This adds two new builders to the `Image` class:
* `frameBuilder`, which allows callers to control the widget
created by an [Image].
* `loadingBuilder`, which allows callers fine-grained control
over how to display loading progress of an image to the user.
`FadeInImage` can be simplified by migrating to the new API.
This is done in a follow-on commit.
https://github.com/flutter/flutter/issues/32374
This converts all remaining "## Sample code" segments into snippets, and fixes
the snippet generator to handle multiple snippets in the same dartdoc block
properly.
I also generated, compiled, and ran each of the existing application samples,
and fixed them up to be more useful and/or just run without errors.
This PR fixes these problems with examples:
1. Switching tabs in a snippet now works if there is more than one snippet in
a single dartdoc block.
2. Generation of snippet code now works if there is more than one snippet.
3. Contrast of text and links in the code sample block has been improved to
recommended levels.
4. Added five new snippet templates, including a "freeform" template to make
it possible to show examples that need to change the app instantiation.
5. Fixed several examples to run properly, a couple by adding the "Scaffold"
widget to the template, a couple by just fixing their code.
6. Fixed visual look of some of the samples when they run by placing many
samples inside of a Scaffold.
7. In order to make it easier to run locally, changed the sample analyzer to
remove the contents of the supplied temp directory before running, since
having files that hang around is problematic (only a problem when running
locally with the `--temp` argument).
8. Added a `SampleCheckerException` class, and handle sample checking
exceptions more gracefully.
9. Deprecated the old "## Sample code" designation, and added enforcement for
the deprecation.
10. Removed unnecessary `new` from templates (although they never appeared in
the samples thanks to dartfmt, but still).
Fixes#26398Fixes#27411
This creates a custom dartdoc tool that will generate snippet blocks in our API docs that allow the user to copy easily to the clipboard, and will also embed the snippet code into a template to show it in a larger context with an app.
This PR adds the snippet tool, a template, and a couple of HTML skeleton files, one for snippets that are designed to be in an application setting, and one where it simply puts a nice container around existing snippets, making them easier to copy to the clipboard.
