From 9ad0ce469fc909726759a2d4eb21d02befc1e039 Mon Sep 17 00:00:00 2001
From: Taka <taka@vm-linux-dev>
Date: Wed, 17 Jul 2019 07:16:16 +0000
Subject: [PATCH] Allow the current ChartImage to be scrolled using the
 keyboard.

---
 src/MainForm.ui.cs | 40 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 40 insertions(+)

diff --git a/src/MainForm.ui.cs b/src/MainForm.ui.cs
index 9a6c70b..13d4c7e 100644
--- a/src/MainForm.ui.cs
+++ b/src/MainForm.ui.cs
@@ -131,12 +131,52 @@ public partial class MainForm : Form
         // check for special keypresses
         if ( keyCode == Keys.Left || keyCode == Keys.Right ) {
             // send the keypress to the search results
+            // NOTE: We could also respond to Up/Down and scroll the ChartImage vertically,
+            // but that would be confusing, given that Left/Right selects a search result.
             mSearchResults.Focus() ;
             mDisableProcessCmdKey = true ;
             SendKeys.SendWait( "{" + keyCode.ToString() + "}" ) ;
             mDisableProcessCmdKey = false ;
             return true ;
         }
+        if ( keyCode == Keys.PageUp || keyCode == Keys.PageDown ) {
+            // scroll the ChartImage up/down
+            if ( mChartImagePictureBox.Image == null )
+                return false ;
+            double ratio = (double)mChartImagePanel.Height / (double)mChartImagePictureBox.Height ;
+            VScrollProperties vscroll = mChartImagePanel.VerticalScroll ;
+            int scrollRange = vscroll.Maximum - vscroll.Minimum ;
+            int pageSize = (int)( ratio * scrollRange * 0.8 ) ;
+            if ( keyCode == Keys.PageUp )
+                pageSize = - pageSize ;
+            int scrollY = vscroll.Value + pageSize ;
+            scrollChartImagePanel( null, scrollY ) ;
+            return true ;
+        }
+        if ( keyCode == Keys.Home ) {
+            int? scrollX=null, scrollY=null ;
+            if ( (modifierKeys & Keys.Control) != 0 )
+                scrollX = scrollY = 0 ;
+            if ( (modifierKeys & Keys.Shift) != 0 )
+                scrollX = 0 ;
+            else
+                scrollY = 0 ;
+            setChartImagePanelScrollPos( scrollX, scrollY ) ;
+            return true ;
+        }
+        if ( keyCode == Keys.End ) {
+            int? scrollX=null, scrollY=null ;
+            if ( (modifierKeys & Keys.Control) != 0 ) {
+                scrollX = 0 ;
+                scrollY = ChartImagePanel_MaxScrollY() ;
+            }
+            if ( (modifierKeys & Keys.Shift) != 0 )
+                scrollX = ChartImagePanel_MaxScrollX() ;
+            else
+                scrollY = ChartImagePanel_MaxScrollY() ;
+            setChartImagePanelScrollPos( scrollX, scrollY ) ;
+            return true ;
+        }
         if ( keyCode == Keys.Escape ) {
             // clear the search query
             mSearchQuery.Text = "" ;