From 9319266c01da4e987fab773a20ce1a5d7f1b08a0 Mon Sep 17 00:00:00 2001
From: Hajime Hoshi <hajimehoshi@gmail.com>
Date: Thu, 15 Sep 2022 01:25:26 +0900
Subject: [PATCH] internal/atlas: add a benchmark for adjustDestinationPixel

---
 internal/atlas/export_test.go | 5 ++---
 internal/atlas/image.go       | 6 ++++++
 internal/atlas/image_test.go  | 6 ++++++
 3 files changed, 14 insertions(+), 3 deletions(-)

diff --git a/internal/atlas/export_test.go b/internal/atlas/export_test.go
index 92db960f7..807d093ba 100644
--- a/internal/atlas/export_test.go
+++ b/internal/atlas/export_test.go
@@ -59,6 +59,5 @@ func (i *Image) EnsureIsolatedForTesting() {
 	i.ensureIsolated()
 }
 
-func ResolveDeferredForTesting() {
-	resolveDeferred()
-}
+var ResolveDeferredForTesting = resolveDeferred
+var AdjustDestinationPixelForTesting = adjustDestinationPixel
diff --git a/internal/atlas/image.go b/internal/atlas/image.go
index aaefdb643..bbb314abc 100644
--- a/internal/atlas/image.go
+++ b/internal/atlas/image.go
@@ -799,6 +799,12 @@ func DumpImages(graphicsDriver graphicsdriver.Graphics, dir string) (string, err
 func adjustDestinationPixel(x float32) float32 {
 	// Avoid the center of the pixel, which is problematic (#929, #1171).
 	// Instead, align the vertices with about 1/3 pixels.
+	//
+	// The intention here is roughly this code:
+	//
+	//     float32(math.Floor((float64(x)+1.0/6.0)*3) / 3)
+	//
+	// The actual implementation is more optimized than the above implementation.
 	ix := float32(math.Floor(float64(x)))
 	frac := x - ix
 	switch {
diff --git a/internal/atlas/image_test.go b/internal/atlas/image_test.go
index 4eacbd885..24335a98b 100644
--- a/internal/atlas/image_test.go
+++ b/internal/atlas/image_test.go
@@ -737,4 +737,10 @@ func TestImageWritePixelsModify(t *testing.T) {
 	}
 }
 
+func BenchmarkAdjustPixel(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		atlas.AdjustDestinationPixelForTesting(float32(i) / 17)
+	}
+}
+
 // TODO: Add tests to extend image on an atlas out of the main loop