feat: Windows (CF_DIB) and macOS (AppleScript) clipboard image sync

internal/clipboard/dib_windows_test.go

@@ -0,0 +1,72 @@
+//go:build windows
+
+package clipboard
+
+import (
+	"bytes"
+	"image"
+	"image/color"
+	"image/png"
+	"testing"
+)
+
+func TestDIBRoundTrip(t *testing.T) {
+	// Build a small 4x3 RGBA image with distinct corner colors.
+	img := image.NewRGBA(image.Rect(0, 0, 4, 3))
+	img.Set(0, 0, color.RGBA{255, 0, 0, 255})   // red
+	img.Set(3, 0, color.RGBA{0, 255, 0, 255})   // green
+	img.Set(0, 2, color.RGBA{0, 0, 255, 255})   // blue
+	img.Set(3, 2, color.RGBA{255, 255, 0, 128}) // semi-transparent yellow
+
+	var buf bytes.Buffer
+	if err := png.Encode(&buf, img); err != nil {
+		t.Fatalf("png.Encode: %v", err)
+	}
+	pngData := buf.Bytes()
+
+	dib, err := pngToDIB(pngData)
+	if err != nil {
+		t.Fatalf("pngToDIB: %v", err)
+	}
+	got, err := dibToPNG(dib)
+	if err != nil {
+		t.Fatalf("dibToPNG: %v", err)
+	}
+
+	decoded, err := png.Decode(bytes.NewReader(got))
+	if err != nil {
+		t.Fatalf("decode round-trip: %v", err)
+	}
+	if decoded.Bounds() != img.Bounds() {
+		t.Errorf("bounds = %v, want %v", decoded.Bounds(), img.Bounds())
+	}
+
+	// Spot-check the corner colors survived the round-trip.
+	for _, tc := range []struct {
+		x, y int
+		want color.RGBA
+	}{
+		{0, 0, color.RGBA{255, 0, 0, 255}},
+		{3, 0, color.RGBA{0, 255, 0, 255}},
+		{0, 2, color.RGBA{0, 0, 255, 255}},
+	} {
+		r, g, b, a := decoded.At(tc.x, tc.y).RGBA()
+		got := color.RGBA{uint8(r >> 8), uint8(g >> 8), uint8(b >> 8), uint8(a >> 8)}
+		if got != tc.want {
+			t.Errorf("pixel (%d,%d) = %v, want %v", tc.x, tc.y, got, tc.want)
+		}
+	}
+}
+
+func TestDIBRejectsUnsupportedCompression(t *testing.T) {
+	dib := make([]byte, 44)
+	dib[14] = 32 // biBitCount
+	// biCompression = BI_RLE8 (1) at offset 16
+	dib[16] = 1
+	dib[4] = 1 // width 1
+	dib[8] = 1 // height 1
+
+	if _, err := dibToPNG(dib); err == nil {
+		t.Error("expected error for unsupported compression, got nil")
+	}
+}