From 42c41d7bbdd604ef33baf1eb40780c06da93d0d4 Mon Sep 17 00:00:00 2001
From: Carlos Garnacho <carlosg@gnome.org>
Date: Sun, 27 Jul 2014 13:39:51 +0200
Subject: [PATCH] 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 file changed, 53 insertions(+), 3 deletions(-)

diff --git a/gtk/gtkscrolledwindow.c b/gtk/gtkscrolledwindow.c
index fd090cb0d0..79f8cd8ddd 100644
--- a/gtk/gtkscrolledwindow.c
+++ b/gtk/gtkscrolledwindow.c
@@ -600,6 +600,53 @@ scrolled_window_drag_begin_cb (GtkScrolledWindow *scrolled_window,
   gtk_gesture_set_sequence_state (gesture, sequence, state);
 }
 
+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,
@@ -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;
 }
-- 
2.30.2