Implemented horizontal scrolling sync; plus mousewheel scrolling

ScintillaDiff/ScrollSyncScintilla.cs

@@ -25,11 +25,8 @@ OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 #endregion
 
 using System;
-using System.Collections.Generic;
 using System.ComponentModel;
-using System.Linq;
-using System.Text;
-using System.Threading.Tasks;
+using System.Runtime.InteropServices;
 using System.Windows.Forms;
 using ScintillaNET;
 
@@ -40,7 +37,7 @@ namespace ScintillaDiff
     /// Implements the <see cref="ScintillaNET.Scintilla" />
     /// </summary>
     /// <seealso cref="ScintillaNET.Scintilla" />
-    public class ScrollSyncScintilla: Scintilla
+    public class ScrollSyncScintilla : Scintilla
     {
         // ReSharper disable once CommentTypo
         /// <summary>
@@ -50,25 +47,71 @@ public class ScrollSyncScintilla: Scintilla
         /// https://docs.microsoft.com/en-us/windows/desktop/controls/wm-vscroll
         /// </remarks>
         /// </summary>
-        const int WM_VSCROLL = 0x115;
+        // ReSharper disable once InconsistentNaming
+        private const int WM_VSCROLL = 0x115;
+        // ReSharper disable once CommentTypo
+        /// <summary>
+        /// The WM_HSCROLL message is sent to a window when a scroll event occurs in the window's standard horizontal scroll bar.
+        /// This message is also sent to the owner of a horizontal scroll bar control when a scroll event occurs in the control.
+        /// <remarks>
+        /// https://docs.microsoft.com/en-us/windows/desktop/controls/wm-hscroll
+        /// </remarks>
+        /// </summary>
+        // ReSharper disable once InconsistentNaming
+        private const int WM_HSCROLL = 0x114;
+        /// <summary>
+        /// The WM_MOUSEWHEEL message is Sent to the focus window when the mouse wheel is rotated.
+        /// <remarks>
+        /// https://docs.microsoft.com/en-us/windows/win32/inputdev/wm-mousewheel
+        /// </remarks>
+        /// </summary>
+        // ReSharper disable once InconsistentNaming
+        private const int WM_MOUSEWHEEL = 0x20a;
+
+        /// <summary>
+        /// The SendMessage Win32 function is used to send a specified message to a window or windows.
+        /// <remarks>
+        /// https://docs.microsoft.com/en-us/windows/win32/api/winuser/nf-winuser-sendmessage
+        /// </remarks>
+        /// </summary>
+        [DllImport("user32.dll", CharSet = CharSet.Auto)]
+        private static extern IntPtr SendMessage(IntPtr hWnd, int msg, IntPtr wp, IntPtr lp);
 
         /// <summary>
         /// Processes Windows messages.
         /// </summary>
         /// <param name="m">The Windows Message to process.</param>
         protected override void WndProc(ref Message m)
         {
-            // ReSharper disable once CommentTypo
-            // capture the WM_VSCROLL message..
+            if (m.Msg == WM_MOUSEWHEEL)
+            {
+                // two casts to make this work with 32 bit and 64 bit params
+                var wp = new IntPtr((int)(long)m.WParam < 0 ? 1 : 0);
+                SendMessage(this.Handle, WM_VSCROLL, wp, new IntPtr(0));
+                return;
+            }
+
+            base.WndProc(ref m);
+
+            // vertical scrolling
             if (m.Msg == WM_VSCROLL && ScrollSync != null)
             {
                 // get the first visible line of this control..
                 int scrollTop = FirstVisibleLine;
 
-                // set the value to the another Scintilla control..
+                // set the value to the other Scintilla control..
                 ScrollSync.FirstVisibleLine = scrollTop;
             }
-            base.WndProc(ref m);
+
+            // horizontal scrolling
+            if (m.Msg == WM_HSCROLL && ScrollSync != null)
+            {
+                // get the leftmost pixel
+                int scrollLeft = XOffset;
+
+                // set the value to the other Scintilla control..
+                ScrollSync.XOffset = scrollLeft;
+            }
         }
 
         /// <summary>