Build a "Placeholder" widget

[willmcgugan]

We had a Placeholder widget which could be used to design a layout before you built a full widget. This use an older API.

We should refresh the placeholder idea, make it look nicer that the previous iteration, and add some features

• Pick harmonious alternating colors, by mixing brackground with ~30% from this palette
• Argument to select various modes: plain color, size and location, CSS, lorem ipsum text, etc
• Add click handler to cycle between modes

[rodrigogiraoserrao]

With the commit 83c8a9b we have the scaffolding for the widget Placeholder which:

• has 5 3 different variants that display different things; and
• cycles through the different variants when you click the placeholder.

1. The "default" variant shows a solid colour (from the palette linked) that was associated to the placeholder upon instantiation.
2. The "state" variant shows whether the placeholder has focus (or not) and whether the mouse is over the placeholder or not.
3. The "size" variant shows the size of the placeholder.
4. The "css" variant shows the CSS of the placeholder.
5. The "text" variant shows some Lorem Ipsum text.

[rodrigogiraoserrao]

Questions left unanswered:

• Exactly how should each variant be styled by default?
• Should the background colour (from the palette linked) be customisable?
• Should the placeholders scroll if the content is too large? (E.g., the css variant tends to have lots of content that won't fit small placeholders.)

[rodrigogiraoserrao]

After some discussion, the variants for state and CSS have been removed from consideration.
Thus, placeholders have 3 variants.

[rodrigogiraoserrao]

Fixed with #1229.

[github-actions]

Don't forget to star the repository!

Follow @textualizeio for Textual updates.