tdf#119745: Fix touchpad scrolling for Slides and Pages panes.

Use fractional lines scrolled to calculate distance to scroll view,
instead of jumping forward or backward a full page every call based on
sign. Also fixes existing bugs: horizontal pane can scroll too far to
right; and snapping pane from vertical to horizontal can break scrolling
if view partially scrolled.

Change-Id: I0ead4710a296aac26f1cf1a0fc48e6ea403271a6
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/177836
Tested-by: Jenkins
Reviewed-by: Patrick Luby <guibomacdev@gmail.com>
(cherry picked from commit 143e89dbf85b13e1acccb76877d774a7fca1b016)
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/178084
Reviewed-by: Ilmari Lauhakangas <ilmari.lauhakangas@libreoffice.org>

5 files changed, 61 insertions, 42 deletions

diff --git a/sd/source/ui/slidesorter/controller/SlideSorterController.cxx b/sd/source/ui/slidesorter/controller/SlideSorterController.cxx
index 43c8ec30ee3a..a8d467485b1a 100644
--- a/sd/source/ui/slidesorter/controller/SlideSorterController.cxx
+++ b/sd/source/ui/slidesorter/controller/SlideSorterController.cxx
@@ -382,6 +382,9 @@ bool SlideSorterController::Command (
                 // We do not support zooming with control+mouse wheel.
                 return false;
             }
+            // tdf#119745: ScrollLines gives accurate distance scrolled on touchpad. NotchDelta sign
+            // gives direction. Default is 3 lines at a time, so factor that out.
+            double scrollDistance = -pData->GetScrollLines() * pData->GetNotchDelta() / 3.0;
             // Determine whether to scroll horizontally or vertically.  This
             // depends on the orientation of the scroll bar and the
             // IsHoriz() flag of the event.
@@ -390,13 +393,13 @@ bool SlideSorterController::Command (
             {
                 GetScrollBarManager().Scroll(
                     ScrollBarManager::Orientation_Vertical,
-                    -pData->GetNotchDelta());
+                    scrollDistance);
             }
             else
             {
                 GetScrollBarManager().Scroll(
                     ScrollBarManager::Orientation_Horizontal,
-                    -pData->GetNotchDelta());
+                    scrollDistance);
             }
             mrSlideSorter.GetView().UpdatePageUnderMouse(rEvent.GetMousePosPixel());
 
diff --git a/sd/source/ui/slidesorter/controller/SlsScrollBarManager.cxx b/sd/source/ui/slidesorter/controller/SlsScrollBarManager.cxx
index 6ee20c8dd93c..6a0244f41655 100644
--- a/sd/source/ui/slidesorter/controller/SlsScrollBarManager.cxx
+++ b/sd/source/ui/slidesorter/controller/SlsScrollBarManager.cxx
@@ -516,7 +516,7 @@ IMPL_LINK_NOARG(ScrollBarManager, AutoScrollTimeoutHandler, Timer *, void)
 
 void ScrollBarManager::Scroll(
     const Orientation eOrientation,
-    const sal_Int32 nDistance)
+    const double nDistance)
 {
     bool bIsVertical (false);
     switch (eOrientation)
@@ -528,51 +528,53 @@ void ScrollBarManager::Scroll(
             return;
     }
 
-    Point aNewTopLeft (
-        mpHorizontalScrollBar ? mpHorizontalScrollBar->GetThumbPos() : 0,
-        mpVerticalScrollBar ? mpVerticalScrollBar->GetThumbPos() : 0);
+    // Get current scrolling view position
+    // Fix bug where 1) scrolling view is partially scrolled, 2) view window is snapped from vertical
+    //  to horizontal or vice-versa, then 3) mouse wheel scrolled. Scrolling broke because we got an
+    //  invalid starting position from the scrollbar that's no longer displayed. Check scrollbars
+    //  visible before getting position from each.
+    bool bHorizontalScrollShown = mpHorizontalScrollBar && mpHorizontalScrollBar->IsVisible();
+    bool bVerticalScrollShown = mpVerticalScrollBar && mpVerticalScrollBar->IsVisible();
+    Point aNewTopLeft(
+        bHorizontalScrollShown ? mpHorizontalScrollBar->GetThumbPos() : 0,
+        bVerticalScrollShown ? mpVerticalScrollBar->GetThumbPos() : 0);
 
     view::Layouter& rLayouter (mrSlideSorter.GetView().GetLayouter());
 
-    // Calculate estimate of new location.
+    // Calculate new location
+    Size objectSize( rLayouter.GetPageObjectSize() );       // Size of a page in pane
+    Size objectAndGapSize = view::Layouter::AddGap(objectSize);   // Add gap between pages to size
     if (bIsVertical)
-        aNewTopLeft.AdjustY(nDistance * rLayouter.GetPageObjectSize().Height() );
+        aNewTopLeft.AdjustY(nDistance * objectAndGapSize.Height() );        // New position
     else
-        aNewTopLeft.AdjustX(nDistance * rLayouter.GetPageObjectSize().Width() );
+        aNewTopLeft.AdjustX(nDistance * objectAndGapSize.Width() );         // New position
 
-    // Adapt location to show whole slides.
+    // Get displayable area for pages
+    ::tools::Rectangle scrollArea = rLayouter.GetTotalBoundingBox();
+
+    // Prevent scrolling out of bounds by limiting scroll destination point.
     if (bIsVertical)
-        if (nDistance > 0)
-        {
-            const sal_Int32 nIndex (rLayouter.GetIndexAtPoint(
-                Point(aNewTopLeft.X(), aNewTopLeft.Y()+mpVerticalScrollBar->GetVisibleSize()),
-                true));
-            aNewTopLeft.setY( rLayouter.GetPageObjectBox(nIndex,true).Bottom()
-                - mpVerticalScrollBar->GetVisibleSize() );
-        }
-        else
-        {
-            const sal_Int32 nIndex (rLayouter.GetIndexAtPoint(
-                Point(aNewTopLeft.X(), aNewTopLeft.Y()),
-                true));
-            aNewTopLeft.setY( rLayouter.GetPageObjectBox(nIndex,true).Top() );
-        }
+    {
+        // Subtract size of view itself to get scrollable area.
+        ::tools::Long scrollbarSize = mpVerticalScrollBar->GetVisibleSize();
+        // Prevent (-) height. std::max needs type specified explicitly so params match.
+        ::tools::Long scrollHeight = std::max(static_cast<::tools::Long>(0), scrollArea.GetHeight() - scrollbarSize);
+        scrollArea.SetHeight(scrollHeight);
+        // Constrain scroll point to valid area
+        ::tools::Long constrainedY = std::clamp(aNewTopLeft.getY(), scrollArea.Top(), scrollArea.Bottom());
+        aNewTopLeft.setY(constrainedY);
+    }
     else
-        if (nDistance > 0)
-        {
-            const sal_Int32 nIndex (rLayouter.GetIndexAtPoint(
-                Point(aNewTopLeft.X()+mpVerticalScrollBar->GetVisibleSize(), aNewTopLeft.Y()),
-                true));
-            aNewTopLeft.setX( rLayouter.GetPageObjectBox(nIndex,true).Right()
-                - mpVerticalScrollBar->GetVisibleSize() );
-        }
-        else
-        {
-            const sal_Int32 nIndex (rLayouter.GetIndexAtPoint(
-                Point(aNewTopLeft.X(), aNewTopLeft.Y()),
-                    true));
-            aNewTopLeft.setX( rLayouter.GetPageObjectBox(nIndex,true).Left() );
-        }
+    {
+        // Subtract size of view itself to get scrollable area.
+        ::tools::Long scrollbarSize = mpHorizontalScrollBar->GetVisibleSize();
+        // Prevent (-) width. std::max needs type specified explicitly so params match.
+        ::tools::Long scrollWidth = std::max(static_cast<::tools::Long>(0), scrollArea.GetWidth() - scrollbarSize);
+        scrollArea.SetWidth(scrollWidth);
+        // Constrain scroll point to valid area
+        ::tools::Long constrainedX = std::clamp(aNewTopLeft.getX(), scrollArea.Left(), scrollArea.Right());
+        aNewTopLeft.setX(constrainedX);
+    }
 
     mrSlideSorter.GetController().GetVisibleAreaManager().DeactivateCurrentSlideTracking();
     SetTopLeft(aNewTopLeft);
diff --git a/sd/source/ui/slidesorter/inc/controller/SlsScrollBarManager.hxx b/sd/source/ui/slidesorter/inc/controller/SlsScrollBarManager.hxx
index df04a3b5952f..1ed5b9fead87 100644
--- a/sd/source/ui/slidesorter/inc/controller/SlsScrollBarManager.hxx
+++ b/sd/source/ui/slidesorter/inc/controller/SlsScrollBarManager.hxx
@@ -155,7 +155,7 @@ public:
     */
     void Scroll(
         const Orientation eOrientation,
-        const sal_Int32 nDistance);
+        const double nDistance);
 
 private:
     SlideSorter& mrSlideSorter;
diff --git a/sd/source/ui/slidesorter/inc/view/SlsLayouter.hxx b/sd/source/ui/slidesorter/inc/view/SlsLayouter.hxx
index b91ae83c544c..c54dee655503 100644
--- a/sd/source/ui/slidesorter/inc/view/SlsLayouter.hxx
+++ b/sd/source/ui/slidesorter/inc/view/SlsLayouter.hxx
@@ -111,6 +111,12 @@ public:
 
     Size const & GetPageObjectSize() const;
 
+    /** Returns the passed Size plus the gap between pages.
+        @param rObjectSize
+            Object size to start from.
+    */
+    static Size AddGap(const Size & rObjectSize);
+
     /** Return the bounding box in window coordinates of the nIndex-th page
         object.
     */
diff --git a/sd/source/ui/slidesorter/view/SlsLayouter.cxx b/sd/source/ui/slidesorter/view/SlsLayouter.cxx
index 8bc0daf3f5e9..371e410d3fee 100644
--- a/sd/source/ui/slidesorter/view/SlsLayouter.cxx
+++ b/sd/source/ui/slidesorter/view/SlsLayouter.cxx
@@ -183,7 +183,7 @@ public:
         const sal_Int32 nColumn,
         const bool bClampToValidRange) const;
 
-        ::tools::Rectangle GetPageObjectBox (
+    ::tools::Rectangle GetPageObjectBox (
         const sal_Int32 nIndex,
         const bool bIncludeBorderAndGap = false) const;
 
@@ -349,6 +349,14 @@ Size const & Layouter::GetPageObjectSize() const
     return mpImplementation->maPageObjectSize;
 }
 
+Size Layouter::AddGap(const Size & rObjectSize)
+{
+    Size newSize = rObjectSize;
+    newSize.AdjustWidth(Implementation::gnHorizontalGap);
+    newSize.AdjustHeight(Implementation::gnVerticalGap);
+    return newSize;
+}
+
 ::tools::Rectangle Layouter::GetPageObjectBox (
     const sal_Int32 nIndex,
     const bool bIncludeBorderAndGap) const