3434using System . IO ;
3535using System . Reflection ;
3636using System . ComponentModel ;
37+ using System . Diagnostics ;
3738using System . Runtime . InteropServices ;
3839using Gdip = System . Drawing . SafeNativeMethods . Gdip ;
3940using System . Runtime . Serialization ;
@@ -42,6 +43,93 @@ namespace System.Drawing.Imaging
4243{
4344 public sealed partial class Metafile : Image
4445 {
46+ // Non-null if a graphics instance was created using
47+ // Graphics.FromImage(this) The metadata holder is responsible for
48+ // freeing the nativeImage if the Metadata instance is disposed before
49+ // the Graphics instance.
50+ private MetafileHolder ? _metafileHolder ;
51+
52+ // A class responsible for disposing of the native Metafile instance
53+ // if it needs to outlive the managed Metafile instance.
54+ //
55+ // The following are both legal with win32 GDI+:
56+ // Metafile mf = ...; // get a metafile instance
57+ // Graphics g = Graphics.FromImage(mf); // get a graphics instance
58+ // g.Dispose(); mf.Dispose(); // dispose of the graphics instance first
59+ // OR
60+ // mf.Dispose(); g.Dispose(); // dispose of the metafile instance first
61+ //
62+ // ligbgdiplus has a bug where disposing of the metafile instance first will
63+ // trigger a use of freed memory when the graphics instance is disposed, which
64+ // could lead to crashes when the native memory is reused.
65+ //
66+ // The metafile holder is designed to take ownership of the native metafile image
67+ // when the managed Metafile instance is disposed while a Graphics instance is still
68+ // not disposed (ie the second code pattern above) and to keep the native image alive until the graphics
69+ // instance is disposed.
70+ //
71+ // Note that the following throws, so we only ever need to keep track of one Graphics
72+ // instance at a time:
73+ // Metafile mf = ...; // get a metafile instance
74+ // Graphics g = Graphics.FromImage(mf);
75+ // Graphics g2 = Graphics.FromImage(mf); // throws OutOfMemoryException on GDI+ on Win32
76+ internal sealed class MetafileHolder : IDisposable
77+ {
78+ private bool _disposed ;
79+ private IntPtr _nativeImage ;
80+
81+
82+ internal bool Disposed { get => _disposed ; }
83+ internal MetafileHolder ( )
84+ {
85+ _disposed = false ;
86+ _nativeImage = IntPtr . Zero ;
87+ }
88+
89+ ~ MetafileHolder ( ) => Dispose ( false ) ;
90+
91+ public void Dispose ( )
92+ {
93+ Dispose ( true ) ;
94+ GC . SuppressFinalize ( this ) ;
95+ }
96+
97+ internal void Dispose ( bool disposing )
98+ {
99+ if ( ! _disposed )
100+ {
101+ IntPtr nativeImage = _nativeImage ;
102+ _nativeImage = IntPtr . Zero ;
103+ _disposed = true ;
104+ if ( nativeImage != IntPtr . Zero )
105+ {
106+ int status = Gdip . GdipDisposeImage ( nativeImage ) ;
107+ Gdip . CheckStatus ( status ) ;
108+ }
109+ }
110+ }
111+
112+ internal void MetafileDisposed ( IntPtr nativeImage )
113+ {
114+ _nativeImage = nativeImage ;
115+ }
116+
117+ internal void GraphicsDisposed ( )
118+ {
119+ Dispose ( ) ;
120+ }
121+ }
122+
123+ internal MetafileHolder ? AddMetafileHolder ( )
124+ {
125+ // If _metafileHolder is not null and hasn't been disposed yet, there's already a graphics instance associated with
126+ // this metafile, the native code will return an error status.
127+ if ( _metafileHolder != null && ! _metafileHolder . Disposed )
128+ return null ;
129+ _metafileHolder = new MetafileHolder ( ) ;
130+ return _metafileHolder ;
131+ }
132+
45133 // Usually called when cloning images that need to have
46134 // not only the handle saved, but also the underlying stream
47135 // (when using MS GDI+ and IStream we must ensure the stream stays alive for all the life of the Image)
@@ -142,6 +230,21 @@ public Metafile(string fileName, IntPtr referenceHdc, Rectangle frameRect, Metaf
142230 Gdip . CheckStatus ( status ) ;
143231 }
144232
233+ protected override void Dispose ( bool disposing )
234+ {
235+ if ( _metafileHolder != null && ! _metafileHolder . Disposed )
236+ {
237+ // There's a graphics instance created from this Metafile,
238+ // transfer responsibility for disposing the nativeImage to the
239+ // MetafileHolder
240+ _metafileHolder . MetafileDisposed ( nativeImage ) ;
241+ _metafileHolder = null ;
242+ nativeImage = IntPtr . Zero ;
243+ }
244+
245+ base . Dispose ( disposing ) ;
246+ }
247+
145248 // methods
146249
147250 public IntPtr GetHenhmetafile ( )
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