[core] Add DDS support for {text,icon}-size (#8593)

* Update gl-js and generate style code

* Factor out packUint8Pair() helper function

* Draft implementation of DDS for {text,icon}-size

Ports https://github.com/mapbox/mapbox-gl-js/pull/4455

* Fix text-size/composite-function-line-placement test

* Refactor to PaintPropertyBinders-like strategy

* Dedupe gl::Program construction

* Use exponential function base for interpolation

* Dedupe coveringZoomStops method

* Fixup tests

* Fix CI errors (hidden within #if block)

3 files changed, 72 insertions, 18 deletions

diff --git a/platform/darwin/src/MGLSymbolStyleLayer.h b/platform/darwin/src/MGLSymbolStyleLayer.h
index 2c32b36c31..7040610093 100644
--- a/platform/darwin/src/MGLSymbolStyleLayer.h
+++ b/platform/darwin/src/MGLSymbolStyleLayer.h
@@ -537,6 +537,15 @@ MGL_EXPORT
  * `MGLCameraStyleFunction` with an interpolation mode of:
    * `MGLInterpolationModeExponential`
    * `MGLInterpolationModeInterval`
+ * `MGLSourceStyleFunction` with an interpolation mode of:
+   * `MGLInterpolationModeExponential`
+   * `MGLInterpolationModeInterval`
+   * `MGLInterpolationModeCategorical`
+   * `MGLInterpolationModeIdentity`
+ * `MGLCompositeStyleFunction` with an interpolation mode of:
+   * `MGLInterpolationModeExponential`
+   * `MGLInterpolationModeInterval`
+   * `MGLInterpolationModeCategorical`
  */
 @property (nonatomic, null_resettable) MGLStyleValue<NSNumber *> *iconScale;
 
@@ -919,6 +928,15 @@ MGL_EXPORT
  * `MGLCameraStyleFunction` with an interpolation mode of:
    * `MGLInterpolationModeExponential`
    * `MGLInterpolationModeInterval`
+ * `MGLSourceStyleFunction` with an interpolation mode of:
+   * `MGLInterpolationModeExponential`
+   * `MGLInterpolationModeInterval`
+   * `MGLInterpolationModeCategorical`
+   * `MGLInterpolationModeIdentity`
+ * `MGLCompositeStyleFunction` with an interpolation mode of:
+   * `MGLInterpolationModeExponential`
+   * `MGLInterpolationModeInterval`
+   * `MGLInterpolationModeCategorical`
  */
 @property (nonatomic, null_resettable) MGLStyleValue<NSNumber *> *textFontSize;
 
diff --git a/platform/darwin/src/MGLSymbolStyleLayer.mm b/platform/darwin/src/MGLSymbolStyleLayer.mm
index c01877f8dc..0f7953311e 100644
--- a/platform/darwin/src/MGLSymbolStyleLayer.mm
+++ b/platform/darwin/src/MGLSymbolStyleLayer.mm
@@ -356,7 +356,7 @@ namespace mbgl {
 - (void)setIconScale:(MGLStyleValue<NSNumber *> *)iconScale {
     MGLAssertStyleLayerIsValid();
 
-    auto mbglValue = MGLStyleValueTransformer<float, NSNumber *>().toInterpolatablePropertyValue(iconScale);
+    auto mbglValue = MGLStyleValueTransformer<float, NSNumber *>().toDataDrivenPropertyValue(iconScale);
     self.rawLayer->setIconSize(mbglValue);
 }
 
@@ -365,9 +365,9 @@ namespace mbgl {
 
     auto propertyValue = self.rawLayer->getIconSize();
     if (propertyValue.isUndefined()) {
-        return MGLStyleValueTransformer<float, NSNumber *>().toStyleValue(self.rawLayer->getDefaultIconSize());
+        return MGLStyleValueTransformer<float, NSNumber *>().toDataDrivenStyleValue(self.rawLayer->getDefaultIconSize());
     }
-    return MGLStyleValueTransformer<float, NSNumber *>().toStyleValue(propertyValue);
+    return MGLStyleValueTransformer<float, NSNumber *>().toDataDrivenStyleValue(propertyValue);
 }
 
 - (void)setIconSize:(MGLStyleValue<NSNumber *> *)iconSize {
@@ -657,7 +657,7 @@ namespace mbgl {
 - (void)setTextFontSize:(MGLStyleValue<NSNumber *> *)textFontSize {
     MGLAssertStyleLayerIsValid();
 
-    auto mbglValue = MGLStyleValueTransformer<float, NSNumber *>().toInterpolatablePropertyValue(textFontSize);
+    auto mbglValue = MGLStyleValueTransformer<float, NSNumber *>().toDataDrivenPropertyValue(textFontSize);
     self.rawLayer->setTextSize(mbglValue);
 }
 
@@ -666,9 +666,9 @@ namespace mbgl {
 
     auto propertyValue = self.rawLayer->getTextSize();
     if (propertyValue.isUndefined()) {
-        return MGLStyleValueTransformer<float, NSNumber *>().toStyleValue(self.rawLayer->getDefaultTextSize());
+        return MGLStyleValueTransformer<float, NSNumber *>().toDataDrivenStyleValue(self.rawLayer->getDefaultTextSize());
     }
-    return MGLStyleValueTransformer<float, NSNumber *>().toStyleValue(propertyValue);
+    return MGLStyleValueTransformer<float, NSNumber *>().toDataDrivenStyleValue(propertyValue);
 }
 
 - (void)setTextSize:(MGLStyleValue<NSNumber *> *)textSize {
diff --git a/platform/darwin/test/MGLSymbolStyleLayerTests.mm b/platform/darwin/test/MGLSymbolStyleLayerTests.mm
index eee61dd5d7..367ebf363c 100644
--- a/platform/darwin/test/MGLSymbolStyleLayerTests.mm
+++ b/platform/darwin/test/MGLSymbolStyleLayerTests.mm
@@ -405,7 +405,7 @@
 
         MGLStyleValue<NSNumber *> *constantStyleValue = [MGLStyleValue<NSNumber *> valueWithRawValue:@0xff];
         layer.iconScale = constantStyleValue;
-        mbgl::style::PropertyValue<float> propertyValue = { 0xff };
+        mbgl::style::DataDrivenPropertyValue<float> propertyValue = { 0xff };
         XCTAssertEqual(rawLayer->getIconSize(), propertyValue,
                        @"Setting iconScale to a constant value should update icon-size.");
         XCTAssertEqualObjects(layer.iconScale, constantStyleValue,
@@ -422,6 +422,29 @@
         XCTAssertEqualObjects(layer.iconScale, functionStyleValue,
                               @"iconScale should round-trip camera functions.");
 
+        functionStyleValue = [MGLStyleValue<NSNumber *> valueWithInterpolationMode:MGLInterpolationModeExponential sourceStops:@{@18: constantStyleValue} attributeName:@"keyName" options:nil];
+        layer.iconScale = functionStyleValue;
+
+        mbgl::style::ExponentialStops<float> exponentialStops = { {{18, 0xff}}, 1.0 };
+        propertyValue = mbgl::style::SourceFunction<float> { "keyName", exponentialStops };
+
+        XCTAssertEqual(rawLayer->getIconSize(), propertyValue,
+                       @"Setting iconScale to a source function should update icon-size.");
+        XCTAssertEqualObjects(layer.iconScale, functionStyleValue,
+                              @"iconScale should round-trip source functions.");
+
+        functionStyleValue = [MGLStyleValue<NSNumber *> valueWithInterpolationMode:MGLInterpolationModeExponential compositeStops:@{@10: @{@18: constantStyleValue}} attributeName:@"keyName" options:nil];
+        layer.iconScale = functionStyleValue;
+
+        std::map<float, float> innerStops { {18, 0xff} };
+        mbgl::style::CompositeExponentialStops<float> compositeStops { { {10.0, innerStops} }, 1.0 };
+
+        propertyValue = mbgl::style::CompositeFunction<float> { "keyName", compositeStops };
+
+        XCTAssertEqual(rawLayer->getIconSize(), propertyValue,
+                       @"Setting iconScale to a composite function should update icon-size.");
+        XCTAssertEqualObjects(layer.iconScale, functionStyleValue,
+                              @"iconScale should round-trip composite functions.");                                                                                                          
                               
 
         layer.iconScale = nil;
@@ -429,11 +452,6 @@
                       @"Unsetting iconScale should return icon-size to the default value.");
         XCTAssertEqualObjects(layer.iconScale, defaultStyleValue,
                               @"iconScale should return the default value after being unset.");
-
-        functionStyleValue = [MGLStyleValue<NSNumber *> valueWithInterpolationMode:MGLInterpolationModeIdentity sourceStops:nil attributeName:@"" options:nil];
-        XCTAssertThrowsSpecificNamed(layer.iconScale = functionStyleValue, NSException, NSInvalidArgumentException, @"MGLStyleValue should raise an exception if it is applied to a property that cannot support it");
-        functionStyleValue = [MGLStyleValue<NSNumber *> valueWithInterpolationMode:MGLInterpolationModeInterval compositeStops:@{@18: constantStyleValue} attributeName:@"" options:nil];
-        XCTAssertThrowsSpecificNamed(layer.iconScale = functionStyleValue, NSException, NSInvalidArgumentException, @"MGLStyleValue should raise an exception if it is applied to a property that cannot support it");
     }
 
     // icon-text-fit
@@ -952,7 +970,7 @@
 
         MGLStyleValue<NSNumber *> *constantStyleValue = [MGLStyleValue<NSNumber *> valueWithRawValue:@0xff];
         layer.textFontSize = constantStyleValue;
-        mbgl::style::PropertyValue<float> propertyValue = { 0xff };
+        mbgl::style::DataDrivenPropertyValue<float> propertyValue = { 0xff };
         XCTAssertEqual(rawLayer->getTextSize(), propertyValue,
                        @"Setting textFontSize to a constant value should update text-size.");
         XCTAssertEqualObjects(layer.textFontSize, constantStyleValue,
@@ -969,6 +987,29 @@
         XCTAssertEqualObjects(layer.textFontSize, functionStyleValue,
                               @"textFontSize should round-trip camera functions.");
 
+        functionStyleValue = [MGLStyleValue<NSNumber *> valueWithInterpolationMode:MGLInterpolationModeExponential sourceStops:@{@18: constantStyleValue} attributeName:@"keyName" options:nil];
+        layer.textFontSize = functionStyleValue;
+
+        mbgl::style::ExponentialStops<float> exponentialStops = { {{18, 0xff}}, 1.0 };
+        propertyValue = mbgl::style::SourceFunction<float> { "keyName", exponentialStops };
+
+        XCTAssertEqual(rawLayer->getTextSize(), propertyValue,
+                       @"Setting textFontSize to a source function should update text-size.");
+        XCTAssertEqualObjects(layer.textFontSize, functionStyleValue,
+                              @"textFontSize should round-trip source functions.");
+
+        functionStyleValue = [MGLStyleValue<NSNumber *> valueWithInterpolationMode:MGLInterpolationModeExponential compositeStops:@{@10: @{@18: constantStyleValue}} attributeName:@"keyName" options:nil];
+        layer.textFontSize = functionStyleValue;
+
+        std::map<float, float> innerStops { {18, 0xff} };
+        mbgl::style::CompositeExponentialStops<float> compositeStops { { {10.0, innerStops} }, 1.0 };
+
+        propertyValue = mbgl::style::CompositeFunction<float> { "keyName", compositeStops };
+
+        XCTAssertEqual(rawLayer->getTextSize(), propertyValue,
+                       @"Setting textFontSize to a composite function should update text-size.");
+        XCTAssertEqualObjects(layer.textFontSize, functionStyleValue,
+                              @"textFontSize should round-trip composite functions.");                                                                                                          
                               
 
         layer.textFontSize = nil;
@@ -976,11 +1017,6 @@
                       @"Unsetting textFontSize should return text-size to the default value.");
         XCTAssertEqualObjects(layer.textFontSize, defaultStyleValue,
                               @"textFontSize should return the default value after being unset.");
-
-        functionStyleValue = [MGLStyleValue<NSNumber *> valueWithInterpolationMode:MGLInterpolationModeIdentity sourceStops:nil attributeName:@"" options:nil];
-        XCTAssertThrowsSpecificNamed(layer.textFontSize = functionStyleValue, NSException, NSInvalidArgumentException, @"MGLStyleValue should raise an exception if it is applied to a property that cannot support it");
-        functionStyleValue = [MGLStyleValue<NSNumber *> valueWithInterpolationMode:MGLInterpolationModeInterval compositeStops:@{@18: constantStyleValue} attributeName:@"" options:nil];
-        XCTAssertThrowsSpecificNamed(layer.textFontSize = functionStyleValue, NSException, NSInvalidArgumentException, @"MGLStyleValue should raise an exception if it is applied to a property that cannot support it");
     }
 
     // text-ignore-placement