[core] Use separate attribute component for line normals

Broadcom GPUs don't cope well with using the least significant bit for this.

3 files changed, 9 insertions, 6 deletions

diff --git a/src/mbgl/programs/attributes.hpp b/src/mbgl/programs/attributes.hpp
index 684d9d6099..3a38453d30 100644
--- a/src/mbgl/programs/attributes.hpp
+++ b/src/mbgl/programs/attributes.hpp
@@ -23,6 +23,7 @@ inline uint16_t packUint8Pair(T a, T b) {
 MBGL_DEFINE_ATTRIBUTE(int16_t, 2, a_pos);
 MBGL_DEFINE_ATTRIBUTE(int16_t, 2, a_extrude);
 MBGL_DEFINE_ATTRIBUTE(int16_t, 4, a_pos_offset);
+MBGL_DEFINE_ATTRIBUTE(int16_t, 3, a_pos_normal);
 MBGL_DEFINE_ATTRIBUTE(float, 3, a_projected_pos);
 MBGL_DEFINE_ATTRIBUTE(int16_t, 2, a_label_pos);
 MBGL_DEFINE_ATTRIBUTE(int16_t, 2, a_anchor_pos);
diff --git a/src/mbgl/programs/line_program.cpp b/src/mbgl/programs/line_program.cpp
index db5c916d32..f9e91f569f 100644
--- a/src/mbgl/programs/line_program.cpp
+++ b/src/mbgl/programs/line_program.cpp
@@ -10,7 +10,7 @@ namespace mbgl {
 
 using namespace style;
 
-static_assert(sizeof(LineLayoutVertex) == 8, "expected LineLayoutVertex size");
+static_assert(sizeof(LineLayoutVertex) == 10, "expected LineLayoutVertex size");
 
 template <class Values, class...Args>
 Values makeValues(const RenderLinePaintProperties::PossiblyEvaluated& properties,
diff --git a/src/mbgl/programs/line_program.hpp b/src/mbgl/programs/line_program.hpp
index ed4a09bf10..95b9362b85 100644
--- a/src/mbgl/programs/line_program.hpp
+++ b/src/mbgl/programs/line_program.hpp
@@ -30,7 +30,7 @@ MBGL_DEFINE_UNIFORM_VECTOR(float, 2, u_gl_units_to_pixels);
 } // namespace uniforms
 
 struct LineLayoutAttributes : gl::Attributes<
-    attributes::a_pos,
+    attributes::a_pos_normal,
     attributes::a_data<uint8_t, 4>>
 {};
 
@@ -50,14 +50,16 @@ public:
     /*
      * @param p vertex position
      * @param e extrude normal
-     * @param t texture normal
+     * @param round whether the vertex uses a round line cap
+     * @param up whether the line normal points up or down
      * @param dir direction of the line cap (-1/0/1)
      */
-    static LayoutVertex layoutVertex(Point<int16_t> p, Point<double> e, Point<bool> t, int8_t dir, int32_t linesofar = 0) {
+    static LayoutVertex layoutVertex(Point<int16_t> p, Point<double> e, bool round, bool up, int8_t dir, int32_t linesofar = 0) {
         return LayoutVertex {
             {{
-                static_cast<int16_t>((p.x * 2) | t.x),
-                static_cast<int16_t>((p.y * 2) | t.y)
+                p.x,
+                p.y,
+                static_cast<int16_t>(attributes::packUint8Pair(round ? 1 : 0, up ? 1 : 0))
             }},
             {{
                 // add 128 to store a byte in an unsigned byte