bug#46493: [feature/pgtk] Low contrast region face

[Yuuki Harano]

On Sat, 13 Feb 2021 16:55:47 +0000,
        "Basil L. Contovounesios" <contovob@tcd.ie> wrote:
> I understand that each toolkit has its look & feel, and that colour
> perception is subjective, but the default contrast on pgtk strikes me as
> a bit too low for text editing.

lisp/faces.el:

(defface region
  '((((class color) (min-colors 88) (background dark))
     :background "blue3" :extend t)
    (((class color) (min-colors 88) (background light) (type gtk))
     :distant-foreground "gtk_selection_fg_color"
     :background "gtk_selection_bg_color" :extend t)

The color name "gtk_selection_bg_color" is handled by src/gtkutil.c:
xg_check_special_colors(), which gets colors from gtk theme.

This issue is not pgtk-specific.

If we want another color for bg on pgtk, we can change this face definition as 
follows:

(defface region
  '((((class color) (min-colors 88) (background dark))
     :background "blue3" :extend t)
    (((class color) (min-colors 88) (background light) (type pgtk))    ; add 
this line
     :background "lightgoldenrod2" :extend t)                          ; add 
this line
    (((class color) (min-colors 88) (background light) (type gtk))
     :distant-foreground "gtk_selection_fg_color"
     :background "gtk_selection_bg_color" :extend t)

-- 
Yuuki Harano