bug#16822: 24.3.50; show-paren-mode adds confusion to active region

bug#16822: 24.3.50; show-paren-mode adds confusion to active region

[yynyygy]

When show-paren-mode is on, it adds confusion to the active
region. Suppose I have some text which is (hello),

1. I set the region to (hello and place the cursor on the left paren.
2. I set the region to (hello) and place the cursor on the left paren.

Note that in Case 1, the right paren is not part of the region while in
Case 2 it is. In the two cases above, I get exactly the same color on
the screen, then how can I distinguish between these two different
cases?

Compared to the more rational behavior of Emacs 24.3, I think the paren
which is part of the region should have the same color with the region
while the paren which is not part of the region can has matching paren
color. In this way, the user can tell which part is selected and which
part is not.



In GNU Emacs 24.3.50.1 (i686-pc-linux-gnu, GTK+ Version 3.8.7)
 of 2014-02-19 on gentoo
Windowing system distributor `The X.Org Foundation', version 11.0.11403000
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 `configure --prefix=/usr/local/emacs/'

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bug#16822: 24.3.50; show-paren-mode adds confusion to active region

[Drew Adams]

> When show-paren-mode is on, it adds confusion to the active
> region. Suppose I have some text which is (hello),
> 
> 1. I set the region to (hello and place the cursor on the left paren.
> 2. I set the region to (hello) and place the cursor on the left paren.
> 
> Note that in Case 1, the right paren is not part of the region while in
> Case 2 it is. In the two cases above, I get exactly the same color on
> the screen, then how can I distinguish between these two different
> cases?
> 
> Compared to the more rational behavior of Emacs 24.3, I think the paren
> which is part of the region should have the same color with the region
> while the paren which is not part of the region can has matching paren
> color. In this way, the user can tell which part is selected and which
> part is not.

Well put.

Yes, it used to be the case that the region highlighting was used
to show clearly what text is in the region (each char), as specified
by the doc:

http://www.gnu.org/software/emacs/manual/html_node/elisp/Displaying-Faces.html

That policy was changed recently, introducing the behavior change
that you report.  Now, other highlighting can take precedence
visually over region highlighting for various chars of the region.

Some people like the change.  Some don't.  Regression or improvement -
take your pick.  (No, you cannot take your pick in practice, e.g.,
via customization.  But you can at least make up your own mind.)

If you are interested, see bugs #15899, #16192, #15618, and this very
long emacs-devel thread:
http://lists.gnu.org/archive/html/emacs-devel/2014-01/msg01272.html

15899: http://debbugs.gnu.org/cgi/bugreport.cgi?bug=15899
16192: http://debbugs.gnu.org/cgi/bugreport.cgi?bug=16192
15618: http://debbugs.gnu.org/cgi/bugreport.cgi?bug=15618

bug#16822: 24.3.50; show-paren-mode adds confusion to active region

[Stefan Monnier]

> take your pick.  (No, you cannot take your pick in practice, e.g.,
> via customization.  But you can at least make up your own mind.)

Maybe not via M-x customize, indeed, but since it's now written in
Elisp, you definitely can change it in your ~/.emacs.


        Stefan

bug#16822: 24.3.50; show-paren-mode adds confusion to active region

[Lars Ingebrigtsen]

yynyygy@gmail.com writes:

> When show-paren-mode is on, it adds confusion to the active
> region. Suppose I have some text which is (hello),
>
> 1. I set the region to (hello and place the cursor on the left paren.
> 2. I set the region to (hello) and place the cursor on the left paren.
>
> Note that in Case 1, the right paren is not part of the region while in
> Case 2 it is. In the two cases above, I get exactly the same color on
> the screen, then how can I distinguish between these two different
> cases?



-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no

bug#16822: 24.3.50; show-paren-mode adds confusion to active region

[Lars Ingebrigtsen]

[-- Attachment #1: Type: text/plain, Size: 684 bytes --]

yynyygy@gmail.com writes:

> When show-paren-mode is on, it adds confusion to the active
> region. Suppose I have some text which is (hello),
>
> 1. I set the region to (hello and place the cursor on the left paren.
> 2. I set the region to (hello) and place the cursor on the left paren.
>
> Note that in Case 1, the right paren is not part of the region while in
> Case 2 it is. In the two cases above, I get exactly the same color on
> the screen, then how can I distinguish between these two different
> cases?

This is still the case in Emacs 28.  Whether I put the mark after the
"o" or after the ")", and then go to the start of the line (in
*scratch*), I get this displayed:


[-- Attachment #2: Type: image/png, Size: 1601 bytes --]

[-- Attachment #3: Type: text/plain, Size: 218 bytes --]


Perhaps the solution here is just to introduce a new face for parens
that are part of the region?  Any opinions?

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no

bug#16822: 24.3.50; show-paren-mode adds confusion to active region

[Eli Zaretskii]

> From: Lars Ingebrigtsen <larsi@gnus.org>
> Date: Thu, 15 Jul 2021 06:59:21 +0200
> Cc: 16822@debbugs.gnu.org
> 
> yynyygy@gmail.com writes:
> 
> > When show-paren-mode is on, it adds confusion to the active
> > region. Suppose I have some text which is (hello),
> >
> > 1. I set the region to (hello and place the cursor on the left paren.
> > 2. I set the region to (hello) and place the cursor on the left paren.
> >
> > Note that in Case 1, the right paren is not part of the region while in
> > Case 2 it is. In the two cases above, I get exactly the same color on
> > the screen, then how can I distinguish between these two different
> > cases?
> 
> This is still the case in Emacs 28.  Whether I put the mark after the
> "o" or after the ")", and then go to the start of the line (in
> *scratch*), I get this displayed:
> [...]
> Perhaps the solution here is just to introduce a new face for parens
> that are part of the region?  Any opinions?

I admit that I don't understand the problem.  Why should the display
be different in these two cases?  It sounds like the (unspelled-out)
assumption is that showing the region is more important than showing
the (mis)matched parens?  But if this is the assumption, then I don't
think I agree: show-paren-mode is for _temporary_ display of the
parens, so if it temporarily obscures the region, it's perfectly okay.

Adding a new face would bump into the problem of making sure the
colors of this new face are always visible and distinguishable from
the other two colors.  I don't see how that could work reliably.

bug#16822: 24.3.50; show-paren-mode adds confusion to active region

[Lars Ingebrigtsen]

Eli Zaretskii <eliz@gnu.org> writes:

> I admit that I don't understand the problem.  Why should the display
> be different in these two cases?  It sounds like the (unspelled-out)
> assumption is that showing the region is more important than showing
> the (mis)matched parens?  But if this is the assumption, then I don't
> think I agree: show-paren-mode is for _temporary_ display of the
> parens, so if it temporarily obscures the region, it's perfectly okay.
>
> Adding a new face would bump into the problem of making sure the
> colors of this new face are always visible and distinguishable from
> the other two colors.  I don't see how that could work reliably.

I was thinking that perhaps the region-blink-face would tweak the
foreground (while the normal only tweaks the background), so by merging
we'd see some difference.

But you're right -- it's hard to see what the use case here is, really,
beyond "it'd be nice".  So I'm closing this bug report.

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no