[core] Add Projection matrix to CustomLayerRenderParameters to transform web mercator world coordinates to GL coordinates.

include/mbgl/style/layers/custom_layer.hpp

@@ -2,6 +2,8 @@
 
 #include <mbgl/style/layer.hpp>
 
+#include <array>
+
 namespace mbgl {
 namespace style {
 
@@ -17,6 +19,7 @@ struct CustomLayerRenderParameters {
     double bearing;
     double pitch;
     double fieldOfView;
+    std::array<double, 16> projectionMatrix;
 };
 
 class CustomLayerHost {

src/mbgl/renderer/layers/render_custom_layer.cpp

@@ -6,6 +6,7 @@
 #include <mbgl/style/layers/custom_layer_impl.hpp>
 #include <mbgl/map/transform_state.hpp>
 #include <mbgl/gl/gl.hpp>
+#include <mbgl/util/mat4.hpp>
 
 namespace mbgl {
 
@@ -72,6 +73,9 @@ void RenderCustomLayer::render(PaintParameters& paintParameters, RenderSource*)
     parameters.bearing = -state.getAngle() * util::RAD2DEG;
     parameters.pitch = state.getPitch();
     parameters.fieldOfView = state.getFieldOfView();
+    mat4 projMatrix;
+    state.getProjMatrix(projMatrix);
+    parameters.projectionMatrix = projMatrix;
 
     MBGL_CHECK_ERROR(host->render(parameters));