From: Adrien Plazas <kekun.plazas@laposte.net>
Date: Thu, 11 Jul 2019 10:44:14 +0200
Subject: headerbar: Use a back button in dialogs on mobile

This will allow to drop the close buttons and make the dialogs and
transient windows look like proper mobile dialogs.
---
 gtk/gtkheaderbar.c | 38 +++++++++++++++++++++++++++++++++++++-
 1 file changed, 37 insertions(+), 1 deletion(-)

diff --git a/gtk/gtkheaderbar.c b/gtk/gtkheaderbar.c
index 0ef94e3..9a4833a 100644
--- a/gtk/gtkheaderbar.c
+++ b/gtk/gtkheaderbar.c
@@ -30,6 +30,7 @@
 #include "gtkwindowprivate.h"
 #include "gtkwidgetprivate.h"
 #include "gtkcontainerprivate.h"
+#include "gtkdialog.h"
 #include "a11y/gtkheaderbaraccessible.h"
 
 #include <string.h>
@@ -88,6 +89,7 @@ struct _GtkHeaderBarPrivate
   GtkWidget *titlebar_icon;
 
   GtkCssGadget *gadget;
+  GSettings *settings;
 };
 
 typedef struct _Child Child;
@@ -280,6 +282,7 @@ _gtk_header_bar_update_window_buttons (GtkHeaderBar *bar)
   GMenuModel *menu;
   gboolean shown_by_shell;
   gboolean is_sovereign_window;
+  gboolean is_mobile_dialog;
 
   toplevel = gtk_widget_get_toplevel (widget);
   if (!gtk_widget_is_toplevel (toplevel))
@@ -310,7 +313,15 @@ _gtk_header_bar_update_window_buttons (GtkHeaderBar *bar)
                 "gtk-decoration-layout", &layout_desc,
                 NULL);
 
-  if (priv->decoration_layout_set)
+  is_mobile_dialog = GTK_IS_DIALOG (toplevel) ||
+                     (GTK_IS_WINDOW (toplevel) && !!gtk_window_get_transient_for (GTK_WINDOW (toplevel)));
+
+  if (is_mobile_dialog && _gtk_get_is_phone ())
+    {
+      g_free (layout_desc);
+      layout_desc = g_strdup ("back:");
+    }
+  else if (priv->decoration_layout_set)
     {
       g_free (layout_desc);
       layout_desc = g_strdup (priv->decoration_layout);
@@ -457,6 +468,23 @@ _gtk_header_bar_update_window_buttons (GtkHeaderBar *bar)
                   if (GTK_IS_ACCESSIBLE (accessible))
                     atk_object_set_name (accessible, _("Close"));
                 }
+              else if (strcmp (t[j], "back") == 0 &&
+                       gtk_window_get_deletable (window))
+                {
+                  button = gtk_button_new ();
+                  gtk_widget_set_valign (button, GTK_ALIGN_CENTER);
+                  image = gtk_image_new_from_icon_name ("go-previous-symbolic", GTK_ICON_SIZE_BUTTON);
+                  g_object_set (image, "use-fallback", TRUE, NULL);
+                  gtk_container_add (GTK_CONTAINER (button), image);
+                  gtk_widget_set_can_focus (button, TRUE);
+                  gtk_widget_show_all (button);
+                  g_signal_connect_swapped (button, "clicked",
+                                            G_CALLBACK (gtk_window_close), window);
+
+                  accessible = gtk_widget_get_accessible (button);
+                  if (GTK_IS_ACCESSIBLE (accessible))
+                    atk_object_set_name (accessible, _("Back"));
+                }
 
               if (button)
                 {
@@ -1514,6 +1542,8 @@ gtk_header_bar_destroy (GtkWidget *widget)
       priv->titlebar_end_separator = NULL;
     }
 
+  g_clear_object (&priv->settings);
+
   GTK_WIDGET_CLASS (gtk_header_bar_parent_class)->destroy (widget);
 }
 
@@ -2154,6 +2184,12 @@ gtk_header_bar_init (GtkHeaderBar *bar)
                                                      NULL,
                                                      NULL);
 
+  priv->settings = _gtk_get_purism_settings ();
+
+  if (priv->settings)
+    g_signal_connect_object (priv->settings, "changed::is-phone",
+           G_CALLBACK (_gtk_header_bar_update_window_buttons), bar,
+           G_CONNECT_SWAPPED);
 }
 
 static void