[ios, macos] Offsets as vectors, padding as edge insets

An offset style attribute is now exposed publicly as an NSValue representing a CGVector instead of an NSArray of NSNumbers. A padding style attribute is now exposed publicly as an NSValue representing an NSEdgeInsets or UIEdgeInsets instead of an NSArray of NSNumbers. This change also fixes round-tripping of padding values due to a difference between the style specification and Foundation regarding the order of edges around a box. Used a designated initializer on NSEdgeInsets/UIEdgeInsets to ensure correct order when converting from C++ to Objective-C.

Fixes #5947, fixes #6065.

8 files changed, 103 insertions, 48 deletions

diff --git a/platform/darwin/scripts/generate-style-code.js b/platform/darwin/scripts/generate-style-code.js
index 08b358b798..c7dace62a9 100644
--- a/platform/darwin/scripts/generate-style-code.js
+++ b/platform/darwin/scripts/generate-style-code.js
@@ -176,10 +176,10 @@ global.describeValue = function (value, property, layerType) {
                 units = ` ${units}`.replace(/pixel/, 'point');
             }
             if (property.name.indexOf('padding') !== -1) {
-                //if (value.reduce((a, b) => a + b, 0) === 0) {
-                //    return '`NSEdgeInsetsZero` or `UIEdgeInsetsZero`';
-                //}
-                return `${value[0]}${units} on the top, ${value[1]}${units} on the right, ${value[2]}${units} on the bottom, and ${value[3]}${units} on the left`;
+                if (value.reduce((a, b) => a + b, 0) === 0) {
+                    return '`NSEdgeInsetsZero` or `UIEdgeInsetsZero`';
+                }
+                return `${value[0]}${units} on the top, ${value[3]}${units} on the left, ${value[2]}${units} on the bottom, and ${value[1]}${units} on the right`;
             }
             if (property.name.indexOf('offset') !== -1 || property.name.indexOf('translate') !== -1) {
                 return `${value[0]}${units} from the left and ${value[1]}${units} from the top`;
diff --git a/platform/darwin/src/MGLStyleAttribute.mm b/platform/darwin/src/MGLStyleAttribute.mm
index 8c51f80758..9e3c22914b 100644
--- a/platform/darwin/src/MGLStyleAttribute.mm
+++ b/platform/darwin/src/MGLStyleAttribute.mm
@@ -2,8 +2,7 @@
 
 #import "MGLStyleAttributeValue_Private.h"
 #import "MGLStyleAttributeFunction_Private.h"
-
-#import "MGLTypes.h"
+#import "NSValue+MGLStyleAttributeAdditions_Private.h"
 
 @interface MGLStyleAttribute()
 @end
@@ -58,7 +57,7 @@
 {
     if (property.isConstant()) {
         auto offset = property.asConstant();
-        return @[@(offset[0]), @(offset[1])];
+        return [NSValue mgl_valueWithOffsetArray:offset];
     } else if (property.isFunction()) {
         return [MGLStyleAttributeFunction functionWithOffsetPropertyValue:property.asFunction()];
     } else {
@@ -70,7 +69,7 @@
 {
     if (property.isConstant()) {
         auto padding = property.asConstant();
-        return @[@(padding[0]), @(padding[1]), @(padding[2]), @(padding[3])];
+        return [NSValue mgl_valueWithPaddingArray:padding];
     } else if (property.isFunction()) {
         return [MGLStyleAttributeFunction functionWithPaddingPropertyValue:property.asFunction()];
     } else {
diff --git a/platform/darwin/src/MGLStyleAttributeFunction.mm b/platform/darwin/src/MGLStyleAttributeFunction.mm
index 5216e32d97..46fa3ec6a7 100644
--- a/platform/darwin/src/MGLStyleAttributeFunction.mm
+++ b/platform/darwin/src/MGLStyleAttributeFunction.mm
@@ -93,14 +93,9 @@
 - (mbgl::style::PropertyValue<std::array<float, 4> >)mbgl_paddingPropertyValue
 {
     __block std::vector<std::pair<float, std::array<float, 4>>> stops;
-    [self.stops enumerateKeysAndObjectsUsingBlock:^(NSNumber * _Nonnull zoomKey, NSArray *  _Nonnull padding, BOOL * _Nonnull stop) {
-        NSAssert([padding isKindOfClass:[NSArray class]], @"Stops should be NSArray");
-        NSNumber *top = padding[0];
-        NSNumber *left = padding[1];
-        NSNumber *bottom = padding[2];
-        NSNumber *right = padding[2];
-        auto pad = std::array<float, 4>({{top.floatValue, left.floatValue, bottom.floatValue, right.floatValue}});
-        stops.emplace_back(zoomKey.floatValue, pad);
+    [self.stops enumerateKeysAndObjectsUsingBlock:^(NSNumber * _Nonnull zoomKey, NSValue * _Nonnull padding, BOOL * _Nonnull stop) {
+        NSAssert([padding isKindOfClass:[NSArray class]], @"Stops should be NSValue");
+        stops.emplace_back(zoomKey.floatValue, padding.mgl_paddingArrayValue);
     }];
     return mbgl::style::Function<std::array<float, 4>>({{stops}}, _base.floatValue);
 }
@@ -108,12 +103,9 @@
 - (mbgl::style::PropertyValue<std::array<float, 2> >)mbgl_offsetPropertyValue
 {
     __block std::vector<std::pair<float, std::array<float, 2>>> stops;
-    [self.stops enumerateKeysAndObjectsUsingBlock:^(NSNumber * _Nonnull zoomKey, NSArray *  _Nonnull offset, BOOL * _Nonnull stop) {
-        NSAssert([offset isKindOfClass:[NSArray class]], @"Stops should be NSArray");
-        NSNumber *dx = offset[0];
-        NSNumber *dy = offset[1];
-        auto off = std::array<float, 2>({{dx.floatValue, dy.floatValue}});
-        stops.emplace_back(zoomKey.floatValue, off);
+    [self.stops enumerateKeysAndObjectsUsingBlock:^(NSNumber * _Nonnull zoomKey, NSValue * _Nonnull offset, BOOL * _Nonnull stop) {
+        NSAssert([offset isKindOfClass:[NSValue class]], @"Stops should be NSValue");
+        stops.emplace_back(zoomKey.floatValue, offset.mgl_offsetArrayValue);
     }];
     return mbgl::style::Function<std::array<float, 2>>({{stops}}, _base.floatValue);
 }
@@ -176,7 +168,7 @@
     auto stops = property.getStops();
     NSMutableDictionary *convertedStops = [NSMutableDictionary dictionaryWithCapacity:stops.size()];
     for (auto stop : stops) {
-        convertedStops[@(stop.first)] = @[@(stop.second[0]), @(stop.second[1])];
+        convertedStops[@(stop.first)] = [NSValue mgl_valueWithOffsetArray:stop.second];
     }
     function.base = @(property.getBase());
     function.stops = convertedStops;
diff --git a/platform/darwin/src/MGLSymbolStyleLayer.h b/platform/darwin/src/MGLSymbolStyleLayer.h
index d77488bdca..643f0fce20 100644
--- a/platform/darwin/src/MGLSymbolStyleLayer.h
+++ b/platform/darwin/src/MGLSymbolStyleLayer.h
@@ -155,7 +155,7 @@ typedef NS_ENUM(NSUInteger, MGLSymbolStyleLayerTextTranslateAnchor) {
 
  This property is measured in points.
  
- If this property is set to `nil`, the layer uses an implicit default value of 0 points on the top, 0 points on the right, 0 points on the bottom, and 0 points on the left.
+ If this property is set to `nil`, the layer uses an implicit default value of `NSEdgeInsetsZero` or `UIEdgeInsetsZero`.
  
  This property is only applied to the style if `iconImage` is non-`nil`, and `iconTextFit` is non-`nil`, and `textField` is non-`nil`. Otherwise, it is ignored.
  */
diff --git a/platform/darwin/src/NSArray+MGLStyleAttributeAdditions.mm b/platform/darwin/src/NSArray+MGLStyleAttributeAdditions.mm
index 1456068938..fb60cf0f72 100644
--- a/platform/darwin/src/NSArray+MGLStyleAttributeAdditions.mm
+++ b/platform/darwin/src/NSArray+MGLStyleAttributeAdditions.mm
@@ -10,24 +10,6 @@
 
 @implementation NSArray (MGLStyleAttributeAdditions)
 
-- (mbgl::style::PropertyValue<std::array<float, 2>>)mbgl_offsetPropertyValue
-{
-    NSAssert(self.count == 2, @"Offset must contain 2 values (dx, dy)");
-    NSNumber *dx = self[0];
-    NSNumber *dy = self[1];
-    return {{dx.floatValue, dy.floatValue}};
-}
-
-- (mbgl::style::PropertyValue<std::array<float, 4> >)mbgl_paddingPropertyValue
-{
-    NSAssert(self.count == 4, @"Padding must contain 4 values (top, left, bottom & right)");
-    NSNumber *top = self[0];
-    NSNumber *left = self[1];
-    NSNumber *bottom = self[2];
-    NSNumber *right = self[3];
-    return {{top.floatValue, left.floatValue, bottom.floatValue, right.floatValue}};
-}
-
 - (mbgl::style::PropertyValue<std::vector<std::string> >)mbgl_stringArrayPropertyValue
 {
     std::vector<std::string>fonts;
diff --git a/platform/darwin/src/NSValue+MGLStyleAttributeAdditions.mm b/platform/darwin/src/NSValue+MGLStyleAttributeAdditions.mm
index 633a74d276..79038a66fd 100644
--- a/platform/darwin/src/NSValue+MGLStyleAttributeAdditions.mm
+++ b/platform/darwin/src/NSValue+MGLStyleAttributeAdditions.mm
@@ -2,8 +2,36 @@
 
 #import "NSValue+MGLStyleAttributeAdditions_Private.h"
 
+#include <array>
+
+#if TARGET_OS_IPHONE
+    #import <UIKit/UIKit.h>
+    #define MGLEdgeInsets UIEdgeInsets
+#else
+    #define MGLEdgeInsets NSEdgeInsets
+#endif
+
 @implementation NSValue (MGLStyleAttributeAdditions)
 
++ (instancetype)mgl_valueWithOffsetArray:(std::array<float, 2>)offsetArray
+{
+    CGVector vector = CGVectorMake(offsetArray[0], offsetArray[1]);
+    return [NSValue value:&vector withObjCType:@encode(CGVector)];
+}
+
++ (instancetype)mgl_valueWithPaddingArray:(std::array<float, 4>)paddingArray
+{
+    // Style specification defines padding in clockwise order: top, right, bottom, left.
+    // Foundation defines padding in counterclockwise order: top, left, bottom, right.
+    MGLEdgeInsets insets = {
+        .top = paddingArray[0],
+        .right = paddingArray[1],
+        .bottom = paddingArray[2],
+        .left = paddingArray[3],
+    };
+    return [NSValue value:&insets withObjCType:@encode(MGLEdgeInsets)];
+}
+
 - (BOOL)isFunction
 {
     return NO;
@@ -11,9 +39,45 @@
 
 - (mbgl::style::PropertyValue<uint8_t>)mbgl_enumPropertyValue
 {
+    NSAssert(strcmp(self.objCType, @encode(uint8_t)) == 0, @"Value does not represent a uint8_t");
     uint8_t value = 0;
     [self getValue:&value];
     return mbgl::style::PropertyValue<uint8_t> { value };
 }
 
+- (mbgl::style::PropertyValue<std::array<float, 2>>)mbgl_offsetPropertyValue
+{
+    return { self.mgl_offsetArrayValue };
+}
+
+- (std::array<float, 2>)mgl_offsetArrayValue
+{
+    NSAssert(strcmp(self.objCType, @encode(CGVector)) == 0, @"Value does not represent a CGVector");
+    CGVector vector;
+    [self getValue:&vector];
+    return {
+        static_cast<float>(vector.dx),
+        static_cast<float>(vector.dy),
+    };
+}
+
+- (mbgl::style::PropertyValue<std::array<float, 4>>)mbgl_paddingPropertyValue
+{
+    return { self.mgl_paddingArrayValue };
+}
+
+- (std::array<float, 4>)mgl_paddingArrayValue
+{
+    NSAssert(strcmp(self.objCType, @encode(MGLEdgeInsets)) == 0, @"Value does not represent an NSEdgeInsets/UIEdgeInsets");
+    MGLEdgeInsets insets;
+    [self getValue:&insets];
+    // Style specification defines padding in clockwise order: top, right, bottom, left.
+    return {
+        static_cast<float>(insets.top),
+        static_cast<float>(insets.right),
+        static_cast<float>(insets.bottom),
+        static_cast<float>(insets.left),
+    };
+}
+
 @end
diff --git a/platform/darwin/src/NSValue+MGLStyleAttributeAdditions_Private.h b/platform/darwin/src/NSValue+MGLStyleAttributeAdditions_Private.h
index 5bca9407ac..578e0ad9c0 100644
--- a/platform/darwin/src/NSValue+MGLStyleAttributeAdditions_Private.h
+++ b/platform/darwin/src/NSValue+MGLStyleAttributeAdditions_Private.h
@@ -5,5 +5,14 @@
 #include <mbgl/style/property_value.hpp>
 
 @interface NSValue (MGLStyleAttributeAdditions_Private) <MGLStyleAttributeValue>
+
++ (instancetype)mgl_valueWithOffsetArray:(std::array<float, 2>)offsetArray;
++ (instancetype)mgl_valueWithPaddingArray:(std::array<float, 4>)paddingArray;
+
 - (mbgl::style::PropertyValue<uint8_t>)mbgl_enumPropertyValue;
+- (mbgl::style::PropertyValue<std::array<float, 2>>)mbgl_offsetPropertyValue;
+
+- (std::array<float, 2>)mgl_offsetArrayValue;
+- (std::array<float, 4>)mgl_paddingArrayValue;
+
 @end
diff --git a/platform/darwin/test/MGLRuntimeStylingHelper.m b/platform/darwin/test/MGLRuntimeStylingHelper.m
index fbdc8e5225..f44b855ef4 100644
--- a/platform/darwin/test/MGLRuntimeStylingHelper.m
+++ b/platform/darwin/test/MGLRuntimeStylingHelper.m
@@ -1,21 +1,30 @@
 #import "MGLRuntimeStylingHelper.h"
 
 #if TARGET_OS_IPHONE || TARGET_OS_SIMULATOR
-#import <UIKit/UIKit.h>
+    #import <UIKit/UIKit.h>
+    #define MGLEdgeInsets UIEdgeInsets
 #else
-#import <Cocoa/Cocoa.h>
+    #import <Cocoa/Cocoa.h>
+    #define MGLEdgeInsets NSEdgeInsets
 #endif
 
 @implementation MGLRuntimeStylingHelper
 
-+ (NSArray *)testPadding
++ (NSValue *)testPadding
 {
-    return @[@1.0f, @1.0f, @1.0f, @1.0f];
+    MGLEdgeInsets insets = {
+        .top = 1,
+        .left = 1,
+        .bottom = 1,
+        .right = 1,
+    };
+    return [NSValue value:&insets withObjCType:@encode(MGLEdgeInsets)];
 }
 
-+ (NSArray *)testOffset
++ (NSValue *)testOffset
 {
-    return @[@1.0f, @1.0f];
+    CGVector vector = CGVectorMake(1, 1);
+    return [NSValue value:&vector withObjCType:@encode(CGVector)];
 }
 
 + (NSArray *)testFont