Re: [MACTCL] Partial PNG transparency not working in Cocoa Tk

[Adrian R. <adr...@gm...>]

From what I can tell the gstate is just a shortcut for avoiding creating a new one by focusing the view.  So it should be possible to use:

[view lockFocusIfCanDraw]
draw, calling the NSCopyBits with NSNullObject instead of gstate
[view unlockFocus]

But it might not be that simple — I don’t fully understand the NSGraphicsContext-related calls below.



On 2013.12.6, at 19:58, Linus Nyberg <li...@fa...> wrote:

> Hi and thank both of you for replying.
> 
> I can confirm that the same thing works fine on Mac OS X Lion.
> Unfortunately, Mavericks is not going away any time soon, and it’s a little scary that we appear to be the only ones trying to show transparent icons on the latest Mac OS X.
> 
> I now managed to download and compile the sources for Tcl/Tk 8.6.1 and using printf:s around the code I managed to track down the problem:
> - The way Tk composits photo images with alpha by creating an image of the background window and manually blending that image with the transparent image (see TkImgPhotoDisplay() in tkImgPhInstance.c).
> - When it fails to create the image of the background image, it simply draws the image without alpha (see TkImgPhotoDisplay() @ “We failed to get the image so draw without blending alpha. It's the best we can do”).
> - The problem is in case is that exactly that fails.
> - The reason for the failure is inside XCopyArea() in tkMacOSXDraw.c. There we can find this code:
> 	NSView *view = TkMacOSXDrawableView(srcDraw); 
> 	NSWindow *w = [view window];
> 	NSInteger gs = [w windowNumber] > 0 ? [w gState] : 0;
> 
> … and gs becomes 0, which makes the method return prematurely.
> When googling for NSWindow gState, I found this:
> https://developer.apple.com/library/mac/releasenotes/AppKit/RN-AppKit/#//apple_ref/doc/uid/TP30000741-CH2-SW51
> where it states:
>> Beginning in Mac OS X 10.9 -[NSView allocateGState] and -[NSView releaseGState] are no ops. These methods were seldom used. Additionally, methods that relied on the side effects of these methods, specifically -[NSView gState] and -[NSWindow gState] will now always return 0.
> 
> That would explain it, I think… But I don’t know what “gState” is and I don’t know how to solve it.
> Any ideas??
> 
> Best regards,
> 
> Linus
> 
> On 3 dec 2013, at 15:40, Kevin Walzer <kw...@co...> wrote:
> 
>> On 11/29/13, 3:58 AM, Wojciech Kocjan wrote:
>>> - happens on OS X 10.9 only - does not happen on 10.8 and below (also,
>>> transparency works fine on all other systems and all other OS X
>>> versions, so I suspect this is a change in OS X 10.9 that broke it)
>>> 
>>> - happens with latest Tcl/Tk from fossil, latest ActiveTcl
>>> 
>>> - happens with both tkpng and Img
>>> 
>>> - I can also confirm it only happens with Cocoa, not Carbon
>>> 
>>> So this is definitely an issue with Tk.
>> 
>> I'm not certain where to start with this. I've seen reports in Apple's 
>> dev forums about wonky color calibration in Mavericks (sRGB is no longer 
>> accurately rendered in many contexts, which is causing headaches for 
>> graphics shops), yet Linus reports that images created with the 
>> tk::mac::IconBitmap command (which is just a thin wrapper around various 
>> NSImage methods) work just fine. NSImage is itself an opaque wrapper 
>> around many, many different things.
>> 
>> If the issues with alpha channel rendering are based in the system 
>> changes in Mavericks, I am not optimistic about fixing them...it does 
>> not seem like a good idea to try to special-case image code in the Img, 
>> TkPNG, and 8.6 core, I would think. (Nor would I even know where to 
>> start here.)
>> 
>> --Kevin
>> 
>> -- 
>> Kevin Walzer
>> Code by Kevin/Mobile Code by Kevin
>> http://www.codebykevin.com
>> http://www.wtmobilesoftware.com
>> 
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