app: allow to position overlay widgets absolutely

app/widgets/gimpoverlaybox.c

@@ -363,7 +363,7 @@ gimp_overlay_box_add_child (GimpOverlayBox *box,
 }
 
 void
-gimp_overlay_box_set_child_packing (GimpOverlayBox *box,
+gimp_overlay_box_set_child_alignment (GimpOverlayBox *box,
                                       GtkWidget      *widget,
                                       gdouble         xalign,
                                       gdouble         yalign)
@@ -375,11 +375,13 @@ gimp_overlay_box_set_child_packing (GimpOverlayBox *box,
       xalign = CLAMP (xalign, 0.0, 1.0);
       yalign = CLAMP (yalign, 0.0, 1.0);
 
-      if (child->xalign != xalign ||
+      if (child->has_position     ||
+          child->xalign != xalign ||
           child->yalign != yalign)
         {
           gimp_overlay_child_invalidate (box, child);
 
+          child->has_position = FALSE;
           child->xalign       = xalign;
           child->yalign       = yalign;
 
@@ -388,6 +390,31 @@ gimp_overlay_box_set_child_packing (GimpOverlayBox *box,
     }
 }
 
+void
+gimp_overlay_box_set_child_position (GimpOverlayBox *box,
+                                     GtkWidget      *widget,
+                                     gdouble         x,
+                                     gdouble         y)
+{
+  GimpOverlayChild *child = gimp_overlay_child_find (box, widget);
+
+  if (child)
+    {
+      if (! child->has_position ||
+          child->x != x         ||
+          child->y != y)
+        {
+          gimp_overlay_child_invalidate (box, child);
+
+          child->has_position = TRUE;
+          child->x            = x;
+          child->y            = y;
+
+          gtk_widget_queue_resize (widget);
+        }
+    }
+}
+
 void
 gimp_overlay_box_set_child_angle (GimpOverlayBox *box,
                                   GtkWidget      *widget,
@@ -453,13 +480,21 @@ gimp_overlay_box_scroll (GimpOverlayBox *box,
 
   /*  Undraw all overlays  */
   for (list = box->children; list; list = g_list_next (list))
-    gimp_overlay_child_invalidate (box, list->data);
+    {
+      GimpOverlayChild *child = list->data;
+
+      gimp_overlay_child_invalidate (box, child);
+    }
 
   gdk_window_scroll (window, offset_x, offset_y);
 
   /*  Re-draw all overlays  */
   for (list = box->children; list; list = g_list_next (list))
-    gimp_overlay_child_invalidate (box, list->data);
+    {
+      GimpOverlayChild *child = list->data;
+
+      gimp_overlay_child_invalidate (box, child);
+    }
 
   /*  Make sure expose events are processed before scrolling again  */
   gdk_window_process_updates (window, FALSE);

app/widgets/gimpoverlaybox.h

@@ -49,22 +49,26 @@ GType       gimp_overlay_box_get_type          (void) G_GNUC_CONST;
 
 GtkWidget * gimp_overlay_box_new                 (void);
 
-void        gimp_overlay_box_add_child         (GimpOverlayBox *canvas,
+void        gimp_overlay_box_add_child           (GimpOverlayBox *box,
                                                   GtkWidget      *child,
                                                   gdouble         xalign,
                                                   gdouble         yalign);
-void        gimp_overlay_box_set_child_packing (GimpOverlayBox *canvas,
+void        gimp_overlay_box_set_child_alignment (GimpOverlayBox *box,
                                                   GtkWidget      *child,
                                                   gdouble         xalign,
                                                   gdouble         yalign);
-void        gimp_overlay_box_set_child_angle   (GimpOverlayBox *canvas,
+void        gimp_overlay_box_set_child_position  (GimpOverlayBox *box,
+                                                  GtkWidget      *child,
+                                                  gdouble         x,
+                                                  gdouble         y);
+void        gimp_overlay_box_set_child_angle     (GimpOverlayBox *box,
                                                   GtkWidget      *child,
                                                   gdouble         angle);
-void        gimp_overlay_box_set_child_opacity (GimpOverlayBox *canvas,
+void        gimp_overlay_box_set_child_opacity   (GimpOverlayBox *box,
                                                   GtkWidget      *child,
                                                   gdouble         opacity);
 
-void        gimp_overlay_box_scroll            (GimpOverlayBox *canvas,
+void        gimp_overlay_box_scroll              (GimpOverlayBox *box,
                                                   gint            offset_x,
                                                   gint            offset_y);
 

app/widgets/gimpoverlaychild.c

@@ -72,6 +72,9 @@ gimp_overlay_child_new (GimpOverlayBox *box,
   child->widget       = widget;
   child->xalign       = CLAMP (xalign, 0.0, 1.0);
   child->yalign       = CLAMP (yalign, 0.0, 1.0);
+  child->x            = 0.0;
+  child->y            = 0.0;
+  child->has_position = FALSE;
   child->angle        = angle;
   child->opacity      = CLAMP (opacity, 0.0, 1.0);
 
@@ -271,6 +274,13 @@ gimp_overlay_child_size_allocate (GimpOverlayBox   *box,
   available_width  = allocation.width  - 2 * border;
   available_height = allocation.height - 2 * border;
 
+  if (child->has_position)
+    {
+      x = child->x;
+      y = child->y;
+    }
+  else
+    {
       x = border;
       y = border;
 
@@ -279,6 +289,7 @@ gimp_overlay_child_size_allocate (GimpOverlayBox   *box,
 
       if (available_height > bounds.height)
         y += child->yalign * (available_height - bounds.height) - bounds.y;
+    }
 
   cairo_matrix_init_translate (&child->matrix, x, y);
 

app/widgets/gimpoverlaychild.h

@@ -29,8 +29,13 @@ struct _GimpOverlayChild
 {
   GtkWidget      *widget;
   GdkWindow      *window;
+
+  gboolean        has_position;
   gdouble         xalign;
   gdouble         yalign;
+  gdouble         x;
+  gdouble         y;
+
   gdouble         angle;
   gdouble         opacity;