[libadwaita/wip/exalm/card: 24/34] stylesheet: Add button.opaque style class

[Alexander Mikhaylenko <alexm src gnome org>]

commit e01716390844b1df534f9e4ed4df186d3cd35df0
Author: Alexander Mikhaylenko <alexm gnome org>
Date:   Tue Oct 19 16:38:58 2021 +0500

    stylesheet: Add button.opaque style class
    
    Have an explicit way to do colored buttons instead of having apps abuse
    .suggested-action and .destructive-action.
    
    Fixes https://gitlab.gnome.org/GNOME/libadwaita/-/issues/251

 src/stylesheet/widgets/_buttons.scss | 19 ++++++++++++++-----
 1 file changed, 14 insertions(+), 5 deletions(-)
---
diff --git a/src/stylesheet/widgets/_buttons.scss b/src/stylesheet/widgets/_buttons.scss
index da0e9ab2..1db816c0 100644
--- a/src/stylesheet/widgets/_buttons.scss
+++ b/src/stylesheet/widgets/_buttons.scss
@@ -5,6 +5,8 @@ $button_checked_color: gtkalpha(currentColor, .2);
 $button_checked_hover_color: gtkalpha(currentColor, .25);
 $button_checked_active_color: gtkalpha(currentColor, .35);
 
+$opaque_button_default_bg: gtkmix($window_bg_color, $window_fg_color, 85%);
+
 %button,
 button {
   @at-root %button_basic, & {
@@ -145,7 +147,7 @@ button {
     }
   }
 
-  @at-root %filled_button {
+  @at-root %opaque_button {
     box-shadow: none;
 
     @include focus-ring($outer: true, $offset: 1px);
@@ -174,8 +176,15 @@ button {
     }
   }
 
+  &.opaque {
+    @extend %opaque_button;
+
+    background-color: $opaque_button_default_bg;
+    color: $window_fg_color;
+  }
+
   &.destructive-action {
-    @extend %filled_button;
+    @extend %opaque_button;
 
     color: $destructive_fg_color;
 
@@ -185,7 +194,7 @@ button {
   }
 
   &.suggested-action {
-    @extend %filled_button;
+    @extend %opaque_button;
 
     color: $accent_fg_color;
 
@@ -466,7 +475,7 @@ splitbutton {
 
   &.suggested-action {
     > button, > menubutton > button {
-      @extend %filled_button;
+      @extend %opaque_button;
 
       color: $accent_fg_color;
 
@@ -478,7 +487,7 @@ splitbutton {
 
   &.destructive-action {
     > button, > menubutton > button {
-      @extend %filled_button;
+      @extend %opaque_button;
 
       color: $destructive_fg_color;