[PATCH] src/pgtkterm.c: Honor system DPI settings

["Jindřich Makovička" <makovick@gmail.com>]

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Hi,

unlike most of other GTK3 applications, including the current X11
Emacs, PGTK build of Emacs seems to ignore the system DPI settings,
always forcing the DPI of 96. This makes the fonts much smaller, which
is especially annoying in the GTK menus - other fonts can be configured
in the Faces customization.

I tried to change Emacs to retrieve the display resolution instead of
enforcing 96 DPI, as in the attached patch, and it seems to work on my
display with system DPI set to 130 - the menu font size returns to
normal, and font scaling is consistent with regular X11 Emacs with the
same configuration. I also tried the Broadway display with this patch,
and Emacs has the same font scaling as other GTK3 apps, which is what
one would expect.

Could the attached patch be included in the PGTK branch, or is there
some fundamental reason PGTK Emacs uses its own DPI settings?

Regards,
-- 
Jindrich Makovicka

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From f1c2ef5f5d59e259db9890d8528caf9ee3f007cc Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Jind=C5=99ich=20Makovi=C4=8Dka?= <makovick@gmail.com>
Date: Sat, 29 May 2021 09:44:39 +0200
Subject: [PATCH] * src/pgtkterm.c: Honor system DPI settings

---
 src/pgtkterm.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/src/pgtkterm.c b/src/pgtkterm.c
index f79329f7dd..6f70fb92ce 100644
--- a/src/pgtkterm.c
+++ b/src/pgtkterm.c
@@ -6974,8 +6974,11 @@ #define NUM_ARGV 10
   {
     GdkScreen *gscr = gdk_display_get_default_screen (dpyinfo->gdpy);
 
-    gdouble dpi = 96.0 * pgtk_text_scaling_factor();
-    gdk_screen_set_resolution (gscr, dpi);
+    gdouble dpi = gdk_screen_get_resolution (gscr);
+    if (dpi < 0)
+	dpi = 96.0;
+
+    dpi *= pgtk_text_scaling_factor();
     dpyinfo->resx = dpi;
     dpyinfo->resy = dpi;
   }
-- 
2.32.0.rc0