From 00ba2267ede311da0cd53261780fb0b781ca42dd Mon Sep 17 00:00:00 2001
From: Eli Zaretskii <eliz@gnu.org>
Date: Mon, 14 Jan 2019 17:36:04 +0200
Subject: [PATCH] Attempt to fix hangs on MS-Windows due to C-g

* src/w32uniscribe.c (uniscribe_otf_capability): Set
inhibit-quit around calls to otf_features, because the latter
cons Lisp data structures while we are in a critical section.
* src/xdisp.c (ALLOCATE_HDC) [HAVE_NTGUI]: Set inhibit-quit.
(RELEASE_HDC) [HAVE_NTGUI]: Restore inhibit-quit.
(OPTIONAL_HDC, DECLARE_HDC): Remove macros, their job is now
done by ALLOCATE_HDC and by a single #ifdef.
(draw_glyphs): Adapt to the above changes in macros.
(Bug#34059)
---
 src/w32uniscribe.c |  6 ++++++
 src/xdisp.c        | 31 ++++++++++++++++++-------------
 2 files changed, 24 insertions(+), 13 deletions(-)

diff --git a/src/w32uniscribe.c b/src/w32uniscribe.c
index 33959cd05c8..28050d6ac76 100644
--- a/src/w32uniscribe.c
+++ b/src/w32uniscribe.c
@@ -176,6 +176,11 @@ uniscribe_otf_capability (struct font *font)
   Lisp_Object features;
 
   f = XFRAME (selected_frame);
+  /* Prevent quitting while we cons the lists in otf_features.
+     That's because get_frame_dc acquires the critical section, so we
+     cannot quit before we release it in release_frame_dc.  */
+  Lisp_Object prev_quit = Vinhibit_quit;
+  Vinhibit_quit = Qt;
   context = get_frame_dc (f);
   old_font = SelectObject (context, FONT_HANDLE (font));
 
@@ -186,6 +191,7 @@ uniscribe_otf_capability (struct font *font)
 
   SelectObject (context, old_font);
   release_frame_dc (f, context);
+  Vinhibit_quit = prev_quit;
 
   return capability;
 }
diff --git a/src/xdisp.c b/src/xdisp.c
index 274ab8ddf51..94ce1c29a0c 100644
--- a/src/xdisp.c
+++ b/src/xdisp.c
@@ -25619,22 +25619,28 @@ dump_glyph_string (struct glyph_string *s)
    face-override for drawing S.  */
 
 #ifdef HAVE_NTGUI
-#define OPTIONAL_HDC(hdc)  HDC hdc,
-#define DECLARE_HDC(hdc)   HDC hdc;
-#define ALLOCATE_HDC(hdc, f) hdc = get_frame_dc ((f))
-#define RELEASE_HDC(hdc, f)  release_frame_dc ((f), (hdc))
-#endif
-
-#ifndef OPTIONAL_HDC
-#define OPTIONAL_HDC(hdc)
-#define DECLARE_HDC(hdc)
-#define ALLOCATE_HDC(hdc, f)
-#define RELEASE_HDC(hdc, f)
+/* We set inhibit-quit here due to paranoia: get_frame_dc acquires the
+   critical section, and we cannot QUIT while we hold the critical
+   section.  If any of the code run by callers of ALLOCATE_HDC happens
+   to call Lisp (might be possible due to all the hooks lying around),
+   we must prevent it from quitting.  */
+# define ALLOCATE_HDC(hdc, f)			\
+  Lisp_Object prev_quit = Vinhibit_quit;	\
+  Vinhibit_quit = Qt;				\
+  HDC hdc = get_frame_dc ((f))
+# define RELEASE_HDC(hdc, f)			\
+  release_frame_dc ((f), (hdc));		\
+  Vinhibit_quit = prev_quit
+#else
+# define ALLOCATE_HDC(hdc, f)
+# define RELEASE_HDC(hdc, f)
 #endif
 
 static void
 init_glyph_string (struct glyph_string *s,
-		   OPTIONAL_HDC (hdc)
+#ifdef HAVE_NTGUI
+		   HDC hdc,
+#endif
 		   XChar2b *char2b, struct window *w, struct glyph_row *row,
 		   enum glyph_row_area area, int start, enum draw_glyphs_face hl)
 {
@@ -26674,7 +26680,6 @@ draw_glyphs (struct window *w, int x, struct glyph_row *row,
   struct glyph_string *clip_head = NULL, *clip_tail = NULL;
   int i, j, x_reached, last_x, area_left = 0;
   struct frame *f = XFRAME (WINDOW_FRAME (w));
-  DECLARE_HDC (hdc);
 
   ALLOCATE_HDC (hdc, f);
 
-- 
2.39.5