From dd530195e3c9a694767f21f2a8e8a9591078c696 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Caol=C3=A1n=20McNamara?= <caolanm@redhat.com>
Date: Fri, 27 Jun 2014 14:36:01 +0100
Subject: [PATCH] Resolves: fdo#65634 improve wheel-scrolling sidebar panels

Change-Id: I213d85a1e2bbd2377f6f0326433ddd57dc346721
---
 sfx2/source/sidebar/Deck.cxx  | 24 ++----------------------
 sfx2/source/sidebar/Deck.hxx  |  5 +----
 vcl/source/window/winproc.cxx | 42 +++++++++++++++++++++++++++++++++++++++---
 3 files changed, 42 insertions(+), 29 deletions(-)

diff --git a/sfx2/source/sidebar/Deck.cxx b/sfx2/source/sidebar/Deck.cxx
index 3d0f43c..9f89268 100644
--- a/sfx2/source/sidebar/Deck.cxx
+++ b/sfx2/source/sidebar/Deck.cxx
@@ -206,7 +206,7 @@ long Deck::Notify (NotifyEvent& rEvent)
             switch (pCommandEvent->GetCommand())
             {
                 case COMMAND_WHEEL:
-                    return ProcessWheelEvent(pCommandEvent, rEvent)
+                    return ProcessWheelEvent(pCommandEvent)
                         ? sal_True
                         : sal_False;
 
@@ -218,24 +218,13 @@ long Deck::Notify (NotifyEvent& rEvent)
     return Window::Notify(rEvent);
 }
 
-
-
-
-bool Deck::ProcessWheelEvent (
-    CommandEvent* pCommandEvent,
-    NotifyEvent& rEvent)
+bool Deck::ProcessWheelEvent(CommandEvent* pCommandEvent)
 {
     if ( ! mpVerticalScrollBar)
         return false;
     if ( ! mpVerticalScrollBar->IsVisible())
         return false;
 
-    // Ignore all wheel commands from outside the vertical scroll bar.
-    // Otherwise after a scroll we might land on a spin field and
-    // subsequent wheel events would change the value of that control.
-    if (rEvent.GetWindow() != mpVerticalScrollBar.get())
-        return true;
-
     // Get the wheel data and check that it describes a valid vertical
     // scroll.
     const CommandWheelData* pData = pCommandEvent->GetWheelData();
@@ -252,9 +241,6 @@ bool Deck::ProcessWheelEvent (
     return true;
 }
 
-
-
-
 void Deck::SetPanels (const SharedPanelContainer& rPanels)
 {
     maPanels = rPanels;
@@ -288,17 +274,11 @@ void Deck::RequestLayout (void)
         *mpVerticalScrollBar);
 }
 
-
-
-
 ::Window* Deck::GetPanelParentWindow (void)
 {
     return mpScrollContainer.get();
 }
 
-
-
-
 void Deck::ShowPanel (const Panel& rPanel)
 {
     if (mpVerticalScrollBar && mpVerticalScrollBar->IsVisible())
diff --git a/sfx2/source/sidebar/Deck.hxx b/sfx2/source/sidebar/Deck.hxx
index 33eff61..c2f8dfa 100644
--- a/sfx2/source/sidebar/Deck.hxx
+++ b/sfx2/source/sidebar/Deck.hxx
@@ -101,12 +101,9 @@ private:
     ::boost::scoped_ptr<ScrollBar> mpVerticalScrollBar;
 
     DECL_LINK(HandleVerticalScrollBarChange,void*);
-    bool ProcessWheelEvent (
-        CommandEvent* pCommandEvent,
-        NotifyEvent& rEvent);
+    bool ProcessWheelEvent(CommandEvent* pCommandEvent);
 };
 
-
 } } // end of namespace sfx2::sidebar
 
 #endif
diff --git a/vcl/source/window/winproc.cxx b/vcl/source/window/winproc.cxx
index 7a93680..eba587e 100644
--- a/vcl/source/window/winproc.cxx
+++ b/vcl/source/window/winproc.cxx
@@ -1426,10 +1426,27 @@ static sal_Bool ImplCallWheelCommand( Window* pWindow, const Point& rPos,
     return sal_False;
 }
 
-// -----------------------------------------------------------------------
+static bool acceptableWheelScrollTarget(const Window *pMouseWindow)
+{
+    return (pMouseWindow && pMouseWindow->IsInputEnabled() && !pMouseWindow->IsInModalMode());
+}
+
+//If the last event at the same absolute screen position was handled by a
+//different window then reuse that window if the event occurs within 1/2 a
+//second, i.e. so scrolling down something like the calc sidebar that contains
+//widgets that respond to wheel events will continue to send the event to the
+//scrolling widget in favour of the widget that happens to end up under the
+//mouse.
+static bool shouldReusePreviousMouseWindow(const SalWheelMouseEvent& rPrevEvt, const SalWheelMouseEvent& rEvt)
+{
+    return (rEvt.mnX == rPrevEvt.mnX && rEvt.mnY == rPrevEvt.mnY && rEvt.mnTime-rPrevEvt.mnTime < 500/*ms*/);
+}
 
 static long ImplHandleWheelEvent( Window* pWindow, const SalWheelMouseEvent& rEvt, bool scaleDirectly = false )
 {
+    static SalWheelMouseEvent aPreviousEvent;
+    static Window *pPreviousWindow;
+
     ImplDelData aDogTag( pWindow );
 
     ImplSVData* pSVData = ImplGetSVData();
@@ -1485,8 +1502,25 @@ static long ImplHandleWheelEvent( Window* pWindow, const SalWheelMouseEvent& rEv
         bIsFloat = true;
     }
 
-    if ( pMouseWindow &&
-         pMouseWindow->IsEnabled() && pMouseWindow->IsInputEnabled() && ! pMouseWindow->IsInModalMode() )
+    while (acceptableWheelScrollTarget(pMouseWindow))
+    {
+        if (pMouseWindow->IsEnabled())
+            break;
+        //try the parent if this one is disabled
+        pMouseWindow = pMouseWindow->GetParent();
+    }
+
+    // avoid the problem that scrolling via wheel to this point brings a widget
+    // under the mouse that also accepts wheel commands, so stick with the old
+    // widget if the time gap is very small
+    if (shouldReusePreviousMouseWindow(aPreviousEvent, rEvt) && acceptableWheelScrollTarget(pPreviousWindow))
+    {
+        pMouseWindow = pPreviousWindow;
+    }
+
+    aPreviousEvent = rEvt;
+
+    if (acceptableWheelScrollTarget(pMouseWindow) && !pMouseWindow->IsInModalMode())
     {
         // transform coordinates to float window frame coordinates
         Point aRelMousePos( pMouseWindow->OutputToScreenPixel(
@@ -1496,6 +1530,8 @@ static long ImplHandleWheelEvent( Window* pWindow, const SalWheelMouseEvent& rEv
         bRet = ImplCallWheelCommand( pMouseWindow, aRelMousePos, &aWheelData );
     }
 
+    pPreviousWindow = !bRet ? pMouseWindow : NULL;
+
     // if the commad was not handled try the focus window
     if ( bRet )
     {
-- 
1.9.3