Partial fix for homescreen panning issue

[problem]      When flicking left-right quickly, sometimes homescreen page does not move
[cause]        In some cases this is caused by ScrollView using a value before the update
thread has had time to react.
[solution]     Added guard logic in positionSnap calculation.

diff --git a/base/dali-toolkit/internal/controls/scrollable/scroll-view/scroll-view-impl.cpp b/base/dali-toolkit/internal/controls/scrollable/scroll-view/scroll-view-impl.cpp
index 395a3cb..b11b64c 100644 (file)
--- a/base/dali-toolkit/internal/controls/scrollable/scroll-view/scroll-view-impl.cpp
+++ b/base/dali-toolkit/internal/controls/scrollable/scroll-view/scroll-view-impl.cpp
@@ -1357,6 +1357,8 @@ bool ScrollView::SnapWithVelocity(Vector2 velocity)
   const float orthoAngleRange = FLICK_ORTHO_ANGLE_RANGE * M_PI / 180.0f;
   const float flickSpeedThreshold2 = FLICK_SPEED_THRESHOLD*FLICK_SPEED_THRESHOLD;
 
   const float orthoAngleRange = FLICK_ORTHO_ANGLE_RANGE * M_PI / 180.0f;
   const float flickSpeedThreshold2 = FLICK_SPEED_THRESHOLD*FLICK_SPEED_THRESHOLD;
 

+  Vector3 positionSnap = mScrollPostPosition;
+

   // Flick logic X Axis
 
   if(mRulerX->IsEnabled())
   // Flick logic X Axis
 
   if(mRulerX->IsEnabled())


@@ -1368,10 +1370,18 @@ bool ScrollView::SnapWithVelocity(Vector2 velocity)
       if((angle >= -orthoAngleRange) && (angle < orthoAngleRange)) // Swiping East
       {
         biasX = 0.0f, horizontal = Left;
       if((angle >= -orthoAngleRange) && (angle < orthoAngleRange)) // Swiping East
       {
         biasX = 0.0f, horizontal = Left;

+
+        // This guards against an error where no movement occurs, due to the flick finishing
+        // before the update-thread has advanced mScrollPostPosition past the the previous snap point.
+        positionSnap.x += 1.0f;

       }
       else if((angle >= M_PI-orthoAngleRange) || (angle < -M_PI+orthoAngleRange)) // Swiping West
       {
         biasX = 1.0f, horizontal = Right;
       }
       else if((angle >= M_PI-orthoAngleRange) || (angle < -M_PI+orthoAngleRange)) // Swiping West
       {
         biasX = 1.0f, horizontal = Right;

+
+        // This guards against an error where no movement occurs, due to the flick finishing
+        // before the update-thread has advanced mScrollPostPosition past the the previous snap point.
+        positionSnap.x -= 1.0f;

       }
     }
   }
       }
     }
   }


@@ -1406,8 +1416,7 @@ bool ScrollView::SnapWithVelocity(Vector2 velocity)
     alphaFunction = mFlickAlphaFunction;
   }
 
     alphaFunction = mFlickAlphaFunction;
   }
 

-  // Position Snap ////////////////////////////////////////////////////////////
-  Vector3 positionSnap = mScrollPostPosition;
+  // Calculate next positionSnap ////////////////////////////////////////////////////////////

 
   if(mActorAutoSnapEnabled)
   {
 
   if(mActorAutoSnapEnabled)
   {