LT-22452: fix DateSlice mouse wheel scrolling

Author: johnml1135

Src/Common/Controls/DetailControls/BasicTypeSlices.cs

@@ -10,6 +10,7 @@
 // </remarks>
 
 using System;
+using System.Diagnostics;
 using System.Globalization;
 using System.Windows.Forms;
 using System.Xml;
@@ -307,13 +308,58 @@ public override void PropChanged(int hvo, int tag, int ivMin, int cvIns, int cvD
 	/// </summary>
 	public class DateSlice : FieldSlice, IVwNotifyChange
 	{
+		private static readonly TraceSwitch s_wheelTraceSwitch = new TraceSwitch("DateSliceWheel", "");
+		private const int kWmMouseWheel = 0x020A;
+
+		private sealed class WheelForwardingRichTextBox : RichTextBox
+		{
+			protected override void WndProc(ref Message m)
+			{
+				if (m.Msg == kWmMouseWheel)
+				{
+					int delta = (short)((long)m.WParam >> 16);
+					bool handled = TryScrollOwningDataTree(this, delta);
+					TraceWheel(string.Format("RichTextBoxWndProc delta={0} handled={1}", delta, handled));
+					if (handled)
+						return;
+				}
+
+				base.WndProc(ref m);
+			}
+		}
+
+		private static void TraceWheel(string message)
+		{
+			if (s_wheelTraceSwitch.TraceInfo || s_wheelTraceSwitch.TraceVerbose)
+				Trace.WriteLine("DateSliceWheel: " + message);
+		}
+
+		internal static bool TryScrollOwningDataTree(Control control, int delta)
+		{
+			for (Control current = control; current != null; current = current.Parent)
+			{
+				var dataTree = current as DataTree;
+				if (dataTree != null)
+				{
+					bool handled = DataTree.TryHandleWheelScroll(dataTree, delta);
+					TraceWheel(string.Format(
+						"TryScrollOwningDataTree delta={0} dataTreeVisible={1} handled={2}",
+						delta, dataTree.Visible, handled));
+					return handled;
+				}
+			}
+
+			TraceWheel(string.Format("TryScrollOwningDataTree delta={0} no-datatree", delta));
+			return false;
+		}
+
 		/// -----------------------------------------------------------------------------------
 		/// <summary>
 		/// Initializes a new instance of the <see cref="DateSlice"/> class.
 		/// </summary>
 		/// -----------------------------------------------------------------------------------
 		public DateSlice(LcmCache cache, ICmObject obj, int flid)
-			: base(new RichTextBox(), cache, obj, flid)
+			: base(new WheelForwardingRichTextBox(), cache, obj, flid)
 		{
 			// JohnT: per comment at the end of LT-7073, we want the normal window color for this
 			// slice. It's also nice to be able to select and copy. Setting ReadOnly is enough to prevent

Src/Common/Controls/DetailControls/DataTree.cs

@@ -4531,6 +4531,50 @@ private bool EquivalentKeys(object[] newKey, object[] oldKey, bool fCheckInts)
 			}
 			return true;
 		}
+
+		internal static int GetWheelScrollPixels(DataTree dataTree, int delta)
+		{
+			if (delta == 0)
+				return 0;
+
+			int scrollLines = SystemInformation.MouseWheelScrollLines;
+			if (scrollLines == 0)
+				return 0;
+
+			if (scrollLines == int.MaxValue)
+				return Math.Sign(delta) * dataTree.ClientRectangle.Height;
+
+			double linesToScroll = (double)delta / SystemInformation.MouseWheelScrollDelta * scrollLines;
+			return (int)Math.Round(linesToScroll * dataTree.Font.Height, MidpointRounding.AwayFromZero);
+		}
+
+		internal static bool TryGetWheelScrollPosition(DataTree dataTree, int delta, out int newY)
+		{
+			int currentY = -dataTree.AutoScrollPosition.Y;
+			int maxScroll = Math.Max(0,
+				dataTree.AutoScrollMinSize.Height - dataTree.ClientRectangle.Height);
+			int pixelDelta = GetWheelScrollPixels(dataTree, delta);
+			newY = Math.Max(0, Math.Min(currentY - pixelDelta, maxScroll));
+			return newY != currentY;
+		}
+
+		internal static bool CanRedirectWheelMessage(DataTree dataTree)
+		{
+			return dataTree.IsHandleCreated && !dataTree.IsDisposed && dataTree.Visible;
+		}
+
+		internal static bool TryHandleWheelScroll(DataTree dataTree, int delta)
+		{
+			if (!CanRedirectWheelMessage(dataTree))
+				return false;
+
+			int newY;
+			if (!TryGetWheelScrollPosition(dataTree, delta, out newY))
+				return false;
+
+			dataTree.AutoScrollPosition = new Point(0, newY);
+			return true;
+		}
 	}
 
 	class DummyObjectSlice : Slice

Src/Common/Controls/DetailControls/DetailControlsTests/DataTreeTests.cs

@@ -4,7 +4,9 @@
 
 using System;
 using System.Collections.Generic;
+using System.Drawing;
 using System.IO;
+using System.Reflection;
 using System.Windows.Forms;
 using System.Xml;
 using NUnit.Framework;
@@ -31,6 +33,13 @@ public class DataTreeTests : MemoryOnlyBackendProviderRestoredForEachTestTestBas
 		private DataTree m_dtree;
 		private Form m_parent;
 
+		private sealed class ScrollTestDataTree : DataTree
+		{
+			protected override void OnPaint(PaintEventArgs e)
+			{
+			}
+		}
+
 		private CustomFieldForTest m_customField;
 		#region Fixture Setup and Teardown
 		internal static Inventory GenerateParts()
@@ -77,6 +86,30 @@ public override void FixtureSetup()
 		}
 		#endregion
 
+		private static DataTree CreateScrollableDataTree(Form parent)
+		{
+			var dataTree = new ScrollTestDataTree();
+			parent.Size = new Size(400, 200);
+			dataTree.Dock = DockStyle.Fill;
+			parent.Controls.Add(dataTree);
+
+			for (int i = 0; i < 12; i++)
+			{
+				var slice = new Slice(new Panel { Dock = DockStyle.Fill })
+				{
+					Visible = true,
+					Size = new Size(360, 50),
+					Location = new Point(0, i * 50)
+				};
+				dataTree.Controls.Add(slice);
+				slice.Install(dataTree);
+			}
+
+			parent.Show();
+			Application.DoEvents();
+			return dataTree;
+		}
+
 		#region Test setup and teardown
 		/// ------------------------------------------------------------------------------------
 		/// <summary>
@@ -275,6 +308,102 @@ public void GetGuidForJumpToTool_UsesRootObject_WhenNoCurrentSlice()
 			}
 		}
 
+		[Test]
+		public void GetWheelScrollPixels_UsesSystemWheelSettings()
+		{
+			m_dtree.Bounds = new Rectangle(0, 0, 200, 100);
+
+			int delta = SystemInformation.MouseWheelScrollDelta;
+			int scrollLines = SystemInformation.MouseWheelScrollLines;
+			int expectedPixels;
+			if (scrollLines == 0)
+			{
+				expectedPixels = 0;
+			}
+			else if (scrollLines == int.MaxValue)
+			{
+				expectedPixels = m_dtree.ClientRectangle.Height;
+			}
+			else
+			{
+				expectedPixels = (int)Math.Round((double)scrollLines * m_dtree.Font.Height,
+					MidpointRounding.AwayFromZero);
+			}
+
+			Assert.That(DataTree.GetWheelScrollPixels(m_dtree, delta), Is.EqualTo(expectedPixels));
+			Assert.That(DataTree.GetWheelScrollPixels(m_dtree, -delta), Is.EqualTo(-expectedPixels));
+		}
+
+		[Test]
+		public void TryGetWheelScrollPosition_ReturnsFalse_WhenAlreadyAtTop()
+		{
+			m_dtree.Bounds = new Rectangle(0, 0, 200, 100);
+			m_dtree.AutoScrollMinSize = new Size(200, 1000);
+			m_dtree.AutoScrollPosition = new Point(0, 0);
+
+			int newY;
+			bool handled = DataTree.TryGetWheelScrollPosition(m_dtree,
+				SystemInformation.MouseWheelScrollDelta, out newY);
+
+			Assert.That(handled, Is.False);
+			Assert.That(newY, Is.EqualTo(0));
+		}
+
+		[Test]
+		public void CanRedirectWheelMessage_ReturnsFalse_WhenDataTreeHidden()
+		{
+			m_parent.Show();
+			m_dtree.Show();
+			Assert.That(m_dtree.IsHandleCreated, Is.True);
+
+			m_dtree.Hide();
+
+			Assert.That(DataTree.CanRedirectWheelMessage(m_dtree), Is.False);
+		}
+
+		[Test]
+		public void TryHandleWheelScroll_UpdatesScrollPosition_WhenScrollingIsPossible()
+		{
+			using (var parent = new Form())
+			{
+				var dataTree = CreateScrollableDataTree(parent);
+				dataTree.AutoScrollPosition = new Point(0, 0);
+
+				bool handled = DataTree.TryHandleWheelScroll(dataTree, -SystemInformation.MouseWheelScrollDelta);
+
+				Assert.That(handled, Is.True);
+				Assert.That(-dataTree.AutoScrollPosition.Y, Is.GreaterThan(0));
+			}
+		}
+
+		[Test]
+		public void TryScrollOwningDataTree_ScrollsContainingDataTree_FromDateSliceHostedControl()
+		{
+			using (var parent = new Form())
+			{
+				var dataTree = CreateScrollableDataTree(parent);
+				dataTree.AutoScrollPosition = new Point(0, 0);
+
+				using (var host = new Panel())
+				using (var control = new RichTextBox())
+				{
+					host.Bounds = new Rectangle(0, 0, 150, 20);
+					control.Dock = DockStyle.Fill;
+					host.Controls.Add(control);
+					dataTree.Controls.Add(host);
+					host.Show();
+					control.Show();
+					Application.DoEvents();
+
+					bool handled = DateSlice.TryScrollOwningDataTree(control,
+						-SystemInformation.MouseWheelScrollDelta);
+
+					Assert.That(handled, Is.True);
+					Assert.That(-dataTree.AutoScrollPosition.Y, Is.GreaterThan(0));
+				}
+			}
+		}
+
 		/// <summary></summary>
 		[Test]
 		public void OwnedObjects()