app: add virtual function gboolean GimpCanvasItem::hit()

and implement it for GimpCanvasHandle and GimpCanvasGroup.

app/display/gimpcanvasgroup.c

@@ -72,6 +72,11 @@ static void             gimp_canvas_group_draw         (GimpCanvasItem   *item,
                                                         cairo_t          *cr);
 static cairo_region_t * gimp_canvas_group_get_extents  (GimpCanvasItem   *item,
                                                         GimpDisplayShell *shell);
+static gboolean         gimp_canvas_group_hit          (GimpCanvasItem   *item,
+                                                        GimpDisplayShell *shell,
+                                                        gdouble           x,
+                                                        gdouble           y);
+
 static void             gimp_canvas_group_child_update (GimpCanvasItem   *item,
                                                         cairo_region_t   *region,
                                                         GimpCanvasGroup  *group);
@@ -94,6 +99,7 @@ gimp_canvas_group_class_init (GimpCanvasGroupClass *klass)
 
   item_class->draw           = gimp_canvas_group_draw;
   item_class->get_extents    = gimp_canvas_group_get_extents;
+  item_class->hit            = gimp_canvas_group_hit;
 
   g_object_class_install_property (object_class, PROP_GROUP_STROKING,
                                    g_param_spec_boolean ("group-stroking",
@@ -224,6 +230,24 @@ gimp_canvas_group_get_extents (GimpCanvasItem   *item,
   return region;
 }
 
+static gboolean
+gimp_canvas_group_hit (GimpCanvasItem   *item,
+                       GimpDisplayShell *shell,
+                       gdouble           x,
+                       gdouble           y)
+{
+  GimpCanvasGroupPrivate *private = GET_PRIVATE (item);
+  GList                  *list;
+
+  for (list = private->items; list; list = g_list_next (list))
+    {
+      if (gimp_canvas_item_hit (list->data, x, y))
+        return TRUE;
+    }
+
+  return FALSE;
+}
+
 static void
 gimp_canvas_group_child_update (GimpCanvasItem  *item,
                                 cairo_region_t  *region,

app/display/gimpcanvashandle.c

@@ -85,6 +85,10 @@ static void             gimp_canvas_handle_draw         (GimpCanvasItem   *item,
                                                          cairo_t          *cr);
 static cairo_region_t * gimp_canvas_handle_get_extents  (GimpCanvasItem   *item,
                                                          GimpDisplayShell *shell);
+static gboolean         gimp_canvas_handle_hit          (GimpCanvasItem   *item,
+                                                         GimpDisplayShell *shell,
+                                                         gdouble           x,
+                                                         gdouble           y);
 
 
 G_DEFINE_TYPE (GimpCanvasHandle, gimp_canvas_handle,
@@ -104,6 +108,7 @@ gimp_canvas_handle_class_init (GimpCanvasHandleClass *klass)
 
   item_class->draw           = gimp_canvas_handle_draw;
   item_class->get_extents    = gimp_canvas_handle_get_extents;
+  item_class->hit            = gimp_canvas_handle_hit;
 
   g_object_class_install_property (object_class, PROP_TYPE,
                                    g_param_spec_enum ("type", NULL, NULL,
@@ -380,6 +385,50 @@ gimp_canvas_handle_get_extents (GimpCanvasItem   *item,
   return cairo_region_create_rectangle ((cairo_rectangle_int_t *) &rectangle);
 }
 
+static gboolean
+gimp_canvas_handle_hit (GimpCanvasItem   *item,
+                        GimpDisplayShell *shell,
+                        gdouble           x,
+                        gdouble           y)
+{
+  GimpCanvasHandlePrivate *private = GET_PRIVATE (item);
+  gdouble                  handle_tx, handle_ty;
+  gdouble                  tx, ty;
+
+  gimp_canvas_handle_transform (item, shell, &handle_tx, &handle_ty);
+
+  gimp_display_shell_transform_xy_f (shell,
+                                     x, y,
+                                     &tx, &ty);
+
+  switch (private->type)
+    {
+    case GIMP_HANDLE_SQUARE:
+    case GIMP_HANDLE_FILLED_SQUARE:
+     return (tx == CLAMP (tx, handle_tx, handle_tx + private->width) &&
+              ty == CLAMP (ty, handle_ty, handle_ty + private->height));
+
+    case GIMP_HANDLE_CIRCLE:
+    case GIMP_HANDLE_FILLED_CIRCLE:
+    case GIMP_HANDLE_CROSS:
+      {
+        gint width = private->width;
+
+        if (width != private->height)
+          width = (width + private->height) / 2;
+
+        width /= 2;
+
+        return ((SQR (handle_tx - tx) + SQR (handle_ty - ty)) < SQR (width));
+      }
+
+    default:
+      break;
+    }
+
+  return FALSE;
+}
+
 GimpCanvasItem *
 gimp_canvas_handle_new (GimpDisplayShell *shell,
                         GimpHandleType    type,

app/display/gimpcanvasitem.c

@@ -96,6 +96,10 @@ static void             gimp_canvas_item_real_stroke      (GimpCanvasItem   *ite
 static void             gimp_canvas_item_real_fill        (GimpCanvasItem   *item,
                                                            GimpDisplayShell *shell,
                                                            cairo_t          *cr);
+static gboolean         gimp_canvas_item_real_hit         (GimpCanvasItem   *item,
+                                                           GimpDisplayShell *shell,
+                                                           gdouble           x,
+                                                           gdouble           y);
 
 
 G_DEFINE_TYPE (GimpCanvasItem, gimp_canvas_item,
@@ -121,6 +125,7 @@ gimp_canvas_item_class_init (GimpCanvasItemClass *klass)
   klass->get_extents                        = gimp_canvas_item_real_get_extents;
   klass->stroke                             = gimp_canvas_item_real_stroke;
   klass->fill                               = gimp_canvas_item_real_fill;
+  klass->hit                                = gimp_canvas_item_real_hit;
 
   item_signals[UPDATE] =
     g_signal_new ("update",
@@ -318,6 +323,15 @@ gimp_canvas_item_real_fill (GimpCanvasItem   *item,
   cairo_fill (cr);
 }
 
+static gboolean
+gimp_canvas_item_real_hit (GimpCanvasItem   *item,
+                           GimpDisplayShell *shell,
+                           gdouble           x,
+                           gdouble           y)
+{
+  return FALSE;
+}
+
 
 /*  public functions  */
 
@@ -355,6 +369,20 @@ gimp_canvas_item_get_extents (GimpCanvasItem *item)
   return NULL;
 }
 
+gboolean
+gimp_canvas_item_hit (GimpCanvasItem   *item,
+                      gdouble           x,
+                      gdouble           y)
+{
+  GimpCanvasItemPrivate *private;
+
+  g_return_val_if_fail (GIMP_IS_CANVAS_ITEM (item), NULL);
+
+  private = GET_PRIVATE (item);
+
+  return GIMP_CANVAS_ITEM_GET_CLASS (item)->hit (item, private->shell, x, y);
+}
+
 void
 gimp_canvas_item_set_visible (GimpCanvasItem *item,
                               gboolean        visible)

app/display/gimpcanvasitem.h

@@ -61,6 +61,11 @@ struct _GimpCanvasItemClass
   void             (* fill)        (GimpCanvasItem   *item,
                                     GimpDisplayShell *shell,
                                     cairo_t          *cr);
+
+  gboolean         (* hit)         (GimpCanvasItem   *item,
+                                    GimpDisplayShell *shell,
+                                    gdouble           x,
+                                    gdouble           y);
 };
 
 
@@ -70,6 +75,10 @@ void             gimp_canvas_item_draw             (GimpCanvasItem   *item,
                                                     cairo_t          *cr);
 cairo_region_t * gimp_canvas_item_get_extents      (GimpCanvasItem   *item);
 
+gboolean         gimp_canvas_item_hit              (GimpCanvasItem   *item,
+                                                    gdouble           x,
+                                                    gdouble           y);
+
 void             gimp_canvas_item_set_visible      (GimpCanvasItem   *item,
                                                     gboolean          visible);
 gboolean         gimp_canvas_item_get_visible      (GimpCanvasItem   *item);