Emoji make exception in TyperAnimatedTextKit

[eunjin3786]

════════ Exception caught by rendering library ═════════════════════════════════════════════════════
'dart:ui/painting.dart': Failed assertion: line 3968: '': is not true.

[awhitford]

Can you please provide some sample code and a stack trace? The above assertion is not very much to go on.

[eunjin3786]

@awhitford

Thankyou 👍

class SettingsWidget extends StatelessWidget {

  @override
  Widget build(BuildContext context) {
    return Padding(
        padding: EdgeInsets.all(10),
        child: Center(
          child: TyperAnimatedTextKit(
            text: ["hello world ☺️👍🍥️"],
            isRepeatingAnimation: true,
            speed: Duration(milliseconds: 60)
          ),
        )
    );
  }
}

════════ Exception caught by rendering library ═════════════════════════════════════════════════════
'dart:ui/painting.dart': Failed assertion: line 3968: '': is not true.
The relevant error-causing widget was:
TyperAnimatedTextKit file:///Users/kakao/Documents/onion_family/lib/widget/main/settings_widget.dart:14:18
The following RenderObject was being processed when the exception was fired: RenderParagraph#a695f relayoutBoundary=up3
parentData: (can use size)
constraints: BoxConstraints(0.0<=w<=394.0, 0.0<=h<=792.0)
size: Size(114.0, 27.0)
textAlign: start
textDirection: ltr
softWrap: wrapping at box width
overflow: clip
locale: en_US
maxLines: unlimited
text: TextSpan
inherit: false
color: label(color = Color(0xff000000), darkColor = Color(0xffffffff), resolved by: Builder)
debugLabel: label
color: Color(0xff000000)
darkColor: Color(0xffffffff)
last resolved: Builder
family: .SF Pro Text
size: 17.0
letterSpacing: -0.4
decoration: TextDecoration.none
"hello world ☺️👍?"
RenderObject: RenderParagraph#a695f relayoutBoundary=up3
parentData: (can use size)
constraints: BoxConstraints(0.0<=w<=394.0, 0.0<=h<=792.0)
size: Size(114.0, 27.0)
textAlign: start
textDirection: ltr
softWrap: wrapping at box width
overflow: clip
locale: en_US
maxLines: unlimited
text: TextSpan
inherit: false
color: label(color = Color(0xff000000), darkColor = Color(0xffffffff), resolved by: Builder)
debugLabel: label
color: Color(0xff000000)
darkColor: Color(0xffffffff)
last resolved: Builder
family: .SF Pro Text
size: 17.0
letterSpacing: -0.4
decoration: TextDecoration.none
"hello world ☺️👍?"
════════════════════════════════════════════════════════════════════════════════════════════════════

[awhitford]

This looks like the offending widget:

Animated-Text-Kit/lib/src/typer.dart

Lines 145 to 149 in fa78a43

	return Text(
	_texts[_index]['text'].substring(0, offset),
	style: widget.textStyle,
	textAlign: widget.textAlign,
	);

I see this message:

flutter: ══╡ EXCEPTION CAUGHT BY RENDERING LIBRARY ╞═════════════════════════════════════════════════════════
flutter: The following ArgumentError was thrown during performLayout():
flutter: Invalid argument(s): string is not well-formed UTF-16
flutter:
flutter: The relevant error-causing widget was:
flutter:   Text
flutter:   file:///Users/anthony/flutter/.pub-cache/hosted/pub.dartlang.org/animated_text_kit-2.3.0/lib/src/typer.dart:145:26
flutter:
flutter: When the exception was thrown, this was the stack:
flutter: #0      ParagraphBuilder.addText (dart:ui/text.dart:2178:7)
flutter: #1      TextSpan.build (package:flutter/src/painting/text_span.dart:208:15)
flutter: #2      TextPainter.layout (package:flutter/src/painting/text_painter.dart:560:14)
flutter: #3      RenderParagraph._layoutText (package:flutter/src/rendering/paragraph.dart:497:18)
flutter: #4      RenderParagraph._layoutTextWithConstraints (package:flutter/src/rendering/paragraph.dart:520:5)

This looks like a known issue: dart-lang/sdk#35798

This reminds me of the Flutter 1.22 announcement where they mentioned the characters package.

The String Length of '☺️👍🍥️' is not 3, but actually 7. However, it is only 3 Characters.

The solution is to rework the widget to use the new Characters package, rather than use String.substring.

[awhitford]

Note that the Typewriter has the same flaw and will also need to be fixed, but let's wait for the Typer fix to be reviewed first.

[awhitford]

PR #122 addresses Typewriter.