[ios, macos] Replaced MGLStyleAttributeValue with MGLStyleValue

MGLStyleValue is an umbrella class serving as a variant container for MGLStyleConstantValue and MGLStyleFunction. These classes use lightweight generics to indicate the underlying type. A templated C++ class concisely converts between mbgl::style::PropertyValue and MGLStyleValue.

platform/darwin/src/MGLLineStyleLayer.h

@@ -3,6 +3,7 @@
 
 #import "MGLStyleAttributeValue.h"
 #import "MGLVectorStyleLayer.h"
+#import "MGLStyleAttributeFunction.h"
 
 NS_ASSUME_NONNULL_BEGIN
 
@@ -84,7 +85,7 @@ typedef NS_ENUM(NSUInteger, MGLLineTranslateAnchor) {
  
  The default value of this property is an `NSValue` object containing `MGLLineJoinMiter`. Set this property to `nil` to reset it to the default value.
  */
-@property (nonatomic, null_resettable) id <MGLStyleAttributeValue> lineJoin;
+@property (nonatomic, null_resettable) MGLStyleValue <NSValue *> *lineJoin;
 
 /**
  Used to automatically convert miter joins to bevel joins for sharp angles.
@@ -93,7 +94,7 @@ typedef NS_ENUM(NSUInteger, MGLLineTranslateAnchor) {
  
  This property is only applied to the style if `lineJoin` is set to an `NSValue` object containing `MGLLineJoinMiter`. Otherwise, it is ignored.
  */
-@property (nonatomic, null_resettable) id <MGLStyleAttributeValue> lineMiterLimit;
+@property (nonatomic, null_resettable) MGLStyleValue <NSNumber *> *lineMiterLimit;
 
 /**
  Used to automatically convert round joins to miter joins for shallow angles.

platform/darwin/src/MGLLineStyleLayer.mm

@@ -56,20 +56,24 @@
     MGLGetEnumProperty(LineCap, LineCapType, MGLLineCap);
 }
 
-- (void)setLineJoin:(id <MGLStyleAttributeValue, MGLStyleAttributeValue_Private>)lineJoin {
-    MGLSetEnumProperty(lineJoin, LineJoin, LineJoinType, MGLLineJoin);
+- (void)setLineJoin:(MGLStyleValue <NSValue *> *)lineJoin {
+    auto propertyValue = MGLStyleValueTransformer<mbgl::style::LineJoinType, NSValue *>().toPropertyValue(lineJoin);
+    self.layer->setLineJoin(propertyValue);
 }
 
-- (id <MGLStyleAttributeValue>)lineJoin {
-    MGLGetEnumProperty(LineJoin, LineJoinType, MGLLineJoin);
+- (MGLStyleValue <NSValue *> *)lineJoin {
+    auto propertyValue = self.layer->getLineJoin() ?: self.layer->getDefaultLineJoin();
+    return MGLStyleValueTransformer<mbgl::style::LineJoinType, NSValue *>().toStyleValue(propertyValue);
 }
 
-- (void)setLineMiterLimit:(id <MGLStyleAttributeValue, MGLStyleAttributeValue_Private>)lineMiterLimit {
-    self.layer->setLineMiterLimit(lineMiterLimit.mbgl_floatPropertyValue);
+- (void)setLineMiterLimit:(MGLStyleValue <NSNumber *> *)lineMiterLimit {
+    auto mbglValue = MGLStyleValueTransformer<float, NSNumber *>().toPropertyValue(lineMiterLimit);
+    self.layer->setLineMiterLimit(mbglValue);
 }
 
-- (id <MGLStyleAttributeValue>)lineMiterLimit {
-    return [MGLStyleAttribute mbgl_numberWithPropertyValueNumber:self.layer->getLineMiterLimit() ?: self.layer->getDefaultLineMiterLimit()];
+- (MGLStyleValue <NSNumber *> *)lineMiterLimit {
+    auto propertyValue = self.layer->getLineMiterLimit() ?: self.layer->getDefaultLineMiterLimit();
+    return MGLStyleValueTransformer<float, NSNumber *>().toStyleValue(propertyValue);
 }
 
 - (void)setLineRoundLimit:(id <MGLStyleAttributeValue, MGLStyleAttributeValue_Private>)lineRoundLimit {

platform/darwin/src/MGLStyleAttributeFunction.h

@@ -14,4 +14,34 @@ NS_ASSUME_NONNULL_BEGIN
 
 @end
 
+@interface MGLStyleValue<T> : NSObject
+
++ (instancetype)valueWithRawValue:(T)rawValue;
++ (instancetype)valueWithBase:(CGFloat)base stops:(NSDictionary<NSNumber *, MGLStyleValue<T> *> *)stops;
++ (instancetype)valueWithStops:(NSDictionary<NSNumber *, MGLStyleValue<T> *> *)stops;
+
+@end
+
+@interface MGLStyleConstantValue<T> : MGLStyleValue
+
++ (instancetype)valueWithRawValue:(T)rawValue;
+
+- (instancetype)initWithRawValue:(T)rawValue;
+
+@property (nonatomic) T rawValue;
+
+@end
+
+@interface MGLStyleFunction<T> : MGLStyleValue
+
++ (instancetype)functionWithBase:(CGFloat)base stops:(NSDictionary<NSNumber *, MGLStyleValue<T> *> *)stops;
++ (instancetype)functionWithStops:(NSDictionary<NSNumber *, MGLStyleValue<T> *> *)stops;
+
+- (instancetype)initWithBase:(CGFloat)base stops:(NSDictionary<NSNumber *, MGLStyleValue<T> *> *)stops;
+
+@property (nonatomic) CGFloat base;
+@property (nonatomic, copy) NSDictionary<NSNumber *, MGLStyleValue<T> *> *stops;
+
+@end
+
 NS_ASSUME_NONNULL_END

platform/darwin/src/MGLStyleAttributeFunction.mm

@@ -4,6 +4,68 @@
 #import "MGLStyleAttributeValue_Private.h"
 #import "MGLStyleAttributeFunction_Private.h"
 
+@implementation MGLStyleValue
+
++ (instancetype)valueWithRawValue:(id)rawValue {
+    return [MGLStyleConstantValue valueWithRawValue:rawValue];
+}
+
++ (instancetype)valueWithBase:(CGFloat)base stops:(NSDictionary *)stops {
+    return [MGLStyleFunction functionWithBase:base stops:stops];
+}
+
++ (instancetype)valueWithStops:(NSDictionary *)stops {
+    return [MGLStyleFunction functionWithStops:stops];
+}
+
+@end
+
+@implementation MGLStyleConstantValue
+
++ (instancetype)valueWithRawValue:(id)rawValue {
+    return [[self alloc] initWithRawValue:rawValue];
+}
+
+- (instancetype)initWithRawValue:(id)rawValue {
+    if (self = [super init]) {
+        _rawValue = rawValue;
+    }
+    return self;
+}
+
+@end
+
+@implementation MGLStyleFunction
+
++ (instancetype)functionWithBase:(CGFloat)base stops:(NSDictionary *)stops {
+    return [[self alloc] initWithBase:base stops:stops];
+}
+
++ (instancetype)functionWithStops:(NSDictionary *)stops {
+    return [[self alloc] initWithBase:1 stops:stops];
+}
+
+- (instancetype)init {
+    if (self = [super init]) {
+        _base = 1;
+    }
+    return self;
+}
+
+- (instancetype)initWithBase:(CGFloat)base stops:(NSDictionary *)stops {
+    if (self = [self init]) {
+        _base = base;
+        _stops = stops;
+    }
+    return self;
+}
+
+@end
+
+
+
+
+
 @interface MGLStyleAttributeFunction() <MGLStyleAttributeValue_Private>
 @end
 

platform/darwin/src/MGLStyleAttributeFunction_Private.h

@@ -1,9 +1,20 @@
 #import "MGLStyleAttributeFunction.h"
 
+#import "NSValue+MGLStyleAttributeAdditions_Private.h"
+
+#if TARGET_OS_IPHONE
+    #import "UIColor+MGLAdditions.h"
+#else
+    #import "NSColor+MGLAdditions.h"
+#endif
+
 #include <mbgl/util/color.hpp>
+#include <mbgl/util/variant.hpp>
 #include <mbgl/style/function.hpp>
 #include <mbgl/style/property_value.hpp>
 
+#include <array>
+
 #define MGLSetEnumProperty(name, Name, MBGLType, ObjCType) \
     if (name.isFunction) { \
         NSAssert([name isKindOfClass:[MGLStyleAttributeFunction class]], @"" #name @" should be a function"); \
@@ -70,4 +81,140 @@
 
 + (instancetype)functionWithEnumProperyValue:(mbgl::style::Function<bool>)property type:(const char *)type;
 
-@end;
+@end
+
+template <typename MBGLType, typename ObjCType>
+class MGLStyleValueTransformer {
+public:
+    
+    MGLStyleValue<ObjCType> *toStyleValue(const mbgl::style::PropertyValue<MBGLType> &mbglValue) {
+        if (mbglValue.isConstant()) {
+            return toStyleConstantValue(mbglValue.asConstant());
+        } else if (mbglValue.isFunction()) {
+            return toStyleFunction(mbglValue.asFunction());
+        } else {
+            return nil;
+        }
+    }
+    
+    mbgl::style::PropertyValue<MBGLType> toPropertyValue(MGLStyleValue<ObjCType> *value) {
+        if ([value isKindOfClass:[MGLStyleConstantValue class]]) {
+            MBGLType mbglValue;
+            getMBGLValue([(MGLStyleConstantValue<ObjCType> *)value rawValue], mbglValue);
+            return mbglValue;
+        } else if ([value isKindOfClass:[MGLStyleFunction class]]) {
+            MGLStyleFunction<ObjCType> *function = (MGLStyleFunction<ObjCType> *)value;
+            __block std::vector<std::pair<float, MBGLType>> mbglStops;
+            [function.stops enumerateKeysAndObjectsUsingBlock:^(NSNumber * _Nonnull zoomKey, MGLStyleValue<ObjCType> * _Nonnull stopValue, BOOL * _Nonnull stop) {
+                NSCAssert([stopValue isKindOfClass:[MGLStyleValue class]], @"Stops should be MGLStyleValues");
+                auto mbglStopValue = toPropertyValue(stopValue);
+                NSCAssert(mbglStopValue.isConstant(), @"Stops must be constant");
+                mbglStops.emplace_back(zoomKey.floatValue, mbglStopValue.asConstant());
+            }];
+            return mbgl::style::Function<MBGLType>({{mbglStops}}, function.base);
+        } else {
+            return {};
+        }
+    }
+    
+private:
+    
+    MGLStyleConstantValue<ObjCType> *toStyleConstantValue(const MBGLType mbglValue) {
+        auto rawValue = toMGLRawStyleValue(mbglValue);
+        return [MGLStyleConstantValue<ObjCType> valueWithRawValue:rawValue];
+    }
+    
+    MGLStyleFunction<ObjCType> *toStyleFunction(const mbgl::style::Function<MBGLType> &mbglFunction) {
+        const auto &mbglStops = mbglFunction.getStops();
+        NSMutableDictionary *stops = [NSMutableDictionary dictionaryWithCapacity:mbglStops.size()];
+        for (const auto &mbglStop : mbglStops) {
+            auto rawValue = toMGLRawStyleValue(mbglStop.second);
+            stops[@(mbglStop.first)] = [MGLStyleValue valueWithRawValue:rawValue];
+        }
+        return [MGLStyleFunction<ObjCType> functionWithBase:mbglFunction.getBase() stops:stops];
+    }
+    
+    NSNumber *toMGLRawStyleValue(const bool mbglStopValue) {
+        return @(mbglStopValue);
+    }
+    
+    NSNumber *toMGLRawStyleValue(const float mbglStopValue) {
+        return @(mbglStopValue);
+    }
+    
+    NSString *toMGLRawStyleValue(const std::string &mbglStopValue) {
+        return @(mbglStopValue.c_str());
+    }
+    
+    // Offsets
+    NSValue *toMGLRawStyleValue(const std::array<float, 2> &mbglStopValue) {
+        return [NSValue mgl_valueWithOffsetArray:mbglStopValue];
+    }
+    
+    // Padding
+    NSValue *toMGLRawStyleValue(const std::array<float, 4> &mbglStopValue) {
+        return [NSValue mgl_valueWithPaddingArray:mbglStopValue];
+    }
+    
+    // Enumerations
+    template <typename MBGLEnum = MBGLType, class = typename std::enable_if<std::is_enum<MBGLEnum>::value>::type>
+    ObjCType toMGLRawStyleValue(const MBGLType &mbglStopValue) {
+        NSUInteger rawValue = static_cast<NSUInteger>(mbglStopValue);
+        return [NSValue value:&rawValue withObjCType:@encode(NSUInteger)];
+    }
+    
+    MGLColor *toMGLRawStyleValue(const mbgl::Color mbglStopValue) {
+        return [MGLColor mbgl_colorWithColor:mbglStopValue];
+    }
+    
+    ObjCType toMGLRawStyleValue(const std::vector<MBGLType> &mbglStopValue) {
+        NSMutableArray *array = [NSMutableArray arrayWithCapacity:mbglStopValue.size()];
+        for (const auto &mbglElement: mbglStopValue) {
+            [array addObject:toMGLRawStyleValue(mbglElement)];
+        }
+        return array;
+    }
+    
+private:
+    
+    void getMBGLValue(NSNumber *rawValue, bool &mbglValue) {
+        mbglValue = !!rawValue.boolValue;
+    }
+    
+    void getMBGLValue(NSNumber *rawValue, float &mbglValue) {
+        mbglValue = !!rawValue.boolValue;
+    }
+    
+    void getMBGLValue(NSString *rawValue, std::string &mbglValue) {
+        mbglValue = rawValue.UTF8String;
+    }
+    
+    // Offsets
+    void getMBGLValue(NSValue *rawValue, std::array<float, 2> &mbglValue) {
+        mbglValue = rawValue.mgl_offsetArrayValue;
+    }
+    
+    // Padding
+    void getMBGLValue(NSValue *rawValue, std::array<float, 4> &mbglValue) {
+        mbglValue = rawValue.mgl_paddingArrayValue;
+    }
+    
+    // Enumerations
+    template <typename MBGLEnum = MBGLType, class = typename std::enable_if<std::is_enum<MBGLEnum>::value>::type>
+    void getMBGLValue(ObjCType rawValue, MBGLType &mbglValue) {
+        [rawValue getValue:&mbglValue];
+    }
+    
+    void getMBGLValue(MGLColor *rawValue, mbgl::Color &mbglValue) {
+        mbglValue = rawValue.mbgl_color;
+    }
+    
+    void getMBGLValue(ObjCType rawValue, std::vector<MBGLType> &mbglValue) {
+        mbglValue.reserve(rawValue.count);
+        for (id obj in rawValue) {
+            MBGLType mbglElement;
+            getMBGLValue(obj, mbglElement);
+            mbglValue.push_back(mbglElement);
+        }
+    }
+};

platform/darwin/src/MGLStyleAttributeValue.h

@@ -2,4 +2,4 @@
 
 @protocol MGLStyleAttributeValue <NSObject>
 @optional
-@end
+@end