Reimplement style values atop NSExpression (#10726)

* [ios, macos] Import headers, not implementation files

* [core] Added accessors for various expression parameters

Added missing parameter accessors to various expression operator classes, as well as a method on InterpolatorBase and Step that enumerates the stops and their values.

* [ios, macos] Silenced warning in test of error condition

* [ios, macos] Made MGLSphericalPosition boxable

* [ios, macos] Implemented array enumeration during conversion

* [ios, macos] Temporarily ignore heatmap layer type

* [ios, macos] Migrated MGLSymbolStyleLayer.text to NSExpression

MGLSymbolStyleLayer.text is now of type NSExpression instead of MGLStyleValue, as a first step toward migrating the entire layer API from style values to expressions.

Implemented conversions from NSExpression to JSON arrays and vice versa. The most common NSExpression functions are now converted into style expressions, but not all of the most common style expression operators are supported yet.

* [ios, macos] Implemented string coercion

* [ios, macos] Color literals

* [ios, macos] Null constant expressions

* [ios, macos] Convert dictionary literals

* [ios, macos] Interpolation expressions

* [ios, macos] to-boolean, to-number, get from object

* [ios, macos] Variable expressions

Implemented custom expression functions for assigning and referring to variables within the context of an expression. Variables are assigned via a “context dictionary” and applied to an subexpression that is given as another argument to the same expression. Also implemented built-in variable expressions for zoom level and heatmap density.

* [ios, macos] Convert colors, offsets, padding in expressions to JSON objects

* [ios, macos] Expression-based style property getters

Implemented a conversion from mbgl::style::PropertyValues to Objective-C JSON objects, which are then converted to NSExpressions.

* [ios, macos] Consolidated property value–expression conversion in MGLStyleValueTransformer

* [ios, macos] Predicate and expression guide

Extracted documentation about predicates from a documentation comment in MGLVectorStyleLayer.h to a new jazzy guide. Added details about NSExpression support as well. Began updating the “For Style Authors” guide to reflect the transition from style values to expressions.

* [ios, macos] Updated style authoring guide

Updated the Information for Style Authors guide to discuss expressions instead of style functions. Included a table mapping style specification expression operators to NSExpression syntaxes.

* [ios, macos] Migrated codegen templates to expressions

* [ios, macos] Applied expression changes via codegen

Ran make darwin-style-code.

* [macos] Migrated macosapp to expressions

* [ios, macos] Updated style function guide

This guide needs to be thoroughly rewritten, but for now the example code has been migrated to expressions.

* [ios, macos] Eviscerated style function tests

* [ios, macos] Updated changelogs

* [ios] Migrated iosapp to expressions

* [ios, macos] Exposed JSON conversion methods publicly

* [ios, macos] Removed MGLStyleValue, MGLStyleFunction

1 files changed, 17 insertions, 17 deletions

diff --git a/platform/macos/app/MapDocument.m b/platform/macos/app/MapDocument.m
index eb20063996..94b0cffcdc 100644
--- a/platform/macos/app/MapDocument.m
+++ b/platform/macos/app/MapDocument.m
@@ -716,7 +716,7 @@ NS_ARRAY_OF(id <MGLAnnotation>) *MBXFlattenedShapes(NS_ARRAY_OF(id <MGLAnnotatio
     [self.mapView.style addLayer:lineLayer];
     MGLSymbolStyleLayer *labelLayer = [[MGLSymbolStyleLayer alloc] initWithIdentifier:@"graticule.labels"
                                                                                source:source];
-    labelLayer.text = [MGLStyleValue valueWithRawValue:@"{value}"];
+    labelLayer.text = [NSExpression expressionWithFormat:@"value"];
     [self.mapView.style addLayer:labelLayer];
 }
 
@@ -787,16 +787,16 @@ NS_ARRAY_OF(id <MGLAnnotation>) *MBXFlattenedShapes(NS_ARRAY_OF(id <MGLAnnotatio
     self.mapView.style.transition = transition;
 
     MGLStyleLayer *waterLayer = [self.mapView.style layerWithIdentifier:@"water"];
-    MGLStyleValue *colorFunction = [MGLStyleValue<NSColor *> valueWithInterpolationMode:MGLInterpolationModeExponential cameraStops:@{
-        @0.0: [MGLStyleValue<NSColor *> valueWithRawValue:[NSColor redColor]],
-        @10.0: [MGLStyleValue<NSColor *> valueWithRawValue:[NSColor yellowColor]],
-        @20.0: [MGLStyleValue<NSColor *> valueWithRawValue:[NSColor blackColor]],
-    } options:nil];
+    NSExpression *colorExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{
+        @0.0: [NSColor redColor],
+        @10.0: [NSColor yellowColor],
+        @20.0: [NSColor blackColor],
+    }];
     
     if ([waterLayer respondsToSelector:@selector(fillColor)]) {
-        [waterLayer setValue:colorFunction forKey:@"fillColor"];
+        [waterLayer setValue:colorExpression forKey:@"fillColor"];
     } else if ([waterLayer respondsToSelector:@selector(lineColor)]) {
-        [waterLayer setValue:colorFunction forKey:@"lineColor"];
+        [waterLayer setValue:colorExpression forKey:@"lineColor"];
     }
 
     NSString *filePath = [[NSBundle bundleForClass:self.class] pathForResource:@"amsterdam" ofType:@"geojson"];
@@ -805,8 +805,8 @@ NS_ARRAY_OF(id <MGLAnnotation>) *MBXFlattenedShapes(NS_ARRAY_OF(id <MGLAnnotatio
     [self.mapView.style addSource:source];
 
     MGLCircleStyleLayer *circleLayer = [[MGLCircleStyleLayer alloc] initWithIdentifier:@"test" source:source];
-    circleLayer.circleColor = [MGLStyleValue<NSColor *> valueWithRawValue:[NSColor greenColor]];
-    circleLayer.circleRadius = [MGLStyleValue<NSNumber *> valueWithRawValue:[NSNumber numberWithInteger:40]];
+    circleLayer.circleColor = [NSExpression expressionForConstantValue:[NSColor greenColor]];
+    circleLayer.circleRadius = [NSExpression expressionForConstantValue:@40];
 //    fillLayer.predicate = [NSPredicate predicateWithFormat:@"%K == %@", @"type", @"park"];
     [self.mapView.style addLayer:circleLayer];
 
@@ -818,13 +818,13 @@ NS_ARRAY_OF(id <MGLAnnotation>) *MBXFlattenedShapes(NS_ARRAY_OF(id <MGLAnnotatio
         MGLSymbolStyleLayer *theaterLayer = [[MGLSymbolStyleLayer alloc] initWithIdentifier:@"theaters" source:streetsSource];
         theaterLayer.sourceLayerIdentifier = @"poi_label";
         theaterLayer.predicate = [NSPredicate predicateWithFormat:@"maki == 'theatre'"];
-        theaterLayer.iconImageName = [MGLStyleValue valueWithRawValue:NSImageNameIChatTheaterTemplate];
-        theaterLayer.iconScale = [MGLStyleValue valueWithRawValue:@2];
-        theaterLayer.iconColor = [MGLStyleValue valueWithInterpolationMode:MGLInterpolationModeExponential cameraStops:@{
-            @16.0: [MGLStyleValue valueWithRawValue:[NSColor redColor]],
-            @18.0: [MGLStyleValue valueWithRawValue:[NSColor yellowColor]],
-            @20.0: [MGLStyleValue valueWithRawValue:[NSColor blackColor]],
-        } options:nil];
+        theaterLayer.iconImageName = [NSExpression expressionForConstantValue:NSImageNameIChatTheaterTemplate];
+        theaterLayer.iconScale = [NSExpression expressionForConstantValue:@2];
+        theaterLayer.iconColor = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{
+            @16.0: [NSColor redColor],
+            @18.0: [NSColor yellowColor],
+            @20.0: [NSColor blackColor],
+        }];
         [self.mapView.style addLayer:theaterLayer];
     }