[core] Implement data-driven styling for {text,icon}-{color,opacity,halo-color,halo-blur,halo-width} (#7939)

* Add symbol dds attributes and adapt style code generation

* Update to mapbox-gl-js/master

* Refactor SymbolFeature as a subclass of GeometryTileFeature

Prepares for enabling DDS on symbol paint properties by allowing the
SymbolFeatures, which we keep around after constructing SymbolLayout,
to be used in evaluating data-driven paint properties later in the
layout process.

* Draft approach for splitting icon/text paint properties

The `Program` types are set up to bind GL attributes to each of the
data-driven paint properties specified in the `PaintProperties` type
provided.  Since `SymbolPaintProperties` specifies both `Text*` and
`Icon*` properties, the symbolIcon, symbolIconSDF, and symbolGlyph
programs each attempt to bind roughly double the number of attributes
that they actually need.

This change addresses this by:
- Adding the more specific `IconPaintProperties` and `TextPaintProperties` types, which are subsets of the full `SymbolPaintProperties`.
- The symbol layer continues to use its `SymbolPaintProperties paint` member to track layer property state, but it provides helpers that construct objects of each the specific `{Icon,Text}PaintProperties::Evaluated` type, for use by the painter.
- The three symbol programs instantiate `Program<>` using the appropriate `{Icon,Text}PaintProperties` type.

* check in generated style code

* Populate paint buffers for symbol DDS properties

* Address first round of review comments

* Refactor VectorTile{Layer,Feature} to explicitly share data

* Update submodule

1 files changed, 41 insertions, 15 deletions

diff --git a/src/mbgl/style/layers/symbol_layer_impl.cpp b/src/mbgl/style/layers/symbol_layer_impl.cpp
index 32547e465a..ff59b14d65 100644
--- a/src/mbgl/style/layers/symbol_layer_impl.cpp
+++ b/src/mbgl/style/layers/symbol_layer_impl.cpp
@@ -16,9 +16,14 @@ bool SymbolLayer::Impl::evaluate(const PropertyEvaluationParameters& parameters)
     // text-size and icon-size are layout properties but they also need to be evaluated as paint properties:
     iconSize = layout.evaluate<IconSize>(parameters);
     textSize = layout.evaluate<TextSize>(parameters);
-
-    passes = ((paint.evaluated.get<IconOpacity>() > 0 && (paint.evaluated.get<IconColor>().a > 0 || paint.evaluated.get<IconHaloColor>().a > 0) && iconSize > 0)
-           || (paint.evaluated.get<TextOpacity>() > 0 && (paint.evaluated.get<TextColor>().a > 0 || paint.evaluated.get<TextHaloColor>().a > 0) && textSize > 0))
+    
+    auto hasIconOpacity = paint.evaluated.get<IconColor>().constantOr(Color::black()).a > 0 ||
+        paint.evaluated.get<IconHaloColor>().constantOr(Color::black()).a > 0;
+    auto hasTextOpacity = paint.evaluated.get<TextColor>().constantOr(Color::black()).a > 0 ||
+        paint.evaluated.get<TextHaloColor>().constantOr(Color::black()).a > 0;
+    
+    passes = ((paint.evaluated.get<IconOpacity>().constantOr(1) > 0 && hasIconOpacity && iconSize > 0)
+           || (paint.evaluated.get<TextOpacity>().constantOr(1) > 0 && hasTextOpacity && textSize > 0))
         ? RenderPass::Translucent : RenderPass::None;
 
     return paint.hasTransition();
@@ -38,20 +43,43 @@ std::unique_ptr<SymbolLayout> SymbolLayer::Impl::createLayout(const BucketParame
                                           *spriteAtlas);
 }
 
-SymbolPropertyValues SymbolLayer::Impl::iconPropertyValues(const SymbolLayoutProperties::Evaluated& layout_) const {
-    return SymbolPropertyValues {
-        layout_.get<IconRotationAlignment>(), // icon-pitch-alignment is not yet implemented; inherit the rotation alignment
-        layout_.get<IconRotationAlignment>(),
-        layout_.get<IconSize>(),
+IconPaintProperties::Evaluated SymbolLayer::Impl::iconPaintProperties() const {
+    return IconPaintProperties::Evaluated {
         paint.evaluated.get<IconOpacity>(),
         paint.evaluated.get<IconColor>(),
         paint.evaluated.get<IconHaloColor>(),
         paint.evaluated.get<IconHaloWidth>(),
         paint.evaluated.get<IconHaloBlur>(),
         paint.evaluated.get<IconTranslate>(),
+        paint.evaluated.get<IconTranslateAnchor>()
+    };
+}
+
+TextPaintProperties::Evaluated SymbolLayer::Impl::textPaintProperties() const {
+    return TextPaintProperties::Evaluated {
+        paint.evaluated.get<TextOpacity>(),
+        paint.evaluated.get<TextColor>(),
+        paint.evaluated.get<TextHaloColor>(),
+        paint.evaluated.get<TextHaloWidth>(),
+        paint.evaluated.get<TextHaloBlur>(),
+        paint.evaluated.get<TextTranslate>(),
+        paint.evaluated.get<TextTranslateAnchor>()
+    };
+}
+
+
+SymbolPropertyValues SymbolLayer::Impl::iconPropertyValues(const SymbolLayoutProperties::Evaluated& layout_) const {
+    return SymbolPropertyValues {
+        layout_.get<IconRotationAlignment>(), // icon-pitch-alignment is not yet implemented; inherit the rotation alignment
+        layout_.get<IconRotationAlignment>(),
+        layout_.get<IconSize>(),
+        paint.evaluated.get<IconTranslate>(),
         paint.evaluated.get<IconTranslateAnchor>(),
         iconSize,
-        1.0f
+        1.0f,
+        paint.evaluated.get<IconHaloColor>().constantOr(Color::black()).a > 0 &&
+            paint.evaluated.get<IconHaloWidth>().constantOr(1),
+        paint.evaluated.get<IconColor>().constantOr(Color::black()).a > 0
     };
 }
 
@@ -60,15 +88,13 @@ SymbolPropertyValues SymbolLayer::Impl::textPropertyValues(const SymbolLayoutPro
         layout_.get<TextPitchAlignment>(),
         layout_.get<TextRotationAlignment>(),
         layout_.get<TextSize>(),
-        paint.evaluated.get<TextOpacity>(),
-        paint.evaluated.get<TextColor>(),
-        paint.evaluated.get<TextHaloColor>(),
-        paint.evaluated.get<TextHaloWidth>(),
-        paint.evaluated.get<TextHaloBlur>(),
         paint.evaluated.get<TextTranslate>(),
         paint.evaluated.get<TextTranslateAnchor>(),
         textSize,
-        24.0f
+        24.0f,
+        paint.evaluated.get<TextHaloColor>().constantOr(Color::black()).a > 0 &&
+            paint.evaluated.get<TextHaloWidth>().constantOr(1),
+        paint.evaluated.get<TextColor>().constantOr(Color::black()).a > 0
     };
 }