alpha patterns

internal/generator/v210a_test.go

@@ -0,0 +1,116 @@
+package generator
+
+import (
+	"errors"
+	"strings"
+	"testing"
+)
+
+type fakeFrameGenerator struct {
+	generateErr error
+	closeErr    error
+	closed      bool
+	calls       int
+}
+
+func (g *fakeFrameGenerator) GenerateFrame(dst []byte, frameIndex int) error {
+	g.calls++
+	if g.generateErr != nil {
+		return g.generateErr
+	}
+	for i := range dst {
+		dst[i] = byte(frameIndex)
+	}
+	return nil
+}
+
+func (g *fakeFrameGenerator) Close() error {
+	g.closed = true
+	return g.closeErr
+}
+
+func TestV210AGeneratorLayoutAndAlpha(t *testing.T) {
+	const width, height = 304, 200
+	fill := &fakeFrameGenerator{}
+	g, err := NewV210AGenerator(fill, width, height)
+	if err != nil {
+		t.Fatalf("NewV210AGenerator: %v", err)
+	}
+	dst := make([]byte, V210AFrameSize(width, height))
+	if err := g.GenerateFrame(dst, 7); err != nil {
+		t.Fatalf("GenerateFrame: %v", err)
+	}
+
+	fillSize := V210FrameSize(width, height)
+	for i, b := range dst[:fillSize] {
+		if b != 7 {
+			t.Fatalf("fill byte %d = %#x, want 0x07", i, b)
+		}
+	}
+	alpha := dst[fillSize:]
+	if got := sampleAlpha(alpha, width, width/2, height/2); got != alphaTransparent {
+		t.Errorf("square center = %d, want transparent %d", got, alphaTransparent)
+	}
+	if got := sampleAlpha(alpha, width, 10, height/2); got != alphaOpaque {
+		t.Errorf("outside square = %d, want opaque %d", got, alphaOpaque)
+	}
+}
+
+func TestV210AGeneratorRestoresAlphaBase(t *testing.T) {
+	const width, height = 304, 200
+	g, err := NewV210AGenerator(&fakeFrameGenerator{}, width, height)
+	if err != nil {
+		t.Fatalf("NewV210AGenerator: %v", err)
+	}
+	dst := make([]byte, V210AFrameSize(width, height))
+	if err := g.GenerateFrame(dst, 0); err != nil {
+		t.Fatalf("GenerateFrame(0): %v", err)
+	}
+	alpha := dst[V210FrameSize(width, height):]
+	if got := sampleAlpha(alpha, width, width/2, height/2); got != alphaTransparent {
+		t.Fatalf("frame 0 center = %d, want transparent %d", got, alphaTransparent)
+	}
+
+	if err := g.GenerateFrame(dst, 79); err != nil {
+		t.Fatalf("GenerateFrame(79): %v", err)
+	}
+	if got := sampleAlpha(alpha, width, width/2, height/2); got != alphaOpaque {
+		t.Errorf("old square position = %d, want restored opaque %d", got, alphaOpaque)
+	}
+	if got := sampleAlpha(alpha, width, 250, height/2); got != alphaTransparent {
+		t.Errorf("new square position = %d, want transparent %d", got, alphaTransparent)
+	}
+}
+
+func TestV210AGeneratorErrors(t *testing.T) {
+	if _, err := NewV210AGenerator(nil, 1920, 1080); err == nil || !strings.Contains(err.Error(), "nil") {
+		t.Fatalf("nil fill error = %v", err)
+	}
+
+	fillErr := errors.New("fill failed")
+	g, err := NewV210AGenerator(&fakeFrameGenerator{generateErr: fillErr}, 100, 20)
+	if err != nil {
+		t.Fatalf("NewV210AGenerator: %v", err)
+	}
+	if err := g.GenerateFrame(make([]byte, V210AFrameSize(100, 20)-1), 0); err == nil || !strings.Contains(err.Error(), "too small") {
+		t.Fatalf("small destination error = %v", err)
+	}
+	if err := g.GenerateFrame(make([]byte, V210AFrameSize(100, 20)), 3); !errors.Is(err, fillErr) {
+		t.Fatalf("fill error = %v, want wrapped %v", err, fillErr)
+	}
+}
+
+func TestV210AGeneratorClosesFill(t *testing.T) {
+	closeErr := errors.New("close failed")
+	fill := &fakeFrameGenerator{closeErr: closeErr}
+	g, err := NewV210AGenerator(fill, 100, 20)
+	if err != nil {
+		t.Fatalf("NewV210AGenerator: %v", err)
+	}
+	if err := g.Close(); !errors.Is(err, closeErr) {
+		t.Fatalf("Close = %v, want %v", err, closeErr)
+	}
+	if !fill.closed {
+		t.Fatal("wrapped fill generator was not closed")
+	}
+}