internal/shaderir/msl: bug fix: mod for a vector and a scalar didn't work

Updates #2029

internal/shaderir/msl/msl.go

@@ -54,8 +54,8 @@ using namespace metal;
 
 constexpr sampler texture_sampler{filter::nearest};
 
-template<typename T>
+template<typename T, typename U>
-T mod(T x, T y) {
+T mod(T x, U y) {
 	return x - y * floor(x/y);
 }`
 

shader_test.go

@@ -625,3 +625,32 @@ func Fragment(position vec4, texCoord vec2, color vec4) vec4 {
 		}
 	}
 }
+
+// Issue #2029
+func TestShaderModVectorAndFloat(t *testing.T) {
+	const w, h = 16, 16
+
+	dst := ebiten.NewImage(w, h)
+	s, err := ebiten.NewShader([]byte(`package main
+
+func Fragment(position vec4, texCoord vec2, color vec4) vec4 {
+	r := mod(vec3(0.25, 0.5, 0.75), 0.5)
+	return vec4(r, 1)
+}
+`))
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	dst.DrawRectShader(w, h, s, nil)
+
+	for j := 0; j < h; j++ {
+		for i := 0; i < w; i++ {
+			got := dst.At(i, j).(color.RGBA)
+			want := color.RGBA{0x40, 0, 0x40, 0xff}
+			if !sameColors(got, want, 2) {
+				t.Errorf("dst.At(%d, %d): got: %v, want: %v", i, j, got, want)
+			}
+		}
+	}
+}