[core] Use gl::Program to resolve some rough edges in the GL binding types

* Extract `ignore` util to separate header.
* `Segment` now tracks offset and length of indices, rather than primitives. This is more natural.
* Introduce `VertexVector` and `IndexVector` types. These types carry information about the intended draw mode (`Triangles`, `LineStrip`, etc.), and ensure that elements are always appended in a group size appropriate for that draw mode, for both indexed and unindexed rendering.
* `Program`, rather than `Drawable`, is now the unifying object for draw calls. `Program` is the best place to type check the draw call, because it is typed to carry information about the intended primitive, vertex type, attributes, and uniforms.
* Use the debug shaders for debug tile rendering, like gl-js.
* Fix the draw mode for background. It was drawing triangle strips with a triangles array. Surprised this didn’t cause issues. Now it’s type checked.

1 files changed, 34 insertions, 20 deletions

diff --git a/src/mbgl/renderer/painter.cpp b/src/mbgl/renderer/painter.cpp
index d9e7f9fd35..a09e3b73fc 100644
--- a/src/mbgl/renderer/painter.cpp
+++ b/src/mbgl/renderer/painter.cpp
@@ -41,30 +41,44 @@ namespace mbgl {
 
 using namespace style;
 
-Painter::Painter(gl::Context& context_, const TransformState& state_)
-    : context(context_),
-      state(state_),
-      tileTriangleVertexBuffer(context.createVertexBuffer(std::vector<FillVertex> {{
+static gl::VertexVector<FillVertex, gl::Triangles> tileTriangles() {
+    gl::VertexVector<FillVertex, gl::Triangles> result;
+    result.emplace_back(
             FillAttributes::vertex({ 0,            0 }),
             FillAttributes::vertex({ util::EXTENT, 0 }),
-            FillAttributes::vertex({ 0, util::EXTENT }),
-            FillAttributes::vertex({ util::EXTENT, 0 }),
-            FillAttributes::vertex({ 0, util::EXTENT }),
-            FillAttributes::vertex({ util::EXTENT, util::EXTENT })
-      }})),
-      tileLineStripVertexBuffer(context.createVertexBuffer(std::vector<FillVertex> {{
-            FillAttributes::vertex({ 0, 0 }),
+            FillAttributes::vertex({ 0, util::EXTENT }));
+    result.emplace_back(
             FillAttributes::vertex({ util::EXTENT, 0 }),
-            FillAttributes::vertex({ util::EXTENT, util::EXTENT }),
             FillAttributes::vertex({ 0, util::EXTENT }),
-            FillAttributes::vertex({ 0, 0 })
-      }})),
-      rasterVertexBuffer(context.createVertexBuffer(std::vector<RasterVertex> {{
-            RasterProgram::vertex({ 0, 0 }, { 0, 0 }),
-            RasterProgram::vertex({ util::EXTENT, 0 }, { 32767, 0 }),
-            RasterProgram::vertex({ 0, util::EXTENT }, { 0, 32767 }),
-            RasterProgram::vertex({ util::EXTENT, util::EXTENT }, { 32767, 32767 })
-      }})) {
+            FillAttributes::vertex({ util::EXTENT, util::EXTENT }));
+    return result;
+}
+
+static gl::VertexVector<FillVertex, gl::LineStrip> tileLineStrip() {
+    gl::VertexVector<FillVertex, gl::LineStrip> result;
+    result.emplace_back(FillAttributes::vertex({ 0, 0 }));
+    result.emplace_back(FillAttributes::vertex({ util::EXTENT, 0 }));
+    result.emplace_back(FillAttributes::vertex({ util::EXTENT, util::EXTENT }));
+    result.emplace_back(FillAttributes::vertex({ 0, util::EXTENT }));
+    result.emplace_back(FillAttributes::vertex({ 0, 0 }));
+    return result;
+}
+
+static gl::VertexVector<RasterVertex, gl::TriangleStrip> rasterTriangleStrip() {
+    gl::VertexVector<RasterVertex, gl::TriangleStrip> result;
+    result.emplace_back(RasterProgram::vertex({ 0, 0 }, { 0, 0 }));
+    result.emplace_back(RasterProgram::vertex({ util::EXTENT, 0 }, { 32767, 0 }));
+    result.emplace_back(RasterProgram::vertex({ 0, util::EXTENT }, { 0, 32767 }));
+    result.emplace_back(RasterProgram::vertex({ util::EXTENT, util::EXTENT }, { 32767, 32767 }));
+    return result;
+}
+
+Painter::Painter(gl::Context& context_, const TransformState& state_)
+    : context(context_),
+      state(state_),
+      tileTriangleVertexBuffer(context.createVertexBuffer(tileTriangles())),
+      tileLineStripVertexBuffer(context.createVertexBuffer(tileLineStrip())),
+      rasterVertexBuffer(context.createVertexBuffer(rasterTriangleStrip())) {
 #ifndef NDEBUG
     gl::debugging::enable();
 #endif