[gtk+] GtkButtonBox: remove spacing when buttons are linked

[Lars Uebernickel <larsu src gnome org>]

commit 2dda89cbd52e09cfbc24a9139caa7a65a5f73f2c
Author: Lars Uebernickel <lars uebernickel canonical com>
Date:   Wed Jul 8 16:36:07 2015 +0200

    GtkButtonBox: remove spacing when buttons are linked
    
    GtkButtonBox adds the "linked" class to its style context when its
    layout is set to GTK_BUTTONBOX_EXPAND. It shouldn't ever make sense to
    have spacing between buttons in that case, as themes generally draw
    linked elements with a continuous border.
    
    Thus, always set spacing to 0 and ignore GtkDialog's button-spacing
    style property when the layout is set to EXPAND.
    
    Also remove the now-redundant css rules which set button-spacing to 0
    for message dialogs.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=752131

 gtk/gtkbbox.c                       |    1 +
 gtk/gtkbbox.h                       |    5 ++++-
 gtk/gtkdialog.c                     |    5 +++--
 gtk/theme/Adwaita/_common.scss      |    2 --
 gtk/theme/HighContrast/_common.scss |    1 -
 5 files changed, 8 insertions(+), 6 deletions(-)
---
diff --git a/gtk/gtkbbox.c b/gtk/gtkbbox.c
index 260e1c7..68ec484 100644
--- a/gtk/gtkbbox.c
+++ b/gtk/gtkbbox.c
@@ -359,6 +359,7 @@ gtk_button_box_set_layout (GtkButtonBox      *widget,
       if (priv->layout_style == GTK_BUTTONBOX_EXPAND)
         {
           gtk_style_context_add_class (gtk_widget_get_style_context (GTK_WIDGET (widget)), "linked");
+          gtk_box_set_spacing (GTK_BOX (widget), 0);
           gtk_box_set_homogeneous (GTK_BOX (widget), TRUE);
         }
       else
diff --git a/gtk/gtkbbox.h b/gtk/gtkbbox.h
index 46f1e59..a191feb 100644
--- a/gtk/gtkbbox.h
+++ b/gtk/gtkbbox.h
@@ -81,7 +81,10 @@ struct _GtkButtonBoxClass
  * @GTK_BUTTONBOX_END: Buttons are grouped towards the end of the box,
  *   (on the right for a HBox, or the bottom for a VBox).
  * @GTK_BUTTONBOX_CENTER: Buttons are centered in the box. Since 2.12.
- * @GTK_BUTTONBOX_EXPAND: Buttons expand to fill the box. Since 3.12.
+ * @GTK_BUTTONBOX_EXPAND: Buttons expand to fill the box. This entails giving
+ *   buttons a "linked" appearance, making button sizes homogeneous, and
+ *   setting spacing to 0 (same as calling gtk_box_set_homogeneous() and
+ *   gtk_box_set_spacing() manually). Since 3.12.
  *
  * Used to dictate the style that a #GtkButtonBox uses to layout the buttons it
  * contains.
diff --git a/gtk/gtkdialog.c b/gtk/gtkdialog.c
index 78ee012..21cc18b 100644
--- a/gtk/gtkdialog.c
+++ b/gtk/gtkdialog.c
@@ -696,8 +696,9 @@ update_spacings (GtkDialog *dialog)
       _gtk_box_set_spacing_set (GTK_BOX (priv->vbox), FALSE);
     }
 
-  gtk_box_set_spacing (GTK_BOX (priv->action_area),
-                       button_spacing);
+  /* don't set spacing when buttons are linked */
+  if (gtk_button_box_get_layout (GTK_BUTTON_BOX (priv->action_area)) != GTK_BUTTONBOX_EXPAND)
+    gtk_box_set_spacing (GTK_BOX (priv->action_area), button_spacing);
 
   if (!_gtk_container_get_border_width_set (GTK_CONTAINER (priv->action_area)))
     {
diff --git a/gtk/theme/Adwaita/_common.scss b/gtk/theme/Adwaita/_common.scss
index fe888c7..58ebbf4 100644
--- a/gtk/theme/Adwaita/_common.scss
+++ b/gtk/theme/Adwaita/_common.scss
@@ -2761,8 +2761,6 @@ GtkCalendar {
 }
 
 .message-dialog { // Message Dialog styling
-  -GtkDialog-button-spacing: 0;
-
   @if $variant==light {
     // the bright variant as a slightly darker bg which in this case clashes with the window decoration, 
overriding
     &.background { background-color: $bg_color; }
diff --git a/gtk/theme/HighContrast/_common.scss b/gtk/theme/HighContrast/_common.scss
index c7eef9d..50dcdf7 100644
--- a/gtk/theme/HighContrast/_common.scss
+++ b/gtk/theme/HighContrast/_common.scss
@@ -1998,7 +1998,6 @@ GtkCalendar {
 }
 
 .message-dialog { // Message Dialog styling
-  -GtkDialog-button-spacing: 0;
   .titlebar {
     border-style: none;
     box-shadow: inset 0 1px $borders_edge;