patch 9.1.1748: macOS: Default scheduler priority too low

Problem:  macOS: Default scheduler priority too low
Solution: Explicitly set TASK_DEFAULT_APPLICATION scheduler priority
          to improve responsiveness (Luna Razzaghipour).

closes: #18120

Signed-off-by: Luna Razzaghipour <luna@xoria.org>
Signed-off-by: Christian Brabandt <cb@256bit.org>

runtime/doc/version9.txt

@@ -1,4 +1,4 @@
-*version9.txt*  For Vim version 9.1.  Last change: 2025 Sep 09
+*version9.txt*  For Vim version 9.1.  Last change: 2025 Sep 10
 
 
 		  VIM REFERENCE MANUAL    by Bram Moolenaar
@@ -41621,6 +41621,7 @@ Platform specific~
 - The Win32 GUI comes with better toolbar icons.
 
 - Better fullscreen support for Haiku |os_haiku.txt|.
+
 							*new-other-9.2*
 Other new features ~
 ------------------
@@ -41763,6 +41764,7 @@ Others: ~
 Platform specific ~
 - MS-Winodws: Paths like "\Windows" and "/Windows" are now considered to be
   absolute paths (to the current drive) and no longer relative.
+- macOS: increase default scheduler priority to TASK_DEFAULT_APPLICATION.
 
 							*added-9.2*
 Added ~

runtime/doc/vi_diff.txt

@@ -1,4 +1,4 @@
-*vi_diff.txt*   For Vim version 9.1.  Last change: 2025 Sep 08
+*vi_diff.txt*   For Vim version 9.1.  Last change: 2025 Sep 10
 
 
 		  VIM REFERENCE MANUAL    by Bram Moolenaar
@@ -1381,7 +1381,7 @@ System				| Status:~
 Amiga (OS4, AROS & MorphOS):	| still supported (?)
 Haiku:				| supported
 Linux:				| fully supported (on maintained versions)
-Mac OS:				| fully supported up until v10.6 (?)
+macOS:				| fully supported up until v10.6 (?)
 MS-Windows 7, 8, 10, 11:	| fully supported
 OpenVMS:			| supported
 QNX:				| still supported (?)

src/os_mac.h

@@ -46,6 +46,11 @@
 #include <time.h>
 #include <dirent.h>
 
+/*
+ * Mach interface
+ */
+#include <mach/task.h>
+
 /*
  * MacOS specific #define
  */

src/os_unix.c

@@ -3676,6 +3676,15 @@ mch_early_init(void)
     signal_stack = alloc(get_signal_stack_size());
     init_signal_stack();
 #endif
+
+    /*
+     * Inform the macOS scheduler that Vim renders UI, and so shouldn’t have its
+     * threads’ quality of service classes clamped.
+     */
+#ifdef MACOS_X
+    integer_t policy = TASK_DEFAULT_APPLICATION;
+    task_policy_set(mach_task_self(), TASK_CATEGORY_POLICY, &policy, 1);
+#endif
 }
 
 #if defined(EXITFREE) || defined(PROTO)

src/version.c

@@ -724,6 +724,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1748,
 /**/
     1747,
 /**/