feat(widget): support adding padding to Block

[orhun]

Upstream: #551

Description

If we want to render a widget inside a block with a certain distance from its borders, we need to create another Layout element based on the outer Block, add a margin and render the Widget into it. Adding a padding property on the block element skips the creation of this second Layout.

This property works especially when rendering texts, as we can just create a block with padding and use it as the text wrapper:

let block = Block::default().borders(Borders::ALL).padding(4);
let paragraph = Paragraph::new("example paragraph").block(block);
f.render_widget(paragraph, area);

Rendering another widget should be easy too, using the .inner method:

let block = Block::default().borders(Borders::ALL).padding(4);
let inner_block = Block::default().borders(Borders::ALL);
let inner_area = block.inner(area);

f.render_widget(block, area);
f.render_widget(inner_block, inner_area);

Testing guidelines

The block.rs example contains two cases of use: one with an inner text and another with an inner block:

I've also changed the paragraph tests to include a padding of value 1 to the rendering tests.

Checklist

• I have read the contributing guidelines.
• I have added relevant tests.
• I have documented all new additions.

[orhun]

alpha-tango-kilo said: This would be awesome! I hope this gets merged 🙌

[appsubscribe]

Hi, do you know when we can merge this PR? it would be great if this gets merged. Thanks!

[sayanarijit]

lgtm from me.
Let's resolve the conflict.

[orhun]

I resolved the conflict, please review @mindoodoo @sayanarijit @sophacles @joshka

[pythops]

Waiting for that one 👀
Thanks @orhun 🙏

[sophacles]

Overall looks good, and is functionality I was looking for not long ago. Curious about what you and the other reviewers think of my suggestion above

[joshka]

I'd suggest going left,right,top,bottom on the padding values instead of just horizontal/vertical. With vertical and horizontal being pub fields, that's a breaking change if done later.

Padding will be useful to insert between other things (e.g. ListItems). There at least I'd expect that the top padding to be able to be set differently to the bottom padding (and there are probably use cases for left/right there too). Even the block seems like it would maybe be useful to see different values on each edge.

[sayanarijit]

Since we're going with border style attributes, can we use the similar bitwise API as borders?

Nope, sorry, we need the values for each side, which isn't possible with bitwise API.

[joshka]

LGTM (I think the only thing I can see is missing is a test for the left/right/top/bottom)