theme: OSK opaque

- the on screen keyboard is not an overlay in most cases. the semi-opacity
  is distracting.
- use opaque background color
- see discussion on https://gitlab.gnome.org/GNOME/gnome-shell/merge_requests/1028

  FIXME: whitespace at the bottom without scaling everything down (padding)
  FIXME: don't behave as overlay anywhere (even for entries above the fold)

data/theme/gnome-shell-sass/widgets/_keyboard.scss

@@ -3,14 +3,13 @@
 $key_size: 1.2em;
 $key_border_radius: $base_border_radius + 3px;
 $key_bg_color:  $bg_color;
-// $default_key_bg_color: darken($key_bg_color, 4%);
-$default_key_bg_color: if($variant=='light', darken($osd_bg_color, 11%), lighten($osd_bg_color, 2%));
+$default_key_bg_color: darken($bg_color, 2%);
 
 
 // draw keys using button function
 #keyboard {
-  background-color: transparentize(if($variant=='light', darken($bg_color, 5%), darken($bg_color, 8%)), 0.1);
-  box-shadow: inset 0 1px 0 0 $osd_outer_borders_color;
+  background-color: $bg_color;
+  box-shadow: inset 0 1px 0 0 $borders_color;
 
   .page-indicator {
     padding: $base_padding;
@@ -71,11 +70,11 @@ $default_key_bg_color: if($variant=='light', darken($osd_bg_color, 11%), lighten
 
 // long press on a key popup
 .keyboard-subkeys {
-  color: $osd_fg_color;
+  color: $fg_color;
   -arrow-border-radius: $modal_radius;
-  -arrow-background-color: $osd_bg_color;
+  -arrow-background-color: $bg_color;
   -arrow-border-width: 1px;
-  -arrow-border-color: lighten($osd_bg_color, 9%);
+  -arrow-border-color: $borders_color;
   -arrow-base: 20px;
   -arrow-rise: 10px;
   -boxpointer-gap: $base_spacing;