feat: support customizing text attribute key and rendering

[LucasXu0]

• support customizing the text attributes key

For example, we want to embed a page icon and page link into the paragraph.

1. customize a new attributes for delta, here's {'mention': {'id': 'page_id'}}

    final document = Document.blank()
      ..addParagraph(
        builder: (index) {
          return Delta()
            ..insert(
              '\$',
              attributes: {
                'mention': {'id': 'PAGE_ID'},
              },
            );
        },
      );

2. customize the textSpanDecorator function inside editor style, VERY IMPORTANT: The length of the text must be 1 if you provide the WidgetSpan; otherwise, the selection will be inaccurate.

final editorStyle = EditorStyle.desktop(
      // Example for customizing a new attribute key.
      textSpanDecorator: (textInsert, textSpan) {
        final attributes = textInsert.attributes;
        if (attributes == null) {
          return textSpan;
        }
        final mention = attributes['mention'] as Map?;
        if (mention != null) {
          return WidgetSpan(
            child: MouseRegion(
              cursor: SystemMouseCursors.click,
              child: GestureDetector(
                behavior: HitTestBehavior.translucent,
                child: Row(
                  mainAxisSize: MainAxisSize.min,
                  children: [
                    const Icon(Icons.edit_document),
                    Text(mention['id']),
                  ],
                ),
              ),
            ),
          );
        }
        return textSpan;
      },
    );

3. bingo.

[codecov]

Codecov Report

Merging #244 (d664873) into main (cd0f67a) will increase coverage by 0.02%.
The diff coverage is 72.72%.

@@            Coverage Diff             @@
##             main     #244      +/-   ##
==========================================
+ Coverage   62.70%   62.73%   +0.02%     
==========================================
  Files         230      230              
  Lines       10332    10337       +5     
==========================================
+ Hits         6479     6485       +6     
+ Misses       3853     3852       -1     

Impacted Files	Coverage Δ
lib/src/render/style/editor_style.dart	6.81% <0.00%> (+0.93%)	⬆️
lib/src/render/rich_text/flowy_rich_text.dart	90.81% <100.00%> (+1.73%)	⬆️

[MichalNemec]

amazing! will try it out and give feedback!

[MichalNemec]

works flawlessly! When can we expect version with this included on pub.dev?

[MichalNemec]

Coming back to it. It seems like whenever you do this and continue to type afterwards, its bugging out the text.

Test it out: type in whatever, select it, do the action and then type afterwards, it takes only the first letter (w) and then it starts to bug out.