handle separators in split titlebars correctly

common/gtk-3.0/3.20/gtk-dark.css

@@ -1020,6 +1020,7 @@ headerbar:last-child, headerbar:last-child:backdrop {
   .tiled headerbar:last-child:backdrop {
     border-radius: 0; }
 
+window > .titlebar:not(headerbar), window > .titlebar:not(headerbar):backdrop,
 window.csd > .titlebar:not(headerbar),
 window.csd > .titlebar:not(headerbar):backdrop {
   padding: 0;
@@ -1030,7 +1031,7 @@ window.csd > .titlebar:not(headerbar):backdrop {
   box-shadow: none; }
 
 .titlebar:not(headerbar) > separator {
-  background: rgba(38, 42, 51, 0.97); }
+  background-image: linear-gradient(to top, rgba(38, 42, 51, 0.97)); }
 
 .primary-toolbar separator, headerbar separator.titlebutton, .titlebar:not(headerbar) separator.titlebutton {
   min-width: 1px;

common/gtk-3.0/3.20/gtk-darker.css

@@ -1019,6 +1019,7 @@ headerbar:last-child, headerbar:last-child:backdrop {
   .tiled headerbar:last-child:backdrop {
     border-radius: 0; }
 
+window > .titlebar:not(headerbar), window > .titlebar:not(headerbar):backdrop,
 window.csd > .titlebar:not(headerbar),
 window.csd > .titlebar:not(headerbar):backdrop {
   padding: 0;
@@ -1029,7 +1030,7 @@ window.csd > .titlebar:not(headerbar):backdrop {
   box-shadow: none; }
 
 .titlebar:not(headerbar) > separator {
-  background: rgba(38, 42, 51, 0.97); }
+  background-image: linear-gradient(to top, rgba(38, 42, 51, 0.97)); }
 
 .primary-toolbar separator, headerbar separator.titlebutton, .titlebar:not(headerbar) separator.titlebutton {
   min-width: 1px;

common/gtk-3.0/3.20/gtk-solid-dark.css

@@ -1020,6 +1020,7 @@ headerbar:last-child, headerbar:last-child:backdrop {
   .tiled headerbar:last-child:backdrop {
     border-radius: 0; }
 
+window > .titlebar:not(headerbar), window > .titlebar:not(headerbar):backdrop,
 window.csd > .titlebar:not(headerbar),
 window.csd > .titlebar:not(headerbar):backdrop {
   padding: 0;
@@ -1030,7 +1031,7 @@ window.csd > .titlebar:not(headerbar):backdrop {
   box-shadow: none; }
 
 .titlebar:not(headerbar) > separator {
-  background: #262a33; }
+  background-image: linear-gradient(to top, #262a33); }
 
 .primary-toolbar separator, headerbar separator.titlebutton, .titlebar:not(headerbar) separator.titlebutton {
   min-width: 1px;

common/gtk-3.0/3.20/gtk-solid-darker.css

@@ -1019,6 +1019,7 @@ headerbar:last-child, headerbar:last-child:backdrop {
   .tiled headerbar:last-child:backdrop {
     border-radius: 0; }
 
+window > .titlebar:not(headerbar), window > .titlebar:not(headerbar):backdrop,
 window.csd > .titlebar:not(headerbar),
 window.csd > .titlebar:not(headerbar):backdrop {
   padding: 0;
@@ -1029,7 +1030,7 @@ window.csd > .titlebar:not(headerbar):backdrop {
   box-shadow: none; }
 
 .titlebar:not(headerbar) > separator {
-  background: #262a33; }
+  background-image: linear-gradient(to top, #262a33); }
 
 .primary-toolbar separator, headerbar separator.titlebutton, .titlebar:not(headerbar) separator.titlebutton {
   min-width: 1px;

common/gtk-3.0/3.20/gtk-solid.css

@@ -1019,6 +1019,7 @@ headerbar:last-child, headerbar:last-child:backdrop {
   .tiled headerbar:last-child:backdrop {
     border-radius: 0; }
 
+window > .titlebar:not(headerbar), window > .titlebar:not(headerbar):backdrop,
 window.csd > .titlebar:not(headerbar),
 window.csd > .titlebar:not(headerbar):backdrop {
   padding: 0;
@@ -1029,7 +1030,7 @@ window.csd > .titlebar:not(headerbar):backdrop {
   box-shadow: none; }
 
 .titlebar:not(headerbar) > separator {
-  background: #d4d5db; }
+  background-image: linear-gradient(to top, #d4d5db); }
 
 .primary-toolbar separator, headerbar separator.titlebutton, .titlebar:not(headerbar) separator.titlebutton {
   min-width: 1px;

common/gtk-3.0/3.20/gtk.css

@@ -1019,6 +1019,7 @@ headerbar:last-child, headerbar:last-child:backdrop {
   .tiled headerbar:last-child:backdrop {
     border-radius: 0; }
 
+window > .titlebar:not(headerbar), window > .titlebar:not(headerbar):backdrop,
 window.csd > .titlebar:not(headerbar),
 window.csd > .titlebar:not(headerbar):backdrop {
   padding: 0;
@@ -1029,7 +1030,7 @@ window.csd > .titlebar:not(headerbar):backdrop {
   box-shadow: none; }
 
 .titlebar:not(headerbar) > separator {
-  background: rgba(212, 213, 219, 0.95); }
+  background-image: linear-gradient(to top, rgba(212, 213, 219, 0.95)); }
 
 .primary-toolbar separator, headerbar separator.titlebutton, .titlebar:not(headerbar) separator.titlebutton {
   min-width: 1px;

common/gtk-3.0/3.20/sass/_common.scss

@@ -1105,17 +1105,19 @@ headerbar {
 
 // Fixes split headerbars too
 .titlebar:not(headerbar) {
-  window.csd > &,
+  window > &,
-  window.csd > &:backdrop {
+  window.csd > & {
-    padding: 0;
+    &, &:backdrop {
-    background-color: transparent;
+      padding: 0;
-    background-image: none;
+      background-color: transparent;
-    border-style: none;
+      background-image: none;
-    border-color: transparent;
+      border-style: none;
-    box-shadow: none;
+      border-color: transparent;
+      box-shadow: none;
+    }
   }
 
-  > separator { background: $header_border; }
+  > separator { background-image: linear-gradient(to top, $header_border); }
 
   @extend %titlebar;
 }