From b7c439bb975a28dd3af8a5b1e555afc304ff1037 Mon Sep 17 00:00:00 2001
From: Daniel Grunwald <daniel@danielgrunwald.de>
Date: Wed, 13 Mar 2013 21:26:37 +0100
Subject: [PATCH] Disable IME while the caret is within a read-only section.

---
 .../Editing/ImeSupport.cs                     | 80 +++++++++++++------
 .../Editing/TextArea.cs                       |  1 +
 2 files changed, 57 insertions(+), 24 deletions(-)

diff --git a/src/Libraries/AvalonEdit/ICSharpCode.AvalonEdit/Editing/ImeSupport.cs b/src/Libraries/AvalonEdit/ICSharpCode.AvalonEdit/Editing/ImeSupport.cs
index 23c3c41c36..91d7cdc0fb 100644
--- a/src/Libraries/AvalonEdit/ICSharpCode.AvalonEdit/Editing/ImeSupport.cs
+++ b/src/Libraries/AvalonEdit/ICSharpCode.AvalonEdit/Editing/ImeSupport.cs
@@ -27,24 +27,62 @@ namespace ICSharpCode.AvalonEdit.Editing
 		IntPtr previousContext;
 		IntPtr defaultImeWnd;
 		HwndSource hwndSource;
+		EventHandler requerySuggestedHandler; // we need to keep the event handler instance alive because CommandManager.RequerySuggested uses weak references
+		bool isReadOnly;
 		
 		public ImeSupport(TextArea textArea)
 		{
 			if (textArea == null)
 				throw new ArgumentNullException("textArea");
 			this.textArea = textArea;
-			InputMethod.SetIsInputMethodSuspended(this.textArea, true);
+			InputMethod.SetIsInputMethodSuspended(this.textArea, textArea.Options.EnableImeSupport);
+			// We listen to CommandManager.RequerySuggested for both caret offset changes and changes to the set of read-only sections.
+			// This is because there's no dedicated event for read-only section changes; but RequerySuggested needs to be raised anyways
+			// to invalidate the Paste command.
+			requerySuggestedHandler = OnRequerySuggested;
+			CommandManager.RequerySuggested += requerySuggestedHandler;
 			textArea.OptionChanged += TextAreaOptionChanged;
-			currentContext = IntPtr.Zero;
 		}
 
+		void OnRequerySuggested(object sender, EventArgs e)
+		{
+			UpdateImeEnabled();
+		}
+		
 		void TextAreaOptionChanged(object sender, PropertyChangedEventArgs e)
 		{
-			if (e.PropertyName == "EnableImeSupport" && textArea.IsKeyboardFocused) {
-				CreateContext();
+			if (e.PropertyName == "EnableImeSupport") {
+				InputMethod.SetIsInputMethodSuspended(this.textArea, textArea.Options.EnableImeSupport);
+				UpdateImeEnabled();
 			}
 		}
-
+		
+		public void OnGotKeyboardFocus(KeyboardFocusChangedEventArgs e)
+		{
+			UpdateImeEnabled();
+		}
+		
+		public void OnLostKeyboardFocus(KeyboardFocusChangedEventArgs e)
+		{
+			if (e.OldFocus == textArea && currentContext != IntPtr.Zero)
+				ImeNativeWrapper.NotifyIme(currentContext);
+			ClearContext();
+		}
+		
+		void UpdateImeEnabled()
+		{
+			if (textArea.Options.EnableImeSupport && textArea.IsKeyboardFocused) {
+				bool newReadOnly = !textArea.ReadOnlySectionProvider.CanInsert(textArea.Caret.Offset);
+				if (hwndSource == null || isReadOnly != newReadOnly) {
+					ClearContext(); // clear existing context (on read-only change)
+					isReadOnly = newReadOnly;
+					CreateContext();
+				}
+			} else {
+				ClearContext();
+			}
+		}
+		
 		void ClearContext()
 		{
 			if (hwndSource != null) {
@@ -57,20 +95,17 @@ namespace ICSharpCode.AvalonEdit.Editing
 			}
 		}
 		
-		public void OnGotKeyboardFocus(KeyboardFocusChangedEventArgs e)
-		{
-			CreateContext();
-		}
-
 		void CreateContext()
 		{
-			ClearContext(); // clear old context if necessary
-			if (!textArea.Options.EnableImeSupport)
-				return;
 			hwndSource = (HwndSource)PresentationSource.FromVisual(this.textArea);
 			if (hwndSource != null) {
-				defaultImeWnd = ImeNativeWrapper.ImmGetDefaultIMEWnd(IntPtr.Zero);
-				currentContext = ImeNativeWrapper.ImmGetContext(defaultImeWnd);
+				if (isReadOnly) {
+					defaultImeWnd = IntPtr.Zero;
+					currentContext = IntPtr.Zero;
+				} else {
+					defaultImeWnd = ImeNativeWrapper.ImmGetDefaultIMEWnd(IntPtr.Zero);
+					currentContext = ImeNativeWrapper.ImmGetContext(defaultImeWnd);
+				}
 				previousContext = ImeNativeWrapper.ImmAssociateContext(hwndSource.Handle, currentContext);
 				Debug.Assert(hwndSource != null);
 				Debug.Assert(currentContext != null);
@@ -86,21 +121,18 @@ namespace ICSharpCode.AvalonEdit.Editing
 			}
 		}
 		
-		public void OnLostKeyboardFocus(KeyboardFocusChangedEventArgs e)
-		{
-			if (e.OldFocus == textArea && currentContext != IntPtr.Zero)
-				ImeNativeWrapper.NotifyIme(currentContext);
-			ClearContext();
-		}
-		
 		IntPtr WndProc(IntPtr hWnd, int msg, IntPtr wParam, IntPtr lParam, ref bool handled)
 		{
 			switch (msg) {
 				case ImeNativeWrapper.WM_INPUTLANGCHANGE:
 					// Don't mark the message as handled; other windows
 					// might want to handle it as well.
-					ClearContext();
-					CreateContext();
+					
+					// If we have a context, recreate it
+					if (hwndSource != null) {
+						ClearContext();
+						CreateContext();
+					}
 					break;
 				case ImeNativeWrapper.WM_IME_COMPOSITION:
 					UpdateCompositionWindow();
diff --git a/src/Libraries/AvalonEdit/ICSharpCode.AvalonEdit/Editing/TextArea.cs b/src/Libraries/AvalonEdit/ICSharpCode.AvalonEdit/Editing/TextArea.cs
index 31607759f8..13a95958f1 100644
--- a/src/Libraries/AvalonEdit/ICSharpCode.AvalonEdit/Editing/TextArea.cs
+++ b/src/Libraries/AvalonEdit/ICSharpCode.AvalonEdit/Editing/TextArea.cs
@@ -596,6 +596,7 @@ namespace ICSharpCode.AvalonEdit.Editing
 				if (value == null)
 					throw new ArgumentNullException("value");
 				readOnlySectionProvider = value;
+				CommandManager.InvalidateRequerySuggested(); // the read-only status effects Paste.CanExecute and the IME
 			}
 		}
 		#endregion