* There is only one screen in GTK 3.22 or later
* Finding the screen from that used by GtkPanelPlug is out of process only
* Any in-process applet calling mate_panel_applet_request_focus needs this to avoid a segfault
* One known user: dictionary applet

*Otherwise taskbuttons for programs using URLs or filenames in the window name can balloon across the whole taskbar

*Empty space between buttons removed
*padding in buttons similar to x11

*Vertical panel: do not modify buttons, they just plain work!
*We have a working window list on vertical panels in wayland only

*Horizontal panels:

*expand buttons like in X11 until more expanded buttons won't fit
*When expanded buttons won't fit,  resize buttons to fit tasklist
*When ellipsized text plus icon won't fit, remove the label
*When one more button with icon won't fit, remove the icon
	*but bring back the (compressable) label as in x11.
	*Prevents window list buttons disappearing when theme does not set a border

*Use automatic signal handling for changing icon size so this code doesn't get called when the applet is removed

It was listing outdated values, and missing new ones.

Fixes #1132.

- button-widget.c: replace tabs with 4 spaces and reformat as necessary
- button-widget.h: tab to 4 spaces
- button-widget.c: adjust indents and bracket style

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Co-authored-by: raveit65 <mate@raveit.de>

*Custom icons not findable by gtk_icon_theme_load_surface are still blurry

  *we need this for theming