Sadly, it turns out that our memory string optimisation procedures corrupted the headp after the GC was run. Turns out because (I might be wrong though) that the GC appears to try to use leftover string space for heap allocations, which sometimes caused random corruptions but mostly crashes as were directly modifying the underlying string length. Fixes #51.

ClassicalSharp/2D/Screens/BlockSelectScreen.cs

@@ -130,7 +130,7 @@ namespace ClassicalSharp {
 			
 			Block block = blocksTable[selectedIndex].BlockId;
 			UpdateBlockInfoString( block );
-			string value = buffer.UpdateCachedString();
+			string value = buffer.GetString();
 			
 			Size size = Utils2D.MeasureSize( value, font, true );
 			int x = startX + ( blockSize * blocksPerRow ) / 2 - size.Width / 2;

ClassicalSharp/2D/Screens/FpsScreen.cs

@@ -38,7 +38,7 @@ namespace ClassicalSharp {
 						.Append( ref ptr2, ", vertices: " ).AppendNum( ref ptr2, game.Vertices );
 				}
 				
-				string textString = text.UpdateCachedString();			
+				string textString = text.GetString();
 				fpsTextWidget.SetText( textString );
 				maxDelta = 0;
 				accumulator = 0;

ClassicalSharp/2D/Widgets/TextInputWidget.cs

@@ -40,7 +40,7 @@ namespace ClassicalSharp {
 			X = 10;
 			DrawTextArgs caretArgs = new DrawTextArgs( graphicsApi, "_", Color.White, false );
 			chatCaretTexture = Utils2D.MakeTextTexture( boldFont, 0, 0, ref caretArgs );
-			string value = chatInputText.UpdateCachedString();
+			string value = chatInputText.GetString();
 			
 			if( chatInputText.Empty ) {
 				caretPos = -1;
@@ -50,27 +50,32 @@ namespace ClassicalSharp {
 			if( caretPos == -1 ) {
 				chatCaretTexture.X1 = 10 + size.Width;
 				size.Width += chatCaretTexture.Width;
+				DrawString( size, value, true );
 			} else {
 				string subString = chatInputText.GetSubstring( caretPos );
 				Size trimmedSize = Utils2D.MeasureSize( subString, font, false );
-				chatInputText.RestoreLength();
 				
 				chatCaretTexture.X1 = 10 + trimmedSize.Width;
 				Size charSize = Utils2D.MeasureSize( new String( value[caretPos], 1 ), font, false );
 				chatCaretTexture.Width = charSize.Width;
+				DrawString( size, value, false );
+			}
 		}
-			size.Height = Math.Max( size.Height, chatCaretTexture.Height );
 		
+		void DrawString( Size size, string value, bool skipCheck ) {
+			size.Height = Math.Max( size.Height, chatCaretTexture.Height );
 			int y = game.Height - ChatInputYOffset - size.Height / 2;
+			
 			using( Bitmap bmp = Utils2D.CreatePow2Bitmap( size ) ) {
 				using( Graphics g = Graphics.FromImage( bmp ) ) {
 					Utils2D.DrawRect( g, backColour, 0, 0, bmp.Width, bmp.Height );
 					DrawTextArgs args = new DrawTextArgs( graphicsApi, value, Color.White, false );
-					args.SkipPartsCheck = true;
+					args.SkipPartsCheck = skipCheck;
 					Utils2D.DrawText( g, font, ref args, 0, 0 );
 				}
 				chatInputTexture = Utils2D.Make2DTexture( graphicsApi, bmp, size, 10, y );
 			}
+			
 			chatCaretTexture.Y1 = chatInputTexture.Y1;
 			Y = y;
 			Width = size.Width;

ClassicalSharp/Network/NetworkProcessor.cs

@@ -341,7 +341,7 @@ namespace ClassicalSharp {
 							sentWomId = true;
 						}
 						gzipStream = null;
-						GC.Collect();
+						GC.Collect( 0 );
 					} break;
 					
 				case PacketId.SetBlock:

ClassicalSharp/Utils/StringBuffer.cs

@@ -3,34 +3,11 @@ using System.Reflection;
 
 namespace ClassicalSharp {
 	
-	// Class used to minimise memory allocations of strings.
-	// Really, only useful for FpsScreen and TextInputWidget as they allocate lots of very small strings.
-	// Seriously, you should *not* use this anywhere else, as Empty and Length are O(N).
 	internal sealed unsafe class StringBuffer {
 		
 		internal string value;
 		internal int capacity;
 		
-		static readonly FieldInfo arrayField, lengthField;
-		static bool supportsLengthSetting;
-		
-		static StringBuffer() {
-			if( OpenTK.Configuration.RunningOnMono )
-				return;
-			
-			arrayField = typeof( String ).GetField( "m_arrayLength", BindingFlags.NonPublic | BindingFlags.Instance );
-			lengthField = typeof( String ).GetField( "m_stringLength", BindingFlags.NonPublic | BindingFlags.Instance );
-			
-			// Make sure we are running on a framework that has both methods -
-			// otherwise we play it safe and just use TrimEnd().
-			if( arrayField != null && lengthField != null ) {
-				supportsLengthSetting = true;
-			} else {
-				arrayField = null;
-				lengthField = null;
-			}
-		}
-		
 		public StringBuffer( int capacity ) {
 			this.capacity = capacity;
 			value = new String( '\0', capacity );
@@ -140,11 +117,8 @@ namespace ClassicalSharp {
 			}
 		}
 		
-		/// <summary> Hack that modifies the underlying string's length to avoid memory allocations. </summary>
+		public string GetString() {
-		/// <returns> The underlying string - ***do not*** store this because it is mutable!
+			return value.TrimEnd( trimEnd );
-		/// You should only use this string for temporary measuring and drawing. </returns>
-		public string UpdateCachedString() {
-			return supportsLengthSetting ? SetLength( Length ) : value.TrimEnd( trimEnd );
 		}
 		static char[] trimEnd = { '\0' };
 		
@@ -153,18 +127,7 @@ namespace ClassicalSharp {
 		}
 		
 		public string GetSubstring( int length ) {
-			return supportsLengthSetting ? SetLength( length ) : GetCopy( length );
+			return GetCopy( length );
-		}
-		
-		public void RestoreLength() {
-			if( supportsLengthSetting )
-				SetLength( Length );
-		}
-		
-		string SetLength( int len ) {
-			arrayField.SetValue( value, len + 1 );
-			lengthField.SetValue( value, len );
-			return value;
 		}
 		
 		string GetCopy( int len ) {