Introduction of a protocol for the Custom Command widget in lxqt-panel

[Reiddragon]

Is your feature request related to a problem? Please describe.
Currently, the Custom Command widget requires that the command exits after each update, and the update must be either text or an icon sent over stdio.

Describe the solution you'd like
My proposed changes are the following:

• Allow commands to keep running and send updates as needed.
• Introduce some kind of protocol for sending updates.
• Allow the command to send both an icon and text, where the icon may be either an icon class name to be fetched from the theme, or binary image data as is currently allowed.

Context

Having written a couple programs to run as backends for the Custom Command widget, I found the current behaviour to be rather limiting. This proposal is largely inspired by the i3bar-protocol as I've worked with it in the past and found it quite flexible (but of course, in the case of an LXQt widget protocol it would only be for individual blocks, not an entire status generator).

[jjramsey]

What about colors for the text?

[stefonarch]

What about colors for the text?

I would be +1 for that, but it's not related to this feature request.

[tsujan]

I would be +1 for that, but it's not related to this feature request.

Please add a separate feature request for it; otherwise, it'll be forgotten.

[jjramsey]

While #2304 is nice, it's not quite what I had in mind. What's in that feature is a more static coloration. I was thinking of something more along the line of swaybar's support for colorizing parts of its status bar, where the colors can change with the status, something like what I've done here: rcaelers/workrave#597

What might make sense would be to have LXQt's custom command support commands that continuously write to standard output, possibly with each line of output formatted according to some rich text that Qt can accept. Maybe it would be less analogous to swaybar's protocol and more like Waybar's custom module using a continuous script. Not sure how that would support icons, though, especially changing ones.

[tsujan]

The widget of Custom Command is just a button with a text or an icon. Qt doesn't accept rich texts on buttons.

Of course, someone might make a different plugin with another widget that accepts rich texts.

[jjramsey]

Fair enough. How flexible is the Custom Command widget's support for SVG? Does the SVG image need to be about the size and shape of an icon, or can it be fairly arbitrary? If it's the latter, that might be a gateway to a de facto "rich text" support.

[tsujan]

Does the SVG image need to be about the size and shape of an icon

It can have any size, but since icons are shown on the panel, and so, have relatively small sizes, it should be clearly visible with small sizes.

As for shape, icons don't have a predetermined shape. The shape can be that of a text, like this icon (converted to PNG from SVG):

[jjramsey]

That icon still looks to have an aspect ratio of about 1. What does the LXQt panel do with more oblong SVG images, say, a horizontal progress bar, maybe with text superimposed?

[tsujan]

Icons have the same width and height everywhere, not just in Qt — this isn't just about LXQt panel

Any image can be put into a rectangular, transparent area, especially SVG images.

[tsujan]

Anyway, if you want a wide shape with a small height, the answer is no, it isn't supported by a button.

[jjramsey]

Anyway, if you want a wide shape with a small height, the answer is no, it isn't supported by a button.

Ok, so scratch trying to use SVG to get around the lack of rich text in buttons.

In principle, would it be possible for a button to change its colors dynamically, or are they fixed at the outset?

[tsujan]

Text color is already added to Custom Command in git, but it's static.

Yes, theoretically, it's possible to change the text color of a button in response to a signal, but I don't think we want to complicate the code for such a special case.

[jjramsey]

Do you think a swaybar- or Waybar-like protocol would ever be supported for the Custom Command widget, or do you think that's too out-of-scope for LXQt, and the solution/workaround would just be to use Waybar, SFWBar, Eww, AGS, etc. (either in addition or in place of the LXQt Panel)?

[tsujan]

Personally (not as the voice of LXQt), no, I don't think they could be added to Custom Command, but they aren't out-of-scope for LXQt either.

lxqt-panel and waybar are very different apps; there are things in each that don't exist in the other. Custom Command does the job that it's made for. But who knows? A contributor might make another plugin with a totally different approach — after all, the main code allows plugins.