gl_engine: use vertex array buffer and index buffer when render primitive

VAO is new object in modern GL API, which can split and manage vertex
buffer and attribute state. This is optional in GLES and is mandatory in
GL.

Also index buffer is faster then pass cpu data in GL draw call.

src/lib/gl_engine/tvgGlGeometry.cpp

@@ -29,6 +29,13 @@
 #define NORMALIZED_LEFT_3D -1.0f
 #define NORMALIZED_RIGHT_3D 1.0f
 
+GlGeometry::~GlGeometry()
+{
+    if (mVao) {
+        glDeleteVertexArrays(1, &mVao);
+    }
+}
+
 uint32_t GlGeometry::getPrimitiveCount()
 {
     return mPrimitives.size();
@@ -214,7 +221,8 @@ bool GlGeometry::tesselate(TVG_UNUSED const RenderShape& rshape, float viewWd, f
 void GlGeometry::disableVertex(uint32_t location)
 {
     GL_CHECK(glDisableVertexAttribArray(location));
-    mGpuBuffer->unbind(GlGpuBuffer::Target::ARRAY_BUFFER);
+    mVertexBuffer->unbind(GlGpuBuffer::Target::ARRAY_BUFFER);
+    mIndexBuffer->unbind(GlGpuBuffer::Target::ELEMENT_ARRAY_BUFFER);
 }
 
 
@@ -222,20 +230,27 @@ void GlGeometry::draw(const uint32_t location, const uint32_t primitiveIndex, Re
 {
     if (primitiveIndex >= mPrimitives.size()) return;
 
+    if (mVao == 0) glGenVertexArrays(1, &mVao);
+    glBindVertexArray(mVao);
+
     VertexDataArray& geometry = (flag == RenderUpdateFlag::Stroke) ? mPrimitives[primitiveIndex].mStroke : mPrimitives[primitiveIndex].mFill;
 
     updateBuffer(location, geometry);
-    GL_CHECK(glDrawElements(GL_TRIANGLES, geometry.indices.size(), GL_UNSIGNED_INT, geometry.indices.data()));
+
+    GL_CHECK(glVertexAttribPointer(location, 3, GL_FLOAT, GL_FALSE, sizeof(VertexData), 0));
+    GL_CHECK(glEnableVertexAttribArray(location));
+
+    GL_CHECK(glDrawElements(GL_TRIANGLES, geometry.indices.size(), GL_UNSIGNED_INT, 0));
 }
 
 
 void GlGeometry::updateBuffer(uint32_t location, const VertexDataArray& vertexArray)
 {
-    if (mGpuBuffer.get() == nullptr) mGpuBuffer = make_unique<GlGpuBuffer>();
+    if (mVertexBuffer == nullptr) mVertexBuffer = std::make_unique<GlGpuBuffer>();
+    if (mIndexBuffer == nullptr) mIndexBuffer = std::make_unique<GlGpuBuffer>();
 
-    mGpuBuffer->updateBufferData(GlGpuBuffer::Target::ARRAY_BUFFER, vertexArray.vertices.size() * sizeof(VertexData), vertexArray.vertices.data());
+    mVertexBuffer->updateBufferData(GlGpuBuffer::Target::ARRAY_BUFFER, vertexArray.vertices.size() * sizeof(VertexData), vertexArray.vertices.data());
-    GL_CHECK(glVertexAttribPointer(location, 3, GL_FLOAT, GL_FALSE, sizeof(VertexData), 0));
+    mIndexBuffer->updateBufferData(GlGpuBuffer::Target::ELEMENT_ARRAY_BUFFER, vertexArray.indices.size() * sizeof(uint32_t), vertexArray.indices.data());
-    GL_CHECK(glEnableVertexAttribArray(location));
 }
 
 

src/lib/gl_engine/tvgGlGeometry.h

@@ -266,6 +266,8 @@ class GlGeometry
 {
 public:
 
+    ~GlGeometry();
+
     uint32_t getPrimitiveCount();
     const GlSize getPrimitiveSize(const uint32_t primitiveIndex) const;
     bool decomposeOutline(const RenderShape& rshape);
@@ -290,7 +292,9 @@ private:
     void decomposeCubicCurve(GlPrimitive& primitve, const GlPoint &pt1, const GlPoint &cpt1, const GlPoint &cpt2, const GlPoint &pt2, GlPoint &min, GlPoint &max);
     void updateBuffer(const uint32_t location, const VertexDataArray& vertexArray);
 
-    unique_ptr<GlGpuBuffer> mGpuBuffer;
+    GLuint mVao = 0;
+    std::unique_ptr<GlGpuBuffer> mVertexBuffer;
+    std::unique_ptr<GlGpuBuffer> mIndexBuffer;
     vector<GlPrimitive>     mPrimitives;
     GlTransform             mTransform;
 };

src/lib/gl_engine/tvgGlGpuBuffer.h

@@ -31,7 +31,7 @@ public:
     enum class Target
     {
         ARRAY_BUFFER = GL_ARRAY_BUFFER,
-        ELEMENT_ARRAY_BUFFER = GL_ARRAY_BUFFER
+        ELEMENT_ARRAY_BUFFER = GL_ELEMENT_ARRAY_BUFFER,
     };
 
     GlGpuBuffer();