Merge WebKit at r80534: Intial merge by Git

Change-Id: Ia7a83357124c9e1cdb1debf55d9661ec0bd09a61

1 files changed, 14 insertions, 2 deletions

diff --git a/Source/WebCore/platform/gtk/MainFrameScrollbarGtk.cpp b/Source/WebCore/platform/gtk/MainFrameScrollbarGtk.cpp
index d1571a5..d8cdb79 100644
--- a/Source/WebCore/platform/gtk/MainFrameScrollbarGtk.cpp
+++ b/Source/WebCore/platform/gtk/MainFrameScrollbarGtk.cpp
@@ -60,6 +60,8 @@ MainFrameScrollbarGtk::~MainFrameScrollbarGtk()
 
 void MainFrameScrollbarGtk::attachAdjustment(GtkAdjustment* adjustment)
 {
+    if (m_adjustment.get() == adjustment)
+        return;
     if (m_adjustment)
         detachAdjustment();
 
@@ -67,9 +69,9 @@ void MainFrameScrollbarGtk::attachAdjustment(GtkAdjustment* adjustment)
     if (!m_adjustment)
         return;
 
-    g_signal_connect(m_adjustment.get(), "value-changed", G_CALLBACK(MainFrameScrollbarGtk::gtkValueChanged), this);
     updateThumbProportion();
     updateThumbPosition();
+    g_signal_connect(m_adjustment.get(), "value-changed", G_CALLBACK(MainFrameScrollbarGtk::gtkValueChanged), this);
 }
 
 void MainFrameScrollbarGtk::detachAdjustment()
@@ -109,7 +111,17 @@ void MainFrameScrollbarGtk::updateThumbProportion()
 
 void MainFrameScrollbarGtk::gtkValueChanged(GtkAdjustment*, MainFrameScrollbarGtk* that)
 {
-    that->scrollableArea()->scrollToOffsetWithoutAnimation(that->orientation(), static_cast<int>(gtk_adjustment_get_value(that->m_adjustment.get())));
+    // If we've been removed from our parent, we no longer get to control the WebCore
+    // scrollbar. If this is the case, deactivate this signal handler. WebCore will
+    // create a fresh MainFrameScrollbar when the scrollbar reappears.
+    if (!that->parent()) {
+        that->detachAdjustment();
+        return;
+    }
+
+    int newValue = static_cast<int>(gtk_adjustment_get_value(that->m_adjustment.get()));
+    if (newValue != that->value())
+        that->scrollableArea()->scrollToOffsetWithoutAnimation(that->orientation(), newValue);
 }
 
 void MainFrameScrollbarGtk::paint(GraphicsContext* context, const IntRect& rect)