From 1c66f1de86cd3cd360cf3c8de371126a9e1e9fc9 Mon Sep 17 00:00:00 2001
From: XScreenSaver owners <xscreensaver-owner@fedoraproject.org>
Date: Mon, 3 May 2021 21:33:26 +0900
Subject: [PATCH] fontglide.c: pick_font_1 exclude substitution rectagle glyph

Currently (with using XFT) pick_font_1 picks up one font randomly
from all installed fonts, according to XftListFonts.
So when some non-latin fonts are installed and selected by pick_font_1,
(e.g. Lohit-Gujarati.ttf: used for Gujarati language, part of India)
such font may fail to show strings returned by xscreensaver-text
correctly, and may show substitusion rectagle glyph.

So to select a font which can show glyph properly, use XftCharExists
(ref: blank_character_p in texfont.c)

Also, to show debug message correctly with /* DEBUG */ defined,
copy name2 to pattern.
---
 hacks/fontglide.c | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/hacks/fontglide.c b/hacks/fontglide.c
index 3eff604..be1ac63 100644
--- a/hacks/fontglide.c
+++ b/hacks/fontglide.c
@@ -270,6 +270,7 @@ pick_font_1 (state *s, sentence *se)
       /* #### This gets a link error with FcFontSetDestroy missing. */
       /* if (fs) XftFontSetDestroy (fs); */
 
+      sprintf(pattern, "%s", name2);
       se->xftfont = font;
       ok = True;
       goto DONE_2;
@@ -571,6 +572,22 @@ pick_font_1 (state *s, sentence *se)
       }
   }
 
+# if defined(HAVE_XFT) && !defined(HAVE_JWXYZ)   /* Real Xft under real X11 */
+  {
+    unsigned long uc = 0;
+    utf8_decode ((const unsigned char *)"M", 1, &uc);
+    if (!XftCharExists (s->dpy, se->xftfont, (FcChar32) uc))
+    {
+# ifdef DEBUG
+        if (s->debug_p)
+          fprintf (stderr, "%s: skipping font returning substitution rectangle: %s\n",
+                    progname, pattern2);
+#endif
+        return False;
+    }
+  }
+# endif
+
 
 # ifdef DEBUG
   if (s->debug_p) 
-- 
2.31.1