internal/graphicsdriver/opengl: reland: refactoring: remove usages of graphics.IndicesCount

Updates #2460

internal/graphics/vertex.go

@@ -48,7 +48,7 @@ const (
 )
 
 const (
-	IndicesCount     = (1 << 16) / 3 * 3 // Adjust num for triangles.
+	IndicesCount     = (1 << 16) / 3 * 3 // Adjust num for triangles. TODO: Remove this (#2460).
 	VertexFloatCount = 8
 )
 

internal/graphicsdriver/opengl/program.go

@@ -114,9 +114,13 @@ type openGLState struct {
 	// arrayBuffer is OpenGL's array buffer (vertices data).
 	arrayBuffer buffer
 
+	arrayBufferSizeInBytes int
+
 	// elementArrayBuffer is OpenGL's element array buffer (indices data).
 	elementArrayBuffer buffer
 
+	elementArrayBufferSizeInBytes int
+
 	lastProgram       program
 	lastUniforms      map[string][]uint32
 	lastActiveTexture int
@@ -145,19 +149,45 @@ func (s *openGLState) reset(context *context) error {
 		}
 	}
 	s.arrayBuffer = 0
+	s.arrayBufferSizeInBytes = 0
 	s.elementArrayBuffer = 0
+	s.elementArrayBufferSizeInBytes = 0
 
 	return nil
 }
 
-func (s *openGLState) setVertices(context *context, vertices []float32, indices []uint16) {
-	if s.arrayBuffer == 0 {
-		s.arrayBuffer = context.newArrayBuffer(graphics.IndicesCount * graphics.VertexFloatCount * floatSizeInBytes)
-		context.ctx.BindBuffer(gl.ARRAY_BUFFER, uint32(s.arrayBuffer))
+func pow2(x int) int {
+	p2 := 1
+	for p2 < x {
+		p2 *= 2
 	}
-	if s.elementArrayBuffer == 0 {
-		s.elementArrayBuffer = context.newElementArrayBuffer(graphics.IndicesCount * 2)
-		context.ctx.BindBuffer(gl.ELEMENT_ARRAY_BUFFER, uint32(s.elementArrayBuffer))
+	return p2
+}
+
+func (s *openGLState) setVertices(context *context, vertices []float32, indices []uint16) {
+	if size := len(vertices) * 4; s.arrayBufferSizeInBytes < size {
+		if s.arrayBuffer != 0 {
+			context.ctx.DeleteBuffer(uint32(s.arrayBuffer))
+		}
+
+		newSize := pow2(size)
+		// newArrayBuffer calls BindBuffer.
+		s.arrayBuffer = context.newArrayBuffer(newSize)
+		s.arrayBufferSizeInBytes = newSize
+
+		// Reenable the array buffer layout explicitly after resetting the array buffer.
+		theArrayBufferLayout.enable(context)
+	}
+
+	if size := len(indices) * 2; s.elementArrayBufferSizeInBytes < size {
+		if s.elementArrayBuffer != 0 {
+			context.ctx.DeleteBuffer(uint32(s.elementArrayBuffer))
+		}
+
+		newSize := pow2(size)
+		// newElementArrayBuffer calls BindBuffer.
+		s.elementArrayBuffer = context.newElementArrayBuffer(newSize)
+		s.elementArrayBufferSizeInBytes = newSize
 	}
 
 	// Note that the vertices and the indices passed to BufferSubData is not under GC management in the gl package.
@@ -213,9 +243,6 @@ func (g *Graphics) textureVariableName(idx int) string {
 func (g *Graphics) useProgram(program program, uniforms []uniformVariable, textures [graphics.ShaderImageCount]textureVariable) error {
 	if g.state.lastProgram != program {
 		g.context.ctx.UseProgram(uint32(program))
-		if g.state.lastProgram == 0 {
-			theArrayBufferLayout.enable(&g.context)
-		}
 
 		g.state.lastProgram = program
 		for k := range g.state.lastUniforms {