Clarified XMLDoc for GetCanvasPointer().

DotSDL/Graphics/SdlWindow.cs

@@ -237,8 +237,9 @@ namespace DotSDL.Graphics {
         }
 
         /// <summary>
-        /// Gets an <see cref="IntPtr"/> that points to what should be displayed on the window's background. You usually
-        /// do not need to override this method.
+        /// Gets an <see cref="IntPtr"/> that points to what should be displayed on the window's background. This is
+        /// useful if you're maintaining your own ARGB framebuffer and don't plan to use DotSDL's <see cref="Canvas"/>
+        /// object. You usually do not need to override this method.
         /// </summary>
         /// <remarks>If an invalid <see cref="IntPtr"/> is generated by this method, your application may
         /// crash with a segmentation fault. When in doubt, override <see cref="OnDraw"/> instead!</remarks>