gui: a rendered PDF page per file, and Settings in the top right

2 files changed, 73 insertions, 2 deletions

diff --git a/gui/internal/model/preview.go b/gui/internal/model/preview.go
index 6ca029e..d2a2830 100644
--- a/gui/internal/model/preview.go
+++ b/gui/internal/model/preview.go
@@ -30,6 +30,10 @@ type Preview struct {
 	Image string // a file to show: the file itself, or a rendered page
 	Text  string
 	Note  string // what this is, or why there is nothing
+	// Dir is the directory a rendered page was written to, for the caller
+	// to remove once it is done with the image; "" when nothing was
+	// rendered and the file itself is being shown.
+	Dir string
 }
 
 // previewBytes is how much of a text file is read, and previewLines how
@@ -72,17 +76,28 @@ func MakePreview(ctx context.Context, path, tmp string) Preview {
 
 // pdfPreview renders the first page if poppler can, and falls back to the
 // document's text - the same pdftotext krino's own (content ...) tests use.
+//
+// Each render goes in a directory of its own. pdftoppm names its output
+// after the page number, so a shared directory would hold several files
+// called page-1.png and the wrong one could be picked up - which is what
+// happened: a preview showed the page of a PDF looked at earlier (his
+// report, 2026-09-17).
 func pdfPreview(ctx context.Context, path, tmp string, sz int64) Preview {
 	if _, err := exec.LookPath("pdftoppm"); err == nil {
-		out := filepath.Join(tmp, "page")
+		dir, err := os.MkdirTemp(tmp, "page-")
+		if err != nil {
+			return Preview{Note: err.Error()}
+		}
+		out := filepath.Join(dir, "page")
 		cmd := exec.CommandContext(ctx, "pdftoppm", "-png", "-f", "1", "-l", "1",
 			"-scale-to", "700", "--", path, out)
 		if err := cmd.Run(); err == nil {
 			if rendered := firstMatch(out + "*.png"); rendered != "" {
-				return Preview{Kind: PreviewImage, Image: rendered,
+				return Preview{Kind: PreviewImage, Image: rendered, Dir: dir,
 					Note: fmt.Sprintf("page 1, %s", size(sz))}
 			}
 		}
+		os.RemoveAll(dir)
 	}
 	if _, err := exec.LookPath("pdftotext"); err != nil {
 		return Preview{Note: fmt.Sprintf("PDF, %s - install poppler-utils to see it", size(sz))}
diff --git a/gui/internal/model/preview_test.go b/gui/internal/model/preview_test.go
index 8c19922..b620a92 100644
--- a/gui/internal/model/preview_test.go
+++ b/gui/internal/model/preview_test.go
@@ -5,6 +5,7 @@ package model
 import (
 	"context"
 	"os"
+	"os/exec"
 	"path/filepath"
 	"strings"
 	"testing"
@@ -96,3 +97,58 @@ func TestPreviewShowsOnlyTheHead(t *testing.T) {
 		t.Error("a cut file does not say it was cut")
 	}
 }
+
+// TestPdfPreviewsDoNotMixUp: two PDFs looked at one after the other each
+// get their own rendered page. pdftoppm names its file after the page
+// number, so previews sharing a directory would collide - one of his ended
+// up showing another document's cover.
+func TestPdfPreviewsDoNotMixUp(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()
+	pdf := func(name, text string) string {
+		p := filepath.Join(dir, name)
+		f, err := os.Create(p)
+		if err != nil {
+			t.Fatal(err)
+		}
+		defer f.Close()
+		cmd := exec.Command("groff", "-Tpdf", "-ms")
+		cmd.Stdin = strings.NewReader(".TL\n" + text + "\n")
+		cmd.Stdout = f
+		if err := cmd.Run(); err != nil {
+			t.Skipf("groff cannot write a PDF here: %v", err)
+		}
+		return p
+	}
+	first := pdf("first.pdf", "The first document")
+	second := pdf("second.pdf", "The second document")
+
+	tmp := t.TempDir()
+	a := MakePreview(context.Background(), first, tmp)
+	b := MakePreview(context.Background(), second, tmp)
+	if a.Kind != PreviewImage || b.Kind != PreviewImage {
+		t.Fatalf("previews = %+v, %+v", a, b)
+	}
+	if a.Image == b.Image {
+		t.Fatalf("both previews point at %s", a.Image)
+	}
+	sameBytes := func(x, y string) bool {
+		bx, err1 := os.ReadFile(x)
+		by, err2 := os.ReadFile(y)
+		return err1 == nil && err2 == nil && string(bx) == string(by)
+	}
+	if sameBytes(a.Image, b.Image) {
+		t.Error("the second preview is a copy of the first page rendered")
+	}
+	// The caller is told where to clean up.
+	for _, p := range []Preview{a, b} {
+		if p.Dir == "" {
+			t.Error("a rendered page comes with no directory to remove")
+		}
+	}
+}