tdf#119745: Use scroll distance from Windows to calculate scroll lines.

Calculate lines scrolled using scroll distance from Windows message instead of fixed value. Use Windows macros for mouse wheel distance and modifier keys (from Microsoft WM_MOUSEWHEEL dev page).

Change-Id: I30ddf1641103a15549f38983c60c35e0d514bb38
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/174713
Reviewed-by: Mike Kaganski <mike.kaganski@collabora.com>
Tested-by: Jenkins

1 files changed, 41 insertions, 10 deletions

diff --git a/vcl/win/window/salframe.cxx b/vcl/win/window/salframe.cxx
index f61d5a316c15..3a688858b312 100644
--- a/vcl/win/window/salframe.cxx
+++ b/vcl/win/window/salframe.cxx
@@ -3363,7 +3363,7 @@ static bool ImplHandleWheelMsg( HWND hWnd, UINT nMsg, WPARAM wParam, LPARAM lPar
     WinSalFrame*   pFrame = GetWindowPtr( hWnd );
     if ( pFrame )
     {
-        WORD    nWinModCode = LOWORD( wParam );
+        WORD    nWinModCode = GET_KEYSTATE_WPARAM( wParam );     // Key modifiers
         POINT   aWinPt;
         aWinPt.x    = static_cast<short>(LOWORD( lParam ));
         aWinPt.y    = static_cast<short>(HIWORD( lParam ));
@@ -3374,32 +3374,63 @@ static bool ImplHandleWheelMsg( HWND hWnd, UINT nMsg, WPARAM wParam, LPARAM lPar
         aWheelEvt.mnX           = aWinPt.x;
         aWheelEvt.mnY           = aWinPt.y;
         aWheelEvt.mnCode        = 0;
-        aWheelEvt.mnDelta       = static_cast<short>(HIWORD( wParam ));
-        aWheelEvt.mnNotchDelta  = aWheelEvt.mnDelta/WHEEL_DELTA;
+        aWheelEvt.mnDelta       = GET_WHEEL_DELTA_WPARAM( wParam );     // Distance scrolled passed in message param
+        aWheelEvt.mnNotchDelta  = aWheelEvt.mnDelta/WHEEL_DELTA;        // Number of mouse notches/detents scrolled
         if( aWheelEvt.mnNotchDelta == 0 )
         {
+            // Keep mnNotchDelta nonzero unless distance scrolled was exactly zero.
+            // Many places use its sign to indicate direction scrolled.
             if( aWheelEvt.mnDelta > 0 )
                 aWheelEvt.mnNotchDelta = 1;
             else if( aWheelEvt.mnDelta < 0 )
                 aWheelEvt.mnNotchDelta = -1;
         }
 
-        if( nMsg == WM_MOUSEWHEEL )
+        if( nMsg == WM_MOUSEWHEEL )     // Vertical scroll
         {
-            if ( aSalShlData.mnWheelScrollLines == WHEEL_PAGESCROLL )
-                aWheelEvt.mnScrollLines = SAL_WHEELMOUSE_EVENT_PAGESCROLL;
-            else
-                aWheelEvt.mnScrollLines = aSalShlData.mnWheelScrollLines;
+            if ( aSalShlData.mnWheelScrollLines == WHEEL_PAGESCROLL )  // Mouse wheel set to "One screen at a time"
+            {
+                // Note: mnDelta may hit a multiple of WHEEL_DELTA via touchpad scrolling. That's the tradeoff to keep
+                //  smooth touchpad scrolling with mouse wheel set to screen.
+
+                if ( (aWheelEvt.mnDelta % WHEEL_DELTA) == 0 )   // Mouse wheel sends WHEEL_DELTA (or multiple of it)
+                    aWheelEvt.mnScrollLines = SAL_WHEELMOUSE_EVENT_PAGESCROLL;          // "Magic" page scroll value
+                else    // Touchpad can send smaller values. Use default 3 lines to scroll at a time.
+                    aWheelEvt.mnScrollLines = aWheelEvt.mnDelta / double(WHEEL_DELTA) * 3.0;  // Calculate actual lines using distance
+            }
+            else    // Mouse wheel set to "Multiple lines at a time"
+            {
+                // Windows legacy touchpad support sends touchpad scroll gesture as multiple mouse wheel messages.
+                // Calculate number of mouse notches scrolled using distance from Windows.
+                aWheelEvt.mnScrollLines = aWheelEvt.mnDelta / double(WHEEL_DELTA);
+                // Multiply by user setting for number of lines to scroll at a time.
+                aWheelEvt.mnScrollLines *= aSalShlData.mnWheelScrollLines;
+            }
             aWheelEvt.mbHorz        = false;
         }
-        else
+        else    // Horizontal scroll
         {
-            aWheelEvt.mnScrollLines = aSalShlData.mnWheelScrollChars;
+            // Windows legacy touchpad support sends touchpad scroll gesture as multiple mouse wheel messages.
+            // Calculate number of mouse notches scrolled using distance from Windows.
+            aWheelEvt.mnScrollLines = aWheelEvt.mnDelta / double(WHEEL_DELTA);
+            // Multiply by user setting for number of characters to scroll at a time.
+            aWheelEvt.mnScrollLines *= aSalShlData.mnWheelScrollChars;
             aWheelEvt.mbHorz        = true;
 
             // fdo#36380 - seems horiz scrolling has swapped direction
             aWheelEvt.mnDelta *= -1;
             aWheelEvt.mnNotchDelta *= -1;
+            aWheelEvt.mnScrollLines *= -1.0;
+        }
+
+        // Do not change magic value for page scrolling
+        if (aWheelEvt.mnScrollLines != SAL_WHEELMOUSE_EVENT_PAGESCROLL)
+        {
+            // Scrolling code multiplies (scroll lines * number of notches), so pull # notches out to prevent double multiply.
+            if (aWheelEvt.mnNotchDelta != 0)    // No divide by zero!
+                aWheelEvt.mnScrollLines /= aWheelEvt.mnNotchDelta;
+            else
+                aWheelEvt.mnScrollLines = abs(aWheelEvt.mnScrollLines);     // Just ensure (+) value
         }
 
         if ( nWinModCode & MK_SHIFT )