listbase: Add rubberband selection

Implement the typical rubberband selection, including
autoscroll. This is only useful with multiselection,
and not very compatible with single-click-activate.
Therefore, it is not enabled by default, and needs
to be turned on explicitly.

gtk/gtklistbase.c

@@ -28,6 +28,12 @@
 #include "gtkscrollable.h"
 #include "gtksingleselection.h"
 #include "gtktypebuiltins.h"
+#include "gtkgesturedrag.h"
+#include "gtkwidgetprivate.h"
+#include "gtkcssnodeprivate.h"
+#include "gtkstylecontextprivate.h"
+#include "gtksnapshot.h"
+#include "gtkmultiselection.h"
 
 typedef struct _GtkListBasePrivate GtkListBasePrivate;
 
@@ -50,6 +56,18 @@ struct _GtkListBasePrivate
   GtkListItemTracker *selected;
   /* the item that has input focus */
   GtkListItemTracker *focus;
+
+  gboolean enable_rubberband;
+  gboolean doing_rubberband;
+  double rb_x1;
+  double rb_y1;
+  double rb_x2;
+  double rb_y2;
+  GtkGesture *drag_gesture;
+  GtkCssNode *rubberband_node;
+  GtkSelectionModel *old_selection;
+  gboolean modify;
+  gboolean extend;
 };
 
 enum
@@ -1061,6 +1079,20 @@ gtk_list_base_add_custom_move_binding (GtkWidgetClass  *widget_class,
                                 "(bbb)", TRUE, TRUE, TRUE);
 }
 
+static void gtk_list_base_snapshot_rubberband (GtkListBase *self,
+                                               GtkSnapshot *snapshot);
+
+static void
+gtk_list_base_snapshot (GtkWidget   *widget,
+                        GtkSnapshot *snapshot)
+{
+  GtkListBase *self = GTK_LIST_BASE (widget);
+
+  GTK_WIDGET_CLASS (gtk_list_base_parent_class)->snapshot (widget, snapshot);
+
+  gtk_list_base_snapshot_rubberband (self, snapshot);
+}
+
 static void
 gtk_list_base_class_init (GtkListBaseClass *klass)
 {
@@ -1069,6 +1101,7 @@ gtk_list_base_class_init (GtkListBaseClass *klass)
   gpointer iface;
 
   widget_class->focus = gtk_list_base_focus;
+  widget_class->snapshot = gtk_list_base_snapshot;
 
   gobject_class->dispose = gtk_list_base_dispose;
   gobject_class->get_property = gtk_list_base_get_property;
@@ -1186,6 +1219,258 @@ gtk_list_base_class_init (GtkListBaseClass *klass)
   gtk_widget_class_add_binding_action (widget_class, GDK_KEY_backslash, GDK_CONTROL_MASK, "list.unselect-all", NULL);
 }
 
+static void gtk_list_base_update_rubberband_selection (GtkListBase *self);
+
+static void
+gtk_list_base_start_rubberband (GtkListBase *self,
+                                double       x,
+                                double       y,
+                                gboolean     modify,
+                                gboolean     extend)
+{
+  GtkListBasePrivate *priv = gtk_list_base_get_instance_private (self);
+  GtkCssNode *widget_node;
+  double value_x, value_y;
+  GtkSelectionModel *selection;
+
+  if (priv->doing_rubberband)
+    return;
+
+  value_x = gtk_adjustment_get_value (priv->adjustment[GTK_ORIENTATION_HORIZONTAL]);
+  value_y = gtk_adjustment_get_value (priv->adjustment[GTK_ORIENTATION_VERTICAL]);
+
+  priv->rb_x1 = priv->rb_x2 = x + value_x;
+  priv->rb_y1 = priv->rb_y2 = y + value_y;
+
+  priv->modify = modify;
+  priv->extend = extend;
+
+  widget_node = gtk_widget_get_css_node (GTK_WIDGET (self));
+  priv->rubberband_node = gtk_css_node_new ();
+  gtk_css_node_set_name (priv->rubberband_node,
+                         g_quark_from_static_string ("rubberband"));
+  gtk_css_node_set_parent (priv->rubberband_node, widget_node);
+  gtk_css_node_set_state (priv->rubberband_node, gtk_css_node_get_state (widget_node));
+  g_object_unref (priv->rubberband_node);
+
+  selection = gtk_list_item_manager_get_model (priv->item_manager);
+
+  if (modify)
+    priv->old_selection = GTK_SELECTION_MODEL (gtk_multi_selection_copy (selection));
+
+  priv->doing_rubberband = TRUE;
+}
+
+static void
+gtk_list_base_stop_rubberband (GtkListBase *self)
+{
+  GtkListBasePrivate *priv = gtk_list_base_get_instance_private (self);
+
+  if (!priv->doing_rubberband)
+    return;
+
+  priv->doing_rubberband = FALSE;
+  gtk_css_node_set_parent (priv->rubberband_node, NULL);
+  priv->rubberband_node = NULL;
+
+  g_clear_object (&priv->old_selection);
+
+  gtk_widget_queue_draw (GTK_WIDGET (self));
+}
+
+#define SCROLL_EDGE_SIZE 15
+
+static void
+gtk_list_base_update_rubberband (GtkListBase *self,
+                                 double       x,
+                                 double       y)
+{
+  GtkListBasePrivate *priv = gtk_list_base_get_instance_private (self);
+  double value_x, value_y;
+
+  if (!priv->doing_rubberband)
+    return;
+
+  value_x = gtk_adjustment_get_value (priv->adjustment[GTK_ORIENTATION_HORIZONTAL]);
+  value_y = gtk_adjustment_get_value (priv->adjustment[GTK_ORIENTATION_VERTICAL]);
+
+  priv->rb_x2 = x + value_x;
+  priv->rb_y2 = y + value_y;
+
+  gtk_list_base_update_rubberband_selection (self);
+
+  gtk_widget_queue_draw (GTK_WIDGET (self));
+}
+
+static void
+gtk_list_base_update_rubberband_selection (GtkListBase *self)
+{
+  GtkListBasePrivate *priv = gtk_list_base_get_instance_private (self);
+  GdkRectangle rect;
+  GdkRectangle alloc;
+  double value_x, value_y;
+  GtkSelectionModel *model;
+  GtkListItemManagerItem *item;
+
+  value_x = gtk_adjustment_get_value (priv->adjustment[GTK_ORIENTATION_HORIZONTAL]);
+  value_y = gtk_adjustment_get_value (priv->adjustment[GTK_ORIENTATION_VERTICAL]);
+
+  rect.x = MIN (priv->rb_x1, priv->rb_x2) - value_x;
+  rect.y = MIN (priv->rb_y1, priv->rb_y2) - value_y;
+  rect.width = ABS (priv->rb_x1 - priv->rb_x2) + 1;
+  rect.height = ABS (priv->rb_y1 - priv->rb_y2) + 1;
+
+  model = gtk_list_item_manager_get_model (priv->item_manager);
+
+  for (item = gtk_list_item_manager_get_first (priv->item_manager);
+       item != NULL;
+       item = gtk_rb_tree_node_get_next (item))
+    {
+      guint pos;
+      gboolean was_selected, selected;
+
+      if (!item->widget)
+        continue;
+
+      pos = gtk_list_item_manager_get_item_position (priv->item_manager, item);
+
+      gtk_widget_get_allocation (item->widget, &alloc);
+
+      selected = gdk_rectangle_intersect (&rect, &alloc, &alloc);
+
+      if (priv->modify)
+        {
+          was_selected = gtk_selection_model_is_selected (priv->old_selection, pos);
+          selected = selected ^ was_selected;
+        }
+
+      if (selected)
+        gtk_selection_model_select_item (model, pos, FALSE);
+      else if (!priv->extend)
+        gtk_selection_model_unselect_item (model, pos);
+    }
+}
+
+static void
+gtk_list_base_snapshot_rubberband (GtkListBase *self,
+                                   GtkSnapshot *snapshot)
+{
+  GtkListBasePrivate *priv = gtk_list_base_get_instance_private (self);
+  GtkStyleContext *context;
+  GdkRectangle rect;
+  double value_x, value_y;
+
+  if (!priv->doing_rubberband)
+    return;
+
+  value_x = gtk_adjustment_get_value (priv->adjustment[GTK_ORIENTATION_HORIZONTAL]);
+  value_y = gtk_adjustment_get_value (priv->adjustment[GTK_ORIENTATION_VERTICAL]);
+
+  rect.x = MIN (priv->rb_x1, priv->rb_x2) - value_x;
+  rect.y = MIN (priv->rb_y1, priv->rb_y2) - value_y;
+  rect.width = ABS (priv->rb_x1 - priv->rb_x2) + 1;
+  rect.height = ABS (priv->rb_y1 - priv->rb_y2) + 1;
+
+  context = gtk_widget_get_style_context (GTK_WIDGET (self));
+
+  gtk_style_context_save_to_node (context, priv->rubberband_node);
+
+  gtk_snapshot_render_background (snapshot, context, rect.x, rect.y, rect.width, rect.height);
+  gtk_snapshot_render_frame (snapshot, context, rect.x, rect.y, rect.width, rect.height);
+
+  gtk_style_context_restore (context);
+
+}
+
+static void
+get_selection_modifiers (GtkGesture *gesture,
+                         gboolean   *modify,
+                         gboolean   *extend)
+{
+  GdkEventSequence *sequence;
+  GdkEvent *event;
+  GdkModifierType state;
+
+  *modify = FALSE;
+  *extend = FALSE;
+
+  sequence = gtk_gesture_get_last_updated_sequence (gesture);
+  event = gtk_gesture_get_last_event (gesture, sequence);
+  state = gdk_event_get_modifier_state (event);
+  if ((state & GDK_CONTROL_MASK) == GDK_CONTROL_MASK)
+    *modify = TRUE;
+  if ((state & GDK_SHIFT_MASK) == GDK_SHIFT_MASK)
+    *extend = TRUE;
+}
+
+static void
+gtk_list_base_drag_begin (GtkGestureDrag *gesture,
+                          double          start_x,
+                          double          start_y,
+                          GtkListBase    *self)
+{
+  gboolean modify;
+  gboolean extend;
+
+  get_selection_modifiers (GTK_GESTURE (gesture), &modify, &extend);
+  gtk_list_base_start_rubberband (self, start_x, start_y, modify, extend);
+}
+
+static void
+gtk_list_base_drag_update (GtkGestureDrag *gesture,
+                           double          offset_x,
+                           double          offset_y,
+                           GtkListBase    *self)
+{
+  double start_x, start_y;
+  gtk_gesture_drag_get_start_point (gesture, &start_x, &start_y);
+  gtk_list_base_update_rubberband (self, start_x + offset_x, start_y + offset_y);
+}
+
+static void
+gtk_list_base_drag_end (GtkGestureDrag *gesture,
+                        double          offset_x,
+                        double          offset_y,
+                        GtkListBase    *self)
+{
+  gtk_list_base_drag_update (gesture, offset_x, offset_y, self);
+  gtk_list_base_stop_rubberband (self);
+}
+
+void
+gtk_list_base_set_enable_rubberband (GtkListBase *self,
+                                     gboolean     enable)
+{
+  GtkListBasePrivate *priv = gtk_list_base_get_instance_private (self);
+
+  if (priv->enable_rubberband == enable)
+    return;
+
+  priv->enable_rubberband = enable;
+
+  if (enable)
+    {
+      priv->drag_gesture = gtk_gesture_drag_new ();
+      g_signal_connect (priv->drag_gesture, "drag-begin", G_CALLBACK (gtk_list_base_drag_begin), self);
+      g_signal_connect (priv->drag_gesture, "drag-update", G_CALLBACK (gtk_list_base_drag_update), self);
+      g_signal_connect (priv->drag_gesture, "drag-end", G_CALLBACK (gtk_list_base_drag_end), self);
+      gtk_widget_add_controller (GTK_WIDGET (self), GTK_EVENT_CONTROLLER (priv->drag_gesture));
+    }
+  else
+    {
+      gtk_widget_remove_controller (GTK_WIDGET (self), GTK_EVENT_CONTROLLER (priv->drag_gesture));
+      priv->drag_gesture = NULL;
+    }
+}
+
+gboolean
+gtk_list_base_get_enable_rubberband (GtkListBase *self)
+{
+  GtkListBasePrivate *priv = gtk_list_base_get_instance_private (self);
+
+  return priv->enable_rubberband;
+}
+
 static void
 gtk_list_base_init_real (GtkListBase      *self,
                          GtkListBaseClass *g_class)
@@ -1537,4 +1822,3 @@ gtk_list_base_set_model (GtkListBase *self,
 
   return TRUE;
 }
-

gtk/gtklistbaseprivate.h

@@ -99,5 +99,8 @@ gboolean               gtk_list_base_grab_focus_on_item         (GtkListBase
                                                                  gboolean                select,
                                                                  gboolean                modify,
                                                                  gboolean                extend);
+void                   gtk_list_base_set_enable_rubberband      (GtkListBase            *self,
+                                                                 gboolean                enable);
+gboolean               gtk_list_base_get_enable_rubberband      (GtkListBase            *self);
 
 #endif /* __GTK_LIST_BASE_PRIVATE_H__ */

gtk/gtklistitemwidget.c

@@ -29,6 +29,7 @@
 #include "gtkintl.h"
 #include "gtklistitemfactoryprivate.h"
 #include "gtklistitemprivate.h"
+#include "gtklistbaseprivate.h"
 #include "gtkmain.h"
 #include "gtkselectionmodel.h"
 #include "gtkwidget.h"
@@ -309,6 +310,8 @@ gtk_list_item_widget_click_gesture_pressed (GtkGestureClick   *gesture,
 {
   GtkListItemWidgetPrivate *priv = gtk_list_item_widget_get_instance_private (self);
   GtkWidget *widget = GTK_WIDGET (self);
+  GtkWidget * parent = gtk_widget_get_parent (widget);
+  gboolean rubberband;
 
   if (priv->list_item && !priv->list_item->selectable && !priv->list_item->activatable)
     {
@@ -316,7 +319,12 @@ gtk_list_item_widget_click_gesture_pressed (GtkGestureClick   *gesture,
       return;
     }
 
-  if (!priv->list_item || priv->list_item->selectable)
+  if (GTK_IS_LIST_BASE (parent))
+    rubberband = gtk_list_base_get_enable_rubberband (GTK_LIST_BASE (parent));
+  else
+    rubberband = FALSE;
+
+  if (!rubberband && (!priv->list_item || priv->list_item->selectable))
     {
       GdkModifierType state;
       GdkEvent *event;