I believe Cocoa has a problem pasting images. Attached demo shows that when the clipboard contains an image copied from another application, the normal questions about "do you have an image" are always answered false. (press the Info button).
The issue, I believe is that Cocoa offers image formats that Lazarus cannot handle : public.html; Apple HTML pasteboard type; public.tiff; NeXT TIFF v4.0 pasteboard type
Carbon works fine. With both Carbon and Cocoa, an internally copied picture is reported as being image/bmp, is identified as an image and pastes fine.
I'm using Lazarus fixes_2_0 r60228, this looks similar to bug 34840 but is, in fact completely different !
Be cool if someone else can duplicate my results, if so, I'll report it in the bug tracker.
Run up the attached demo, build with fixes or trunk (1.8.4 not viable on Cocoa), copy an image from a webpage, maybe the one top left of this page and then go back to the app, click the info button. I expect you will see HasPictureFormat; FindPictureFormatID; return false, 0 and false. And cannot paste that picture with the paste button.
Davo