HighContrast: update for separators deprecations

HighContrast still has a long way to go, but let's get at least
separators working again.

gtk/theme/HighContrast/_common.scss

@@ -439,9 +439,7 @@ button {
   }
 
   .primary-toolbar & { -gtk-icon-shadow: none; } // tango icons don't need added shadows
-//  .separator {
-//    -GtkWidget-wide-separators: true;
-//   }
+
   .linked > &,
   .linked > &:hover,
   .linked > &:active,
@@ -763,10 +761,6 @@ combobox {
     color: $insensitive_fg_color;
   }
   .menuitem { text-shadow: none; }
-  & separator.vertical {
-    // always disable separators
-    -GtkWidget-wide-separators: true;
-  }
   &.combobox-entry entry {
     border-radius: 3px 0 0 3px;
     &:dir(rtl) {
@@ -898,8 +892,6 @@ headerbar {
   }
   .header-bar-separator,
   & > GtkBox > separator.vertical {
-    -GtkWidget-wide-separators: true;
-    -GtkWidget-separator-width: 1px;
     border-width: 0 1px;
     border-color: $fg_color;
     border-style: solid;
@@ -998,6 +990,7 @@ treeview.view {
   }
 
   &.separator:backdrop {
+    min-height: 2px;
     color: transparentize(black, 0.9);
   }
 
@@ -1931,16 +1924,9 @@ scrolledwindow {
 
 //vbox and hbox separators
 separator {
-  // always disable separators
-  // -GtkWidget-wide-separators: true;
-  color: $borders_color;
-
-  // Font and File button separators
-  GtkFileChooserButton &.vertical,
-  button.font &.vertical {
-    // always disable separators
-    -GtkWidget-wide-separators: true;
-  }
+  background: $borders_color;
+  min-width: 1px;
+  min-height: 1px;
 }
 
 /*********

gtk/theme/HighContrast/gtk.css

@@ -906,10 +906,6 @@ combobox {
     color: gray; }
   combobox .menuitem {
     text-shadow: none; }
-  combobox separator.vertical,
-  combobox placessidebar .view separator.vertical:backdrop,
-  placessidebar .view combobox separator.vertical:backdrop {
-    -GtkWidget-wide-separators: true; }
   combobox.combobox-entry entry {
     border-radius: 3px 0 0 3px; }
     combobox.combobox-entry entry:dir(rtl) {
@@ -989,8 +985,6 @@ headerbar {
   headerbar .header-bar-separator,
   headerbar > GtkBox > separator.vertical,
   placessidebar .view headerbar > GtkBox > separator.vertical:backdrop {
-    -GtkWidget-wide-separators: true;
-    -GtkWidget-separator-width: 1px;
     border-width: 0 1px;
     border-color: #000;
     border-style: solid; }
@@ -1162,6 +1156,7 @@ treeview.view {
     treeview.view:insensitive:backdrop {
       color: gray; }
   treeview.view.separator:backdrop {
+    min-height: 2px;
     color: rgba(0, 0, 0, 0.1); }
   treeview.view:backdrop {
     color: #000;
@@ -2189,11 +2184,9 @@ scrollbar scrolledwindow trough {
 
 separator, placessidebar .view separator,
 placessidebar .view separator:backdrop {
-  color: gray; }
-  GtkFileChooserButton separator.vertical,
-  GtkFileChooserButton placessidebar .view separator.vertical:backdrop,
-  placessidebar .view GtkFileChooserButton separator.vertical:backdrop, button.font separator.vertical {
-    -GtkWidget-wide-separators: true; }
+  background: gray;
+  min-width: 1px;
+  min-height: 1px; }
 
 /*********
  * Lists *