Include Gtk3 window decoration icons in Greybird (Fixes #170)

This means switching icon themes will not have any effect
on the window controls. This is desirable as long as Xfwm4
still draws decorations, as otherwise the icons may be
inconsistent.

gtk-3.0/_common.scss

@@ -4235,14 +4235,30 @@ decoration {
   }
 }
 
-// Window Close button
+// Window buttons
 button.titlebutton {
   @extend %button_basic;
 
   @extend %button_basic.flat;
 
   @include _button_text_shadow;
 
+  &.close, &.maximize, &.minimize {
+    color: transparent;
+    background-color: transparent;
+    background-position: center;
+    background-repeat: no-repeat;
+
+    // fade the png buttons out on unfocused windows
+    &:backdrop { opacity: 0.5; }
+  }
+  // Load png assets for each button
+  @each $k in ('close','maximize', 'minimize') {
+    @each $l, $m in ('',''), (':backdrop','-backdrop'), (':hover','-hover'), (':active','-active') {
+      &.#{$k}#{$l} { background-image: url('assets/titlebutton-#{$k}#{$m}#{$asset_suffix}.png'); }
+    }
+  }
+
   .selection-mode & {
     @extend %button.flat.suggested-action;
 

gtk-3.0/assets/titlebutton-close-backdrop-dark.png

@@ -0,0 +1 @@
+titlebutton-close-dark.png

gtk-3.0/assets/titlebutton-close-backdrop.png

@@ -0,0 +1 @@
+titlebutton-close.png

gtk-3.0/assets/titlebutton-close-hover-dark.png

@@ -0,0 +1 @@
+titlebutton-close-dark.png

gtk-3.0/assets/titlebutton-maximize-backdrop-dark.png

@@ -0,0 +1 @@
+titlebutton-maximize-dark.png

gtk-3.0/assets/titlebutton-maximize-backdrop.png

@@ -0,0 +1 @@
+titlebutton-maximize.png

gtk-3.0/assets/titlebutton-maximize-hover-dark.png

@@ -0,0 +1 @@
+titlebutton-maximize-dark.png

gtk-3.0/assets/titlebutton-minimize-backdrop-dark.png

@@ -0,0 +1 @@
+titlebutton-minimize-dark.png

gtk-3.0/assets/titlebutton-minimize-backdrop.png

@@ -0,0 +1 @@
+titlebutton-minimize.png

gtk-3.0/assets/titlebutton-minimize-hover-dark.png

@@ -0,0 +1 @@
+titlebutton-minimize-dark.png

gtk-3.0/gtk-contained-dark.css

@@ -4141,6 +4141,37 @@ decoration {
 button.titlebutton {
   text-shadow: 0 -1px rgba(0, 0, 0, 0.81176);
   -gtk-icon-shadow: 0 -1px rgba(0, 0, 0, 0.81176); }
+  button.titlebutton.close, button.titlebutton.maximize, button.titlebutton.minimize {
+    color: transparent;
+    background-color: transparent;
+    background-position: center;
+    background-repeat: no-repeat; }
+    button.titlebutton.close:backdrop, button.titlebutton.maximize:backdrop, button.titlebutton.minimize:backdrop {
+      opacity: 0.5; }
+  button.titlebutton.close {
+    background-image: url("assets/titlebutton-close-dark.png"); }
+  button.titlebutton.close:backdrop {
+    background-image: url("assets/titlebutton-close-backdrop-dark.png"); }
+  button.titlebutton.close:hover {
+    background-image: url("assets/titlebutton-close-hover-dark.png"); }
+  button.titlebutton.close:active {
+    background-image: url("assets/titlebutton-close-active-dark.png"); }
+  button.titlebutton.maximize {
+    background-image: url("assets/titlebutton-maximize-dark.png"); }
+  button.titlebutton.maximize:backdrop {
+    background-image: url("assets/titlebutton-maximize-backdrop-dark.png"); }
+  button.titlebutton.maximize:hover {
+    background-image: url("assets/titlebutton-maximize-hover-dark.png"); }
+  button.titlebutton.maximize:active {
+    background-image: url("assets/titlebutton-maximize-active-dark.png"); }
+  button.titlebutton.minimize {
+    background-image: url("assets/titlebutton-minimize-dark.png"); }
+  button.titlebutton.minimize:backdrop {
+    background-image: url("assets/titlebutton-minimize-backdrop-dark.png"); }
+  button.titlebutton.minimize:hover {
+    background-image: url("assets/titlebutton-minimize-hover-dark.png"); }
+  button.titlebutton.minimize:active {
+    background-image: url("assets/titlebutton-minimize-active-dark.png"); }
   button.titlebutton:backdrop {
     -gtk-icon-shadow: none; }
 

gtk-3.0/gtk-contained.css

@@ -4171,6 +4171,37 @@ decoration {
 button.titlebutton {
   text-shadow: 0 1px rgba(255, 255, 255, 0.76923);
   -gtk-icon-shadow: 0 1px rgba(255, 255, 255, 0.76923); }
+  button.titlebutton.close, button.titlebutton.maximize, button.titlebutton.minimize {
+    color: transparent;
+    background-color: transparent;
+    background-position: center;
+    background-repeat: no-repeat; }
+    button.titlebutton.close:backdrop, button.titlebutton.maximize:backdrop, button.titlebutton.minimize:backdrop {
+      opacity: 0.5; }
+  button.titlebutton.close {
+    background-image: url("assets/titlebutton-close.png"); }
+  button.titlebutton.close:backdrop {
+    background-image: url("assets/titlebutton-close-backdrop.png"); }
+  button.titlebutton.close:hover {
+    background-image: url("assets/titlebutton-close-hover.png"); }
+  button.titlebutton.close:active {
+    background-image: url("assets/titlebutton-close-active.png"); }
+  button.titlebutton.maximize {
+    background-image: url("assets/titlebutton-maximize.png"); }
+  button.titlebutton.maximize:backdrop {
+    background-image: url("assets/titlebutton-maximize-backdrop.png"); }
+  button.titlebutton.maximize:hover {
+    background-image: url("assets/titlebutton-maximize-hover.png"); }
+  button.titlebutton.maximize:active {
+    background-image: url("assets/titlebutton-maximize-active.png"); }
+  button.titlebutton.minimize {
+    background-image: url("assets/titlebutton-minimize.png"); }
+  button.titlebutton.minimize:backdrop {
+    background-image: url("assets/titlebutton-minimize-backdrop.png"); }
+  button.titlebutton.minimize:hover {
+    background-image: url("assets/titlebutton-minimize-hover.png"); }
+  button.titlebutton.minimize:active {
+    background-image: url("assets/titlebutton-minimize-active.png"); }
   button.titlebutton:backdrop {
     -gtk-icon-shadow: none; }