1 files changed, 34 insertions, 0 deletions
diff --git a/platform/macos/src/MGLCompassCell.m b/platform/macos/src/MGLCompassCell.m
new file mode 100644
index 0000000000..b3a4ad4544
--- /dev/null
+++ b/platform/macos/src/MGLCompassCell.m
@@ -0,0 +1,34 @@
+#import "MGLCompassCell.h"
+
+@implementation MGLCompassCell
+
+- (instancetype)init {
+    if (self = [super init]) {
+        self.sliderType = NSCircularSlider;
+        // A tick mark for each cardinal direction.
+        self.numberOfTickMarks = 4;
+        // This slider goes backwards!
+        self.minValue = -360;
+        self.maxValue = 0;
+    }
+    return self;
+}
+
+- (void)drawKnob:(NSRect)knobRect {
+    // Draw a red triangle pointing whichever way the slider is facing.
+    NSBezierPath *trianglePath = [NSBezierPath bezierPath];
+    [trianglePath moveToPoint:NSMakePoint(NSMinX(knobRect), NSMaxY(knobRect))];
+    [trianglePath lineToPoint:NSMakePoint(NSMaxX(knobRect), NSMaxY(knobRect))];
+    [trianglePath lineToPoint:NSMakePoint(NSMidX(knobRect), NSMinY(knobRect))];
+    [trianglePath closePath];
+    NSAffineTransform *transform = [NSAffineTransform transform];
+    [transform translateXBy:NSMidX(knobRect) yBy:NSMidY(knobRect)];
+    [transform scaleBy:0.8];
+    [transform rotateByDegrees:self.doubleValue];
+    [transform translateXBy:-NSMidX(knobRect) yBy:-NSMidY(knobRect)];
+    [trianglePath transformUsingAffineTransform:transform];
+    [[NSColor redColor] setFill];
+    [trianglePath fill];
+}
+
+@end