From 7767bcfdd88858a4e494c89b5b0b296db22f0e63 Mon Sep 17 00:00:00 2001
From: Hajime Hoshi <hajimehoshi@gmail.com>
Date: Sun, 28 Oct 2018 22:54:36 +0900
Subject: [PATCH] graphicsutil: Better allocation of vertices

---
 internal/graphicsutil/vertices.go | 25 ++++++++++++++++---------
 1 file changed, 16 insertions(+), 9 deletions(-)

diff --git a/internal/graphicsutil/vertices.go b/internal/graphicsutil/vertices.go
index 78f484485..d76ef773f 100644
--- a/internal/graphicsutil/vertices.go
+++ b/internal/graphicsutil/vertices.go
@@ -27,18 +27,25 @@ type verticesBackend struct {
 	head    int
 }
 
-func (v *verticesBackend) sliceForOneQuad() []float32 {
+func (v *verticesBackend) slice(n int) []float32 {
 	const num = 256
-	size := 4 * graphicscommand.VertexFloatNum()
-	if v.backend == nil {
-		v.backend = make([]float32, size*num)
+	if n > num {
+		panic("not reached")
 	}
-	s := v.backend[v.head : v.head+size]
-	v.head += size
-	if v.head+size > len(v.backend) {
+
+	need := n * graphicscommand.VertexFloatNum()
+	if v.head+need > len(v.backend) {
 		v.backend = nil
 		v.head = 0
 	}
+
+	if v.backend == nil {
+		size := 4 * graphicscommand.VertexFloatNum()
+		v.backend = make([]float32, size*num)
+	}
+
+	s := v.backend[v.head : v.head+need]
+	v.head += need
 	return s
 }
 
@@ -70,7 +77,7 @@ func QuadVertices(width, height int, sx0, sy0, sx1, sy1 int, a, b, c, d, tx, ty
 func quadVerticesImpl(x, y, u0, v0, u1, v1, a, b, c, d, tx, ty, cr, cg, cb, ca float32) []float32 {
 	// Specifying a range explicitly here is redundant but this helps optimization
 	// to eliminate boundry checks.
-	vs := theVerticesBackend.sliceForOneQuad()[0:40]
+	vs := theVerticesBackend.slice(4)[0:40]
 
 	ax, by, cx, dy := a*x, b*y, c*x, d*y
 
@@ -150,7 +157,7 @@ func Vertex(width, height int, dx, dy, sx, sy float32, cr, cg, cb, ca float32) [
 	//
 	// NaN would make more sense to represent an invalid state, but vertices including NaN values doesn't work on
 	// some machines (#696). Let's use negative numbers to represent such state.
-	vs := theVerticesBackend.sliceForOneQuad()[0:10]
+	vs := theVerticesBackend.slice(1)[0:10]
 	vs[0] = dx
 	vs[1] = dy
 	vs[2] = sx / wf