Add page spin to preview other pages

cbconvert.go

@@ -43,7 +43,7 @@ type Options struct {
 	NoUpscale bool
 	// Document rendering resolution in DPI (PDF, EPUB, etc.); 0 uses the default
 	DPI int
-	// 0=NearestNeighbor, 1=Box, 2=Linear, 3=MitchellNetravali, 4=CatmullRom, 6=Gaussian, 7=Lanczos
+	// 0=NearestNeighbor, 1=Box, 2=Linear, 3=MitchellNetravali, 4=CatmullRom, 5=Gaussian, 6=Lanczos
 	Filter int
 	// Do not convert the cover image
 	NoCover bool
@@ -410,7 +410,7 @@ func (c *Converter) Thumbnail(file File) error {
 	if c.Opts.Width > 0 || c.Opts.Height > 0 {
 		cover = c.resizeFit(cover)
 	} else {
-		cover = resize(cover, 256, 0, filters[c.Opts.Filter])
+		cover = resize(cover, 256, 0, resampleFilter(c.Opts.Filter))
 	}
 
 	var buf bytes.Buffer
@@ -542,15 +542,30 @@ func (c *Converter) Meta(fileName string) (any, error) {
 	return "", nil
 }
 
-// Preview returns image preview.
+// Preview returns the cover as an image preview.
 func (c *Converter) Preview(fileName string, fileInfo os.FileInfo, width, height int) (Image, error) {
-	var img Image
-
 	i, err := c.coverImage(fileName, fileInfo)
 	if err != nil {
-		return img, fmt.Errorf("%s: %w", fileName, err)
+		return Image{}, fmt.Errorf("%s: %w", fileName, err)
 	}
 
+	return c.previewImage(fileName, i, width, height)
+}
+
+// PreviewPage returns the page-th image (0-based) as an image preview.
+func (c *Converter) PreviewPage(fileName string, fileInfo os.FileInfo, page, width, height int) (Image, error) {
+	i, err := c.pageImage(fileName, fileInfo, page)
+	if err != nil {
+		return Image{}, fmt.Errorf("%s: %w", fileName, err)
+	}
+
+	return c.previewImage(fileName, i, width, height)
+}
+
+// previewImage applies the configured transforms and fits the result into width x height.
+func (c *Converter) previewImage(fileName string, i image.Image, width, height int) (Image, error) {
+	var img Image
+
 	i = c.imageTransform(i)
 
 	var w bytes.Buffer
@@ -563,15 +578,13 @@ func (c *Converter) Preview(fileName string, fileInfo os.FileInfo, width, height
 	img.Height = i.Bounds().Dy()
 	img.SizeHuman = humanize.IBytes(uint64(len(w.Bytes())))
 
-	r := bytes.NewReader(w.Bytes())
+	dec, err := c.imageDecode(bytes.NewReader(w.Bytes()))
-
-	dec, err := c.imageDecode(r)
 	if err != nil {
 		return img, fmt.Errorf("%s: %w", fileName, err)
 	}
 
 	if width != 0 && height != 0 {
-		dec = fit(dec, width, height, filters[c.Opts.Filter])
+		dec = fit(dec, width, height, resampleFilter(c.Opts.Filter))
 	}
 
 	img.Image = dec

cbconvert_cover.go

@@ -85,6 +85,132 @@ func (c *Converter) coverDirectory(dir string) (image.Image, error) {
 	return img, nil
 }
 
+// pageArchive extracts the page-th image (natural reading order) from an archive.
+func (c *Converter) pageArchive(fileName string, page int) (image.Image, error) {
+	contents, err := c.archiveList(fileName)
+	if err != nil {
+		return nil, fmt.Errorf("pageArchive: %w", err)
+	}
+
+	images := imagesFromSlice(contents)
+	sort.Sort(sortorder.Natural(images))
+
+	if page < 0 || page >= len(images) {
+		return nil, fmt.Errorf("pageArchive: page %d out of range (%d pages)", page+1, len(images))
+	}
+
+	data, err := c.archiveFile(fileName, images[page])
+	if err != nil {
+		return nil, fmt.Errorf("pageArchive: %w", err)
+	}
+
+	img, err := c.imageDecode(bytes.NewReader(data))
+	if err != nil {
+		return nil, fmt.Errorf("pageArchive: %w", err)
+	}
+
+	return img, nil
+}
+
+// pageDocument extracts the page-th rendered page from a document.
+func (c *Converter) pageDocument(fileName string, page int) (image.Image, error) {
+	doc, err := fitz.New(fileName)
+	if err != nil {
+		return nil, fmt.Errorf("pageDocument: %w", err)
+	}
+	defer doc.Close()
+
+	if page < 0 || page >= doc.NumPage() {
+		return nil, fmt.Errorf("pageDocument: page %d out of range (%d pages)", page+1, doc.NumPage())
+	}
+
+	img, err := doc.ImageDPI(page, c.renderDPI())
+	if err != nil {
+		return nil, fmt.Errorf("pageDocument: %w", err)
+	}
+
+	return img, nil
+}
+
+// pageDirectory extracts the page-th image (natural reading order) from a directory.
+func (c *Converter) pageDirectory(dir string, page int) (image.Image, error) {
+	contents, err := imagesFromPath(dir)
+	if err != nil {
+		return nil, fmt.Errorf("pageDirectory: %w", err)
+	}
+
+	images := imagesFromSlice(contents)
+	sort.Sort(sortorder.Natural(images))
+
+	if page < 0 || page >= len(images) {
+		return nil, fmt.Errorf("pageDirectory: page %d out of range (%d pages)", page+1, len(images))
+	}
+
+	file, err := os.Open(images[page])
+	if err != nil {
+		return nil, fmt.Errorf("pageDirectory: %w", err)
+	}
+	defer file.Close()
+
+	img, err := c.imageDecode(file)
+	if err != nil {
+		return nil, fmt.Errorf("pageDirectory: %w", err)
+	}
+
+	return img, nil
+}
+
+// pageImage returns the page-th image of a comic file, document or directory.
+func (c *Converter) pageImage(fileName string, fileInfo os.FileInfo, page int) (image.Image, error) {
+	var err error
+	var img image.Image
+
+	switch {
+	case fileInfo.IsDir():
+		img, err = c.pageDirectory(fileName, page)
+	case isDocument(fileName):
+		img, err = c.pageDocument(fileName, page)
+	case isArchive(fileName):
+		img, err = c.pageArchive(fileName, page)
+	}
+
+	if err != nil {
+		return nil, fmt.Errorf("pageImage: %w", err)
+	}
+
+	return img, nil
+}
+
+// PageCount returns the number of pages (images) in a comic file, document or directory.
+func (c *Converter) PageCount(fileName string, fileInfo os.FileInfo) (int, error) {
+	switch {
+	case fileInfo.IsDir():
+		contents, err := imagesFromPath(fileName)
+		if err != nil {
+			return 0, fmt.Errorf("PageCount: %w", err)
+		}
+
+		return len(imagesFromSlice(contents)), nil
+	case isDocument(fileName):
+		doc, err := fitz.New(fileName)
+		if err != nil {
+			return 0, fmt.Errorf("PageCount: %w", err)
+		}
+		defer doc.Close()
+
+		return doc.NumPage(), nil
+	case isArchive(fileName):
+		contents, err := c.archiveList(fileName)
+		if err != nil {
+			return 0, fmt.Errorf("PageCount: %w", err)
+		}
+
+		return len(imagesFromSlice(contents)), nil
+	}
+
+	return 0, nil
+}
+
 // coverName returns the filename that is the most likely to be the cover.
 func (c *Converter) coverName(images []string) string {
 	if len(images) == 0 {

cbconvert_image.go

@@ -38,6 +38,15 @@ var filters = map[int]transform.ResampleFilter{
 	lanczos:           transform.Lanczos,
 }
 
+// resampleFilter returns the resample filter for index i, falling back to Linear for an unknown index.
+func resampleFilter(i int) transform.ResampleFilter {
+	if f, ok := filters[i]; ok {
+		return f
+	}
+
+	return filters[linear]
+}
+
 func resize(img image.Image, width, height int, filter transform.ResampleFilter) *image.RGBA {
 	dstW, dstH := width, height
 
@@ -96,14 +105,14 @@ func withinBounds(img image.Image, width, height int) bool {
 // resizeFit resizes img to the configured width/height, honoring Fit and NoUpscale.
 func (c *Converter) resizeFit(img image.Image) image.Image {
 	if c.Opts.Fit {
-		return fit(img, c.Opts.Width, c.Opts.Height, filters[c.Opts.Filter])
+		return fit(img, c.Opts.Width, c.Opts.Height, resampleFilter(c.Opts.Filter))
 	}
 
 	if c.Opts.NoUpscale && withinBounds(img, c.Opts.Width, c.Opts.Height) {
 		return img
 	}
 
-	return resize(img, c.Opts.Width, c.Opts.Height, filters[c.Opts.Filter])
+	return resize(img, c.Opts.Width, c.Opts.Height, resampleFilter(c.Opts.Filter))
 }
 
 func rotate(img image.Image, angle float64) *image.RGBA {

cbconvert_test.go

@@ -211,6 +211,40 @@ func TestConvertDPI(t *testing.T) {
 	}
 }
 
+func TestPreviewPage(t *testing.T) {
+	for _, name := range []string{"testdata/test.cbz", "testdata/test.pdf"} {
+		conv := New(NewOptions())
+
+		files, err := conv.Files([]string{name})
+		if err != nil {
+			t.Fatal(err)
+		}
+		if len(files) != 1 {
+			t.Fatalf("%s: expected 1 file, got %d", name, len(files))
+		}
+		file := files[0]
+
+		n, err := conv.PageCount(file.Path, file.Stat)
+		if err != nil {
+			t.Fatal(err)
+		}
+		if n < 2 {
+			t.Fatalf("%s: expected >= 2 pages, got %d", name, n)
+		}
+
+		for _, page := range []int{0, 1, n - 1} {
+			img, err := conv.PreviewPage(file.Path, file.Stat, page, 0, 0)
+			if err != nil || img.Image == nil {
+				t.Fatalf("%s: page %d: img=%v err=%v", name, page, img.Image, err)
+			}
+		}
+
+		if _, err := conv.PreviewPage(file.Path, file.Stat, n, 0, 0); err == nil {
+			t.Errorf("%s: page %d (out of range) should error", name, n)
+		}
+	}
+}
+
 func TestConvertResize(t *testing.T) {
 	tmpDir, err := os.MkdirTemp(os.TempDir(), "cbc")
 	if err != nil {

cmd/cbconvert-gui/handlers.go

@@ -7,9 +7,10 @@ import (
 	"os"
 	"path/filepath"
 	"slices"
+	"sort"
 	"strconv"
-	"strings"
 
+	"github.com/fvbommel/sortorder"
 	"github.com/gen2brain/cbconvert"
 	"github.com/gen2brain/iup-go/iup"
 )
@@ -24,7 +25,7 @@ func selectRow(i int) {
 	iup.GetHandle("Table").SetAttribute("FOCUSCELL", fmt.Sprintf("%d:1", i+1))
 }
 
-// onSort re-syncs the files slice to the table's displayed order after a sort, so rows keep mapping to the right file.
+// onSort re-syncs the files slice to the table's displayed order after a sort.
 func onSort(ih iup.Ihandle, col int) int {
 	n := len(files)
 	if n < 2 {
@@ -73,16 +74,49 @@ func onSort(ih iup.Ihandle, col int) int {
 	return iup.DEFAULT
 }
 
-// appendFile adds a file as a new row to the table and the files slice.
+// addFiles appends files, natural-sorts the list, and rebuilds the table.
-func appendFile(file cbconvert.File) {
+func addFiles(fs []cbconvert.File) {
-	files = append(files, file)
+	if len(fs) == 0 {
+		return
+	}
+
+	wasEmpty := len(files) == 0
+
+	var selPath string
+	if index >= 0 && index < len(files) {
+		selPath = files[index].Path
+	}
+
+	files = append(files, fs...)
+	sort.Slice(files, func(i, j int) bool {
+		return sortorder.NaturalLess(files[i].Name, files[j].Name)
+	})
 
 	t := iup.GetHandle("Table")
-	lin := len(files)
+	t.SetAttribute("NUMLIN", strconv.Itoa(len(files)))
-	t.SetAttribute("NUMLIN", strconv.Itoa(lin))
+	for i, f := range files {
-	iup.SetAttributeId2(t, "", lin, 1, file.Name)
+		lin := i + 1
-	iup.SetAttributeId2(t, "", lin, 2, cbconvert.FileType(file.Path))
+		iup.SetAttributeId2(t, "", lin, 1, f.Name)
-	iup.SetAttributeId2(t, "", lin, 3, strconv.FormatFloat(float64(file.Stat.Size())/(1024*1024), 'f', 2, 64))
+		iup.SetAttributeId2(t, "", lin, 2, cbconvert.FileType(f.Path))
+		iup.SetAttributeId2(t, "", lin, 3, strconv.FormatFloat(float64(f.Stat.Size())/(1024*1024), 'f', 2, 64))
+	}
+
+	if wasEmpty {
+		selectRow(0)
+		setActive()
+		previewPost()
+
+		return
+	}
+
+	index = -1
+	for i, f := range files {
+		if f.Path == selPath {
+			selectRow(i)
+			break
+		}
+	}
+	setActive()
 }
 
 func previewPost() {
@@ -90,30 +124,77 @@ func previewPost() {
 		return
 	}
 
-	width, height := previewSize()
+	file := files[index]
-	iup.GetHandle("Loading").SetAttributes("VISIBLE=YES, START=YES")
+
-	if strings.ToLower(iup.GetGlobal("DRIVER")) == "motif" {
+	// On a new file, fetch the count first; the Page POSTMESSAGE handler clamps previewPage and renders.
-		iup.GetHandle("Preview").SetAttribute("IMAGE", "")
+	if file.Path != previewPath {
+		previewPath = file.Path
+		iup.GetHandle("Loading").SetAttributes("VISIBLE=YES, START=YES")
+		go pageCountPost(file)
+
+		return
 	}
 
+	previewRender()
+}
+
+// previewRenderSize is the size the cover is rendered at.
+const previewRenderSize = 1200
+
+// previewRender renders the current file at previewPage off the UI thread.
+func previewRender() {
+	if index == -1 || len(files) == 0 {
+		return
+	}
+
+	file := files[index]
+
+	iup.GetHandle("Loading").SetAttributes("VISIBLE=YES, START=YES")
+
 	opts := options()
+	page := previewPage
 
 	go func(opts cbconvert.Options) {
 		conv := cbconvert.New(opts)
 
 		var s string
-		file := files[index]
 
-		img, err := conv.Preview(file.Path, file.Stat, width, height)
+		img, err := conv.PreviewPage(file.Path, file.Stat, page, previewRenderSize, previewRenderSize)
 		if err != nil {
 			s = err.Error()
 			fmt.Println(err)
 		}
 
-		iup.PostMessage(iup.GetHandle("Preview"), s, 0, img)
+		iup.PostMessage(iup.GetHandle("Preview"), s, page, img)
 	}(opts)
 }
 
+// pageCountPost computes the file's page count off the UI thread and posts it, tagged with the path, to the Page spin.
+func pageCountPost(file cbconvert.File) {
+	n, err := cbconvert.New(cbconvert.NewOptions()).PageCount(file.Path, file.Stat)
+	if err != nil || n < 1 {
+		n = 1
+	}
+
+	iup.PostMessage(iup.GetHandle("Page"), file.Path, n, nil)
+}
+
+// onPageChanged re-renders the preview for the spin's page; dedupes so spin and typing don't both fire.
+func onPageChanged() int {
+	page := iup.GetHandle("Page").GetInt("VALUE") - 1
+	if page < 0 {
+		page = 0
+	}
+	if page == previewPage {
+		return iup.DEFAULT
+	}
+
+	previewPage = page
+	previewRender()
+
+	return iup.DEFAULT
+}
+
 func onAddFiles(ih iup.Ihandle) int {
 	args, err := fileDlg("Add Files", true, false, inputDirKey)
 	if err != nil {
@@ -134,21 +215,7 @@ func onAddFiles(ih iup.Ihandle) int {
 			return iup.DEFAULT
 		}
 
-		wasEmpty := len(files) == 0
+		addFiles(fs)
-
-		for _, file := range fs {
-			appendFile(file)
-		}
-
-		if wasEmpty && len(files) > 0 {
-			selectRow(0)
-		}
-
-		setActive()
-
-		if wasEmpty {
-			previewPost()
-		}
 	}
 
 	return iup.DEFAULT
@@ -174,21 +241,7 @@ func onAddDir(ih iup.Ihandle) int {
 			return iup.DEFAULT
 		}
 
-		wasEmpty := len(files) == 0
+		addFiles(fs)
-
-		for _, file := range fs {
-			appendFile(file)
-		}
-
-		if wasEmpty && len(files) > 0 {
-			selectRow(0)
-		}
-
-		setActive()
-
-		if wasEmpty {
-			previewPost()
-		}
 	}
 
 	return iup.DEFAULT
@@ -207,16 +260,31 @@ func onRemove(ih iup.Ihandle) int {
 	}
 
 	setActive()
-	previewPost()
+	if len(files) == 0 {
+		clearPreview()
+	} else {
+		previewPost()
+	}
 
 	return iup.DEFAULT
 }
 
+// clearPreview resets the preview state and repaints the canvas to its empty state.
+func clearPreview() {
+	hasCover = false
+	previewPath = ""
+	previewPage = 0
+
+	iup.GetHandle("PreviewInfo").SetAttribute("TITLE", "")
+	iup.Update(iup.GetHandle("Preview"))
+}
+
 func onRemoveAll(ih iup.Ihandle) int {
 	index = -1
 	files = make([]cbconvert.File, 0)
 
 	iup.GetHandle("Table").SetAttribute("NUMLIN", "0")
+	clearPreview()
 	setActive()
 
 	return iup.DEFAULT

cmd/cbconvert-gui/main.go

@@ -33,6 +33,10 @@ var (
 
 	activeConv *cbconvert.Converter
 	busy       bool
+
+	previewPage int    // 0-based page shown in the preview
+	previewPath string // path of the file whose page range is loaded
+	hasCover    bool   // whether a cover image is loaded for the preview canvas
 )
 
 func init() {
@@ -78,7 +82,7 @@ func main() {
 	img, _ := png.Decode(bytes.NewReader(appLogo))
 	iup.ImageFromImage(img).SetHandle("logo")
 
-	dlg := iup.Dialog(layout()).SetAttributes(fmt.Sprintf(`TITLE="CBconvert %s", ICON=logo, SHRINK=YES`, appVersion)).SetHandle("dlg")
+	dlg := iup.Dialog(layout()).SetAttributes(fmt.Sprintf(`TITLE="CBconvert %s", ICON=logo`, appVersion)).SetHandle("dlg")
 
 	dlg.SetCallback("POSTMESSAGE_CB", iup.PostMessageFunc(func(ih iup.Ihandle, s string, i int, p any) int {
 		sp := strings.Split(s, ": ")
@@ -89,15 +93,6 @@ func main() {
 		return iup.DEFAULT
 	}))
 
-	dlg.SetCallback("RESIZE_CB", iup.ResizeFunc(func(ih iup.Ihandle, width, height int) int {
-		iup.GetHandle("Preview").SetAttribute("IMAGE", "logo")
-		iup.Refresh(ih)
-
-		previewPost()
-
-		return iup.DEFAULT
-	}))
-
 	dlg.SetCallback("THEMECHANGED_CB", iup.ThemeChangedFunc(func(ih iup.Ihandle, darkMode int) int {
 		t := iup.GetHandle("Table")
 		tableRowColors(t, darkMode == 1)

cmd/cbconvert-gui/state.go

@@ -10,6 +10,12 @@ func setActive() {
 	opts := options()
 	count := iup.GetHandle("Table").GetInt("NUMLIN")
 
+	if count > 0 && index != -1 {
+		iup.GetHandle("PageBox").SetAttribute("VISIBLE", "YES")
+	} else {
+		iup.GetHandle("PageBox").SetAttribute("VISIBLE", "NO")
+	}
+
 	if count == 0 {
 		iup.GetHandle("Remove").SetAttribute("ACTIVE", "NO")
 		iup.GetHandle("RemoveAll").SetAttribute("ACTIVE", "NO")

cmd/cbconvert-gui/widgets.go

@@ -4,6 +4,7 @@ import (
 	"bytes"
 	"fmt"
 	"image/gif"
+	"math"
 	"net/url"
 	"strconv"
 	"strings"
@@ -58,7 +59,7 @@ func list() iup.Ihandle {
 		"TITLE1":         "Title",
 		"TITLE2":         "Type",
 		"TITLE3":         "Size (MiB)",
-		"WIDTH1":         "150",
+		"WIDTH1":         "300",
 		"WIDTH2":         "50",
 		"WIDTH3":         "100",
 		"ALIGNMENT2":     "ACENTER",
@@ -102,21 +103,7 @@ func list() iup.Ihandle {
 			return iup.DEFAULT
 		}
 
-		wasEmpty := len(files) == 0
+		addFiles(fs)
-
-		for _, file := range fs {
-			appendFile(file)
-		}
-
-		if wasEmpty && len(files) > 0 {
-			selectRow(0)
-		}
-
-		setActive()
-
-		if wasEmpty {
-			previewPost()
-		}
 
 		return iup.DEFAULT
 	}))
@@ -124,49 +111,115 @@ func list() iup.Ihandle {
 	return iup.Vbox(t)
 }
 
-func previewSize() (int, int) {
-	var width, height int
-	sp := strings.Split(iup.GetHandle("Preview").GetAttribute("RASTERSIZE"), "x")
-	if len(sp) == 2 {
-		width, _ = strconv.Atoi(sp[0])
-		height, _ = strconv.Atoi(sp[1])
-	}
-
-	return width, height
-}
-
 func preview() iup.Ihandle {
 	return iup.Frame(
 		iup.Vbox(
-			iup.Label("").SetAttributes("EXPAND=YES, ALIGNMENT=ACENTER, MINSIZE=400x, IMAGE=cover").SetHandle("Preview").
+			iup.Canvas().SetAttributes("EXPAND=YES, MINSIZE=400x, BORDER=NO").SetHandle("Preview").
-				SetCallback("POSTMESSAGE_CB", iup.PostMessageFunc(func(ih iup.Ihandle, s string, i int, p any) int {
+				SetCallback("ACTION", iup.ActionFunc(drawPreview)).
-					img := p.(cbconvert.Image)
+				SetCallback("POSTMESSAGE_CB", iup.PostMessageFunc(previewMessage)),
-
-					iup.GetHandle("Loading").SetAttributes("VISIBLE=NO, STOP=YES")
-
-					if img.Image != nil && len(s) == 0 {
-						iup.Destroy(iup.GetHandle("cover"))
-						iup.ImageFromImage(img.Image).SetHandle("cover")
-
-						ih.SetAttribute("IMAGE", "cover")
-						iup.GetHandle("PreviewInfo").SetAttribute("TITLE", fmt.Sprintf("%s (%dx%d)", img.SizeHuman, img.Width, img.Height))
-					} else {
-						ih.SetAttribute("IMAGE", "logo")
-						iup.GetHandle("PreviewInfo").SetAttribute("TITLE", "")
-
-						sp := strings.Split(s, ": ")
-						if len(sp) > 1 {
-							iup.MessageError(ih, fmt.Sprintf("%s\n\n%s", sp[0], strings.Join(sp[1:], ": ")))
-						}
-					}
-
-					return iup.DEFAULT
-				})),
 			iup.Label("").SetAttributes("EXPAND=HORIZONTAL, ALIGNMENT=ACENTER").SetHandle("PreviewInfo"),
 		),
 	)
 }
 
+// drawPreview draws the cover scaled to fit, else the logo centered.
+func drawPreview(ih iup.Ihandle) int {
+	iup.DrawBegin(ih)
+	defer iup.DrawEnd(ih)
+
+	cw, ch := iup.DrawGetSize(ih)
+	iup.DrawParentBackground(ih)
+
+	name := "logo"
+	if hasCover {
+		name = "cover"
+	}
+
+	iw, ihh, _ := iup.DrawGetImageInfo(name)
+	if iw <= 0 || ihh <= 0 {
+		return iup.DEFAULT
+	}
+
+	dw, dh := iw, ihh
+	if hasCover {
+		s := math.Min(float64(cw)/float64(iw), float64(ch)/float64(ihh))
+		dw = int(float64(iw) * s)
+		dh = int(float64(ihh) * s)
+	}
+
+	iup.DrawImage(ih, name, (cw-dw)/2, (ch-dh)/2, dw, dh)
+
+	return iup.DEFAULT
+}
+
+// previewMessage receives a rendered cover from previewRender and triggers a canvas redraw.
+func previewMessage(ih iup.Ihandle, s string, i int, p any) int {
+	if i != previewPage {
+		return iup.DEFAULT
+	}
+
+	img := p.(cbconvert.Image)
+	iup.GetHandle("Loading").SetAttributes("VISIBLE=NO, STOP=YES")
+
+	if img.Image != nil && len(s) == 0 {
+		iup.Destroy(iup.GetHandle("cover"))
+		iup.ImageFromImage(img.Image).SetHandle("cover")
+		hasCover = true
+		iup.GetHandle("PreviewInfo").SetAttribute("TITLE", fmt.Sprintf("%s (%dx%d)", img.SizeHuman, img.Width, img.Height))
+	} else {
+		hasCover = false
+		iup.GetHandle("PreviewInfo").SetAttribute("TITLE", "")
+
+		sp := strings.Split(s, ": ")
+		if len(sp) > 1 {
+			iup.MessageError(ih, fmt.Sprintf("%s\n\n%s", sp[0], strings.Join(sp[1:], ": ")))
+		}
+	}
+
+	iup.Update(ih)
+
+	return iup.DEFAULT
+}
+
+// pageBox is the page-navigation spin shown in the status bar; hidden until a comic is selected.
+func pageBox() iup.Ihandle {
+	return iup.Hbox(
+		iup.Space().SetAttribute("SIZE", "5"),
+		iup.Label("Page:"),
+		iup.Space().SetAttribute("SIZE", "3"),
+		iup.Text().SetAttributes(`SPIN=YES, SPINMIN=1, SPINMAX=1, VALUE=1, VISIBLECOLUMNS=3, MASK="/d*"`).SetHandle("Page").
+			SetAttribute("TIP", "Preview a different page of the selected comic").
+			SetCallback("SPIN_CB", iup.SpinFunc(func(ih iup.Ihandle, pos int) int {
+				return onPageChanged()
+			})).
+			SetCallback("VALUECHANGED_CB", iup.ValueChangedFunc(func(ih iup.Ihandle) int {
+				return onPageChanged()
+			})).
+			SetCallback("POSTMESSAGE_CB", iup.PostMessageFunc(func(ih iup.Ihandle, s string, i int, p any) int {
+				if s != previewPath {
+					return iup.DEFAULT
+				}
+
+				ih.SetAttribute("SPINMAX", strconv.Itoa(i))
+				iup.GetHandle("PageCount").SetAttribute("TITLE", fmt.Sprintf("/ %d", i))
+
+				if previewPage > i-1 {
+					previewPage = i - 1
+				}
+				if previewPage < 0 {
+					previewPage = 0
+				}
+				ih.SetAttribute("VALUE", strconv.Itoa(previewPage+1))
+
+				previewRender()
+
+				return iup.DEFAULT
+			})),
+		iup.Space().SetAttribute("SIZE", "3"),
+		iup.Label("").SetHandle("PageCount"),
+	).SetAttributes("ALIGNMENT=ACENTER, VISIBLE=NO").SetHandle("PageBox")
+}
+
 func tabInput() iup.Ihandle {
 	return iup.Hbox(
 		iup.Vbox(
@@ -586,6 +639,7 @@ func buttons() iup.Ihandle {
 func status() iup.Ihandle {
 	return iup.Hbox(
 		loading(),
+		pageBox(),
 		iup.Fill(),
 		iup.Label("File 1 of 1").SetHandle("LabelStatus1").SetAttributes("VISIBLE=NO"),
 		iup.Space().SetAttribute("SIZE", "5"),