bug#33442: 26.1.90; Cairo side-by-side windows scrolling fix should be cherry-picked

[Ari Roponen]

Eli Zaretskii <eliz@gnu.org> writes:

>> From: Robert Pluim <rpluim@gmail.com>
>> Date: Thu, 29 Nov 2018 14:19:56 +0100
>> Cc: 33442@debbugs.gnu.org, Dmitry Gutov <dgutov@yandex.ru>
>> 
>> > With the following patch, GDK_SCALE=2 seems to work for me.
>> >
>> 
>> Works for me. Since this is all Cairo-only code, it could even go into
>> emacs-26, I think (with a ChangeLog and perhaps some comments).
>
> OK, let's do that.
>

The following patch fixes the scaling problem in Cairo builds. The
scrolling issue with side-by-side windows is in master branch (commit
6e362a32bc9d21f73a0f29ca6f45481edeea6f29), and can be cherry-picked.


>From c76a784f7c345031f9bf1f88d2e4b13e44053638 Mon Sep 17 00:00:00 2001
From: Ari Roponen <ari.roponen@gmail.com>
Date: Fri, 30 Nov 2018 14:09:09 +0200
Subject: [PATCH 1/1] Fix scaling problem in cairo builds

* src/xterm.c (x_begin_cr_clip) [USE_GTK]:
(x_update_begin) [USE_CAIRO && USE_GTK]: Support scaling.
---
 src/xterm.c | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/src/xterm.c b/src/xterm.c
index 3a7e31e712..42ddc4f5b1 100644
--- a/src/xterm.c
+++ b/src/xterm.c
@@ -360,10 +360,15 @@ x_begin_cr_clip (struct frame *f, GC gc)
 
       if (! FRAME_CR_SURFACE (f))
         {
+         int scale = 1;
+#ifdef USE_GTK
+         scale = xg_get_scale (f);
+#endif
+
          FRAME_CR_SURFACE (f) =
            cairo_image_surface_create (CAIRO_FORMAT_ARGB32,
-                                       FRAME_PIXEL_WIDTH (f),
-                                       FRAME_PIXEL_HEIGHT (f));
+                                       scale * FRAME_PIXEL_WIDTH (f),
+                                       scale * FRAME_PIXEL_HEIGHT (f));
        }
       cr = cairo_create (FRAME_CR_SURFACE (f));
       FRAME_CR_CONTEXT (f) = cr;
@@ -999,8 +1004,9 @@ x_update_begin (struct frame *f)
       if (FRAME_GTK_WIDGET (f))
         {
           GdkWindow *w = gtk_widget_get_window (FRAME_GTK_WIDGET (f));
-          width = gdk_window_get_width (w);
-          height = gdk_window_get_height (w);
+         int scale = xg_get_scale (f);
+         width = scale * gdk_window_get_width (w);
+          height = scale * gdk_window_get_height (w);
         }
       else
 #endif
-- 
2.19.2