[gtk/wip/otte/listview: 168/169] listitem: Change focus handling

[Benjamin Otte <otte src gnome org>]

commit 4e5a4f6ab4601749b843da79af242e82d74c40d1
Author: Benjamin Otte <otte redhat com>
Date:   Tue Oct 15 04:18:10 2019 +0200

    listitem: Change focus handling
    
    Focus in the listitem now works like this:
    1. If any child can take focus, do not ever attempt
       to take focus.
    2. Otherwise, if this item is selectable or activatable,
       allow focusing this widget.
    
    This makes sure every item in a list is focusable for
    activation and selection handling, but no useless widgets
    get focused and moving focus is as fast as possible.

 gtk/gtklistitem.c | 39 +++++++++++++++++++++++++++++++++++++--
 1 file changed, 37 insertions(+), 2 deletions(-)
---
diff --git a/gtk/gtklistitem.c b/gtk/gtklistitem.c
index e4a373ab82..d9249950c7 100644
--- a/gtk/gtklistitem.c
+++ b/gtk/gtklistitem.c
@@ -78,6 +78,41 @@ G_DEFINE_TYPE (GtkListItem, gtk_list_item, GTK_TYPE_BIN)
 
 static GParamSpec *properties[N_PROPS] = { NULL, };
 
+static gboolean
+gtk_list_item_focus (GtkWidget        *widget,
+                     GtkDirectionType  direction)
+{
+  GtkListItem *self = GTK_LIST_ITEM (widget);
+  GtkWidget *child;
+
+  /* The idea of this function is the following:
+   * 1. If any child can take focus, do not ever attempt
+   *    to take focus.
+   * 2. Otherwise, if this item is selectable or activatable,
+   *    allow focusing this widget.
+   *
+   * This makes sure every item in a list is focusable for
+   * activation and selection handling, but no useless widgets
+   * get focused and moving focus is as fast as possible.
+   */
+  child = gtk_bin_get_child (GTK_BIN (self));
+
+  if (child)
+    {
+      if (gtk_widget_get_focus_child (widget))
+        return FALSE;
+      if (gtk_widget_child_focus (child, direction))
+        return TRUE;
+    }
+
+  if (!gtk_widget_get_can_focus (widget) ||
+      !self->selectable)
+    return FALSE;
+
+  gtk_widget_grab_focus (widget);
+  return TRUE;
+}
+
 static void
 gtk_list_item_dispose (GObject *object)
 {
@@ -146,6 +181,8 @@ gtk_list_item_class_init (GtkListItemClass *klass)
   GtkWidgetClass *widget_class = GTK_WIDGET_CLASS (klass);
   GObjectClass *gobject_class = G_OBJECT_CLASS (klass);
 
+  widget_class->focus = gtk_list_item_focus;
+
   gobject_class->dispose = gtk_list_item_dispose;
   gobject_class->get_property = gtk_list_item_get_property;
   gobject_class->set_property = gtk_list_item_set_property;
@@ -471,7 +508,5 @@ gtk_list_item_set_selectable (GtkListItem *self,
 
   self->selectable = selectable;
 
-  gtk_widget_set_can_focus (GTK_WIDGET (self), self->selectable);
-
   g_object_notify_by_pspec (G_OBJECT (self), properties[PROP_SELECTABLE]);
 }