[macos] Round non-freeform zoom gestures/commands to nearest integer

Affects:
 - Double-tap gestures
 - Two-finger tap gestures
 - +/- button pushes
 - Shortcut keys
 - Menu items and shortcut keys (in macapp)

3 files changed, 21 insertions, 5 deletions

diff --git a/platform/macos/CHANGELOG.md b/platform/macos/CHANGELOG.md
index b52d1d7055..87790f75c2 100644
--- a/platform/macos/CHANGELOG.md
+++ b/platform/macos/CHANGELOG.md
@@ -39,6 +39,7 @@
 * Fixed flickering that occurred when panning past the antimeridian. ([#7574](https://github.com/mapbox/mapbox-gl-native/pull/7574))
 * Added a method to MGLMapViewDelegate, `-mapView:shouldChangeFromCamera:toCamera:`, that you can implement to restrict which parts the user can navigate to using gestures. ([#5584](https://github.com/mapbox/mapbox-gl-native/pull/5584))
 * Added a `MGLDistanceFormatter` class for formatting geographic distances. ([#7888](https://github.com/mapbox/mapbox-gl-native/pull/7888))
+* Zooming by double-tap, two-finger tap, zoom buttons, shortcut keys, or demo app menu items or shortcut keys now zooms to the nearest integer zoom level. ([#8027](https://github.com/mapbox/mapbox-gl-native/pull/8027))
 
 ## 0.3.1
 
diff --git a/platform/macos/app/MapDocument.m b/platform/macos/app/MapDocument.m
index 6f63542527..2de189c856 100644
--- a/platform/macos/app/MapDocument.m
+++ b/platform/macos/app/MapDocument.m
@@ -217,11 +217,11 @@ NS_ARRAY_OF(id <MGLAnnotation>) *MBXFlattenedShapes(NS_ARRAY_OF(id <MGLAnnotatio
 }
 
 - (IBAction)zoomIn:(id)sender {
-    [self.mapView setZoomLevel:self.mapView.zoomLevel + 1 animated:YES];
+    [self.mapView setZoomLevel:round(self.mapView.zoomLevel) + 1 animated:YES];
 }
 
 - (IBAction)zoomOut:(id)sender {
-    [self.mapView setZoomLevel:self.mapView.zoomLevel - 1 animated:YES];
+    [self.mapView setZoomLevel:round(self.mapView.zoomLevel) - 1 animated:YES];
 }
 
 - (IBAction)snapToNorth:(id)sender {
diff --git a/platform/macos/src/MGLMapView.mm b/platform/macos/src/MGLMapView.mm
index 3d5f71feb1..654ca84fd0 100644
--- a/platform/macos/src/MGLMapView.mm
+++ b/platform/macos/src/MGLMapView.mm
@@ -1042,7 +1042,22 @@ public:
 }
 
 - (void)zoomBy:(double)zoomDelta animated:(BOOL)animated {
-    [self setZoomLevel:self.zoomLevel + zoomDelta animated:animated];
+    [self setZoomLevel:round(self.zoomLevel) + zoomDelta animated:animated];
+}
+
+- (void)zoomBy:(double)zoomDelta atPoint:(NSPoint)point animated:(BOOL)animated {
+    [self willChangeValueForKey:@"centerCoordinate"];
+    [self willChangeValueForKey:@"zoomLevel"];
+    double newZoom = round(self.zoomLevel) + zoomDelta;
+    MGLMapCamera *oldCamera = self.camera;
+    mbgl::ScreenCoordinate center(point.x, self.bounds.size.height - point.y);
+    _mbglMap->setZoom(newZoom, center, MGLDurationInSecondsFromTimeInterval(animated ? MGLAnimationDuration : 0));
+    if ([self.delegate respondsToSelector:@selector(mapView:shouldChangeFromCamera:toCamera:)]
+        && ![self.delegate mapView:self shouldChangeFromCamera:oldCamera toCamera:self.camera]) {
+        self.camera = oldCamera;
+    }
+    [self didChangeValueForKey:@"zoomLevel"];
+    [self didChangeValueForKey:@"centerCoordinate"];
 }
 
 - (void)scaleBy:(double)scaleFactor atPoint:(NSPoint)point animated:(BOOL)animated {
@@ -1500,7 +1515,7 @@ public:
     _mbglMap->cancelTransitions();
 
     NSPoint gesturePoint = [gestureRecognizer locationInView:self];
-    [self scaleBy:2 atPoint:gesturePoint animated:YES];
+    [self zoomBy:1 atPoint:gesturePoint animated:YES];
 }
 
 - (void)smartMagnifyWithEvent:(NSEvent *)event {
@@ -1512,7 +1527,7 @@ public:
 
     // Tap with two fingers (“right-click”) to zoom out on mice but not trackpads.
     NSPoint gesturePoint = [self convertPoint:event.locationInWindow fromView:nil];
-    [self scaleBy:0.5 atPoint:gesturePoint animated:YES];
+    [self zoomBy:-1 atPoint:gesturePoint animated:YES];
 }
 
 /// Rotate fingers to rotate.