Worked around a weird problem setting the scrollbar positions on Windows.

src/MainForm.cs

@@ -188,4 +188,18 @@ public partial class MainForm : Form
         mSearchResults.ResumeLayout( true ) ;
         mSearchResultsKey = key ;
     }
+
+    private void setChartImagePanelScrollPos( int? hscrollPos, int? vscrollPos )
+    {
+        // FUDGE! These need to be set twice to take effect on Windows :-/
+        if ( hscrollPos != null ) {
+            mChartImagePanel.HorizontalScroll.Value = hscrollPos.Value ;
+            mChartImagePanel.HorizontalScroll.Value = hscrollPos.Value ;
+        }
+        if ( vscrollPos != null ) {
+            mChartImagePanel.VerticalScroll.Value = vscrollPos.Value ;
+            mChartImagePanel.VerticalScroll.Value = vscrollPos.Value ;
+        }
+    }
+
 }

src/MainForm.ui.cs

@@ -225,8 +225,7 @@ public partial class MainForm : Form
         double prevRelScrollPosY = (double)prevScrollPosY / (double)prevMaxScrollY ;
 
         // resize and position the ChartImage
-        mChartImagePanel.HorizontalScroll.Value = 0 ;
-        mChartImagePanel.VerticalScroll.Value = 0 ;
+        setChartImagePanelScrollPos( 0, 0 ) ;
         Size prevChartImagePictureBoxSize = new Size( mChartImagePictureBox.Size.Width, mChartImagePictureBox.Size.Height ) ;
         mChartImagePictureBox.Size = new Size( width, height ) ;
         if ( width < availableWidth )
@@ -320,18 +319,14 @@ public partial class MainForm : Form
     {
         // update the scroll position
         if ( scrollX != null ) {
-            HScrollProperties hscroll = mChartImagePanel.HorizontalScroll ;
             int maxScrollX = ChartImagePanel_MaxScrollX() ;
             int scrollPos = Math.Max( 0, Math.Min( maxScrollX, scrollX.Value ) ) ;
-            hscroll.Value = scrollPos ;
-            hscroll.Value = scrollPos ; // nb: for Windows :shrug:
+            setChartImagePanelScrollPos( scrollPos, null ) ;
         }
         if ( scrollY != null ) {
-            VScrollProperties vscroll = mChartImagePanel.VerticalScroll ;
             int maxScrollY = ChartImagePanel_MaxScrollY() ;
             int scrollPos = Math.Max( 0, Math.Min( maxScrollY, scrollY.Value ) ) ;
-            vscroll.Value = scrollPos ;
-            vscroll.Value = scrollPos ; // nb: for Windows :shrug:
+            setChartImagePanelScrollPos( null, scrollPos ) ;
         }
     }
 
@@ -351,8 +346,7 @@ public partial class MainForm : Form
             mChartImagePictureBox.Image = chartImage.image ;
         } else
             mChartImagePictureBox.Image = null ;
-        mChartImagePanel.HorizontalScroll.Value = 0 ;
-        mChartImagePanel.VerticalScroll.Value = 0 ;
+        setChartImagePanelScrollPos( 0, 0 ) ;
         mUserZoom = 1.0 ;
         doMainFormResize( null ) ;
     }