Latest Cygwin update and Emacs in Mintty

[Ken Brown]

On 6/15/2017 6:47 AM, Ken Brown wrote:
> On 6/14/2017 3:00 PM, Achim Gratz wrote:
>> Achim Gratz writes:
>>> After the latest Cygwin update I'm hitting an interesting problem with
>>> emacs-nox running in a mintty: when Emacs starts, it decides that the
>>> background color is gray instead of the usual white (for all but the
>>> rightmost character in the status line, interestingly enough).  I have
>>> the normal mintty background set slightly off-white (to #F8F8F8) and
>>> mintty reports itself as xterm-256color (the same happens in when TERM
>>> is set to screen-256color).  Emacs starts up with the correct background
>>> color, draws the status bar and the menu bar and only then switches the
>>> background to gray.  The gray it choses is very slightly lighter than
>>> the status bar (so lightly in fact that I can make out the difference on
>>> only one of my three monitors).  Emacs really thinks it is using a white
>>> background, as evidenced by the fact that (set-background-color "white")
>>> will produce exactly the same result.  I get my usual background back
>>> with (set-background-color "#F8F8F8"), but I have no idea where the
>>> wrong setting for the named color "white" comes from.
>>>
>>> I'm just trying this at home remotely logging in from a konsole terminal
>>> on my Linux box: Here the background chosen is slightly darker than the
>>> status bar, the status bar seems to be #B8B8B8 and the background for
>>> "white seems to be #B4B4B4.  Curious and curiouser...
>>
>> Ken, did you have a chance to look into this?
> 
> Sorry, I must have missed this when you first sent it.  I'll take a look.

I also see some strange behavior, but I can't reproduce what you're 
seeing.  Here's what I tried:

1. I edited .minttyrc to set BackgroundColour=#F8F8F8. 
(ForegroundColour is 0,0,0, which I guess is the default.)

2. I ran 'emacs-nox -Q'.  The background color didn't visibly change; 
it's still off-white.  The mode line and menu line appear to be reversed 
(black background, off-white foreground, though I can't really be sure 
that the foreground is off-white rather than white).

3. I evaluated (set-background-color "white").  This caused the 
background to turn gray.  The mode line and menu bar didn't visibly change.

4. I evaluated (set-background-color "#F8F8F8").  The background stayed 
gray.

I need to investigate 3 and 4, but first I'd like to understand why you 
and I are seeing different things.  One difference is the value of TERM. 
  You say "mintty reports itself as xterm-256color".  Do you mean it 
does this by default, or do you have something in your startup files 
that causes this?  When I start mintty, I get the following:

$ echo $TERM
xterm

Ken

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