[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, 6 insertions, 4 deletions

diff --git a/src/mbgl/renderer/symbol_bucket.hpp b/src/mbgl/renderer/symbol_bucket.hpp
index 0b40bb34ae..dcf3f5f495 100644
--- a/src/mbgl/renderer/symbol_bucket.hpp
+++ b/src/mbgl/renderer/symbol_bucket.hpp
@@ -17,7 +17,7 @@ namespace mbgl {
 class SymbolBucket : public Bucket {
 public:
     SymbolBucket(style::SymbolLayoutProperties::Evaluated,
-                 const std::unordered_map<std::string, style::SymbolPaintProperties::Evaluated>&,
+                 const std::unordered_map<std::string, std::pair<style::IconPaintProperties::Evaluated, style::TextPaintProperties::Evaluated>>&,
                  float zoom,
                  bool sdfIcons,
                  bool iconsNeedLinear);
@@ -33,12 +33,14 @@ public:
     const bool sdfIcons;
     const bool iconsNeedLinear;
 
-    std::unordered_map<std::string, SymbolIconProgram::PaintPropertyBinders> paintPropertyBinders;
+    std::unordered_map<std::string, std::pair<
+        SymbolIconProgram::PaintPropertyBinders,
+        SymbolSDFTextProgram::PaintPropertyBinders>> paintPropertyBinders;
 
     struct TextBuffer {
         gl::VertexVector<SymbolLayoutVertex> vertices;
         gl::IndexVector<gl::Triangles> triangles;
-        gl::SegmentVector<SymbolAttributes> segments;
+        gl::SegmentVector<SymbolTextAttributes> segments;
 
         optional<gl::VertexBuffer<SymbolLayoutVertex>> vertexBuffer;
         optional<gl::IndexBuffer<gl::Triangles>> indexBuffer;
@@ -47,7 +49,7 @@ public:
     struct IconBuffer {
         gl::VertexVector<SymbolLayoutVertex> vertices;
         gl::IndexVector<gl::Triangles> triangles;
-        gl::SegmentVector<SymbolAttributes> segments;
+        gl::SegmentVector<SymbolIconAttributes> segments;
 
         optional<gl::VertexBuffer<SymbolLayoutVertex>> vertexBuffer;
         optional<gl::IndexBuffer<gl::Triangles>> indexBuffer;