Test fit to bounds; added MGLCoordinateBounds functions

Added a bunch of functions to work with MGLCoordinateBounds in a separate header analogous to MKGeometry.h. Added resolution-independent tests for common fit to bounds scenarios.

9 files changed, 131 insertions, 16 deletions

diff --git a/gyp/platform-ios.gypi b/gyp/platform-ios.gypi
index 484135a2ec..52a66ea45f 100644
--- a/gyp/platform-ios.gypi
+++ b/gyp/platform-ios.gypi
@@ -36,6 +36,8 @@
         '../platform/ios/MGLUserLocationAnnotationView.m',
         '../include/mbgl/ios/MGLTypes.h',
         '../platform/ios/MGLTypes.m',
+        '../include/mbgl/ios/MGLGeometry.h',
+        '../platform/ios/MGLGeometry.m',
         '../include/mbgl/ios/MGLMultiPoint.h',
         '../platform/ios/MGLMultiPoint_Private.h',
         '../platform/ios/MGLMultiPoint.mm',
diff --git a/include/mbgl/ios/MGLGeometry.h b/include/mbgl/ios/MGLGeometry.h
new file mode 100644
index 0000000000..6226af1d08
--- /dev/null
+++ b/include/mbgl/ios/MGLGeometry.h
@@ -0,0 +1,85 @@
+#pragma once
+
+#import "MGLTypes.h"
+
+#import <CoreLocation/CoreLocation.h>
+
+NS_ASSUME_NONNULL_BEGIN
+
+/** Defines the area spanned by an MGLCoordinateBounds. */
+typedef struct {
+    CLLocationDegrees latitudeDelta;
+    CLLocationDegrees longitudeDelta;
+} MGLCoordinateSpan;
+
+/** Creates a new MGLCoordinateSpan from the given latitudinal and longitudinal deltas. */
+NS_INLINE MGLCoordinateSpan MGLCoordinateSpanMake(CLLocationDegrees latitudeDelta, CLLocationDegrees longitudeDelta) {
+    MGLCoordinateSpan span;
+    span.latitudeDelta = latitudeDelta;
+    span.longitudeDelta = longitudeDelta;
+    return span;
+}
+
+/** Returns `YES` if the two coordinate spans represent the same latitudinal change and the same longitudinal change. */
+NS_INLINE BOOL MGLCoordinateSpanEqualToCoordinateSpan(MGLCoordinateSpan span1, MGLCoordinateSpan span2) {
+    return (span1.latitudeDelta == span2.latitudeDelta &&
+            span1.longitudeDelta == span2.longitudeDelta);
+}
+
+/** An area of zero width and zero height. */
+extern const MGLCoordinateSpan MGLCoordinateSpanZero;
+
+/** A rectangular area as measured on a two-dimensional map projection. */
+typedef struct {
+    CLLocationCoordinate2D sw;
+    CLLocationCoordinate2D ne;
+} MGLCoordinateBounds;
+
+/** Creates a new MGLCoordinateBounds structure from the given southwest and northeast coordinates. */
+NS_INLINE MGLCoordinateBounds MGLCoordinateBoundsMake(CLLocationCoordinate2D sw, CLLocationCoordinate2D ne) {
+    MGLCoordinateBounds bounds;
+    bounds.sw = sw;
+    bounds.ne = ne;
+    return bounds;
+}
+
+/** Returns `YES` if the two coordinate bounds are equal to each other. */
+NS_INLINE BOOL MGLCoordinateBoundsEqualToCoordinateBounds(MGLCoordinateBounds bounds1, MGLCoordinateBounds bounds2) {
+    return (bounds1.sw.latitude == bounds2.sw.latitude &&
+            bounds1.sw.longitude == bounds2.sw.longitude &&
+            bounds1.ne.latitude == bounds2.ne.latitude &&
+            bounds1.ne.longitude == bounds2.ne.longitude);
+}
+
+/** Returns the area spanned by the coordinate bounds. */
+NS_INLINE MGLCoordinateSpan MGLCoordinateBoundsGetCoordinateSpan(MGLCoordinateBounds bounds) {
+    return MGLCoordinateSpanMake(bounds.ne.latitude - bounds.sw.latitude,
+                                 bounds.ne.longitude - bounds.sw.longitude);
+}
+
+/** Returns a coordinate bounds with southwest and northeast coordinates that are offset from those of the source bounds. */
+NS_INLINE MGLCoordinateBounds MGLCoordinateBoundsOffset(MGLCoordinateBounds bounds, MGLCoordinateSpan offset) {
+    MGLCoordinateBounds offsetBounds = bounds;
+    offsetBounds.sw.latitude += offset.latitudeDelta;
+    offsetBounds.sw.longitude += offset.longitudeDelta;
+    offsetBounds.ne.latitude += offset.latitudeDelta;
+    offsetBounds.ne.longitude += offset.longitudeDelta;
+    return offsetBounds;
+}
+
+/** Returns `YES` if the coordinate bounds covers no area.
+*   
+*   Note that a bounds may be empty but have a non-zero coordinate span (e.g., when its northeast point lies due north of its southwest point). */
+NS_INLINE BOOL MGLCoordinateBoundsIsEmpty(MGLCoordinateBounds bounds) {
+    MGLCoordinateSpan span = MGLCoordinateBoundsGetCoordinateSpan(bounds);
+    return span.latitudeDelta == 0 || span.longitudeDelta == 0;
+}
+
+/** Returns a formatted string for the given coordinate bounds. */
+NS_INLINE NSString *MGLStringFromCoordinateBounds(MGLCoordinateBounds bounds) {
+    return [NSString stringWithFormat:@"{{%.1f, %.1f}, {%.1f, %.1f}}",
+            bounds.sw.latitude, bounds.sw.longitude,
+            bounds.ne.latitude, bounds.ne.longitude];
+}
+
+NS_ASSUME_NONNULL_END
diff --git a/include/mbgl/ios/MGLMapView.h b/include/mbgl/ios/MGLMapView.h
index bf42f47e7f..1d4f5b4ac2 100644
--- a/include/mbgl/ios/MGLMapView.h
+++ b/include/mbgl/ios/MGLMapView.h
@@ -1,4 +1,4 @@
-#import "MGLTypes.h"
+#import "MGLGeometry.h"
 
 #import <UIKit/UIKit.h>
 #import <CoreLocation/CoreLocation.h>
diff --git a/include/mbgl/ios/MGLOverlay.h b/include/mbgl/ios/MGLOverlay.h
index 4a07339b29..104a5e608b 100644
--- a/include/mbgl/ios/MGLOverlay.h
+++ b/include/mbgl/ios/MGLOverlay.h
@@ -2,7 +2,7 @@
 #import <CoreLocation/CoreLocation.h>
 
 #import "MGLAnnotation.h"
-#import "MGLTypes.h"
+#import "MGLGeometry.h"
 
 NS_ASSUME_NONNULL_BEGIN
 
diff --git a/include/mbgl/ios/MGLTypes.h b/include/mbgl/ios/MGLTypes.h
index 9213dafb37..75a0d4619f 100644
--- a/include/mbgl/ios/MGLTypes.h
+++ b/include/mbgl/ios/MGLTypes.h
@@ -1,5 +1,6 @@
 #import <Foundation/Foundation.h>
-#import <CoreLocation/CoreLocation.h>
+
+#pragma once
 
 #if !__has_feature(nullability)
     #define NS_ASSUME_NONNULL_BEGIN
@@ -23,18 +24,6 @@ typedef NS_ENUM(NSUInteger, MGLUserTrackingMode) {
     MGLUserTrackingModeFollowWithHeading
 };
 
-typedef struct {
-    CLLocationCoordinate2D sw;
-    CLLocationCoordinate2D ne;
-} MGLCoordinateBounds;
-
-NS_INLINE MGLCoordinateBounds MGLCoordinateBoundsMake(CLLocationCoordinate2D sw, CLLocationCoordinate2D ne) {
-    MGLCoordinateBounds bounds;
-    bounds.sw = sw;
-    bounds.ne = ne;
-    return bounds;
-}
-
 NS_ASSUME_NONNULL_END
 
 #pragma clang diagnostic push
diff --git a/include/mbgl/ios/MapboxGL.h b/include/mbgl/ios/MapboxGL.h
index d3b032b9c9..bcdc5359bf 100644
--- a/include/mbgl/ios/MapboxGL.h
+++ b/include/mbgl/ios/MapboxGL.h
@@ -1,5 +1,6 @@
 #import "MGLAccountManager.h"
 #import "MGLAnnotation.h"
+#import "MGLGeometry.h"
 #import "MGLMapView.h"
 #import "MGLMultiPoint.h"
 #import "MGLOverlay.h"
diff --git a/platform/ios/MGLGeometry.m b/platform/ios/MGLGeometry.m
new file mode 100644
index 0000000000..9eab5565fa
--- /dev/null
+++ b/platform/ios/MGLGeometry.m
@@ -0,0 +1,3 @@
+#import "MGLGeometry.h"
+
+const MGLCoordinateSpan MGLCoordinateSpanZero = {0, 0};
diff --git a/platform/ios/MGLMultiPoint.mm b/platform/ios/MGLMultiPoint.mm
index 5721086e86..624c1658ad 100644
--- a/platform/ios/MGLMultiPoint.mm
+++ b/platform/ios/MGLMultiPoint.mm
@@ -1,5 +1,5 @@
 #import "MGLMultiPoint.h"
-#import "MGLTypes.h"
+#import "MGLGeometry.h"
 
 #import <mbgl/util/geo.hpp>
 
diff --git a/test/ios/MapViewTests.m b/test/ios/MapViewTests.m
index 90447680ae..de4095497a 100644
--- a/test/ios/MapViewTests.m
+++ b/test/ios/MapViewTests.m
@@ -150,6 +150,41 @@
                    @"disabling zoom gesture should disallow pinching");
 }
 
+- (void)testFitToBounds {
+    // No-op
+    MGLCoordinateBounds initialBounds = tester.mapView.visibleCoordinateBounds;
+    [tester.mapView setVisibleCoordinateBounds:initialBounds animated:NO];
+    XCTAssertEqualObjects(MGLStringFromCoordinateBounds(initialBounds),
+                          MGLStringFromCoordinateBounds(tester.mapView.visibleCoordinateBounds),
+                          @"setting visible coordinate bounds to currently visible coordinate bounds should be a no-op");
+    
+    // Roundtrip after zooming
+    tester.mapView.zoomLevel -= 3;
+    [tester.mapView setVisibleCoordinateBounds:initialBounds animated:NO];
+    XCTAssertEqualObjects(MGLStringFromCoordinateBounds(initialBounds),
+                          MGLStringFromCoordinateBounds(tester.mapView.visibleCoordinateBounds),
+                          @"after zooming out, setting visible coordinate bounds back to %@ should not leave them at %@",
+                          MGLStringFromCoordinateBounds(initialBounds),
+                          MGLStringFromCoordinateBounds(tester.mapView.visibleCoordinateBounds));
+    tester.mapView.zoomLevel += 3;
+    [tester.mapView setVisibleCoordinateBounds:initialBounds animated:NO];
+    XCTAssertEqualObjects(MGLStringFromCoordinateBounds(initialBounds),
+                          MGLStringFromCoordinateBounds(tester.mapView.visibleCoordinateBounds),
+                          @"after zooming in, setting visible coordinate bounds back to %@ should not leave them at %@",
+                          MGLStringFromCoordinateBounds(initialBounds),
+                          MGLStringFromCoordinateBounds(tester.mapView.visibleCoordinateBounds));
+    
+    // Roundtrip after panning
+    MGLCoordinateBounds offsetBounds = MGLCoordinateBoundsOffset(initialBounds, MGLCoordinateSpanMake(0, 30));
+    [tester.mapView setVisibleCoordinateBounds:offsetBounds animated:NO];
+    [tester.mapView setVisibleCoordinateBounds:initialBounds animated:NO];
+    XCTAssertEqualObjects(MGLStringFromCoordinateBounds(initialBounds),
+                          MGLStringFromCoordinateBounds(tester.mapView.visibleCoordinateBounds),
+                          @"after panning 30° to the east, setting visible coordinate bounds back to %@ should not leave them at %@",
+                          MGLStringFromCoordinateBounds(initialBounds),
+                          MGLStringFromCoordinateBounds(tester.mapView.visibleCoordinateBounds));
+}
+
 - (void)testPan {
     CLLocationCoordinate2D centerCoordinate = tester.mapView.centerCoordinate;