Retreieve the refresh rate of the display and reflect it with
dpy_set_ui_info() and update_displaychangelistener(), allowing the
guest and DisplayChangeListener to consume the information.

The information will be used as a hint how often the display should
be updated. For example, when we run 30 Hz physical display updates
it is pointless for the guest to update the screen at 60Hz
frequency, the guest can spare some work instead.

Signed-off-by: Akihiko Odaki <akihiko.odaki@gmail.com>
---
 meson.build |  3 ++-
 ui/cocoa.m  | 12 ++++++++++++
 2 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/meson.build b/meson.build
index 0c2e11ff071..0f83f3730af 100644
--- a/meson.build
+++ b/meson.build
@@ -575,7 +575,8 @@ if get_option('attr').allowed()
   endif
 endif
 
-cocoa = dependency('appleframeworks', modules: 'Cocoa', required: get_option('cocoa'))
+cocoa = dependency('appleframeworks', modules: ['Cocoa', 'CoreVideo'],
+                   required: get_option('cocoa'))
 if cocoa.found() and get_option('sdl').enabled()
   error('Cocoa and SDL cannot be enabled at the same time')
 endif
diff --git a/ui/cocoa.m b/ui/cocoa.m
index 84c84e98fc5..0000a3949c6 100644
--- a/ui/cocoa.m
+++ b/ui/cocoa.m
@@ -561,8 +561,20 @@ - (void) updateUIInfoLocked
         CGDirectDisplayID display = [[description objectForKey:@"NSScreenNumber"] unsignedIntValue];
         NSSize screenSize = [[[self window] screen] frame].size;
         CGSize screenPhysicalSize = CGDisplayScreenSize(display);
+        CVDisplayLinkRef displayLink;
 
         frameSize = isFullscreen ? screenSize : [self frame].size;
+
+        if (!CVDisplayLinkCreateWithCGDisplay(display, &displayLink)) {
+            CVTime period = CVDisplayLinkGetNominalOutputVideoRefreshPeriod(displayLink);
+            CVDisplayLinkRelease(displayLink);
+            if (!(period.flags & kCVTimeIsIndefinite)) {
+                update_displaychangelistener(&dcl,
+                                             1000 * period.timeValue / period.timeScale);
+                info.refresh_rate = (int64_t)1000 * period.timeScale / period.timeValue;
+            }
+        }
+
         info.width_mm = frameSize.width / screenSize.width * screenPhysicalSize.width;
         info.height_mm = frameSize.height / screenSize.height * screenPhysicalSize.height;
     } else {
-- 
2.32.1 (Apple Git-133)

On 2/7/22 16:25, Akihiko Odaki wrote:
> Retreieve the refresh rate of the display and reflect it with
> dpy_set_ui_info() and update_displaychangelistener(), allowing the
> guest and DisplayChangeListener to consume the information.
> 
> The information will be used as a hint how often the display should
> be updated. For example, when we run 30 Hz physical display updates
> it is pointless for the guest to update the screen at 60Hz
> frequency, the guest can spare some work instead.
> 
> Signed-off-by: Akihiko Odaki <akihiko.odaki@gmail.com>
> ---
>   meson.build |  3 ++-
>   ui/cocoa.m  | 12 ++++++++++++
>   2 files changed, 14 insertions(+), 1 deletion(-)

Thanks, patch queued.

On Sat, 2 Jul 2022 at 15:25, Akihiko Odaki <akihiko.odaki@gmail.com> wrote:
>
> Retreieve the refresh rate of the display and reflect it with
> dpy_set_ui_info() and update_displaychangelistener(), allowing the
> guest and DisplayChangeListener to consume the information.
>
> The information will be used as a hint how often the display should
> be updated. For example, when we run 30 Hz physical display updates
> it is pointless for the guest to update the screen at 60Hz
> frequency, the guest can spare some work instead.
>
> Signed-off-by: Akihiko Odaki <akihiko.odaki@gmail.com>
> ---

Reviewed-by: Peter Maydell <peter.maydell@linaro.org>

thanks
-- PMM