add a "thin" horiz scrollbar

[nitzan-shaked]

First, a screenshot:

I don't like the horizontal scrollbar; even at "size" 1 it is still too fat. So I added an option for a "thin" version, refactoring ScrollBarRender along the way.

I didn't presume to know how you'd like the CSS to behave, so I went for the simplest I could think of: add a new "scrollbar-thin" boolean style. I am not married to the css design around it, I really only want the "thin" version.

There's no need to do anything special for a "thin" vertical scrollbar: imo it looks very nice at width 1.

[nitzan-shaked]

I also changed the demo to show it off -- the DataTable has a thin scrollbar.

[willmcgugan]

A scrollbar size of 1 presents a too small click target when zoomed out. It also makes the horizontal and vertical bars a different side of you set them both to 1.

You can easily change it via CSS. See https://textual.textualize.io/styles/scrollbar_size/

[nitzan-shaked]

Possibly so, but sometimes (e.g. when not zoomed out) I think it's the perfect size.
Also, often I don't actually click -- I want it as a visual aid, but I scroll with the mouse.

"But you can't scroll left/right with the mouse, and you changed the horizontal scrollbar, so that makes no sense", I hear you say. (I have good hearing). Well I also created a PR that makes MouseScrollUp and MouseScrollDown with modifiers, so I use ctrl-wheel to scroll left/right.

Finally -- what you wrote about easily changing with CSS -- makes me think maybe my descr on this PR isn't so good. Maybe I should attach a screenshot?

(EDIT: added a screenshot)

[willmcgugan]

Ok, I see what you've done now. I can see why you might like this, but there are some downsides.

Because you're using half blocks, you have less sub-cell resolution. With the current scrollbar characters, you have 8 characters which can give the scrolling a pixel perfect look. Not a deal breaker, but it is a downside.

The CSS changes don't fit with conventions. You won't see a true or false value in browser CSS. You would have something like scrollbar-variant: thin which leaves the possibility of having multiple different styles, not just regular and thin.

The thin scrollbars scrollbar-size don't work together. I'm guessing from the code that thin overrides size, which would no-doubt cause confusion in the future. CSS rules tend to be independent and not contradict each other like this.

So this is not a change I would want to accept right now. However, as a compromise I would accept some mechanism to substitute a different scrollbar renderable in code.

I might be open to the possibility of adding these thin scrollbars down the line, if we can solve the contradictory rules issues. Perhaps scrollbar-size: 0.5 1

[nitzan-shaked]

I agree with all your comments, and as a matter of fact suspected you'd say them. Which is why I wrote that I'm completely not married to the css "design", and only wish for the thin scrollbar to exist. I obviously agree there's a downside to the the half-blocks in terms of resolution, but also agree it should be a user choice so not a deal breaker.

I'm very happy you propose a "plugin renderer" as a solution, because I figured that unless you accept sort-of as is then that is the right path to go.

With all that in mind: I'm happy to conjure something up but just want to say ahead of time:

If we go with the plugin approach then the way I see it that is something that the application writer would "configure". Presumably register a ScrollBarRender-derived class against a "scrollbar style". So the styles would be strings, and the CSS will be such. So while I like "scrollbar-size-horizontal: 0.5" it doesn't make much sense if we go with "scrollbar-variant: thin".

If you have a better idea I'm happy to accommodate. If you think the above sounds reasonable then I'll go ahead and do that.

Finally, just nothing that a such a renderer class would also be responsible for measuring the resulting scrollbar, for the sake of all those methods that need that (basically: all the measuring methods I changed to take "thin" into account).

Agreed?

[willmcgugan]

You might want to open a discussion with a proposal before doing any more work.