[MACTCL] Drop Carbon support from Tk-Aqua?

[Kevin W. <kw...@co...>]

Hi all,

After extensive discussion on the Tcl-Core mailing list, we've done a 
full merge of the Tk-Cocoa backport into the main branch of Tk 8.5, so 
that it will more closely track development in 8.6 and not require the 
complexity of maintaining a separate branch. Going forward, Tk 8.5 as 
well as Tk 8.6 will be based on Cocoa.

As a result of this, the question of what to do with the older Carbon 
version of Tk--in both 8.5 and 8.6--has arisen.

When Tk-Cocoa was first merged into Tk 8.6/trunk a few years ago, it was 
decided to set up a separate "Carbon" subdirectory in the Tk source 
tree, which someone could build using an "--enable-carbon" switch during 
the configure phase. It probably would not be too hard to set up 
something similar for 8.5.

However, I'm not aware of any Tk 8.6-based projects that make a point of 
using Carbon, nor am I aware of any in 8.5; ActiveState switched 
ActiveTcl to the Cocoa-based version a couple of years ago, and the 
version of Tk that Apple ships with OS X has been Cocoa-based since 
10.6. Most projects simply go with Cocoa because that is now the most 
widely-supported version; if a project is using Carbon, it is likely by 
happenstance (an older build of Tk, for instance).

Adding to these observations is the fact that that the Carbon version is 
increasingly hard to build on recent versions of OS X, especially in a 
64-bit environment.  I've heard reports that it won't build at all on 
10.8 (can't confirm that myself as I'm still on Lion); Apple has moved 
from deprecating to actively removing some part of the Carbon framework 
from OS X. No significant work has been done on the Carbon version of Tk 
for about five years, since Daniel Steffen began working on the Cocoa port.

Based on all this, from my perspective it makes little sense to continue 
supporting the Carbon version of Tk. It seems at this point just to take 
up space in the Tk source tree, but is not used anywhere that I can see. 
My vote would be to remove it from both 8.5 and 8.6, set the line of 
demarcation on Carbon at Tk 8.5.12, and move forward.

However, I think it make sense to discuss this issue more before 
proceeding with such a change. In the Tcl chatroom I volunteered today 
to start a conversation on this issue on the Tcl-Mac list, and based on 
the feedback here, will also discuss the issue on Tcl-Core.

I will also fully acknowledge that the Cocoa port is not perfect, 
specifically with regard to performance and integration between the Tk 
and Cocoa event loops; the Carbon version is superior in this respect, 
and a few years ago a couple of people mentioned on this list that they 
prefer the Carbon version for that reason. Until Daniel Steffen or 
someone else with more expertise than me has time to dive into the 
event-loop integration questions,  the Cocoa port will continue to have 
this issue. Nonetheless, these factors in my view do not outweigh the 
facts that the Carbon port is now obsolete, cannot build in a 64-bit 
environment, and is unsupported in every major binary distribution of Tk 
on the Mac. I believe that Tk would not suffer by removing that code 
from the source tree in both 8.5 and 8.6.

Comments are not only welcome but invited. If there is a clear 
constituency for keeping the Carbon port around, we need to be aware of 
that.

Thanks,
Kevin


-- 
Kevin Walzer
Code by Kevin
http://www.codebykevin.com