GNU bug report logs - #40784
Clarifying the difference between fringe bitmaps and XBM images

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Message #5 received at submit <at> debbugs.gnu.org (full text, mbox):

From: Clément Pit-Claudel <cpitclaudel <at> gmail.com>
To: bug-gnu-emacs <bug-gnu-emacs <at> gnu.org>
Subject: Clarifying the difference between fringe bitmaps and XBM images
Date: Wed, 22 Apr 2020 17:52:23 -0400

[Message part 1 (text/plain, inline)]

Hi all,

I was experimenting with XBM images today and it took me a while to realize that the bits in XBM and fringe bitmaps are not in the same order.  The attached patch attempts to highlight this.

Cheers,
Clément.

[0001-Point-out-the-difference-in-bit-order-between-fringe.patch (text/x-patch, attachment)]

Message #8 received at 40784 <at> debbugs.gnu.org (full text, mbox):

From: Eli Zaretskii <eliz <at> gnu.org>
To: Clément Pit-Claudel <cpitclaudel <at> gmail.com>
Cc: 40784 <at> debbugs.gnu.org
Subject: Re: bug#40784: Clarifying the difference between fringe bitmaps and
 XBM images
Date: Thu, 23 Apr 2020 17:30:47 +0300

> From: Clément Pit-Claudel <cpitclaudel <at> gmail.com>
> Date: Wed, 22 Apr 2020 17:52:23 -0400
> 
> I was experimenting with XBM images today and it took me a while to realize that the bits in XBM and fringe bitmaps are not in the same order.  The attached patch attempts to highlight this.

I don't think I understand the concern, and therefore cannot make up
my mind about the proposed changes.  Can you tell more about your
difficulties?

Thanks.

Message #11 received at 40784 <at> debbugs.gnu.org (full text, mbox):

From: Clément Pit-Claudel <cpitclaudel <at> gmail.com>
To: Eli Zaretskii <eliz <at> gnu.org>
Cc: 40784 <at> debbugs.gnu.org
Subject: Re: bug#40784: Clarifying the difference between fringe bitmaps and
 XBM images
Date: Thu, 23 Apr 2020 10:35:54 -0400

On 23/04/2020 10.30, Eli Zaretskii wrote:
>> From: Clément Pit-Claudel <cpitclaudel <at> gmail.com>
>> Date: Wed, 22 Apr 2020 17:52:23 -0400
>>
>> I was experimenting with XBM images today and it took me a while to realize that the bits in XBM and fringe bitmaps are not in the same order.  The attached patch attempts to highlight this.
> 
> I don't think I understand the concern, and therefore cannot make up
> my mind about the proposed changes.  Can you tell more about your
> difficulties?

Of course: I am currently writing a mode that displays indicators either in the margins or in the fringes, depending on the value of a defcustom.
By default, I intended to use the same bitmaps in the margins and in the fringes.  It took me a while to understand what I was doing wrong: I was seeing reversed bitmaps, but I hadn't considered the possibility that the two places where Emacs supports monochrome bitmaps would accept the same representation (unibyte strings) but use a different bit order. 
The proposed patch updates the documentation to save the next person from experiencing the same pain.

Clément.

Message #14 received at 40784 <at> debbugs.gnu.org (full text, mbox):

From: Eli Zaretskii <eliz <at> gnu.org>
To: Clément Pit-Claudel <cpitclaudel <at> gmail.com>
Cc: 40784 <at> debbugs.gnu.org
Subject: Re: bug#40784: Clarifying the difference between fringe bitmaps and
 XBM images
Date: Thu, 23 Apr 2020 18:14:11 +0300

> Cc: 40784 <at> debbugs.gnu.org
> From: Clément Pit-Claudel <cpitclaudel <at> gmail.com>
> Date: Thu, 23 Apr 2020 10:35:54 -0400
> 
> Of course: I am currently writing a mode that displays indicators either in the margins or in the fringes, depending on the value of a defcustom.
> By default, I intended to use the same bitmaps in the margins and in the fringes.  It took me a while to understand what I was doing wrong: I was seeing reversed bitmaps, but I hadn't considered the possibility that the two places where Emacs supports monochrome bitmaps would accept the same representation (unibyte strings) but use a different bit order. 
> The proposed patch updates the documentation to save the next person from experiencing the same pain.

If so, then why do we need to mention this in the doc string?  Won't
the manual be enough?  It is strange to mention just this factoid in
the doc strings, when one can shoot themselves in the foot with
bitmapped images in many exciting ways.

Message #17 received at 40784 <at> debbugs.gnu.org (full text, mbox):

From: Clément Pit-Claudel <cpitclaudel <at> gmail.com>
To: Eli Zaretskii <eliz <at> gnu.org>
Cc: 40784 <at> debbugs.gnu.org
Subject: Re: bug#40784: Clarifying the difference between fringe bitmaps and
 XBM images
Date: Thu, 23 Apr 2020 11:44:13 -0400

On 23/04/2020 11.14, Eli Zaretskii wrote:
>> Cc: 40784 <at> debbugs.gnu.org
>> From: Clément Pit-Claudel <cpitclaudel <at> gmail.com>
>> Date: Thu, 23 Apr 2020 10:35:54 -0400
>>
>> Of course: I am currently writing a mode that displays indicators either in the margins or in the fringes, depending on the value of a defcustom.
>> By default, I intended to use the same bitmaps in the margins and in the fringes.  It took me a while to understand what I was doing wrong: I was seeing reversed bitmaps, but I hadn't considered the possibility that the two places where Emacs supports monochrome bitmaps would accept the same representation (unibyte strings) but use a different bit order. 
>> The proposed patch updates the documentation to save the next person from experiencing the same pain.
> 
> If so, then why do we need to mention this in the doc string?  Won't
> the manual be enough?  It is strange to mention just this factoid in
> the doc strings, when one can shoot themselves in the foot with
> bitmapped images in many exciting ways.

The docstrings are usually good enough that I seldom read the manuals :/
Having a brief warning in the docstring is useful in that case.  But I'm happy to yield to your judgement.

Clément.

Message #22 received at 40784-done <at> debbugs.gnu.org (full text, mbox):

From: Eli Zaretskii <eliz <at> gnu.org>
To: Clément Pit-Claudel <cpitclaudel <at> gmail.com>
Cc: 40784-done <at> debbugs.gnu.org
Subject: Re: bug#40784: Clarifying the difference between fringe bitmaps and
 XBM images
Date: Sat, 25 Apr 2020 12:59:31 +0300

> Cc: 40784 <at> debbugs.gnu.org
> From: Clément Pit-Claudel <cpitclaudel <at> gmail.com>
> Date: Thu, 23 Apr 2020 11:44:13 -0400
> 
> > If so, then why do we need to mention this in the doc string?  Won't
> > the manual be enough?  It is strange to mention just this factoid in
> > the doc strings, when one can shoot themselves in the foot with
> > bitmapped images in many exciting ways.
> 
> The docstrings are usually good enough that I seldom read the manuals :/
> Having a brief warning in the docstring is useful in that case.  But I'm happy to yield to your judgement.

Thanks, I've updated the manual with this caveat.

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