/AvalonEdit/ICSharpCode.AvalonEdit/Rendering/VisualLineElementGenerator.cs

 1// Copyright (c) 2014 AlphaSierraPapa for the SharpDevelop Team
 2// 
 3// Permission is hereby granted, free of charge, to any person obtaining a copy of this
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 9// The above copyright notice and this permission notice shall be included in all copies or
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11// 
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13// INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
14// PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE
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17// DEALINGS IN THE SOFTWARE.
18
19using System;
20
21namespace ICSharpCode.AvalonEdit.Rendering
22{
23	/// <summary>
24	/// Abstract base class for generators that produce new visual line elements.
25	/// </summary>
26	public abstract class VisualLineElementGenerator
27	{
28		/// <summary>
29		/// Gets the text run construction context.
30		/// </summary>
31		protected ITextRunConstructionContext CurrentContext { get; private set; }
32		
33		/// <summary>
34		/// Initializes the generator for the <see cref="ITextRunConstructionContext"/>
35		/// </summary>
36		public virtual void StartGeneration(ITextRunConstructionContext context)
37		{
38			if (context == null)
39				throw new ArgumentNullException("context");
40			this.CurrentContext = context;
41		}
42		
43		/// <summary>
44		/// De-initializes the generator.
45		/// </summary>
46		public virtual void FinishGeneration()
47		{
48			this.CurrentContext = null;
49		}
50		
51		/// <summary>
52		/// Should only be used by VisualLine.ConstructVisualElements.
53		/// </summary>
54		internal int cachedInterest;
55		
56		/// <summary>
57		/// Gets the first offset >= startOffset where the generator wants to construct an element.
58		/// Return -1 to signal no interest.
59		/// </summary>
60		public abstract int GetFirstInterestedOffset(int startOffset);
61		
62		/// <summary>
63		/// Constructs an element at the specified offset.
64		/// May return null if no element should be constructed.
65		/// </summary>
66		/// <remarks>
67		/// Avoid signalling interest and then building no element by returning null - doing so
68		/// causes the generated <see cref="VisualLineText"/> elements to be unnecessarily split
69		/// at the position where you signalled interest.
70		/// </remarks>
71		public abstract VisualLineElement ConstructElement(int offset);
72	}
73	
74	internal interface IBuiltinElementGenerator
75	{
76		void FetchOptions(TextEditorOptions options);
77	}
78}