ImageView Updates Cause Ram Leak

Carbongrip

Hello I seem to have a ram leak that occurs whenever I update an ImageView frequently. I use this to screen capture a single window and play it in a ImageView. The code works as I intend it to but it causes a ram leak whenever I include remoteWindowFrame.Image = new NSImage(cgImage, new CGSize(cgImage.Width, cgImage.Height));

Here is the code I use...

Timer frameTimer = new Timer(createSingleWindowShot, null, 0, 1000/60);

private void createSingleWindowShot(Object o)
{
    uint testID = 329;
    // Create an image from the passed in windowID with the single window option selected by the user.
    IntPtr windowImage = CGWindowListCreateImage(CGRect.Null, CGWindowListOption.IncludingWindow, testID, CGWindowImageOption.Default);
    CGImage cgImage = new CGImage(windowImage);
    InvokeOnMainThread(delegate {
        remoteWindowFrame.Image = new NSImage(cgImage, new CGSize(cgImage.Width, cgImage.Height));
    });
}

ChrisHamons

Being in C# does not prevent you from having to follow the Create rule:

https://developer.apple.com/library/content/documentation/CoreFoundation/Conceptual/CFMemoryMgmt/Concepts/Ownership.html

specially when you are calling into CG functions directly.

You code does this:

• CGWindowListCreateImage - This is a create function, so you own the memory it returns
• CGImage (IntPtr) - Since you called this one we are not telling the CGImage to "take ownership".
• New NSImage (CGImage, CGSize) - We're not taking ownership of this here either, just using it to init

So you can either:

• Use new CGImage (windowImage, true) to tell the CGImage it owns the memory you manually allocated
• Call CFRelease by hand at the end.

The first is preferred in almost all cases.

Carbongrip

I can't seem to reference CGImage(IntPtr handle, bool owns) and according to the api it doesn't exist. How do I access it?

https://developer.xamarin.com/api/type/MonoMac.CoreGraphics.CGImage/

Im still getting used to mac foundations, I'm used to .Net on Windows WPF.

ChrisHamons

My mistake, CGImage (IntPtr, bool) is internal. I forgot to check.

Try this:

        ObjCRuntime.Runtime.GetINativeObject<CoreGraphics.CGImage> (ptr, true);

ChrisHamons

Im still getting used to mac foundations, I'm used to .Net on Windows WPF.

Expect a bit of a bumpy transition, there is a lot wanting in Cocoa in when compared to some of the nicer bits of WPF (I used to do WPF).

This post has a number of resources that may be useful: https://forums.xamarin.com/discussion/comment/302822/#Comment_302822