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Re: [PATCH] system-type cygwin with window-system w32

From: Daniel Colascione
Subject: Re: [PATCH] system-type cygwin with window-system w32
Date: Mon, 18 Jul 2011 10:04:31 -0700
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On 7/18/11 9:29 AM, Eli Zaretskii wrote:
>> Date: Mon, 18 Jul 2011 03:33:59 -0700
>> From: Daniel Colascione <address@hidden>
>> CC: address@hidden
>>>> -  if (!hprevinst)
>>>> -    {
>>>> -      w32_init_class (hinst);
>>>> -    }
>>>> +  w32_init_class (hinst);
>>> Not sure why the test was deleted here.  Can you explain?
>> hprevinst isn't trivially available under Cygwin, and I don't see what
>> the test is buying us: class registration is inexpensive.
> But then for Cygwin the condition will always be false, and the net
> effect is to always call the function, as you wanted, right?  So I
> would rather we left the code alone.

We'd still need the variable with your proposal, and I don't see what
the existing behavior has, even in the NT case.

>>>> +  htext = GlobalAlloc (GMEM_MOVEABLE | GMEM_DDESHARE, bytes);
>>>> +  if (!htext)
>>>> +    error ("GlobalAlloc: %s", w32_strerror (GetLastError ()));
>>> Such cryptic error messages are not useful, because users are not
>>> required to know what GlobalAlloc is.  Please modify the text to be
>>> more palatable to mere mortals (here and elsewhere in this part of the
>>> patch).
>> Well, it's better than what we used to do much of the time, which was to
>> not check error codes at all.  How would you suggest changing the
>> messages?
> How about calling memory_full?
> Or maybe error ("Not enough memory <TO DO WHATEVER THIS CODE DOES>") ?

The error isn't necessarily fatal --- and in general (speaking to other
instances of w32_strerror in the patch) we don't always know what
exactly went wrong.  It'd be nice to give users an opportunity to figure
it out.  Maybe we can recognize a subset of error codes and forward
those to memory_full.

>> We could just the UI thread for this purpose instead of a dedicated one,
> This is what I had in mind as the alternative, yes.
>> What if I want to create a GUI-less Emacs that can nevertheless
>> can interact with the system clipboard?
> GUI-less Emacs normally doesn't interact with the clipboard, so
> there's no need to choose a design that complicates things just
> because we would like to make this feature available on a single
> platform.

The complexity has to be present regardless.

> Anyway, I'm hardly an expert on this particular issue (i.e. Windows
> GUI and the message pump).  I'm just worried by the fact that we will
> have 2 threads calling GetMessage; in my experience this could lead to
> hard-to-debug problems.

Calling GetMessage in two threads is very common and well-supported, and
won't by itself cause problems. If anything, separating the message
loops makes the program more robust --- each message loop is less
complex and thereby easier to understand.

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