source: branches/2929_PrioritizedGrammarEnumeration/HeuristicLab.ExtLibs/HeuristicLab.AvalonEdit/5.0.1/AvalonEdit-5.0.1/Editing/ImeSupport.cs

// Copyright (c) 2014 AlphaSierraPapa for the SharpDevelop Team
// 
// Permission is hereby granted, free of charge, to any person obtaining a copy of this
// software and associated documentation files (the "Software"), to deal in the Software
// without restriction, including without limitation the rights to use, copy, modify, merge,
// publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons
// to whom the Software is furnished to do so, subject to the following conditions:
// 
// The above copyright notice and this permission notice shall be included in all copies or
// substantial portions of the Software.
// 
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
// INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
// PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE
// FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
// OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
// DEALINGS IN THE SOFTWARE.

using System;
using System.ComponentModel;
using System.Diagnostics;
using System.Linq;
using System.Runtime.CompilerServices;
using System.Runtime.InteropServices;
using System.Security;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Input;
using System.Windows.Interop;
using System.Windows.Media;
using System.Windows.Media.TextFormatting;
using ICSharpCode.AvalonEdit;
using ICSharpCode.AvalonEdit.Document;
using ICSharpCode.AvalonEdit.Rendering;

namespace ICSharpCode.AvalonEdit.Editing
{
  class ImeSupport
  {
    readonly TextArea textArea;
    IntPtr currentContext;
    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, 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;
    }

    void OnRequerySuggested(object sender, EventArgs e)
    {
      UpdateImeEnabled();
    }
    
    void TextAreaOptionChanged(object sender, PropertyChangedEventArgs e)
    {
      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) {
        ImeNativeWrapper.ImmAssociateContext(hwndSource.Handle, previousContext);
        ImeNativeWrapper.ImmReleaseContext(defaultImeWnd, currentContext);
        currentContext = IntPtr.Zero;
        defaultImeWnd = IntPtr.Zero;
        hwndSource.RemoveHook(WndProc);
        hwndSource = null;
      }
    }
    
    void CreateContext()
    {
      hwndSource = (HwndSource)PresentationSource.FromVisual(this.textArea);
      if (hwndSource != null) {
        if (isReadOnly) {
          defaultImeWnd = IntPtr.Zero;
          currentContext = IntPtr.Zero;
        } else {
          defaultImeWnd = ImeNativeWrapper.ImmGetDefaultIMEWnd(IntPtr.Zero);
          currentContext = ImeNativeWrapper.ImmGetContext(defaultImeWnd);
        }
        previousContext = ImeNativeWrapper.ImmAssociateContext(hwndSource.Handle, currentContext);
        hwndSource.AddHook(WndProc);
        // UpdateCompositionWindow() will be called by the caret becoming visible
        
        var threadMgr = ImeNativeWrapper.GetTextFrameworkThreadManager();
        if (threadMgr != null) {
          // Even though the docu says passing null is invalid, this seems to help
          // activating the IME on the default input context that is shared with WPF
          threadMgr.SetFocus(IntPtr.Zero);
        }
      }
    }
    
    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.
          
          // If we have a context, recreate it
          if (hwndSource != null) {
            ClearContext();
            CreateContext();
          }
          break;
        case ImeNativeWrapper.WM_IME_COMPOSITION:
          UpdateCompositionWindow();
          break;
      }
      return IntPtr.Zero;
    }
    
    public void UpdateCompositionWindow()
    {
      if (currentContext != IntPtr.Zero) {
        ImeNativeWrapper.SetCompositionFont(hwndSource, currentContext, textArea);
        ImeNativeWrapper.SetCompositionWindow(hwndSource, currentContext, textArea);
      }
    }
  }
}