>From c382338d44c3ff833e965e1d92106a90b75edec5 Mon Sep 17 00:00:00 2001
From: Alan Third <alan@idiocy.org>
Date: Sat, 10 Mar 2018 00:09:09 +0000
Subject: [PATCH] Fix frame resize flicker on macOS (bug#30699)

* src/nsterm.h (ns_enable_screen_updates): New function.
* src/nsterm.m (ns_enable_screen_updates):
(ns_disable_screen_updates): New functions.
(disable_screen_updates_count): Count of number of times we've called
NSDisableScreenUpdates.
(x_set_window_size): Disable screen updates when not in a live resize
loop.
* src/xdisp.c (redisplay_internal): Reenable NS screenupdates at end
of redisplay.
---
 src/nsterm.h |  3 +++
 src/nsterm.m | 30 ++++++++++++++++++++++++++++++
 src/xdisp.c  |  3 +++
 3 files changed, 36 insertions(+)

diff --git a/src/nsterm.h b/src/nsterm.h
index 8b985930ec..df59a7dbd9 100644
--- a/src/nsterm.h
+++ b/src/nsterm.h
@@ -1160,6 +1160,9 @@ extern void ns_release_autorelease_pool (void *);
 extern const char *ns_get_defaults_value (const char *key);
 extern void ns_init_locale (void);
 
+#ifdef NS_IMPL_COCOA
+extern void ns_enable_screen_updates (void);
+#endif
 
 /* in nsmenu */
 extern void update_frame_tool_bar (struct frame *f);
diff --git a/src/nsterm.m b/src/nsterm.m
index 1919c6defa..b4ec384aaf 100644
--- a/src/nsterm.m
+++ b/src/nsterm.m
@@ -288,6 +288,7 @@ - (NSColor *)colorUsingDefaultColorSpace
 static BOOL ns_fake_keydown = NO;
 #ifdef NS_IMPL_COCOA
 static BOOL ns_menu_bar_is_hidden = NO;
+static int disable_screen_updates_count = 0;
 #endif
 /*static int debug_lock = 0; */
 
@@ -727,6 +728,26 @@ Free a pool and temporary objects it refers to (callable from C)
 }
 
 
+#ifdef NS_IMPL_COCOA
+static void
+ns_disable_screen_updates (void)
+{
+  NSDisableScreenUpdates ();
+  disable_screen_updates_count++;
+}
+
+void
+ns_enable_screen_updates (void)
+{
+  while (disable_screen_updates_count > 0)
+    {
+      NSEnableScreenUpdates ();
+      disable_screen_updates_count--;
+    }
+}
+#endif
+
+
 static BOOL
 ns_menu_bar_should_be_hidden (void)
 /* True, if the menu bar should be hidden.  */
@@ -1877,6 +1898,15 @@ -(void)remove
 
   block_input ();
 
+#ifdef NS_IMPL_COCOA
+  /* To prevent showing the user a blank frame, stop updates being
+     flushed to the screen until after redisplay has completed.  This
+     breaks live resize (resizing with a mouse), so don't do it if
+     we're in a live resize loop.  */
+  if (![view inLiveResize])
+    ns_disable_screen_updates ();
+#endif
+
   if (pixelwise)
     {
       pixelwidth = FRAME_TEXT_TO_PIXEL_WIDTH (f, width);
diff --git a/src/xdisp.c b/src/xdisp.c
index 9170d6b777..d4fdb44b32 100644
--- a/src/xdisp.c
+++ b/src/xdisp.c
@@ -14599,6 +14599,9 @@ redisplay_internal (void)
  end_of_redisplay:
 #ifdef HAVE_NS
   ns_set_doc_edited ();
+#ifdef NS_IMPL_COCOA
+  ns_enable_screen_updates ();
+#endif
 #endif
   if (interrupt_input && interrupts_deferred)
     request_sigio ();
-- 
2.16.1