[fix] detect macOS remote cursor shapes

src/gui/runtime/cursor_state_provider_mac.mm

@@ -5,42 +5,126 @@
 #import <AppKit/AppKit.h>
 #import <CoreGraphics/CGRemoteOperation.h>
 
+#include <cstdint>
+#include <vector>
+
 namespace crossdesk {
 namespace {
 
-bool SameCursor(NSCursor* left, NSCursor* right) {
+struct CursorFingerprint {
-  if (left == right || [left isEqual:right]) return true;
+  uint64_t pixel_hash = 0;
-  return left && right && NSEqualPoints(left.hotSpot, right.hotSpot) &&
+  size_t width = 0;
-         [left.image isEqual:right.image];
+  size_t height = 0;
+  size_t bytes_per_row = 0;
+  CFIndex pixel_bytes = 0;
+  NSPoint hot_spot = NSZeroPoint;
+};
+
+struct KnownCursor {
+  CursorFingerprint fingerprint;
+  CursorShape shape = CursorShape::default_cursor;
+};
+
+bool FingerprintCursor(NSCursor* cursor, CursorFingerprint* fingerprint) {
+  if (!cursor || !fingerprint || !cursor.image) return false;
+
+  NSRect proposed_rect = {NSZeroPoint, cursor.image.size};
+  CGImageRef image =
+      [cursor.image CGImageForProposedRect:&proposed_rect
+                                   context:nil
+                                     hints:nil];
+  if (!image) return false;
+
+  CGDataProviderRef provider = CGImageGetDataProvider(image);
+  if (!provider) return false;
+
+  CFDataRef data = CGDataProviderCopyData(provider);
+  if (!data) return false;
+
+  // NSCursor.currentSystemCursor returns a fresh NSCursor/NSImage wrapper on
+  // each query. Hash the decoded CGImage pixels so it can still be matched to
+  // AppKit's semantic cursor instances without encoding a large TIFF every
+  // frame.
+  constexpr uint64_t kFnvOffsetBasis = 1469598103934665603ULL;
+  constexpr uint64_t kFnvPrime = 1099511628211ULL;
+  uint64_t hash = kFnvOffsetBasis;
+  const UInt8* bytes = CFDataGetBytePtr(data);
+  const CFIndex length = CFDataGetLength(data);
+  for (CFIndex index = 0; index < length; ++index) {
+    hash ^= bytes[index];
+    hash *= kFnvPrime;
+  }
+
+  fingerprint->pixel_hash = hash;
+  fingerprint->width = CGImageGetWidth(image);
+  fingerprint->height = CGImageGetHeight(image);
+  fingerprint->bytes_per_row = CGImageGetBytesPerRow(image);
+  fingerprint->pixel_bytes = length;
+  fingerprint->hot_spot = cursor.hotSpot;
+  CFRelease(data);
+  return true;
+}
+
+bool SameCursor(const CursorFingerprint& left,
+                const CursorFingerprint& right) {
+  return left.pixel_hash == right.pixel_hash && left.width == right.width &&
+         left.height == right.height &&
+         left.bytes_per_row == right.bytes_per_row &&
+         left.pixel_bytes == right.pixel_bytes &&
+         NSEqualPoints(left.hot_spot, right.hot_spot);
+}
+
+void AddKnownCursor(std::vector<KnownCursor>* cursors, NSCursor* cursor,
+                    CursorShape shape) {
+  CursorFingerprint fingerprint;
+  if (FingerprintCursor(cursor, &fingerprint)) {
+    cursors->push_back({fingerprint, shape});
+  }
+}
+
+std::vector<KnownCursor> BuildKnownCursors() {
+  std::vector<KnownCursor> cursors;
+  cursors.reserve(16);
+
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wdeprecated-declarations"
+  AddKnownCursor(&cursors, NSCursor.arrowCursor, CursorShape::default_cursor);
+  AddKnownCursor(&cursors, NSCursor.pointingHandCursor, CursorShape::pointer);
+  AddKnownCursor(&cursors, NSCursor.crosshairCursor, CursorShape::crosshair);
+  AddKnownCursor(&cursors, NSCursor.IBeamCursor, CursorShape::text);
+  AddKnownCursor(&cursors, NSCursor.IBeamCursorForVerticalLayout,
+                 CursorShape::text);
+  AddKnownCursor(&cursors, NSCursor.operationNotAllowedCursor,
+                 CursorShape::not_allowed);
+  AddKnownCursor(&cursors, NSCursor.dragLinkCursor, CursorShape::alias);
+  AddKnownCursor(&cursors, NSCursor.dragCopyCursor, CursorShape::copy);
+  AddKnownCursor(&cursors, NSCursor.openHandCursor, CursorShape::grab);
+  AddKnownCursor(&cursors, NSCursor.closedHandCursor, CursorShape::grabbing);
+  AddKnownCursor(&cursors, NSCursor.resizeLeftRightCursor,
+                 CursorShape::ew_resize);
+  AddKnownCursor(&cursors, NSCursor.resizeUpDownCursor, CursorShape::ns_resize);
+  AddKnownCursor(&cursors, NSCursor.resizeUpCursor, CursorShape::n_resize);
+  AddKnownCursor(&cursors, NSCursor.resizeRightCursor, CursorShape::e_resize);
+  AddKnownCursor(&cursors, NSCursor.resizeDownCursor, CursorShape::s_resize);
+  AddKnownCursor(&cursors, NSCursor.resizeLeftCursor, CursorShape::w_resize);
+#pragma clang diagnostic pop
+
+  return cursors;
 }
 
 CursorShape ShapeFromMacCursor(NSCursor* cursor) {
-  if (SameCursor(cursor, NSCursor.pointingHandCursor))
+  CursorFingerprint fingerprint;
-    return CursorShape::pointer;
+  if (!FingerprintCursor(cursor, &fingerprint)) {
-  if (SameCursor(cursor, NSCursor.crosshairCursor))
+    return CursorShape::default_cursor;
-    return CursorShape::crosshair;
+  }
-  if (SameCursor(cursor, NSCursor.IBeamCursor) ||
+
-      SameCursor(cursor, NSCursor.IBeamCursorForVerticalLayout))
+  // Sampling begins from the UI tick, after AppKit has initialized its cursor
-    return CursorShape::text;
+  // catalog. Cache those fingerprints because only the current cursor needs
-  if (SameCursor(cursor, NSCursor.operationNotAllowedCursor))
+  // to be decoded on subsequent frames.
-    return CursorShape::not_allowed;
+  static const std::vector<KnownCursor> known_cursors = BuildKnownCursors();
-  if (SameCursor(cursor, NSCursor.dragLinkCursor)) return CursorShape::alias;
+  for (const KnownCursor& known : known_cursors) {
-  if (SameCursor(cursor, NSCursor.dragCopyCursor)) return CursorShape::copy;
+    if (SameCursor(fingerprint, known.fingerprint)) return known.shape;
-  if (SameCursor(cursor, NSCursor.openHandCursor)) return CursorShape::grab;
+  }
-  if (SameCursor(cursor, NSCursor.closedHandCursor))
-    return CursorShape::grabbing;
-  if (SameCursor(cursor, NSCursor.resizeLeftRightCursor))
-    return CursorShape::ew_resize;
-  if (SameCursor(cursor, NSCursor.resizeUpDownCursor))
-    return CursorShape::ns_resize;
-  if (SameCursor(cursor, NSCursor.resizeUpCursor))
-    return CursorShape::n_resize;
-  if (SameCursor(cursor, NSCursor.resizeRightCursor))
-    return CursorShape::e_resize;
-  if (SameCursor(cursor, NSCursor.resizeDownCursor))
-    return CursorShape::s_resize;
-  if (SameCursor(cursor, NSCursor.resizeLeftCursor))
-    return CursorShape::w_resize;
   return CursorShape::default_cursor;
 }
 
@@ -62,8 +146,7 @@ bool CursorStateProvider::Sample(CursorState* state) {
 
   state->seq = 0;
   state->visible = visible && cursor != nil;
-  state->shape = state->visible ? ShapeFromMacCursor(cursor)
+  state->shape = state->visible ? ShapeFromMacCursor(cursor) : CursorShape::none;
-                                : CursorShape::none;
   return true;
 }