[gtk+] scrolledwindow: Be smarter at invalidating overshoot areas

[Carlos Garnacho <carlosg src gnome org>]

commit 42c41d7bbdd604ef33baf1eb40780c06da93d0d4
Author: Carlos Garnacho <carlosg gnome org>
Date:   Sun Jul 27 13:39:51 2014 +0200

    scrolledwindow: Be smarter at invalidating overshoot areas
    
    The previous way to invalidate was meant to work on the overshoot window
    so it wouldn't be as taxing. Since the overshoot window is gone, this
    would invalidate way more than intended. So constrain invalidated areas
    to the sides where overshoot is happenning at that moment.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=735223

 gtk/gtkscrolledwindow.c |   56 ++++++++++++++++++++++++++++++++++++++++++++--
 1 files changed, 53 insertions(+), 3 deletions(-)
---
diff --git a/gtk/gtkscrolledwindow.c b/gtk/gtkscrolledwindow.c
index fd090cb..79f8cd8 100644
--- a/gtk/gtkscrolledwindow.c
+++ b/gtk/gtkscrolledwindow.c
@@ -601,6 +601,53 @@ scrolled_window_drag_begin_cb (GtkScrolledWindow *scrolled_window,
 }
 
 static void
+gtk_scrolled_window_invalidate_overshoot (GtkScrolledWindow *scrolled_window)
+{
+  GtkAllocation child_allocation, allocation;
+  gint overshoot_x, overshoot_y;
+  GdkRectangle rect;
+
+  if (!_gtk_scrolled_window_get_overshoot (scrolled_window, &overshoot_x, &overshoot_y))
+    return;
+
+  gtk_widget_get_allocation (GTK_WIDGET (scrolled_window), &allocation);
+  gtk_scrolled_window_relative_allocation (GTK_WIDGET (scrolled_window),
+                                           &child_allocation);
+  child_allocation.x += allocation.x;
+  child_allocation.y += allocation.y;
+
+  if (overshoot_x != 0)
+    {
+      if (overshoot_x < 0)
+        rect.x = child_allocation.x;
+      else
+        rect.x = child_allocation.x + child_allocation.width - MAX_OVERSHOOT_DISTANCE;
+
+      rect.y = child_allocation.y;
+      rect.width = MAX_OVERSHOOT_DISTANCE;
+      rect.height = child_allocation.height;
+
+      gdk_window_invalidate_rect (gtk_widget_get_window (GTK_WIDGET (scrolled_window)),
+                                  &rect, TRUE);
+    }
+
+  if (overshoot_y != 0)
+    {
+      if (overshoot_y < 0)
+        rect.y = child_allocation.y;
+      else
+        rect.y = child_allocation.y + child_allocation.height - MAX_OVERSHOOT_DISTANCE;
+
+      rect.x = child_allocation.x;
+      rect.width = child_allocation.width;
+      rect.height = MAX_OVERSHOOT_DISTANCE;
+
+      gdk_window_invalidate_rect (gtk_widget_get_window (GTK_WIDGET (scrolled_window)),
+                                  &rect, TRUE);
+    }
+}
+
+static void
 scrolled_window_drag_update_cb (GtkScrolledWindow *scrolled_window,
                                 gdouble            offset_x,
                                 gdouble            offset_y,
@@ -611,6 +658,8 @@ scrolled_window_drag_update_cb (GtkScrolledWindow *scrolled_window,
   GtkAdjustment *vadjustment;
   gdouble dx, dy;
 
+  gtk_scrolled_window_invalidate_overshoot (scrolled_window);
+
   if (!priv->capture_button_press)
     {
       GdkEventSequence *sequence;
@@ -636,8 +685,7 @@ scrolled_window_drag_update_cb (GtkScrolledWindow *scrolled_window,
                                                  dy, TRUE, FALSE);
     }
 
-  gdk_window_invalidate_rect (gtk_widget_get_window (GTK_WIDGET (scrolled_window)),
-                              NULL, FALSE);
+  gtk_scrolled_window_invalidate_overshoot (scrolled_window);
 }
 
 static void
@@ -2501,6 +2549,8 @@ scrolled_window_deceleration_cb (GtkWidget         *widget,
   hadjustment = gtk_range_get_adjustment (GTK_RANGE (priv->hscrollbar));
   vadjustment = gtk_range_get_adjustment (GTK_RANGE (priv->vscrollbar));
 
+  gtk_scrolled_window_invalidate_overshoot (scrolled_window);
+
   if (data->hscrolling &&
       gtk_kinetic_scrolling_tick (data->hscrolling, elapsed, &position))
     {
@@ -2525,7 +2575,7 @@ scrolled_window_deceleration_cb (GtkWidget         *widget,
       return G_SOURCE_REMOVE;
     }
 
-  gdk_window_invalidate_rect (gtk_widget_get_window (widget), NULL, FALSE);
+  gtk_scrolled_window_invalidate_overshoot (scrolled_window);
 
   return G_SOURCE_CONTINUE;
 }