internal/shader: bug fix: failed to return an array in HLSL

Closes #2923

internal/shader/shader.go

@@ -740,7 +740,9 @@ func (cs *compileState) parseFuncParams(block *block, fname string, d *ast.FuncD
 		}
 	}
 
-	if len(out) == 1 && out[0].name == "" {
+	// If there is only one returning value, it is treated as a returning value.
+	// An array cannot be a returning value, especially for HLSL (#2923).
+	if len(out) == 1 && out[0].name == "" && out[0].typ.Main != shaderir.Array {
 		ret = out[0].typ
 		out = nil
 	}

internal/shader/testdata/array.expected.vs

@@ -1,25 +1,29 @@
 uniform vec2 U0[4];
 
-vec2[2] F0(void);
-vec2[2] F1(void);
+void F0(out vec2 l0[2]);
+void F1(out vec2 l0[2]);
 
-vec2[2] F0(void) {
-	vec2 l0[2];
-	l0[0] = vec2(0);
-	l0[1] = vec2(0);
-	return l0;
-}
-
-vec2[2] F1(void) {
-	vec2 l0[2];
-	l0[0] = vec2(0);
-	l0[1] = vec2(0);
+void F0(out vec2 l0[2]) {
 	vec2 l1[2];
 	l1[0] = vec2(0);
 	l1[1] = vec2(0);
-	(l0)[0] = vec2(1.0);
-	l1[0] = l0[0];
-	l1[1] = l0[1];
-	(l1)[1] = vec2(2.0);
-	return l1;
+	l0[0] = l1[0];
+	l0[1] = l1[1];
+	return;
+}
+
+void F1(out vec2 l0[2]) {
+	vec2 l1[2];
+	l1[0] = vec2(0);
+	l1[1] = vec2(0);
+	vec2 l2[2];
+	l2[0] = vec2(0);
+	l2[1] = vec2(0);
+	(l1)[0] = vec2(1.0);
+	l2[0] = l1[0];
+	l2[1] = l1[1];
+	(l2)[1] = vec2(2.0);
+	l0[0] = l2[0];
+	l0[1] = l2[1];
+	return;
 }

internal/shader/testdata/array2.expected.metal

@@ -1,11 +1,12 @@
-array<float2, 3> F0(void);
+void F0(thread array<float2, 3>& l0);
 
-array<float2, 3> F0(void) {
-	array<float2, 2> l0 = {};
-	array<float2, 3> l1 = {};
+void F0(thread array<float2, 3>& l0) {
+	array<float2, 2> l1 = {};
+	array<float2, 3> l2 = {};
 	{
-		array<float2, 2> l1 = {};
-		l1 = l0;
+		array<float2, 2> l2 = {};
+		l2 = l1;
 	}
-	return l1;
+	l0 = l2;
+	return;
 }

internal/shader/testdata/array2.expected.vs

@@ -1,19 +1,22 @@
-vec2[3] F0(void);
+void F0(out vec2 l0[3]);
 
-vec2[3] F0(void) {
-	vec2 l0[2];
-	l0[0] = vec2(0);
-	l0[1] = vec2(0);
-	vec2 l1[3];
+void F0(out vec2 l0[3]) {
+	vec2 l1[2];
 	l1[0] = vec2(0);
 	l1[1] = vec2(0);
-	l1[2] = vec2(0);
+	vec2 l2[3];
+	l2[0] = vec2(0);
+	l2[1] = vec2(0);
+	l2[2] = vec2(0);
 	{
-		vec2 l1[2];
-		l1[0] = vec2(0);
-		l1[1] = vec2(0);
-		l1[0] = l0[0];
-		l1[1] = l0[1];
+		vec2 l2[2];
+		l2[0] = vec2(0);
+		l2[1] = vec2(0);
+		l2[0] = l1[0];
+		l2[1] = l1[1];
 	}
-	return l1;
+	l0[0] = l2[0];
+	l0[1] = l2[1];
+	l0[2] = l2[2];
+	return;
 }

internal/shader/testdata/issue2840.expected.vs

@@ -1,16 +1,18 @@
-float[1] F0(void);
-int[1] F1(void);
+void F0(out float l0[1]);
+void F1(out int l0[1]);
 
-float[1] F0(void) {
-	float l0[1];
-	l0[0] = float(0);
-	(l0)[0] = 1.0;
-	return l0;
+void F0(out float l0[1]) {
+	float l1[1];
+	l1[0] = float(0);
+	(l1)[0] = 1.0;
+	l0[0] = l1[0];
+	return;
 }
 
-int[1] F1(void) {
-	int l0[1];
-	l0[0] = 0;
-	(l0)[0] = 1;
-	return l0;
+void F1(out int l0[1]) {
+	int l1[1];
+	l1[0] = 0;
+	(l1)[0] = 1;
+	l0[0] = l1[0];
+	return;
 }

shader_test.go

@@ -2394,3 +2394,38 @@ func Fragment(dstPos vec4, srcPos vec2, color vec4) vec4 {
 		}
 	}
 }
+
+// Issue #2923
+func TestShaderReturnArray(t *testing.T) {
+	const w, h = 16, 16
+
+	dst := ebiten.NewImage(w, h)
+	s, err := ebiten.NewShader([]byte(`//kage:unit pixels
+
+package main
+
+func foo() [4]float {
+	return [4]float{0.25, 0.5, 0.75, 1}
+}
+
+func Fragment(dstPos vec4, srcPos vec2, color vec4) vec4 {
+	a := foo()
+	return vec4(a[0], a[1], a[2], a[3])
+}
+`))
+	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{R: 0x40, G: 0x80, B: 0xc0, A: 0xff}
+			if !sameColors(got, want, 2) {
+				t.Errorf("dst.At(%d, %d): got: %v, want: %v", i, j, got, want)
+			}
+		}
+	}
+}