Fix `screen_get_dpi` on macOS for non fractional display scales and restore documentation.

1 files changed, 10 insertions, 3 deletions

diff --git a/platform/osx/display_server_osx.mm b/platform/osx/display_server_osx.mm
index 49f0e7bfa3..cd5b71890c 100644
--- a/platform/osx/display_server_osx.mm
+++ b/platform/osx/display_server_osx.mm
@@ -2246,11 +2246,18 @@ int DisplayServerOSX::screen_get_dpi(int p_screen) const {
 	NSArray *screenArray = [NSScreen screens];
 	if ((NSUInteger)p_screen < [screenArray count]) {
 		NSDictionary *description = [[screenArray objectAtIndex:p_screen] deviceDescription];
-		NSSize displayDPI = [[description objectForKey:NSDeviceResolution] sizeValue];
-		return (displayDPI.width + displayDPI.height) / 2;
+
+		const NSSize displayPixelSize = [[description objectForKey:NSDeviceSize] sizeValue];
+		const CGSize displayPhysicalSize = CGDisplayScreenSize([[description objectForKey:@"NSScreenNumber"] unsignedIntValue]);
+		float scale = [[screenArray objectAtIndex:p_screen] backingScaleFactor];
+
+		float den2 = (displayPhysicalSize.width / 25.4f) * (displayPhysicalSize.width / 25.4f) + (displayPhysicalSize.height / 25.4f) * (displayPhysicalSize.height / 25.4f);
+		if (den2 > 0.0f) {
+			return ceil(sqrt(displayPixelSize.width * displayPixelSize.width + displayPixelSize.height * displayPixelSize.height) / sqrt(den2) * scale);
+		}
 	}
 
-	return 96;
+	return 72;
 }
 
 float DisplayServerOSX::screen_get_scale(int p_screen) const {