1 files changed, 63 insertions, 9 deletions

diff --git a/gui/internal/model/preview_test.go b/gui/internal/model/preview_test.go
index b620a92..388ff7b 100644
--- a/gui/internal/model/preview_test.go
+++ b/gui/internal/model/preview_test.go
@@ -27,21 +27,21 @@ func TestPreviewKinds(t *testing.T) {
 	binary := write("a.bin", []byte{0, 1, 2, 3, 0})
 	tmp := t.TempDir()
 
-	if p := MakePreview(context.Background(), text, tmp); p.Kind != PreviewText ||
+	if p := MakePreview(context.Background(), text, tmp, 0); p.Kind != PreviewText ||
 		!strings.Contains(p.Text, "second line") {
 		t.Errorf("text preview = %+v", p)
 	}
-	if p := MakePreview(context.Background(), png, tmp); p.Kind != PreviewImage || p.Image != png {
+	if p := MakePreview(context.Background(), png, tmp, 0); p.Kind != PreviewImage || p.Image != png {
 		t.Errorf("image preview = %+v", p)
 	}
-	if p := MakePreview(context.Background(), binary, tmp); p.Kind != PreviewNone ||
+	if p := MakePreview(context.Background(), binary, tmp, 0); p.Kind != PreviewNone ||
 		!strings.Contains(p.Note, "no preview") {
 		t.Errorf("binary preview = %+v", p)
 	}
-	if p := MakePreview(context.Background(), filepath.Join(dir, "gone.txt"), tmp); p.Kind != PreviewNone {
+	if p := MakePreview(context.Background(), filepath.Join(dir, "gone.txt"), tmp, 0); p.Kind != PreviewNone {
 		t.Errorf("a missing file = %+v", p)
 	}
-	if p := MakePreview(context.Background(), dir, tmp); p.Kind != PreviewNone {
+	if p := MakePreview(context.Background(), dir, tmp, 0); p.Kind != PreviewNone {
 		t.Errorf("a directory = %+v", p)
 	}
 }
@@ -59,7 +59,7 @@ func TestPreviewReadsOnly(t *testing.T) {
 	if err != nil {
 		t.Fatal(err)
 	}
-	MakePreview(context.Background(), p, t.TempDir())
+	MakePreview(context.Background(), p, t.TempDir(), 0)
 	after, err := os.Stat(p)
 	if err != nil {
 		t.Fatal(err)
@@ -86,7 +86,7 @@ func TestPreviewShowsOnlyTheHead(t *testing.T) {
 	if err := os.WriteFile(p, []byte(b.String()), 0o644); err != nil {
 		t.Fatal(err)
 	}
-	pv := MakePreview(context.Background(), p, t.TempDir())
+	pv := MakePreview(context.Background(), p, t.TempDir(), 0)
 	if pv.Kind != PreviewText {
 		t.Fatalf("preview = %+v", pv)
 	}
@@ -129,8 +129,8 @@ func TestPdfPreviewsDoNotMixUp(t *testing.T) {
 	second := pdf("second.pdf", "The second document")
 
 	tmp := t.TempDir()
-	a := MakePreview(context.Background(), first, tmp)
-	b := MakePreview(context.Background(), second, tmp)
+	a := MakePreview(context.Background(), first, tmp, 0)
+	b := MakePreview(context.Background(), second, tmp, 0)
 	if a.Kind != PreviewImage || b.Kind != PreviewImage {
 		t.Fatalf("previews = %+v, %+v", a, b)
 	}
@@ -152,3 +152,57 @@ func TestPdfPreviewsDoNotMixUp(t *testing.T) {
 		}
 	}
 }
+
+// pngSize reads a PNG's dimensions from its header, so a test can say how
+// large a page was rendered without decoding it.
+func pngSize(t *testing.T, path string) (w, h int) {
+	t.Helper()
+	data, err := os.ReadFile(path)
+	if err != nil || len(data) < 24 || string(data[1:4]) != "PNG" {
+		t.Fatalf("%s is not a PNG: %v", path, err)
+	}
+	be := func(b []byte) int {
+		return int(b[0])<<24 | int(b[1])<<16 | int(b[2])<<8 | int(b[3])
+	}
+	return be(data[16:20]), be(data[20:24])
+}
+
+// TestPreviewRendersToTheSizeAsked: a taller preview gets a larger page, so
+// dragging the pane open does not just magnify a small render (his request,
+// 2026-09-17).
+func TestPreviewRendersToTheSizeAsked(t *testing.T) {
+	if _, err := exec.LookPath("pdftoppm"); err != nil {
+		t.Skip("pdftoppm is not installed")
+	}
+	if _, err := exec.LookPath("groff"); err != nil {
+		t.Skip("groff is not installed, so there is nothing to make a PDF with")
+	}
+	dir := t.TempDir()
+	path := filepath.Join(dir, "doc.pdf")
+	f, err := os.Create(path)
+	if err != nil {
+		t.Fatal(err)
+	}
+	cmd := exec.Command("groff", "-Tpdf", "-ms")
+	cmd.Stdin = strings.NewReader(".TL\nA document\n")
+	cmd.Stdout = f
+	if err := cmd.Run(); err != nil {
+		f.Close()
+		t.Skipf("groff cannot write a PDF here: %v", err)
+	}
+	f.Close()
+
+	small := MakePreview(context.Background(), path, t.TempDir(), 200)
+	large := MakePreview(context.Background(), path, t.TempDir(), 900)
+	if small.Kind != PreviewImage || large.Kind != PreviewImage {
+		t.Fatalf("previews = %+v, %+v", small, large)
+	}
+	_, sh := pngSize(t, small.Image)
+	_, lh := pngSize(t, large.Image)
+	if lh <= sh {
+		t.Errorf("asking for a taller preview rendered %d px, no more than %d", lh, sh)
+	}
+	if sh < 700 {
+		t.Errorf("the smallest render is %d px, below the floor", sh)
+	}
+}