Re: Cursors: Is superimposing the same glyph a feature?

[Alan Third <alan@idiocy.org>]

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On Fri, Feb 15, 2019 at 11:34:35PM -0800, Keith David Bershatsky wrote:
> 
> Here are my minimal settings in the .emacs file, and then I blew-up the size of the font to get a better screenshot:
> 
> (blink-cursor-mode -1)
> 
> (setq default-frame-alist (list '(cursor-type . (hbar . 1))
>                                 '(background-color . "black")
>                                 '(foreground-color . "white")))
> 
> You may need to blow-up the image and break-out the micrometer to
> discern that the letter "A" with the HBAR_CURSOR is somewhat wider,
> with more jagged edges, and the middle triangle is somewhat smaller
> (because the walls of the letter "A" are thicker). This phenomenon
> is more easily noticed with the naked eye when holding down the
> left/right arrow key (repeating) and watching the character at point
> become bold, and then the bold is removed when moving on to the next
> character at point.

I can see it too. I’d never noticed. I doubt very much it’s
intentional.

It looks like the NS port does the wrong thing here. At the moment it
redraws the glyph on top of the cursor as long as CURSOR_TYPE !=
NO_CURSOR, but looking at an X build, it looks as though HBAR_CURSOR,
for example, should cover the glyph.

So I reckon we should only redraw the glyph if the cursor is filled box or
hollow box.

Patch attached.
-- 
Alan Third

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From 1638ac50070d6802329eae13eeba7926ed4c9149 Mon Sep 17 00:00:00 2001
From: Alan Third <alan@idiocy.org>
Date: Sat, 16 Feb 2019 10:56:13 +0000
Subject: [PATCH] Prevent redrawing the glyph on top of bar cursors

* src/nsterm.m (ns_draw_window_cursor): Limit when we redraw the
glyph.
---
 src/nsterm.m | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/src/nsterm.m b/src/nsterm.m
index bbd2c84214..5d2b0a0812 100644
--- a/src/nsterm.m
+++ b/src/nsterm.m
@@ -3126,8 +3126,9 @@ Note that CURSOR_WIDTH is meaningful only for (h)bar cursors.
           break;
         }
 
-      /* draw the character under the cursor */
-      if (cursor_type != NO_CURSOR)
+      /* Draw the character under the cursor.  Other terms only draw
+         the character on top of box cursors, so do the same here.  */
+      if (cursor_type == FILLED_BOX_CURSOR || cursor_type == HOLLOW_BOX_CURSOR)
         draw_phys_cursor_glyph (w, glyph_row, DRAW_CURSOR);
 
       ns_reset_clipping (f);
-- 
2.20.1