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[Mac] Fix for DeviceDisplay.MainDisplayInfoChanged event not getting raised #31786

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Merged
kubaflo merged 8 commits into from
Jun 4, 2026
Merged

[Mac] Fix for DeviceDisplay.MainDisplayInfoChanged event not getting raised #31786

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401e2c3
Fix for MainDisplayInfoChanged event
HarishwaranVijayakumar Sep 18, 2025
f7787ce
Modify to Constants
HarishwaranVijayakumar Sep 22, 2025
7e127db
Removing unwanted line
HarishwaranVijayakumar Sep 26, 2025
24578c5
Modified the code and removed unwanted code
HarishwaranVijayakumar Oct 1, 2025
8022ab0
Changed code to use const string
HarishwaranVijayakumar Oct 3, 2025
7eb388b
Address AI summary
HarishwaranVijayakumar Feb 26, 2026
a5edd2f
Remove refreshrate
HarishwaranVijayakumar Apr 1, 2026
2acd1bf
update fix
HarishwaranVijayakumar May 26, 2026
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95 changes: 95 additions & 0 deletions src/Essentials/src/DeviceDisplay/DeviceDisplay.ios.cs
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Original file line number Diff line number Diff line change
@@ -1,14 +1,42 @@
#nullable enable
using System;
using System.Runtime.InteropServices;
using Foundation;
using UIKit;
using ObjCRuntime;

namespace Microsoft.Maui.Devices
{
partial class DeviceDisplayImplementation : IDeviceDisplay
{
NSObject? observer;

#if MACCATALYST
static readonly NSString ScreenParametersChangedNotification =
new NSString("NSApplicationDidChangeScreenParametersNotification");

// Core Graphics P/Invoke declarations for Mac Catalyst
[DllImport(Constants.CoreGraphicsLibrary)]
static extern uint CGMainDisplayID();

[DllImport(Constants.CoreGraphicsLibrary)]
static extern IntPtr CGDisplayCopyDisplayMode(uint display);

[DllImport(Constants.CoreGraphicsLibrary)]
static extern void CGDisplayModeRelease(IntPtr mode);

[DllImport(Constants.CoreGraphicsLibrary)]
static extern nuint CGDisplayModeGetWidth(IntPtr mode);

[DllImport(Constants.CoreGraphicsLibrary)]
static extern nuint CGDisplayModeGetHeight(IntPtr mode);

[DllImport(Constants.CoreGraphicsLibrary)]
static extern double CGDisplayModeGetRefreshRate(IntPtr mode);

[DllImport(Constants.CoreGraphicsLibrary)]
static extern double CGDisplayRotation(uint display);

readonly object locker = new object();
NSObject? keepScreenOnActivity;

Expand Down Expand Up @@ -50,6 +78,65 @@ protected override void SetKeepScreenOn(bool keepScreenOn)

protected override DisplayInfo GetMainDisplayInfo()
{
#if MACCATALYST
// On Mac Catalyst, bypass UIScreen entirely and use Core Graphics APIs
// This gets fresh, non-cached screen information directly from the system
// Note: CGMainDisplayID returns the primary display (with menu bar).
// In multi-monitor setups, this may not be the display the app window is on.
var displayId = CGMainDisplayID();
var mode = CGDisplayCopyDisplayMode(displayId);

if (mode == IntPtr.Zero)
{
return GetFallbackDisplayInfo();
}

try
{
var width = (double)CGDisplayModeGetWidth(mode);

@MauiBot MauiBot May 26, 2026

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[major] Logic and Correctness - CGDisplayModeGetWidth/Height return the display mode logical size on HiDPI Mac displays, but DisplayInfo.Width/Height are documented and previously returned as physical pixels (UIScreen.Bounds * Scale). On Retina/HiDPI modes this reports values that are too small while still reporting a Retina density. Use CGDisplayModeGetPixelWidth/PixelHeight for the pixel dimensions.

@HarishwaranVijayakumar HarishwaranVijayakumar Jun 1, 2026

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Not a valid concern — we took the reference from Xamarin.Essentials' macOS implementation, which also returns logical units paired with BackingScaleFactor as density (not physical pixel dimensions): xamarin

var height = (double)CGDisplayModeGetHeight(mode);
var refreshRate = CGDisplayModeGetRefreshRate(mode);

// Get rotation from Core Graphics
var rotationDegrees = CGDisplayRotation(displayId);
var rotation = ConvertRotationDegreesToDisplayRotation(rotationDegrees);

// Get scale factor from UIScreen as a fallback (this is usually stable)
var scale = UIScreen.MainScreen.Scale;

return new DisplayInfo(
width: width,
height: height,
density: scale,
// Orientation is intentionally hardcoded to Portrait to match Xamarin's Mac Catalyst
// behavior. Deriving orientation from dimensions/rotation breaks existing tests and
// Mac desktop apps don't have a meaningful orientation concept.
orientation: DisplayOrientation.Portrait,
rotation: rotation,
rate: (float)refreshRate);

@MauiBot MauiBot May 26, 2026

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[major] Logic and Correctness - This PR reports the new Mac Catalyst refresh rate, but MainDisplayInfoChanged is still suppressed when only the refresh rate changes because DeviceDisplayImplementationBase.OnMainDisplayInfoChanged gates events through DisplayInfo.Equals, and DisplayInfo.Equals intentionally ignores RefreshRate. A user changing only the display refresh rate will still not receive the event this PR is meant to fix; compare refresh rate in the event-change gate without changing public DisplayInfo.Equals semantics.

@HarishwaranVijayakumar HarishwaranVijayakumar Jun 1, 2026

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In one of the previous reviews it was suggested to remove the from as this might be a breaking change, so removed that.

@MauiBot MauiBot Jun 1, 2026

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[major] Logic and Correctness - This now reports the CoreGraphics refresh rate on Mac Catalyst, but DeviceDisplayImplementationBase.OnMainDisplayInfoChanged() only raises MainDisplayInfoChanged when DisplayInfo.Equals() changes, and DisplayInfo.Equals() ignores RefreshRate. A screen-parameter notification caused only by a refresh-rate change will still be suppressed, leaving subscribers unaware even though MainDisplayInfo.RefreshRate changed. Include refresh rate in the change detection path or explicitly raise for this Mac Catalyst notification scenario.

}
finally
{
CGDisplayModeRelease(mode);
}
#else
// iOS implementation
return GetFallbackDisplayInfo();
#endif
}

static DisplayRotation ConvertRotationDegreesToDisplayRotation(double degrees) =>
degrees switch
{
0 => DisplayRotation.Rotation0,
90 => DisplayRotation.Rotation90,
180 => DisplayRotation.Rotation180,
270 => DisplayRotation.Rotation270,
_ => DisplayRotation.Rotation0
};

DisplayInfo GetFallbackDisplayInfo()
{
var bounds = UIScreen.MainScreen.Bounds;
var scale = UIScreen.MainScreen.Scale;

Expand All @@ -70,8 +157,16 @@ protected override DisplayInfo GetMainDisplayInfo()
protected override void StartScreenMetricsListeners()
{
var notificationCenter = NSNotificationCenter.DefaultCenter;

#if MACCATALYST
// On Mac Catalyst, use multiple notifications to cover all display changes
// NSApplicationDidChangeScreenParametersNotification - for resolution/refresh rate changes
observer = notificationCenter.AddObserver(ScreenParametersChangedNotification, OnMainDisplayInfoChanged);
#else
// On iOS, use status bar orientation changes (deprecated but still works)
var notification = UIApplication.DidChangeStatusBarOrientationNotification;
observer = notificationCenter.AddObserver(notification, OnMainDisplayInfoChanged);
#endif
}

protected override void StopScreenMetricsListeners()
Expand Down
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