source: branches/2929_PrioritizedGrammarEnumeration/HeuristicLab.ExtLibs/HeuristicLab.AvalonEdit/5.0.1/AvalonEdit-5.0.1/Snippets/SnippetInputHandler.cs @ 15990

// 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.Collections.Generic;
using System.Linq;
using System.Windows.Input;

using ICSharpCode.AvalonEdit.Editing;

namespace ICSharpCode.AvalonEdit.Snippets
{
  sealed class SnippetInputHandler : TextAreaStackedInputHandler
  {
    readonly InsertionContext context;
    
    public SnippetInputHandler(InsertionContext context)
      : base(context.TextArea)
    {
      this.context = context;
    }
    
    public override void Attach()
    {
      base.Attach();
      
      SelectElement(FindNextEditableElement(-1, false));
    }
    
    public override void Detach()
    {
      base.Detach();
      context.Deactivate(new SnippetEventArgs(DeactivateReason.InputHandlerDetached));
    }
    
    public override void OnPreviewKeyDown(KeyEventArgs e)
    {
      base.OnPreviewKeyDown(e);
      if (e.Key == Key.Escape) {
        context.Deactivate(new SnippetEventArgs(DeactivateReason.EscapePressed));
        e.Handled = true;
      } else if (e.Key == Key.Return) {
        context.Deactivate(new SnippetEventArgs(DeactivateReason.ReturnPressed));
        e.Handled = true;
      } else if (e.Key == Key.Tab) {
        bool backwards = e.KeyboardDevice.Modifiers == ModifierKeys.Shift;
        SelectElement(FindNextEditableElement(TextArea.Caret.Offset, backwards));
        e.Handled = true;
      }
    }
    
    void SelectElement(IActiveElement element)
    {
      if (element != null) {
        TextArea.Selection = Selection.Create(TextArea, element.Segment);
        TextArea.Caret.Offset = element.Segment.EndOffset;
      }
    }
    
    IActiveElement FindNextEditableElement(int offset, bool backwards)
    {
      IEnumerable<IActiveElement> elements = context.ActiveElements.Where(e => e.IsEditable && e.Segment != null);
      if (backwards) {
        elements = elements.Reverse();
        foreach (IActiveElement element in elements) {
          if (offset > element.Segment.EndOffset)
            return element;
        }
      } else {
        foreach (IActiveElement element in elements) {
          if (offset < element.Segment.Offset)
            return element;
        }
      }
      return elements.FirstOrDefault();
    }
  }
}