app: add handle-clicked signal to GimpToolLine

... which is emitted when a handle is single/double/tripple clicked.

The signal handler returns a boolean value.  A return value of TRUE
stops further event processing, while a return value of FALSE allows
it.

app/core/gimpmarshal.list

@@ -25,6 +25,7 @@
 BOOLEAN: BOOLEAN
 BOOLEAN: DOUBLE
 BOOLEAN: ENUM, INT
+BOOLEAN: INT, UINT, ENUM
 BOOLEAN: OBJECT
 BOOLEAN: OBJECT, POINTER
 BOOLEAN: OBJECT, POINTER, STRING

app/display/gimptoolline.c

@@ -88,6 +88,7 @@ enum
   PREPARE_TO_REMOVE_SLIDER,
   REMOVE_SLIDER,
   SELECTION_CHANGED,
+  HANDLE_CLICKED,
   LAST_SIGNAL
 };
 
@@ -273,6 +274,18 @@ gimp_tool_line_class_init (GimpToolLineClass *klass)
                   g_cclosure_marshal_VOID__VOID,
                   G_TYPE_NONE, 0);
 
+  line_signals[HANDLE_CLICKED] =
+    g_signal_new ("handle-clicked",
+                  G_TYPE_FROM_CLASS (klass),
+                  G_SIGNAL_RUN_LAST,
+                  G_STRUCT_OFFSET (GimpToolLineClass, handle_clicked),
+                  NULL, NULL,
+                  gimp_marshal_BOOLEAN__INT_UINT_ENUM,
+                  G_TYPE_BOOLEAN, 3,
+                  G_TYPE_INT,
+                  G_TYPE_UINT,
+                  GIMP_TYPE_BUTTON_PRESS_TYPE);
+
   g_object_class_install_property (object_class, PROP_X1,
                                    g_param_spec_double ("x1", NULL, NULL,
                                                         -GIMP_MAX_IMAGE_SIZE,
@@ -602,6 +615,7 @@ gimp_tool_line_button_press (GimpToolWidget      *widget,
 {
   GimpToolLine        *line    = GIMP_TOOL_LINE (widget);
   GimpToolLinePrivate *private = line->private;
+  gboolean             result  = FALSE;
 
   private->grab          = GRAB_NONE;
   private->remove_slider = FALSE;
@@ -611,6 +625,24 @@ gimp_tool_line_button_press (GimpToolWidget      *widget,
   private->saved_x2 = private->x2;
   private->saved_y2 = private->y2;
 
+  if (press_type         != GIMP_BUTTON_PRESS_NORMAL   &&
+      private->hover      > GIMP_TOOL_LINE_HANDLE_NONE &&
+      private->selection  > GIMP_TOOL_LINE_HANDLE_NONE)
+    {
+      g_signal_emit (line, line_signals[HANDLE_CLICKED], 0,
+                     private->selection, state, press_type, &result);
+
+      if (! result)
+        gimp_tool_widget_hover (widget, coords, state, TRUE);
+    }
+
+  if (press_type == GIMP_BUTTON_PRESS_NORMAL || ! result)
+    {
+      private->saved_x1 = private->x1;
+      private->saved_y1 = private->y1;
+      private->saved_x2 = private->x2;
+      private->saved_y2 = private->y2;
+
       if (GIMP_TOOL_LINE_HANDLE_IS_SLIDER (private->hover))
         {
           private->saved_slider_value =
@@ -647,7 +679,10 @@ gimp_tool_line_button_press (GimpToolWidget      *widget,
           private->grab = GRAB_LINE;
         }
 
-  if (grab == GRAB_NONE)
+      result = (private->grab != GRAB_NONE);
+    }
+
+  if (! result)
     {
       private->hover = GIMP_TOOL_LINE_HANDLE_NONE;
 
@@ -657,7 +692,7 @@ gimp_tool_line_button_press (GimpToolWidget      *widget,
   gimp_tool_line_update_handles (line);
   gimp_tool_line_update_status (line, state, TRUE);
 
-  return private->grab != GRAB_NONE;
+  return result;
 }
 
 void
@@ -700,13 +735,24 @@ gimp_tool_line_button_release (GimpToolWidget        *widget,
                         NULL);
         }
     }
-  else if (grab == GRAB_SELECTION && private->remove_slider)
+  else if (grab == GRAB_SELECTION)
+    {
+      if (private->remove_slider)
         {
           private->remove_slider = FALSE;
 
           g_signal_emit (line, line_signals[REMOVE_SLIDER], 0,
                          private->selection);
         }
+      else if (release_type == GIMP_BUTTON_RELEASE_CLICK)
+        {
+          gboolean result;
+
+          g_signal_emit (line, line_signals[HANDLE_CLICKED], 0,
+                         private->selection, state, GIMP_BUTTON_PRESS_NORMAL,
+                         &result);
+        }
+    }
 }
 
 void

app/display/gimptoolline.h

@@ -70,6 +70,10 @@ struct _GimpToolLineClass
   void     (* remove_slider)            (GimpToolLine        *line,
                                          gint                 slider);
   void     (* selection_changed)        (GimpToolLine        *line);
+  gboolean (* handle_clicked)           (GimpToolLine        *line,
+                                         gint                 handle,
+                                         GdkModifierType      state,
+                                         GimpButtonPressType  press_type);
 };