fix(cursor): capture complete macOS Retina cursor images

src/platform/macos.rs

@@ -35,12 +35,14 @@ use std::{
     sync::Mutex,
 };
 
+mod cursor;
+
 // macOS boolean_t is defined as `int` in <mach/boolean.h>
 type BooleanT = hbb_common::libc::c_int;
 
 static PRIVILEGES_SCRIPTS_DIR: Dir =
     include_dir!("$CARGO_MANIFEST_DIR/src/platform/privileges_scripts");
-static mut LATEST_SEED: i32 = 0;
+static mut LATEST_SEED: (i32, f64) = (0, 0.0);
 
 #[inline]
 fn get_update_temp_dir() -> PathBuf {
@@ -561,7 +563,7 @@ pub fn get_cursor() -> ResultType<Option<u64>> {
 
 fn unsafe_get_cursor() -> ResultType<Option<u64>> {
     unsafe {
-        let seed = CGSCurrentCursorSeed();
+        let seed = (CGSCurrentCursorSeed(), cursor::scale()?);
         if seed == LATEST_SEED {
             return Ok(None);
         }
@@ -573,11 +575,11 @@ fn unsafe_get_cursor() -> ResultType<Option<u64>> {
 
 pub fn reset_input_cache() {
     unsafe {
-        LATEST_SEED = 0;
+        LATEST_SEED = (0, 0.0);
     }
 }
 
-fn get_cursor_id() -> ResultType<(id, u64)> {
+fn get_cursor_id() -> ResultType<(id, u64, f64)> {
     unsafe {
         let c: id = msg_send![class!(NSCursor), currentSystemCursor];
         if c == nil {
@@ -620,7 +622,8 @@ fn get_cursor_id() -> ResultType<(id, u64)> {
                 hcursor += (r + g + b + a) * (255 << i) as f64;
             }
         }
-        Ok((c, hcursor as _))
+        let scale = cursor::scale()?;
+        Ok((c, cursor::cache_id(hcursor as _, scale), scale))
     }
 }
 
@@ -631,10 +634,13 @@ pub fn get_cursor_data(hcursor: u64) -> ResultType<CursorData> {
 // https://github.com/stweil/OSXvnc/blob/master/OSXvnc-server/mousecursor.c
 fn unsafe_get_cursor_data(hcursor: u64) -> ResultType<CursorData> {
     unsafe {
-        let (c, hcursor2) = get_cursor_id()?;
+        let (c, hcursor2, scale) = get_cursor_id()?;
         if hcursor != hcursor2 {
             bail!("cursor changed");
         }
+        if scale > 1.0 {
+            return cursor::data(c, hcursor, scale);
+        }
         let hotspot: NSPoint = msg_send![c, hotSpot];
         let img: id = msg_send![c, image];
         let size: NSSize = msg_send![img, size];
@@ -668,9 +674,9 @@ fn unsafe_get_cursor_data(hcursor: u64) -> ResultType<CursorData> {
                 let g: f64 = msg_send![color, greenComponent];
                 let b: f64 = msg_send![color, blueComponent];
                 let a: f64 = msg_send![color, alphaComponent];
-                colors.push((r * 255.) as _);
+                colors.push((r * a * 255.).round() as _);
-                colors.push((g * 255.) as _);
+                colors.push((g * a * 255.).round() as _);
-                colors.push((b * 255.) as _);
+                colors.push((b * a * 255.).round() as _);
                 colors.push((a * 255.) as _);
             }
         }
@@ -681,6 +687,7 @@ fn unsafe_get_cursor_data(hcursor: u64) -> ResultType<CursorData> {
             hoty: hotspot.y as _,
             width: size.width as _,
             height: size.height as _,
+            scale: 1.0,
             ..Default::default()
         })
     }

src/platform/macos/cursor.rs

@@ -0,0 +1,175 @@
+use super::{CursorData, ResultType};
+use cocoa::{
+    appkit::NSCompositingOperation,
+    base::{id, nil, NO, YES},
+    foundation::{NSInteger, NSPoint, NSRect, NSSize, NSString},
+};
+use hbb_common::{anyhow::Context, bail};
+use objc::{class, msg_send, rc::StrongPtr, sel, sel_impl};
+use std::{
+    collections::hash_map::DefaultHasher,
+    hash::{Hash, Hasher},
+    ptr, slice,
+};
+
+const CHANNELS: usize = 4;
+const BITS_PER_SAMPLE: NSInteger = 8;
+
+pub(super) fn scale() -> ResultType<f64> {
+    if !*scrap::quartz::ENABLE_RETINA.lock().unwrap() {
+        return Ok(1.0);
+    }
+    unsafe {
+        let point: NSPoint = msg_send![class!(NSEvent), mouseLocation];
+        let screens: id = msg_send![class!(NSScreen), screens];
+        let count: usize = msg_send![screens, count];
+        for index in 0..count {
+            let screen: id = msg_send![screens, objectAtIndex: index];
+            let frame: NSRect = msg_send![screen, frame];
+            // AppKit's bottom-left coordinates include the upper screen edge.
+            if point.x >= frame.origin.x
+                && point.y > frame.origin.y
+                && point.x < frame.origin.x + frame.size.width
+                && point.y <= frame.origin.y + frame.size.height
+            {
+                return Ok(msg_send![screen, backingScaleFactor]);
+            }
+        }
+    }
+    bail!("No macOS display contains the cursor")
+}
+
+pub(super) fn cache_id(cursor: u64, scale: f64) -> u64 {
+    let mut hash = DefaultHasher::new();
+    (cursor, scale.to_bits()).hash(&mut hash);
+    hash.finish()
+}
+
+unsafe fn bitmap(size: NSSize) -> ResultType<StrongPtr> {
+    let color_space = StrongPtr::new(NSString::alloc(nil).init_str("NSDeviceRGBColorSpace"));
+    let bitmap: id = msg_send![class!(NSBitmapImageRep), alloc];
+    let bitmap: id = msg_send![bitmap,
+        initWithBitmapDataPlanes: ptr::null_mut::<*mut u8>()
+        pixelsWide: size.width as NSInteger pixelsHigh: size.height as NSInteger
+        bitsPerSample: BITS_PER_SAMPLE samplesPerPixel: CHANNELS as NSInteger
+        hasAlpha: YES isPlanar: NO colorSpaceName: *color_space
+        bitmapFormat: 0usize bytesPerRow: (size.width as usize * CHANNELS) as NSInteger
+        bitsPerPixel: BITS_PER_SAMPLE * CHANNELS as NSInteger];
+    if bitmap == nil {
+        bail!("Could not allocate the macOS cursor bitmap");
+    }
+    Ok(StrongPtr::new(bitmap))
+}
+
+unsafe fn render(image: id, bitmap: id, size: NSSize) -> ResultType<()> {
+    let context: id =
+        msg_send![class!(NSGraphicsContext), graphicsContextWithBitmapImageRep: bitmap];
+    if context == nil {
+        bail!("Could not create the macOS cursor graphics context");
+    }
+    let (): () = msg_send![class!(NSGraphicsContext), saveGraphicsState];
+    let (): () = msg_send![class!(NSGraphicsContext), setCurrentContext: context];
+    // Drawing at the pixel size lets AppKit select the matching image representation.
+    let (): () = msg_send![image,
+        drawInRect: NSRect::new(NSPoint::new(0.0, 0.0), size)
+        fromRect: NSRect::new(NSPoint::new(0.0, 0.0), NSSize::new(0.0, 0.0))
+        operation: NSCompositingOperation::NSCompositeCopy fraction: 1.0f64];
+    let (): () = msg_send![class!(NSGraphicsContext), restoreGraphicsState];
+    Ok(())
+}
+
+pub(super) unsafe fn data(cursor: id, id: u64, scale: f64) -> ResultType<CursorData> {
+    let image: id = msg_send![cursor, image];
+    let logical: NSSize = msg_send![image, size];
+    let size = NSSize::new(
+        (logical.width * scale).round(),
+        (logical.height * scale).round(),
+    );
+    if !size.width.is_finite()
+        || !size.height.is_finite()
+        || size.width <= 0.0
+        || size.height <= 0.0
+        || size.width > i32::MAX as f64
+        || size.height > i32::MAX as f64
+    {
+        bail!("Invalid macOS cursor dimensions");
+    }
+    let length = (size.width as usize)
+        .checked_mul(size.height as usize)
+        .and_then(|pixels| pixels.checked_mul(CHANNELS))
+        .context("Cursor bitmap size overflow")?;
+    let bitmap = bitmap(size)?;
+    render(image, *bitmap, size)?;
+    let pixels: *const u8 = msg_send![*bitmap, bitmapData];
+    if pixels.is_null() {
+        bail!("Could not read the macOS cursor bitmap");
+    }
+    let hotspot: NSPoint = msg_send![cursor, hotSpot];
+    Ok(CursorData {
+        id,
+        colors: slice::from_raw_parts(pixels, length).to_vec().into(),
+        hotx: (hotspot.x * size.width / logical.width).round() as _,
+        hoty: (hotspot.y * size.height / logical.height).round() as _,
+        width: size.width as _,
+        height: size.height as _,
+        scale,
+        ..Default::default()
+    })
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use objc::rc::autoreleasepool;
+
+    #[test]
+    fn retina_cursor_uses_complete_high_resolution_artwork() {
+        autoreleasepool(|| unsafe {
+            let logical = NSSize::new(9.0, 18.0);
+            let image: id = msg_send![class!(NSImage), alloc];
+            let image = StrongPtr::new(msg_send![image, initWithSize: logical]);
+            let mut expected = Vec::new();
+            for scale in [1, 2] {
+                let width = logical.width as usize * scale;
+                let height = logical.height as usize * scale;
+                let rep = bitmap(NSSize::new(width as f64, height as f64)).unwrap();
+                let mut pixels = vec![0; width * height * CHANNELS];
+                for y in 0..height {
+                    for x in 0..width {
+                        if y == 0 || y == height - 1 || x == width / 2 {
+                            let color = if y == 0 {
+                                [255, 0, 0, 255]
+                            } else {
+                                [0, 255, 0, 255]
+                            };
+                            pixels[(y * width + x) * CHANNELS..(y * width + x + 1) * CHANNELS]
+                                .copy_from_slice(&color);
+                        }
+                    }
+                }
+                let buffer: *mut u8 = msg_send![*rep, bitmapData];
+                ptr::copy_nonoverlapping(pixels.as_ptr(), buffer, pixels.len());
+                let (): () = msg_send![*rep, setSize: logical];
+                let (): () = msg_send![*image, addRepresentation: *rep];
+                if scale == 2 {
+                    expected = pixels;
+                }
+            }
+            let cursor: id = msg_send![class!(NSCursor), alloc];
+            let cursor = StrongPtr::new(
+                msg_send![cursor, initWithImage: *image hotSpot: NSPoint::new(4.0, 9.0)],
+            );
+            let result = data(*cursor, 1, 2.0).unwrap();
+            assert_eq!(
+                (result.width, result.height, result.hotx, result.hoty),
+                (18, 36, 8, 18)
+            );
+            assert_eq!(result.colors.as_ref(), expected.as_slice());
+        });
+    }
+
+    #[test]
+    fn cursor_cache_changes_with_display_scale() {
+        assert_ne!(cache_id(123, 1.0), cache_id(123, 2.0));
+    }
+}