Clipping if only one character text overflows #99146

xu-baolin · 2022-02-25T10:25:11Z

packages/flutter/lib/src/painting/text_painter.dart

goderbauer · 2022-02-25T17:38:18Z

packages/flutter/lib/src/rendering/paragraph.dart

@@ -644,7 +650,7 @@ class RenderParagraph extends RenderBox
    size = constraints.constrain(textSize);

    final bool didOverflowHeight = size.height < textSize.height || textDidExceedMaxLines;
-    final bool didOverflowWidth = size.width < textSize.width;
+    final bool didOverflowWidth = size.width < textSize.width || size.width < _textPainter.longestLine;


Why would _textPainter.longestLine ever be smaller than textSize.width (which is _textPainter.size,width) for a one char long text? That seems odd. Is there a bug in how textPainter calculates its actual width?

We also have TextWidthBasis which essentially changed _textPainter.size.width to be _textPainter.longestLine. I am not too familiar with that setting, though.

/cc @justinmc who added it a while back.

Why would _textPainter.longestLine ever be smaller than textSize.width (which is _textPainter.size,width) for a one char long text? That seems odd. Is there a bug in how textPainter calculates its actual width?

The textPainter.size.width always returns the layout constraints.width, this should be the implementation of the engine layer. @LongCatIsLooong may know the details.

_textPainter.longestLine is the width of the longest line of actual text. _textPainter.width is either the same thing or the constraints width depending on TextWidthBasis (code) as you guys noted.

So it's possible and even common for _textPainter.longestLine to be shorter than _textPainter.width, for example:

Here _textPainter.longestLine is just the width of that single character (a few pixels), while _textPainter.width is the width of the green Container (100px).

So the condition in the code here (size.width < _textPainter.longestLine) makes sense to me. That will be true when the available space is less wide than a single character.

PS Sorry it took me so long to respond here! I'm bad with my notifications recently.

justinmc

LGTM 👍

Just a nit about an assert. The discussion around the width conditional seems ok to me.

packages/flutter/lib/src/painting/text_painter.dart

justinmc · 2022-03-22T17:06:44Z

packages/flutter/lib/src/rendering/paragraph.dart

@@ -644,7 +650,7 @@ class RenderParagraph extends RenderBox
    size = constraints.constrain(textSize);

    final bool didOverflowHeight = size.height < textSize.height || textDidExceedMaxLines;
-    final bool didOverflowWidth = size.width < textSize.width;
+    final bool didOverflowWidth = size.width < textSize.width || size.width < _textPainter.longestLine;


_textPainter.longestLine is the width of the longest line of actual text. _textPainter.width is either the same thing or the constraints width depending on TextWidthBasis (code) as you guys noted.

So it's possible and even common for _textPainter.longestLine to be shorter than _textPainter.width, for example:

Here _textPainter.longestLine is just the width of that single character (a few pixels), while _textPainter.width is the width of the green Container (100px).

So the condition in the code here (size.width < _textPainter.longestLine) makes sense to me. That will be true when the available space is less wide than a single character.

justinmc · 2022-03-22T17:07:23Z

packages/flutter/lib/src/rendering/paragraph.dart

@@ -644,7 +650,7 @@ class RenderParagraph extends RenderBox
    size = constraints.constrain(textSize);

    final bool didOverflowHeight = size.height < textSize.height || textDidExceedMaxLines;
-    final bool didOverflowWidth = size.width < textSize.width;
+    final bool didOverflowWidth = size.width < textSize.width || size.width < _textPainter.longestLine;


PS Sorry it took me so long to respond here! I'm bad with my notifications recently.

fluttergithubbot · 2022-03-23T08:20:05Z

This pull request is not suitable for automatic merging in its current state.

The status or check suite Google testing has failed. Please fix the issues identified (or deflake) before re-applying this label.

justinmc · 2022-03-23T15:58:27Z

The failed Google tests were a few visual diff tests where the rightmost pixel of some text had a very slight, unnoticeable change in opacity. It's slightly strange that this happened for text that wasn't a single character long, but probably just due to floating point math for the antialiasing. I've set the Google tests to "passing", but we'll have to accept the new reference images after merge.

xu-baolin · 2022-03-24T03:53:34Z

The failed Google tests were a few visual diff tests where the rightmost pixel of some text had a very slight, unnoticeable change in opacity. It's slightly strange that this happened for text that wasn't a single character long, but probably just due to floating point math for the antialiasing. I've set the Google tests to "passing", but we'll have to accept the new reference images after merge.

Interestingly, if this patch breaks things, it must be that size.width < _textPainter.longestLine is satisfied, and no clipping has occurred before. After clipping, the edges of the characters change slightly. I think this kind of scene is intended, right?

justinmc · 2022-03-30T22:56:35Z

I think it might be this: In the case where TextWidthBasis.longestLine is used and the parent's width tightly wraps the text, then size.width and _textPainter.longestLine should be equal. However, due to some floating point error in their calculation, one is very very slightly different, and size.width < _textPainter.longestLine is true. The text gets clipped, and some tiny subpixel change in the rendered text occurs.

Maybe we should try using something like applyFloatingPointHack here and see if it fixes the Google tests? Or maybe we should just consider it correct and say it should be clipped...

If you want to try the floating point hack thing, I can re-run the Google tests and see if it has any effect.

xu-baolin · 2022-03-31T13:08:50Z

I think it might be this: In the case where TextWidthBasis.longestLine is used and the parent's width tightly wraps the text, then size.width and _textPainter.longestLine should be equal. However, due to some floating point error in their calculation, one is very very slightly different, and size.width < _textPainter.longestLine is true. The text gets clipped, and some tiny subpixel change in the rendered text occurs.

Something's not quite right here, in this scenario, textSize.width is no smaller than _textPainter.longestLine because of applyFloatingPointHack, it is not possible that size.width >= textSize.width but size.width < _textPainter.longestLine

Could you help to file a test to repro the google test? Or just make this breaking intended?

I have no idea make which double value hack to check the test now, or do you have any thoughts?

xu-baolin · 2022-04-14T01:51:32Z

@justinmc Hey, Could we merge this and accept the new golden file? : )

…r#99146)

This reverts commit 08e467d.

) This reverts commit 08e467d (Google test failures after merge).

…" (#102092)" This reverts commit 8817521.

) (#102389) This reverts commit 08e467d (Google test failures after merge). Co-authored-by: Justin McCandless <[email protected]>

This reverts commit 8817521.

) Fixes a text clipping edge case.

…r#99146)" (flutter#102130)" This reverts commit 3f43d9f.

…" (#102130)" (#106967) This reverts commit 3f43d9f.

…" (#102130)" (#106964) This reverts commit 3f43d9f.

* Revert "Reland "Clipping if only one character text overflows (#99146)" (#102130)" This reverts commit 3f43d9f. * Revert "Implement frameData for TestWindow (#105537)" This reverts commit 21841d7.

flutter#102130) Fixes a text clipping edge case.

…r#99146)" (flutter#102130)" (flutter#106964) This reverts commit 3f43d9f.

…lutter#107168) * Revert "Reland "Clipping if only one character text overflows (flutter#99146)" (flutter#102130)" This reverts commit 3f43d9f. * Revert "Implement frameData for TestWindow (flutter#105537)" This reverts commit 21841d7.

flutter-dashboard bot added a: text input Entering text in a text field or keyboard related problems framework flutter/packages/flutter repository. See also f: labels. labels Feb 25, 2022

xu-baolin requested a review from goderbauer February 25, 2022 10:27

goderbauer reviewed Feb 25, 2022

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xu-baolin requested a review from justinmc March 1, 2022 09:01

justinmc approved these changes Mar 22, 2022

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xu-baolin added 2 commits March 23, 2022 14:06

++

f1ec3ed

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30b4570

xu-baolin force-pushed the xbl000225 branch from c6193be to 30b4570 Compare March 23, 2022 06:14

xu-baolin added the waiting for tree to go green label Mar 23, 2022

fluttergithubbot removed the waiting for tree to go green label Mar 23, 2022

LongCatIsLooong added the waiting for tree to go green label Apr 14, 2022

fluttergithubbot merged commit 08e467d into flutter:master Apr 14, 2022

engine-flutter-autoroll mentioned this pull request Apr 14, 2022

Roll Flutter from e2d12060a2bc to 08e467dde7a1 (1 revision) flutter/packages#1536

Merged

engine-flutter-autoroll added a commit to engine-flutter-autoroll/packages that referenced this pull request Apr 14, 2022

08e467d Clipping if only one character text overflows (flutter/flutte…

5650989

…r#99146)

engine-flutter-autoroll mentioned this pull request Apr 14, 2022

Roll Flutter from e2d12060a2bc to 08e467dde7a1 (1 revision) flutter/plugins#5268

Merged

engine-flutter-autoroll added a commit to engine-flutter-autoroll/plugins that referenced this pull request Apr 14, 2022

08e467d Clipping if only one character text overflows (flutter/flutte…

353e920

…r#99146)

justinmc added a commit that referenced this pull request Apr 18, 2022

Revert "Clipping if only one character text overflows (#99146)"

cc7ad72

This reverts commit 08e467d.

justinmc mentioned this pull request Apr 18, 2022

Revert "Clipping if only one character text overflows" #102092

Merged

justinmc added a commit that referenced this pull request Apr 18, 2022

Revert "Clipping if only one character text overflows (#99146)" (#102092

8817521

) This reverts commit 08e467d (Google test failures after merge).

xu-baolin added a commit that referenced this pull request Apr 19, 2022

Revert "Revert "Clipping if only one character text overflows (#99146)…

5408e68

…" (#102092)" This reverts commit 8817521.

godofredoc added a commit that referenced this pull request Apr 23, 2022

Revert "Clipping if only one character text overflows (#99146)" (#102092

7538e04

) (#102389) This reverts commit 08e467d (Google test failures after merge). Co-authored-by: Justin McCandless <[email protected]>

xu-baolin added a commit that referenced this pull request May 18, 2022

Reland "Clipping if only one character text overflows (#99146)"

e1f6ab1

This reverts commit 8817521.

justinmc pushed a commit that referenced this pull request Jun 29, 2022

Reland "Clipping if only one character text overflows (#99146)" (#102130

3f43d9f

) Fixes a text clipping edge case.

XilaiZhang added a commit to XilaiZhang/flutter that referenced this pull request Jul 1, 2022

Revert "Reland "Clipping if only one character text overflows (flutte…

031d597

…r#99146)" (flutter#102130)" This reverts commit 3f43d9f.

XilaiZhang added a commit to XilaiZhang/flutter that referenced this pull request Jul 1, 2022

Revert "Reland "Clipping if only one character text overflows (flutte…

9c54077

…r#99146)" (flutter#102130)" This reverts commit 3f43d9f.

XilaiZhang added a commit to XilaiZhang/flutter that referenced this pull request Jul 1, 2022

Revert "Reland "Clipping if only one character text overflows (flutte…

915ab5d

…r#99146)" (flutter#102130)" This reverts commit 3f43d9f.

XilaiZhang added a commit that referenced this pull request Jul 1, 2022

Revert "Reland "Clipping if only one character text overflows (#99146)…

03e2720

…" (#102130)" (#106967) This reverts commit 3f43d9f.

XilaiZhang added a commit that referenced this pull request Jul 1, 2022

Revert "Reland "Clipping if only one character text overflows (#99146)…

a7fe235

…" (#102130)" (#106964) This reverts commit 3f43d9f.

camsim99 pushed a commit to camsim99/flutter that referenced this pull request Aug 10, 2022

Reland "Clipping if only one character text overflows (flutter#99146)" (

c7c3f5d

flutter#102130) Fixes a text clipping edge case.

camsim99 pushed a commit to camsim99/flutter that referenced this pull request Aug 10, 2022

Revert "Reland "Clipping if only one character text overflows (flutte…

2a5faee

…r#99146)" (flutter#102130)" (flutter#106964) This reverts commit 3f43d9f.

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