400 characters                   [ 138.4 us ... 137.9 us ]      -0.32%
Styled - arabic 8000 characters                    [   3.8 ms ...   3.8 ms ]      -0.96%
Styled - latin 8000 characters                     [   1.4 ms ...   1.4 ms ]      +0.19%
Styled - japanese 8000 characters                  [   2.7 ms ...   2.7 ms ]      +0.01%
Glyph Runs - latin 8000 characters, uniform        [  45.6 us ...  43.3 us ]      -5.14%*
Glyph Runs - latin 8000 characters, non-splitting every 1 chars [ 142.0 us ... 139.2 us ]      -1.98%*
Glyph Runs - latin 8000 characters, non-splitting every 16 chars [  51.7 us ...  49.3 us ]      -4.76%*
Glyph Runs - latin 8000 characters, splitting every 1 chars [ 210.6 us ... 199.2 us ]      -5.43%*
Glyph Runs - latin 8000 characters, splitting every 16 chars [  54.7 us ...  52.9 us ]      -3.16%*
Glyph Runs - arabic 8000 characters, mixed         [ 160.6 us ... 154.6 us ]      -3.74%*
Glyph Runs - latin 8000 characters, mixed          [  70.0 us ...  68.2 us ]      -2.63%*
Glyph Runs - japanese 8000 characters, mixed       [ 135.6 us ... 133.9 us ]      -1.20%*
Content Widths - arabic 20 characters, uniform     [ 100.3 ns ...  99.3 ns ]      -1.04%*
Content Widths - latin 20 characters, uniform      [  59.3 ns ...  63.4 ns ]      +6.82%*
Content Widths - japanese 20 characters, uniform   [ 100.3 ns ... 102.0 ns ]      +1.66%*
Content Widths - arabic 400 characters, uniform    [   1.6 us ...   1.6 us ]      +1.71%*
Content Widths - latin 400 characters, uniform     [ 923.2 ns ... 957.6 ns ]      +3.73%*
Content Widths - japanese 400 characters, uniform  [   1.4 us ...   1.3 us ]      -8.51%*
Content Widths - arabic 8000 characters, uniform   [  29.8 us ...  30.6 us ]      +2.61%*
Content Widths - latin 8000 characters, uniform    [  18.8 us ...  18.5 us ]      -1.35%*
Content Widths - japanese 8000 characters, uniform [  25.1 us ...  23.9 us ]      -4.66%*
Content Widths - arabic 20 characters, mixed       [ 105.2 ns ... 107.9 ns ]      +2.54%*
Content Widths - latin 20 characters, mixed        [  68.1 ns ...  70.7 ns ]      +3.83%*
Content Widths - japanese 20 characters, mixed     [ 111.6 ns ... 114.9 ns ]      +3.02%*
Content Widths - arabic 400 characters, mixed      [   1.6 us ...   1.7 us ]      +6.61%*
Content Widths - latin 400 characters, mixed       [   1.1 us ...   1.1 us ]      -1.37%*
Content Widths - japanese 400 characters, mixed    [   1.6 us ...   1.5 us ]      -3.59%*
Content Widths - arabic 8000 characters, mixed     [  32.0 us ...  32.9 us ]      +3.02%*
Content Widths - latin 8000 characters, mixed      [  20.7 us ...  21.9 us ]      +5.70%*
Content Widths - japanese 8000 characters, mixed   [  31.0 us ...  29.1 us ]      -5.97%*
Content Widths - arabic 8000 characters, spacing   [  33.2 us ...  35.1 us ]      +5.80%*
Content Widths - latin 8000 characters, spacing    [  23.6 us ...  25.3 us ]      +7.16%*
Content Widths - japanese 8000 characters, spacing [  33.0 us ...  33.9 us ]      +2.75%*
Word + Letter Spacing - arabic 20 characters       [   8.4 us ...   8.3 us ]      -1.30%*
Word + Letter Spacing - latin 20 characters        [   3.9 us ...   3.9 us ]      +0.67%
Word + Letter Spacing - japanese 20 characters     [   7.5 us ...   7.4 us ]      -1.08%*
Word + Letter Spacing - arabic 400 characters      [ 171.1 us ... 171.3 us ]      +0.13%
Word + Letter Spacing - latin 400 characters       [  54.4 us ...  54.6 us ]      +0.40%
Word + Letter Spacing - japanese 400 characters    [ 125.4 us ... 125.0 us ]      -0.30%
Word + Letter Spacing - arabic 8000 characters     [   3.4 ms ...   3.4 ms ]      +0.32%
Word + Letter Spacing - latin 8000 characters      [   1.1 ms ...   1.1 ms ]      -0.11%
Word + Letter Spacing - japanese 8000 characters   [   2.4 ms ...   2.4 ms ]      -0.04%
Repeated Justification - latin 8000 characters     [  22.1 us ...  22.3 us ]      +0.79%
Line Breaking - arabic 8000 characters, narrow     [ 161.0 us ... 164.1 us ]      +1.93%*
Line Breaking - arabic 8000 characters, wider      [  92.0 us ...  92.9 us ]      +0.89%
Line Breaking - arabic 8000 characters, unwrapped  [  73.3 us ...  74.6 us ]      +1.83%*
Line Breaking - latin 8000 characters, narrow      [ 130.5 us ... 134.2 us ]      +2.84%*
Line Breaking - latin 8000 characters, wider       [  62.6 us ...  62.6 us ]      +0.07%
Line Breaking - latin 8000 characters, unwrapped   [  40.5 us ...  42.3 us ]      +4.32%*
Line Breaking - japanese 8000 characters, narrow   [ 138.7 us ... 141.0 us ]      +1.65%*
Line Breaking - japanese 8000 characters, wider    [  90.9 us ...  91.8 us ]      +1.04%*
Line Breaking - japanese 8000 characters, unwrapped [  77.4 us ...  78.1 us ]      +0.87%
Line Breaking - arabic 8000 characters, wrapped + spacing [  97.9 us ...  99.2 us ]      +1.26%*
Line Breaking - latin 8000 characters, wrapped + spacing [  69.9 us ...  69.3 us ]      -0.87%
Line Breaking - japanese 8000 characters, wrapped + spacing [  95.8 us ...  96.5 us ]      +0.71%
Long Line - arabic                                 [   3.4 ms ...   3.4 ms ]      -0.71%
Long Line Justify - arabic                         [   3.4 ms ...   3.4 ms ]      -0.53%
Long Line - latin                                  [   1.1 ms ...   1.1 ms ]      +0.53%
Long Line Justify - latin                          [   1.1 ms ...   1.1 ms ]      +0.57%
Long Line - japanese                               [   2.4 ms ...   2.4 ms ]      -0.08%
Long Line Justify - japanese                       [   2.4 ms ...   2.4 ms ]      -0.19%
Page Full - arabic 8000 characters                 [   3.6 ms ...   3.6 ms ]      -0.26%
Page Full - latin 8000 characters                  [   1.2 ms ...   1.2 ms ]      +0.57%
Page Full - japanese 8000 characters               [   2.8 ms ...   2.8 ms ]      -0.04%
Page Build - arabic 8000 characters                [   3.3 ms ...   3.3 ms ]      -0.49%
Page Build - latin 8000 characters                 [   1.0 ms ...   1.0 ms ]      +0.56%
Page Build - japanese 8000 characters              [   2.5 ms ...   2.5 ms ]      -1.01%*
Page Content Widths - arabic 8000 characters       [  29.7 us ...  31.8 us ]      +6.98%*
Page Content Widths - latin 8000 characters        [  18.7 us ...  19.2 us ]      +2.14%*
Page Content Widths - japanese 8000 characters     [  28.6 us ...  27.2 us ]      -4.91%*
Page Break - arabic 8000 characters                [  77.7 us ...  78.2 us ]      +0.72%
Page Break - latin 8000 characters                 [  49.4 us ...  49.1 us ]      -0.66%
Page Break - japanese 8000 characters              [  94.6 us ...  94.9 us ]      +0.31%
Page Resize - arabic 8000 characters               [  80.7 us ...  81.6 us ]      +1.18%*
Page Resize - latin 8000 characters                [  51.5 us ...  51.7 us ]      +0.37%
Page Resize - japanese 8000 characters             [  96.3 us ...  96.2 us ]      -0.09%
Page Glyph Runs - arabic 8000 characters           [ 146.0 us ... 142.0 us ]      -2.75%*
Page Glyph Runs - latin 8000 characters            [  47.8 us ...  46.0 us ]      -3.69%*
Page Glyph Runs - japanese 8000 characters         [ 115.6 us ... 115.0 us ]      -0.55%
Query Cursor - arabic 8000 characters, next visual [  40.0 us ...  40.1 us ]      +0.34%
Query Cursor - latin 8000 characters, next visual  [  50.2 us ...  50.1 us ]      -0.19%
Query Cursor - japanese 8000 characters, next visual [  41.8 us ...  42.0 us ]      +0.56%
Query Cursor - arabic 8000 characters, line down + up [  58.9 us ...  61.5 us ]      +4.39%*
Query Cursor - latin 8000 characters, line down + up [ 190.7 us ... 195.7 us ]      +2.67%*
Query Cursor - japanese 8000 characters, line down + up [  58.4 us ...  60.4 us ]      +3.50%*
Query Cursor - latin 8000 characters, line down + up, long lines [   1.6 ms ...   1.6 ms ]      +4.37%*
Query Cursor - latin 8000 characters, from byte index [ 982.8 ns ... 952.9 ns ]      -3.04%*
Fontique - system fonts init (CoreText)            [  50.5 ms ...  50.4 ms ]      -0.17%

Full Tango output, this branch before the performance fix vs merge-base (102 rows, -t 2)

Default Style - arabic 20 characters               [   9.0 us ...   9.1 us ]      +1.11%*
Default Style - latin 20 characters                [   4.2 us ...   4.4 us ]      +4.98%*
Default Style - japanese 20 characters             [   7.9 us ...   7.9 us ]      +0.27%
Default Style - arabic 400 characters              [ 187.0 us ... 191.1 us ]      +2.19%*
Default Style - latin 400 characters               [  58.8 us ...  65.9 us ]     +12.03%*
Default Style - japanese 400 characters            [ 131.8 us ... 132.6 us ]      +0.55%
Default Style - arabic 8000 characters             [   3.8 ms ...   3.9 ms ]      +2.63%*
Default Style - latin 8000 characters              [   1.2 ms ...   1.3 ms ]     +12.14%*
Default Style - japanese 8000 characters           [   2.6 ms ...   2.6 ms ]      +0.86%
Styled - arabic 20 characters                      [  10.6 us ...  10.5 us ]      -1.60%*
Styled - latin 20 characters                       [   5.9 us ...   5.9 us ]      +0.20%
Styled - japanese 20 characters                    [   8.9 us ...   8.9 us ]      -1.08%*
Styled - arabic 400 characters                     [ 193.6 us ... 192.5 us ]      -0.56%
Styled - latin 400 characters                      [  74.9 us ...  75.8 us ]      +1.18%*
Styled - japanese 400 characters                   [ 148.0 us ... 148.1 us ]      +0.08%
Styled - arabic 8000 characters                    [   4.1 ms ...   4.1 ms ]      -0.46%
Styled - latin 8000 characters                     [   1.5 ms ...   1.5 ms ]      +1.44%*
Styled - japanese 8000 characters                  [   2.9 ms ...   2.9 ms ]      +0.19%
Glyph Runs - latin 8000 characters, uniform        [  47.3 us ...  47.7 us ]      +0.88%
Glyph Runs - latin 8000 characters, non-splitting every 1 chars [ 145.7 us ... 139.2 us ]      -4.48%*
Glyph Runs - latin 8000 characters, non-splitting every 16 chars [  53.7 us ...  58.7 us ]      +9.19%*
Glyph Runs - latin 8000 characters, splitting every 1 chars [ 208.5 us ... 197.5 us ]      -5.28%*
Glyph Runs - latin 8000 characters, splitting every 16 chars [  56.4 us ...  58.5 us ]      +3.71%*
Glyph Runs - arabic 8000 characters, mixed         [ 162.6 us ... 161.4 us ]      -0.72%
Glyph Runs - latin 8000 characters, mixed          [  71.1 us ...  70.4 us ]      -0.87%
Glyph Runs - japanese 8000 characters, mixed       [ 134.8 us ... 131.7 us ]      -2.28%*
Content Widths - arabic 20 characters, uniform     [ 130.3 ns ... 139.5 ns ]      +7.03%*
Content Widths - latin 20 characters, uniform      [  66.9 ns ...  79.1 ns ]     +18.28%*
Content Widths - japanese 20 characters, uniform   [ 145.0 ns ... 159.1 ns ]      +9.71%*
Content Widths - arabic 400 characters, uniform    [   1.8 us ...   2.1 us ]     +16.56%*
Content Widths - latin 400 characters, uniform     [   1.0 us ...   1.2 us ]     +22.20%*
Content Widths - japanese 400 characters, uniform  [   1.7 us ...   2.0 us ]     +17.77%*
Content Widths - arabic 8000 characters, uniform   [  42.6 us ...  48.8 us ]     +14.47%*
Content Widths - latin 8000 characters, uniform    [  20.4 us ...  24.7 us ]     +21.44%*
Content Widths - japanese 8000 characters, uniform [  35.5 us ...  41.7 us ]     +17.55%*
Content Widths - arabic 20 characters, mixed       [ 203.5 ns ... 219.0 ns ]      +7.61%*
Content Widths - latin 20 characters, mixed        [  82.1 ns ...  98.0 ns ]     +19.33%*
Content Widths - japanese 20 characters, mixed     [ 185.7 ns ... 200.9 ns ]      +8.20%*
Content Widths - arabic 400 characters, mixed      [   2.4 us ...   2.7 us ]     +11.70%*
Content Widths - latin 400 characters, mixed       [   1.2 us ...   1.4 us ]     +25.92%*
Content Widths - japanese 400 characters, mixed    [   2.3 us ...   2.7 us ]     +13.28%*
Content Widths - arabic 8000 characters, mixed     [  41.9 us ...  48.2 us ]     +15.00%*
Content Widths - latin 8000 characters, mixed      [  22.9 us ...  28.5 us ]     +24.73%*
Content Widths - japanese 8000 characters, mixed   [  36.8 us ...  42.7 us ]     +16.17%*
Content Widths - arabic 8000 characters, spacing   [  37.0 us ...  42.8 us ]     +15.68%*
Content Widths - latin 8000 characters, spacing    [  24.9 us ...  26.6 us ]      +6.88%*
Content Widths - japanese 8000 characters, spacing [  36.7 us ...  38.6 us ]      +5.22%*
Word + Letter Spacing - arabic 20 characters       [   9.7 us ...   9.4 us ]      -3.07%*
Word + Letter Spacing - latin 20 characters        [   4.6 us ...   4.4 us ]      -4.73%*
Word + Letter Spacing - japanese 20 characters     [   9.3 us ...   9.3 us ]      +0.30%
Word + Letter Spacing - arabic 400 characters      [ 193.9 us ... 190.0 us ]      -2.01%*
Word + Letter Spacing - latin 400 characters       [  67.7 us ...  61.7 us ]      -8.89%*
Word + Letter Spacing - japanese 400 characters    [ 144.6 us ... 143.9 us ]      -0.49%
Word + Letter Spacing - arabic 8000 characters     [   4.1 ms ...   4.1 ms ]      -1.42%*
Word + Letter Spacing - latin 8000 characters      [   1.3 ms ...   1.2 ms ]      -8.86%*
Word + Letter Spacing - japanese 8000 characters   [   2.9 ms ...   2.9 ms ]      -0.34%
Repeated Justification - latin 8000 characters     [  24.9 us ...  25.1 us ]      +0.54%
Line Breaking - arabic 8000 characters, narrow     [ 200.9 us ... 213.9 us ]      +6.48%*
Line Breaking - arabic 8000 characters, wider      [ 104.7 us ... 113.4 us ]      +8.33%*
Line Breaking - arabic 8000 characters, unwrapped  [  88.1 us ...  97.3 us ]     +10.47%*
Line Breaking - latin 8000 characters, narrow      [ 144.5 us ... 159.9 us ]     +10.65%*
Line Breaking - latin 8000 characters, wider       [  68.6 us ...  80.1 us ]     +16.70%*
Line Breaking - latin 8000 characters, unwrapped   [  45.7 us ...  54.3 us ]     +18.72%*
Line Breaking - japanese 8000 characters, narrow   [ 144.7 us ... 160.7 us ]     +11.05%*
Line Breaking - japanese 8000 characters, wider    [ 100.0 us ... 114.2 us ]     +14.29%*
Line Breaking - japanese 8000 characters, unwrapped [  88.6 us ... 102.1 us ]     +15.22%*
Line Breaking - arabic 8000 characters, wrapped + spacing [ 104.7 us ... 113.4 us ]      +8.35%*
Line Breaking - latin 8000 characters, wrapped + spacing [  71.6 us ...  82.9 us ]     +15.80%*
Line Breaking - japanese 8000 characters, wrapped + spacing [  99.0 us ... 112.5 us ]     +13.72%*
Long Line - arabic                                 [   3.6 ms ...   3.6 ms ]      +0.67%
Long Line Justify - arabic                         [   3.6 ms ...   3.5 ms ]      -1.03%*
Long Line - latin                                  [   1.1 ms ...   1.1 ms ]      +0.98%
Long Line Justify - latin                          [   1.1 ms ...   1.1 ms ]      +1.38%*
Long Line - japanese                               [   2.5 ms ...   2.5 ms ]      +0.45%
Long Line Justify - japanese                       [   2.5 ms ...   2.5 ms ]      +0.18%
Page Full - arabic 8000 characters                 [   3.7 ms ...   3.7 ms ]      -1.02%*
Page Full - latin 8000 characters                  [   1.2 ms ...   1.2 ms ]      +0.84%
Page Full - japanese 8000 characters               [   3.0 ms ...   2.9 ms ]      -1.25%*
Page Build - arabic 8000 characters                [   3.5 ms ...   3.5 ms ]      -1.46%*
Page Build - latin 8000 characters                 [   1.1 ms ...   1.1 ms ]      +0.07%
Page Build - japanese 8000 characters              [   2.6 ms ...   2.6 ms ]      -0.40%
Page Content Widths - arabic 8000 characters       [  31.5 us ...  37.3 us ]     +18.51%*
Page Content Widths - latin 8000 characters        [  19.1 us ...  23.3 us ]     +21.65%*
Page Content Widths - japanese 8000 characters     [  34.4 us ...  39.1 us ]     +13.81%*
Page Break - arabic 8000 characters                [  79.4 us ...  87.3 us ]      +9.97%*
Page Break - latin 8000 characters                 [  50.4 us ...  58.9 us ]     +16.81%*
Page Break - japanese 8000 characters              [  99.1 us ... 113.4 us ]     +14.46%*
Page Resize - arabic 8000 characters               [  82.2 us ...  90.2 us ]      +9.73%*
Page Resize - latin 8000 characters                [  52.2 us ...  60.2 us ]     +15.34%*
Page Resize - japanese 8000 characters             [ 100.2 us ... 114.1 us ]     +13.93%*
Page Glyph Runs - arabic 8000 characters           [ 142.5 us ... 144.2 us ]      +1.17%*
Page Glyph Runs - latin 8000 characters            [  48.8 us ...  49.3 us ]      +1.08%*
Page Glyph Runs - japanese 8000 characters         [ 112.2 us ... 110.6 us ]      -1.45%*
Query Cursor - arabic 8000 characters, next visual [  40.5 us ...  40.5 us ]      -0.03%
Query Cursor - latin 8000 characters, next visual  [  50.9 us ...  50.9 us ]      -0.12%
Query Cursor - japanese 8000 characters, next visual [  42.9 us ...  42.8 us ]      -0.12%
Query Cursor - arabic 8000 characters, line down + up [  59.7 us ...  61.9 us ]      +3.71%*
Query Cursor - latin 8000 characters, line down + up [ 196.3 us ... 201.0 us ]      +2.39%*
Query Cursor - japanese 8000 characters, line down + up [  59.4 us ...  61.2 us ]      +3.06%*
Query Cursor - latin 8000 characters, line down + up, long lines [   1.6 ms ...   1.6 ms ]      +4.01%*
Query Cursor - latin 8000 characters, from byte index [   1.0 us ...   1.0 us ]      +0.06%
Fontique - system fonts init (CoreText)            [  48.0 ms ...  47.8 ms ]      -0.28%

…_cluster)

WilliamDGH added 29 commits October 22, 2026 16:50

parley_engine: shape tabs to a glyphless space advance

d57a025

parley: add the TabSize style property

f51be04

parley: add tab_advance for computing tab stop distances

90bae1c

parley: size tabs to tab stops in the line breaker

82acded

parley: position glyphs after a sized tab

0150a5d

parley: size tabs when measuring content widths

b8940cd

parley_tests: snapshot tab stops aligning columns

b71145d

parley_engine: replace shaped_clusters_mut with set_tab_advance

01188fc

parley_tests: lock tab stops in right-to-left text

46fc6b2

parley: size tabs ahead of the breaker's atom loop

42ecef3

parley: size tabs past newlines when breaking by length

c6cfbb4

parley: tidy up comments

0bbd260

parley: cap the tab look-ahead scan

415fb15

parley: keep tab stops lined up under justification

bffee9f

parley: fix tab doc references and the zero-size wording

1386185

parley: fix tab doc references and add tests

7459e60

parley: give tabs no letter or word spacing of their own

510de15

parley: make TabSize a length

2b2b027

parley_engine: shape tabs to a zero advance

98a8ad2

parley: size tabs in the line breaker and store the advances per line

21a73f3

parley_engine: remove set_tab_advance and has_tabs

0fd8024

parley: drop the tab-specific justification rule

29f87d3

parley: merge LineSpacing into EffectiveSpacing

6958edc

parley: make the tab's skip threshold part of TabSize

5e7952a

parley: record no advance for tabs without one

b01a81a

parley_engine: check that marks and joiners after a tab leave it glyphless

parley: trim the tab comments and docs to what they need to say

883c187

parley_tests: add an RTL snapshot

27596c5

parley: trim comments

9a19678

parley: add comment

4065fff

nicoburns mentioned this pull request Oct 28, 2026

Use Parley tab stops (linebender/parley#934) for CSS tab-size DioxusLabs/blitz#1313

Open

nicoburns mentioned this pull request Oct 28, 2026

Support tab-size: <number> on top of tab stops (linebender/parley#934) DioxusLabs/parley#95

Open

nicoburns mentioned this pull request Oct 28, 2026

Recover line-breaking and content-width performance of tab stops (linebender/parley#934) DioxusLabs/parley#96

Open

WilliamDGH added 3 commits October 29, 2026 16:31

parley: handle tabs once per atom in the line breaker, out of line

655a31c

parley: measure content widths with a tab-free loop for text without …

929381a

…tabs

parley: put the glyph atom first again in the glyph run loop

ca4a759

WilliamDGH added 2 commits October 30, 2026 10:31

Merge branch 'main' into tab-stops

d6cf855

parley: fix the merge with main (first_character was renamed to first…

951ee6f

…_cluster)

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Tab stops - #934

Tab stops#934
WilliamDGH wants to merge 34 commits into
linebender:mainfrom
WilliamDGH:tab-stops

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WilliamDGH commented Oct 28, 2026

What is it

parley_engine

parley

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