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[Impeller] Color and monochrome glyphs should get their own atlases. #116818

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chinmaygarde opened this issue Dec 10, 2022 · 2 comments · Fixed by flutter/engine#41780
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[Impeller] Color and monochrome glyphs should get their own atlases. #116818

chinmaygarde opened this issue Dec 10, 2022 · 2 comments · Fixed by flutter/engine#41780
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e: impeller Impeller rendering backend issues and features requests engine flutter/engine repository. See also e: labels. P2 Important issues not at the top of the work list

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@chinmaygarde
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We assume all glyphs are full color and allocate an 8888 atlas. This is unnecessary in most cases and causes a quadrupling of glyph atlas texture memory.
@chinmaygarde chinmaygarde added engine flutter/engine repository. See also e: labels. P2 Important issues not at the top of the work list e: impeller Impeller rendering backend issues and features requests labels Dec 10, 2022
@chinmaygarde chinmaygarde added this to the Impeller on iOS milestone Dec 10, 2022
@chinmaygarde chinmaygarde mentioned this issue Dec 10, 2022
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@jonahwilliams
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We only conditionally use a full color atlas if there is at least one bitmap or colr font, but still there is a loss of efficiency if there is a single one. w.r.t. to this issue and issues for path based rendering, I think there is still a decision to make on how to split up a text run if there is a mix of monochrome glyphs, color/bitmap, or large (path based) glyphs

@chinmaygarde chinmaygarde removed this from the Impeller on iOS milestone Mar 1, 2023
@jonahwilliams jonahwilliams mentioned this issue May 5, 2023
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auto-submit bot pushed a commit to flutter/engine that referenced this issue May 10, 2023
@jonahwilliams
[Impeller] Use separate atlases and shaders for color and alpha (#41780)
688782f 
Creates a separate atlas context and cache for color and alpha bitmap glyphs. Removes SDF shader and uses separate shader for full color glyphs.

Requires #41754

Fixes flutter/flutter#116818
Fixes flutter/flutter#126101

This also fixes #39383 but for light text on a dark background. This problem crops up when we switch to a full color atlas. In this context, the chosen glyph color is important. But with the alpha channel only atlas, its irrelevant.

See diff:

![image](https://user-images.githubusercontent.com/8975114/236598809-f4434764-cd16-4489-9644-4e9a370de7ee.png)

Example app:

```dart
// Copyright 2014 The Flutter Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

import 'package:flutter/material.dart';
import 'package:flutter/widgets.dart';

void main() =>
  runApp(
    Container(
      alignment: Alignment.center,
     child: Text(
      '''
 (Unicode Conference)� ا�ذ� س�ع�د �� 10-12 آذار 1997 ب�د��ة ��ا����ت�س� أ��ا��ا. � س�ج�ع ا��ؤت�ر ب�� خبراء �� �ا�ة �طاعات ا�ص�اعة ع�� ا�شب�ة ا�عا���ة ا�تر��ت �������د� ح�ث ستت�� ع�� ا�صع�د�� ا�د��� �ا��ح�� ع�� حد س�اء ��ا�شة سب� استخدا� �����د �� ا��ظ� ا��ائ�ة ����ا �خص ا�تطب��ات ا�حاس�ب�ة� ا�خط�ط� تص��� ا��ص�ص �ا�ح�سبة �تعددة ا��غات.

������������� � � � �''',
textDirection: TextDirection.rtl, style: TextStyle(fontSize: 24, color: Colors.white),
     ),
    ),
  );

```
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This thread has been automatically locked since there has not been any recent activity after it was closed. If you are still experiencing a similar issue, please open a new bug, including the output of flutter doctor -v and a minimal reproduction of the issue.

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[Impeller] Use separate atlases and shaders for color and alpha jonahwilliams/engine
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@chinmaygarde @jonahwilliams