--center option doesn't play well with --size

[jaminthorns]

I use Chafa for rendering previews of files within other programs, which makes the --size option super useful. Since I'm rendering to a statically-sized preview area, it would be nice to have these previews centered. I thought the --center option would solve this, but it doesn't seem to take the --size option into account.

Instead, it's adding a left offset based on the detected width of the terminal, not the width given through --size. In lf, where the preview takes 1/2 the screen width, this results in a preview that's cut off:

Additionally, it would be nice if there was a vertical offset when --size and --center are both provided so that the image would be vertically centered as well.

[hpjansson]

Hi, thanks for reporting this. You're correct, --center centers with respect to the terminal size. What I think we need is to be able to specify --frame-size to override the terminal size detection. Then we'll have:

stateDiagram-v2
  state frame-size {
    size
}

Loading

If --frame-size is unspecified, it will be read from the terminal. If --size is not specified, it will be chosen to be <= frame-size. When --center is specified, the inner area will be centered on the outer.

Additionally, we could add an --align <x,y> option, e.g. --align top,center or --align center,center. I think the current --center option should keep its semantics: only align horizontally. It's useful for scrolling terminals where you don't expect extra space before the next prompt.

See also #115 (comment) and #84 (comment) for related comments/discussions.

Sound good?

[jaminthorns]

Keeping the semantics of --center makes perfect sense, maybe adding to the description of the flag (in --help and man page) that it only centers horizontally. The --align flag sounds perfect and would allow for even more use cases. That all sounds great, thank you!

[hpjansson]

You should be able to get what you want with the new --view-size and --align options when combined with --size (the inner maximum size). You may need to add --relative on for relative positioning.

Please let me know if you find any issues!