cairo: Add mechanism to debug missing Dispose calls

Enabled by setting a new MONO_CAIRO_DEBUG_DISPOSE environment variable.

cairo/Context.cs

@@ -40,6 +40,49 @@ using Cairo;
 
 namespace Cairo {
 
+	static class CairoDebug
+	{
+		static System.Collections.Generic.Dictionary<IntPtr,string> traces;
+
+		public static readonly bool Enabled;
+
+		static CairoDebug ()
+		{
+			var dbg = Environment.GetEnvironmentVariable ("MONO_CAIRO_DEBUG_DISPOSE");
+			if (dbg == null)
+				return;
+			Enabled = true;
+			traces = new System.Collections.Generic.Dictionary<IntPtr,string> ();
+		}
+
+		public static void OnAllocated (IntPtr obj)
+		{
+			if (!Enabled)
+				throw new InvalidOperationException ();
+
+			traces.Add (obj, Environment.StackTrace);
+		}
+
+		public static void OnDisposed<T> (IntPtr obj, bool disposing)
+		{
+			if (disposing && !Enabled)
+				throw new InvalidOperationException ();
+
+			if (!disposing) {
+				Console.Error.WriteLine ("{0} is leaking, programmer is missing a call to Dispose", typeof(T).FullName);
+				if (Enabled) {
+					Console.Error.WriteLine ("Allocated from:");
+					Console.Error.WriteLine (traces[obj]);
+				} else {
+					Console.Error.WriteLine ("Set MONO_CAIRO_DEBUG_DISPOSE to track allocation traces");
+				}
+			}
+
+			if (Enabled)
+				traces.Remove (obj);
+		}
+	}
+
         public struct Point
         {		
 		public Point (int x, int y)
@@ -204,12 +247,10 @@ namespace Cairo {
 		
                 protected virtual void Dispose (bool disposing)
                 {
-			if (!disposing){
+			if (!disposing || CairoDebug.Enabled)
-				Console.Error.WriteLine ("Cairo.Context: called from finalization thread, programmer is missing a call to Dispose");
+				CairoDebug.OnDisposed<Context> (state, disposing);
-				return;
-			}
 
-			if (state == IntPtr.Zero)
+			if (!disposing|| state == IntPtr.Zero)
 				return;
 
 			//Console.WriteLine ("Destroying");

cairo/FontFace.cs

@@ -61,13 +61,11 @@ namespace Cairo
 
 		protected virtual void Dispose (bool disposing)
 		{
-			if (handle == IntPtr.Zero)
+			if (!disposing || CairoDebug.Enabled)
-				return;
+				CairoDebug.OnDisposed<FontFace> (handle, disposing);
 
-			if (!disposing) {
+			if (!disposing|| handle == IntPtr.Zero)
-				Console.Error.WriteLine ("Cairo.FontFace: called from finalization thread, programmer is missing a call to Dispose");
 				return;
-			}
 
 			NativeMethods.cairo_font_face_destroy (handle);
 			handle = IntPtr.Zero;
@@ -77,6 +75,8 @@ namespace Cairo
 		public FontFace (IntPtr handle)
 		{
 			this.handle = handle;
+			if (CairoDebug.Enabled)
+				CairoDebug.OnAllocated (handle);
 		}
 
 		public IntPtr Handle {

cairo/FontOptions.cs

@@ -47,6 +47,8 @@ namespace Cairo
 		internal FontOptions (IntPtr handle)
 		{
 			this.handle = handle;
+			if (CairoDebug.Enabled)
+				CairoDebug.OnAllocated (handle);
 		}
 
 		public FontOptions Copy ()
@@ -68,13 +70,11 @@ namespace Cairo
 
 		protected virtual void Dispose (bool disposing)
 		{
-			if (handle == IntPtr.Zero)
+			if (!disposing || CairoDebug.Enabled)
-				return;
+				CairoDebug.OnDisposed<FontOptions> (handle, disposing);
 
-			if (!disposing) {
+			if (!disposing|| handle == IntPtr.Zero)
-				Console.Error.WriteLine ("Cairo.FontOptions: called from finalization thread, programmer is missing a call to Dispose");
 				return;
-			}
 
 			NativeMethods.cairo_font_options_destroy (handle);
 			handle = IntPtr.Zero;

cairo/Path.cs

@@ -41,6 +41,8 @@ namespace Cairo {
 		internal Path (IntPtr handle)
 		{
 			this.handle = handle;
+			if (CairoDebug.Enabled)
+				CairoDebug.OnAllocated (handle);
 		}
 
 		~Path ()
@@ -57,12 +59,10 @@ namespace Cairo {
 		
 		protected virtual void Dispose (bool disposing)
 		{
-			if (!disposing) {
+			if (!disposing || CairoDebug.Enabled)
-				Console.Error.WriteLine ("Cairo.Path: called from finalization thread, programmer is missing a call to Dispose");
+				CairoDebug.OnDisposed<Path> (handle, disposing);
-				return;
-			}
 			
-			if (handle == IntPtr.Zero)
+			if (!disposing|| handle == IntPtr.Zero)
 				return;
 
 			NativeMethods.cairo_path_destroy (handle);

cairo/Pattern.cs

@@ -66,12 +66,15 @@ namespace Cairo {
 
 		static Hashtable patterns = new Hashtable ();
 		
-		internal Pattern (IntPtr ptr)
+		internal Pattern (IntPtr handle)
 		{
 			lock (patterns){
-				patterns [ptr] = this;
+				patterns [handle] = this;
 			}
-			pattern = ptr;
+
+			Handle = handle;
+			if (CairoDebug.Enabled)
+				CairoDebug.OnAllocated (handle);
 		}
 
 		~Pattern ()
@@ -98,16 +101,14 @@ namespace Cairo {
 
 		protected virtual void Dispose (bool disposing)
 		{
-			if (!disposing) {
+			if (!disposing || CairoDebug.Enabled)
-				Console.Error.WriteLine ("Cairo.Pattern: called from finalization thread, programmer is missing a call to Dispose");
+				CairoDebug.OnDisposed<Pattern> (Handle, disposing);
-				return;
-			}
 
-			if (pattern == IntPtr.Zero)
+			if (!disposing|| Handle == IntPtr.Zero)
 				return;
 
-			NativeMethods.cairo_pattern_destroy (pattern);
+			NativeMethods.cairo_pattern_destroy (Handle);
-			pattern = IntPtr.Zero;
+			Handle = IntPtr.Zero;
 			lock (patterns){
 				patterns.Remove (this);
 			}
@@ -116,7 +117,7 @@ namespace Cairo {
 		[Obsolete ("Use Dispose()")]
                 public void Destroy ()
                 {
-			Dispose ();
+			NativeMethods.cairo_pattern_destroy (pattern);
                 }
 		
 		public Extend Extend {
@@ -143,6 +144,7 @@ namespace Cairo {
 
                 public IntPtr Handle {
                         get { return pattern; }
+                        private set { pattern = value; }
                 }		
 
 		[Obsolete ("Replaced by Handle property")]

cairo/ScaledFont.cs

@@ -35,11 +35,13 @@ namespace Cairo {
 		internal ScaledFont (IntPtr handle)
 		{
 			this.handle = handle;
+			if (CairoDebug.Enabled)
+				CairoDebug.OnAllocated (handle);
 		}
 
 		public ScaledFont (FontFace fontFace, Matrix matrix, Matrix ctm, FontOptions options)
+			: this (NativeMethods.cairo_scaled_font_create (fontFace.Handle, matrix, ctm, options.Handle))
 		{
-			handle = NativeMethods.cairo_scaled_font_create (fontFace.Handle, matrix, ctm, options.Handle);
 		}
 
 		~ScaledFont ()
@@ -99,13 +101,11 @@ namespace Cairo {
 
 		protected virtual void Dispose (bool disposing)
 		{
-			if (handle == IntPtr.Zero)
+			if (!disposing || CairoDebug.Enabled)
-				return;
+				CairoDebug.OnDisposed<ScaledFont> (handle, disposing);
 
-			if (!disposing) {
+			if (!disposing|| handle == IntPtr.Zero)
-				Console.Error.WriteLine ("Cairo.ScaledFont: called from finalization thread, programmer is missing a call to Dispose");
 				return;
-			}
 
 			NativeMethods.cairo_scaled_font_destroy (handle);
 			handle = IntPtr.Zero;

cairo/Surface.cs

@@ -43,6 +43,7 @@ namespace Cairo {
 		protected static Hashtable surfaces = new Hashtable ();
                 internal IntPtr surface = IntPtr.Zero;
 
+		[Obsolete]
 		protected Surface()
 		{
 		}
@@ -55,6 +56,8 @@ namespace Cairo {
 			}
 			if (!owns)
 				NativeMethods.cairo_surface_reference (ptr);
+			if (CairoDebug.Enabled)
+				CairoDebug.OnAllocated (ptr);
                 }
 
 		static internal Surface LookupExternalSurface (IntPtr p)
@@ -147,12 +150,11 @@ namespace Cairo {
 
 		protected virtual void Dispose (bool disposing)
 		{
-			if (surface == IntPtr.Zero)
+			if (!disposing || CairoDebug.Enabled)
+				CairoDebug.OnDisposed<Surface> (surface, disposing);
+			
+			if (!disposing|| surface == IntPtr.Zero)
 				return;
-			if (!disposing) {
-				Console.Error.WriteLine ("Cairo.Surface: called from finalization thread, programmer is missing a call to Dispose");
-				return;
-			}
 
 			lock (surfaces.SyncRoot)
 				surfaces.Remove (surface);