Make flamegraph SVG width responsive

2 files changed, 7 insertions, 4 deletions

diff --git a/internal/flamegraph/svgwriter.go b/internal/flamegraph/svgwriter.go
index b68f6d8..a2bc3ed 100644
--- a/internal/flamegraph/svgwriter.go
+++ b/internal/flamegraph/svgwriter.go
@@ -67,8 +67,8 @@ func WriteSVG(w io.Writer, t *trie, cfg SVGConfig) error {
 }
 
 func writeSVGHeader(bw *bufio.Writer, cfg SVGConfig, height int) error {
-	_, err := fmt.Fprintf(bw, `<svg xmlns="http://www.w3.org/2000/svg" width="%d" height="%d" viewBox="0 0 %d %d">`+"\n",
-		cfg.Width, height, cfg.Width, height)
+	_, err := fmt.Fprintf(bw, `<svg xmlns="http://www.w3.org/2000/svg" width="100%%" height="%d" viewBox="0 0 %d %d" preserveAspectRatio="xMinYMin meet">`+"\n",
+		height, cfg.Width, height)
 	if err != nil {
 		return err
 	}
diff --git a/internal/flamegraph/svgwriter_test.go b/internal/flamegraph/svgwriter_test.go
index 6fdbe3d..56f2c20 100644
--- a/internal/flamegraph/svgwriter_test.go
+++ b/internal/flamegraph/svgwriter_test.go
@@ -100,8 +100,11 @@ func TestWriteSVGInvalidConfigFallsBack(t *testing.T) {
 	cfg := SVGConfig{Title: "x", Width: 0, FrameHeight: 0, FontSize: 0, MinWidthPx: 0}
 	svg := renderSVGForTest(t, tr, cfg)
 
-	if !strings.Contains(svg, `width="1200"`) {
-		t.Fatalf("expected fallback width, got: %s", svg)
+	if !strings.Contains(svg, `width="100%"`) {
+		t.Fatalf("expected responsive svg width, got: %s", svg)
+	}
+	if !strings.Contains(svg, `viewBox="0 0 1200 `) {
+		t.Fatalf("expected fallback viewBox width, got: %s", svg)
 	}
 	if !strings.Contains(svg, "I/O Flame Graph") {
 		t.Fatalf("expected fallback title, got: %s", svg)