ebiten: implement DroppedFiles to replace AppendDroppedFiles

Closes #2552

examples/dropfile/main.go

@@ -16,42 +16,58 @@ package main
 
 import (
 	"image/png"
+	"io/fs"
 	"log"
+	"sync"
 
 	"github.com/hajimehoshi/ebiten/v2"
 	"github.com/hajimehoshi/ebiten/v2/ebitenutil"
 )
 
 type Game struct {
-	images []*ebiten.Image
+	imageMutex sync.Mutex
+	images     []*ebiten.Image
 }
 
 func (g *Game) Update() error {
-	for _, f := range ebiten.AppendDroppedFiles(nil) {
-		// Calling Close is not mandatory, but it is sligtly good to save memory.
-		defer func() {
-			_ = f.Close()
-		}()
+	if files := ebiten.DroppedFiles(); files != nil {
+		go fs.WalkDir(files, ".", func(path string, d fs.DirEntry, err error) error {
+			if err != nil {
+				return err
+			}
 
-		fi, err := f.Stat()
-		if err != nil {
-			log.Printf("%v", err)
-			continue
-		}
-		log.Printf("Name: %s, Size: %d, IsDir: %t, ModTime: %v", fi.Name(), fi.Size(), fi.IsDir(), fi.ModTime())
+			fi, err := d.Info()
+			if err != nil {
+				return err
+			}
+			log.Printf("Name: %s, Size: %d, IsDir: %t, ModTime: %v", fi.Name(), fi.Size(), fi.IsDir(), fi.ModTime())
 
-		img, err := png.Decode(f)
-		if err != nil {
-			log.Printf("decoding PNG failed: %v", err)
-			continue
-		}
-		g.images = append(g.images, ebiten.NewImageFromImage(img))
+			f, err := files.Open(path)
+			if err != nil {
+				return err
+			}
+			defer f.Close()
+
+			img, err := png.Decode(f)
+			if err != nil {
+				return nil
+			}
+			eimg := ebiten.NewImageFromImage(img)
+
+			g.imageMutex.Lock()
+			g.images = append(g.images, eimg)
+			g.imageMutex.Unlock()
+
+			return nil
+		})
 	}
-
 	return nil
 }
 
 func (g *Game) Draw(screen *ebiten.Image) {
+	g.imageMutex.Lock()
+	defer g.imageMutex.Unlock()
+
 	if len(g.images) == 0 {
 		ebitenutil.DebugPrint(screen, "Drop PNG files onto this window!")
 		return

input.go

@@ -478,8 +478,8 @@ func (i *inputState) windowBeingClosed() bool {
 	return i.state.WindowBeingClosed
 }
 
-func (i *inputState) appendDroppedFiles(files []fs.File) []fs.File {
+func (i *inputState) droppedFiles() fs.FS {
 	i.m.Lock()
 	defer i.m.Unlock()
-	return append(files, i.state.DroppedFiles...)
+	return i.state.DroppedFiles
 }

internal/file/file_js.go

@@ -0,0 +1,293 @@
+// Copyright 2023 The Ebitengine Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package file
+
+import (
+	"errors"
+	"fmt"
+	"io"
+	"io/fs"
+	"syscall/js"
+	"time"
+)
+
+type FileEntryFS struct {
+	rootEntry js.Value
+}
+
+func NewFileEntryFS(root js.Value) *FileEntryFS {
+	return &FileEntryFS{
+		rootEntry: root,
+	}
+}
+
+func (f *FileEntryFS) Open(name string) (fs.File, error) {
+	if !fs.ValidPath(name) {
+		return nil, &fs.PathError{
+			Op:   "open",
+			Path: name,
+			Err:  fs.ErrNotExist,
+		}
+	}
+
+	if name == "." {
+		return &dir{entry: f.rootEntry}, nil
+	}
+
+	var chEntry chan js.Value
+	cbSuccess := js.FuncOf(func(this js.Value, args []js.Value) any {
+		chEntry <- args[0]
+		close(chEntry)
+		return nil
+	})
+	defer cbSuccess.Release()
+
+	cbFailure := js.FuncOf(func(this js.Value, args []js.Value) any {
+		close(chEntry)
+		return nil
+	})
+	defer cbFailure.Release()
+
+	chEntry = make(chan js.Value)
+	f.rootEntry.Call("getFile", name, nil, cbSuccess, cbFailure)
+	if entry := <-chEntry; entry.Truthy() {
+		return &file{entry: entry}, nil
+	}
+
+	chEntry = make(chan js.Value)
+	f.rootEntry.Call("getDirectory", name, nil, cbSuccess, cbFailure)
+	if entry := <-chEntry; entry.Truthy() {
+		return &dir{entry: entry}, nil
+	}
+
+	return nil, &fs.PathError{
+		Op:   "open",
+		Path: name,
+		Err:  fs.ErrNotExist,
+	}
+}
+
+type file struct {
+	entry      js.Value
+	file       js.Value
+	offset     int64
+	uint8Array js.Value
+}
+
+func getFile(entry js.Value) js.Value {
+	ch := make(chan js.Value, 1)
+	cb := js.FuncOf(func(this js.Value, args []js.Value) any {
+		ch <- args[0]
+		return nil
+	})
+	defer cb.Release()
+
+	entry.Call("file", cb)
+	return <-ch
+}
+
+func (f *file) ensureFile() js.Value {
+	if f.file.Truthy() {
+		return f.file
+	}
+
+	f.file = getFile(f.entry)
+	return f.file
+}
+
+func (f *file) Stat() (fs.FileInfo, error) {
+	return &fileInfo{
+		entry: f.entry,
+		file:  f.ensureFile(),
+	}, nil
+}
+
+func (f *file) Read(buf []byte) (int, error) {
+	if !f.uint8Array.Truthy() {
+		chArrayBuffer := make(chan js.Value, 1)
+		cbThen := js.FuncOf(func(this js.Value, args []js.Value) any {
+			chArrayBuffer <- args[0]
+			return nil
+		})
+		defer cbThen.Release()
+
+		chError := make(chan js.Value, 1)
+		cbCatch := js.FuncOf(func(this js.Value, args []js.Value) any {
+			chError <- args[0]
+			return nil
+		})
+		defer cbCatch.Release()
+
+		f.ensureFile().Call("arrayBuffer").Call("then", cbThen).Call("catch", cbCatch)
+		select {
+		case ab := <-chArrayBuffer:
+			f.uint8Array = js.Global().Get("Uint8Array").New(ab)
+		case err := <-chError:
+			return 0, fmt.Errorf("%s", err.Call("toString").String())
+		}
+	}
+
+	size := int64(f.uint8Array.Get("byteLength").Float())
+	if f.offset >= size {
+		return 0, io.EOF
+	}
+
+	if len(buf) == 0 {
+		return 0, nil
+	}
+
+	slice := f.uint8Array.Call("subarray", f.offset, f.offset+int64(len(buf)))
+	n := slice.Get("byteLength").Int()
+	js.CopyBytesToGo(buf[:n], slice)
+	f.offset += int64(n)
+	if f.offset >= size {
+		return n, io.EOF
+	}
+	return n, nil
+}
+
+func (f *file) Close() error {
+	return nil
+}
+
+type dir struct {
+	entry   js.Value
+	entries []js.Value
+	offset  int
+}
+
+func (d *dir) Stat() (fs.FileInfo, error) {
+	return &fileInfo{
+		entry: d.entry,
+	}, nil
+}
+
+func (d *dir) Read(buf []byte) (int, error) {
+	return 0, &fs.PathError{
+		Op:   "read",
+		Path: d.entry.Get("name").String(),
+		Err:  errors.New("is a directory"),
+	}
+}
+
+func (d *dir) Close() error {
+	return nil
+}
+
+func (d *dir) ReadDir(count int) ([]fs.DirEntry, error) {
+	if d.entries == nil {
+		ch := make(chan struct{})
+		var rec js.Func
+		cb := js.FuncOf(func(this js.Value, args []js.Value) any {
+			entries := args[0]
+			if entries.Length() == 0 {
+				close(ch)
+				return nil
+			}
+			for i := 0; i < entries.Length(); i++ {
+				ent := entries.Index(i)
+				// A name can be empty when this directory is a root directory.
+				if ent.Get("name").String() == "" {
+					continue
+				}
+				if !ent.Get("isFile").Bool() && !ent.Get("isDirectory").Bool() {
+					continue
+				}
+				d.entries = append(d.entries, ent)
+			}
+			rec.Value.Call("call")
+			return nil
+		})
+		defer cb.Release()
+
+		reader := d.entry.Call("createReader")
+		rec = js.FuncOf(func(this js.Value, args []js.Value) any {
+			reader.Call("readEntries", cb)
+			return nil
+		})
+		defer rec.Release()
+
+		rec.Value.Call("call")
+		<-ch
+	}
+
+	n := len(d.entries) - d.offset
+
+	if n == 0 {
+		if count <= 0 {
+			return nil, nil
+		}
+		return nil, io.EOF
+	}
+
+	if count > 0 && n > count {
+		n = count
+	}
+
+	ents := make([]fs.DirEntry, n)
+	for i := range ents {
+		fi := &fileInfo{
+			entry: d.entries[d.offset+i],
+		}
+		if fi.entry.Get("isFile").Bool() {
+			fi.file = getFile(fi.entry)
+		}
+		ents[i] = fs.FileInfoToDirEntry(fi)
+	}
+	d.offset += n
+
+	return ents, nil
+}
+
+type fileInfo struct {
+	entry js.Value
+	file  js.Value
+}
+
+func (f *fileInfo) Name() string {
+	return f.entry.Get("name").String()
+}
+
+func (f *fileInfo) Size() int64 {
+	if !f.file.Truthy() {
+		return 0
+	}
+	return int64(f.file.Get("size").Float())
+}
+
+func (f *fileInfo) Mode() fs.FileMode {
+	if !f.file.Truthy() {
+		return 0555 | fs.ModeDir
+	}
+	return 0444
+}
+
+func (f *fileInfo) ModTime() time.Time {
+	if !f.file.Truthy() {
+		return time.Time{}
+	}
+	return time.UnixMilli(int64(f.file.Get("lastModified").Float()))
+}
+
+func (f *fileInfo) IsDir() bool {
+	if !f.file.Truthy() {
+		return true
+	}
+	return false
+}
+
+func (f *fileInfo) Sys() any {
+	return nil
+}

internal/file/file_notjs.go

@@ -0,0 +1,166 @@
+// Copyright 2023 The Ebitengine Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+//go:build !js
+
+package file
+
+import (
+	"errors"
+	"io"
+	"io/fs"
+	"os"
+	"path/filepath"
+	"sort"
+	"strings"
+	"sync"
+	"time"
+)
+
+type VirtualFS struct {
+	root virtualFSRoot
+}
+
+func NewVirtualFS(paths []string) *VirtualFS {
+	fs := &VirtualFS{}
+	fs.root.addRealPaths(paths)
+	return fs
+}
+
+func (v *VirtualFS) Open(name string) (fs.File, error) {
+	if !fs.ValidPath(name) {
+		return nil, &fs.PathError{
+			Op:   "open",
+			Path: name,
+			Err:  fs.ErrNotExist,
+		}
+	}
+
+	if name == "." {
+		return &v.root, nil
+	}
+
+	// A valid path must not include a token "." or "..", except for "." itself.
+	es := strings.Split(name, "/")
+	for _, realPath := range v.root.realPaths {
+		if filepath.Base(realPath) != es[0] {
+			continue
+		}
+		return os.Open(filepath.Join(append([]string{realPath}, es[1:]...)...))
+	}
+
+	return nil, &fs.PathError{
+		Op:   "open",
+		Path: name,
+		Err:  fs.ErrNotExist,
+	}
+}
+
+type virtualFSRoot struct {
+	realPaths []string
+	offset    int
+	m         sync.Mutex
+}
+
+func (v *virtualFSRoot) addRealPaths(paths []string) {
+	v.m.Lock()
+	defer v.m.Unlock()
+
+	for _, path := range paths {
+		// If the path consists entirely of separators, filepath.Base returns a single separator.
+		// On Windows, filepath.Base(`C:\`) == `\`.
+		// Skip root directory paths on purpose. This is almost the same behavior as the Chrome browser.
+		if filepath.Base(path) == string(filepath.Separator) {
+			continue
+		}
+		v.realPaths = append(v.realPaths, path)
+	}
+	sort.Strings(v.realPaths)
+}
+
+func (v *virtualFSRoot) Stat() (fs.FileInfo, error) {
+	return &virtualFSRootFileInfo{}, nil
+}
+
+func (v *virtualFSRoot) Read([]byte) (int, error) {
+	return 0, &fs.PathError{
+		Op:   "read",
+		Path: "/",
+		Err:  errors.New("is a directory"),
+	}
+}
+
+func (v *virtualFSRoot) Close() error {
+	return nil
+}
+
+func (v *virtualFSRoot) ReadDir(count int) ([]fs.DirEntry, error) {
+	v.m.Lock()
+	defer v.m.Unlock()
+
+	n := len(v.realPaths) - v.offset
+
+	if n == 0 {
+		if count <= 0 {
+			return nil, nil
+		}
+		return nil, io.EOF
+	}
+
+	if count > 0 && n > count {
+		n = count
+	}
+
+	ents := make([]fs.DirEntry, n)
+	for i := range ents {
+		fi, err := os.Stat(v.realPaths[v.offset+i])
+		if err != nil {
+			if count <= 0 {
+				return ents, err
+			}
+			return nil, err
+		}
+		ents[i] = fs.FileInfoToDirEntry(fi)
+	}
+	v.offset += n
+
+	return ents, nil
+}
+
+type virtualFSRootFileInfo struct {
+}
+
+func (v *virtualFSRootFileInfo) Name() string {
+	return "."
+}
+
+func (v *virtualFSRootFileInfo) Size() int64 {
+	return 0
+}
+
+func (v *virtualFSRootFileInfo) Mode() fs.FileMode {
+	return 0555 | fs.ModeDir
+}
+
+func (v *virtualFSRootFileInfo) ModTime() time.Time {
+	return time.Time{}
+}
+
+func (v *virtualFSRootFileInfo) IsDir() bool {
+	return true
+}
+
+func (v *virtualFSRootFileInfo) Sys() any {
+	return nil
+}

internal/ui/input.go

@@ -48,7 +48,7 @@ type InputState struct {
 	Touches            []Touch
 	Runes              []rune
 	WindowBeingClosed  bool
-	DroppedFiles       []fs.File
+	DroppedFiles       fs.FS
 }
 
 func (i *InputState) copyAndReset(dst *InputState) {
@@ -61,10 +61,7 @@ func (i *InputState) copyAndReset(dst *InputState) {
 	dst.Touches = append(dst.Touches[:0], i.Touches...)
 	dst.Runes = append(dst.Runes[:0], i.Runes...)
 	dst.WindowBeingClosed = i.WindowBeingClosed
-	for idx := range dst.DroppedFiles {
-		dst.DroppedFiles[idx] = nil
-	}
-	dst.DroppedFiles = append(dst.DroppedFiles[:0], i.DroppedFiles...)
+	dst.DroppedFiles = i.DroppedFiles
 
 	// Reset the members that are updated by deltas, rather than absolute values.
 	i.WheelX = 0
@@ -73,10 +70,7 @@ func (i *InputState) copyAndReset(dst *InputState) {
 
 	// Reset the members that are never reset until they are explicitly done.
 	i.WindowBeingClosed = false
-	for idx := range i.DroppedFiles {
-		i.DroppedFiles[idx] = nil
-	}
-	i.DroppedFiles = i.DroppedFiles[:0]
+	i.DroppedFiles = nil
 }
 
 func (i *InputState) appendRune(r rune) {
@@ -85,7 +79,3 @@ func (i *InputState) appendRune(r rune) {
 	}
 	i.Runes = append(i.Runes, r)
 }
-
-func (i *InputState) appendDroppedFiles(files []fs.File) {
-	i.DroppedFiles = append(i.DroppedFiles, files...)
-}

internal/ui/ui_glfw.go

@@ -21,7 +21,6 @@ import (
 	"errors"
 	"fmt"
 	"image"
-	"io/fs"
 	"os"
 	"runtime"
 	"sync"
@@ -29,6 +28,7 @@ import (
 	"time"
 
 	"github.com/hajimehoshi/ebiten/v2/internal/devicescale"
+	"github.com/hajimehoshi/ebiten/v2/internal/file"
 	"github.com/hajimehoshi/ebiten/v2/internal/gamepad"
 	"github.com/hajimehoshi/ebiten/v2/internal/glfw"
 	"github.com/hajimehoshi/ebiten/v2/internal/graphicsdriver"
@@ -751,22 +751,9 @@ func (u *userInterfaceImpl) registerWindowFramebufferSizeCallback() {
 func (u *userInterfaceImpl) registerDropCallback() {
 	if u.dropCallback == nil {
 		u.dropCallback = glfw.ToDropCallback(func(_ *glfw.Window, names []string) {
-			var files []fs.File
-			for _, name := range names {
-				f, err := os.Open(name)
-				if err != nil {
-					files = append(files, &errorFile{
-						name: name,
-						err:  err,
-					})
-					continue
-				}
-				files = append(files, f)
-			}
-
 			u.m.Lock()
 			defer u.m.Unlock()
-			u.inputState.appendDroppedFiles(files)
+			u.inputState.DroppedFiles = file.NewVirtualFS(names)
 		})
 	}
 	u.window.SetDropCallback(u.dropCallback)
@@ -1544,20 +1531,3 @@ func (u *userInterfaceImpl) setOrigWindowPos(x, y int) {
 func IsScreenTransparentAvailable() bool {
 	return true
 }
-
-type errorFile struct {
-	name string
-	err  error
-}
-
-func (e *errorFile) Stat() (fs.FileInfo, error) {
-	return nil, fmt.Errorf("ui: failed to open %s: %w", e.name, e.err)
-}
-
-func (e *errorFile) Read(buf []byte) (int, error) {
-	return 0, fmt.Errorf("ui: failed to open %s: %w", e.name, e.err)
-}
-
-func (e *errorFile) Close() error {
-	return nil
-}

internal/ui/ui_js.go

@@ -15,14 +15,12 @@
 package ui
 
 import (
-	"fmt"
-	"io"
-	"io/fs"
 	"sync"
 	"syscall/js"
 	"time"
 
 	"github.com/hajimehoshi/ebiten/v2/internal/devicescale"
+	"github.com/hajimehoshi/ebiten/v2/internal/file"
 	"github.com/hajimehoshi/ebiten/v2/internal/gamepad"
 	"github.com/hajimehoshi/ebiten/v2/internal/graphicsdriver"
 	"github.com/hajimehoshi/ebiten/v2/internal/graphicsdriver/opengl"
@@ -650,33 +648,13 @@ func (u *userInterfaceImpl) appendDroppedFiles(data js.Value) {
 	u.dropFileM.Lock()
 	defer u.dropFileM.Unlock()
 
-	chFile := make(chan js.Value, 1)
-	cbFile := js.FuncOf(func(this js.Value, args []js.Value) any {
-		chFile <- args[0]
-		return nil
-	})
-	defer cbFile.Release()
-
 	items := data.Get("items")
-	for i := 0; i < items.Length(); i++ {
-		entry := items.Index(i).Call("webkitGetAsEntry")
-		var f fs.File
-		switch {
-		case entry.Get("isFile").Bool():
-			entry.Call("file", cbFile)
-			jsFile := <-chFile
-			f = &file{
-				v: jsFile,
-			}
-		case entry.Get("isDirectory").Bool():
-			f = &dir{
-				entry: entry,
-			}
-		default:
-			continue
-		}
-		u.inputState.DroppedFiles = append(u.inputState.DroppedFiles, f)
+	if items.Length() <= 0 {
+		return
 	}
+
+	fs := items.Index(0).Call("webkitGetAsEntry").Get("filesystem").Get("root")
+	u.inputState.DroppedFiles = file.NewFileEntryFS(fs)
 }
 
 func (u *userInterfaceImpl) forceUpdateOnMinimumFPSMode() {
@@ -751,133 +729,3 @@ func (u *userInterfaceImpl) updateIconIfNeeded() {
 func IsScreenTransparentAvailable() bool {
 	return true
 }
-
-type file struct {
-	v          js.Value
-	cursor     int64
-	uint8Array js.Value
-}
-
-func (f *file) Stat() (fs.FileInfo, error) {
-	return &fileInfo{v: f.v}, nil
-}
-
-func (f *file) Read(buf []byte) (int, error) {
-	if !f.uint8Array.Truthy() {
-		chArrayBuffer := make(chan js.Value, 1)
-		cbThen := js.FuncOf(func(this js.Value, args []js.Value) any {
-			chArrayBuffer <- args[0]
-			return nil
-		})
-		defer cbThen.Release()
-
-		chError := make(chan js.Value, 1)
-		cbCatch := js.FuncOf(func(this js.Value, args []js.Value) any {
-			chError <- args[0]
-			return nil
-		})
-		defer cbCatch.Release()
-
-		f.v.Call("arrayBuffer").Call("then", cbThen).Call("catch", cbCatch)
-		select {
-		case ab := <-chArrayBuffer:
-			f.uint8Array = js.Global().Get("Uint8Array").New(ab)
-		case err := <-chError:
-			return 0, fmt.Errorf("%s", err.Call("toString").String())
-		}
-	}
-
-	size := int64(f.uint8Array.Get("byteLength").Float())
-	if f.cursor >= size {
-		return 0, io.EOF
-	}
-
-	if len(buf) == 0 {
-		return 0, nil
-	}
-
-	slice := f.uint8Array.Call("subarray", f.cursor, f.cursor+int64(len(buf)))
-	n := slice.Get("byteLength").Int()
-	js.CopyBytesToGo(buf[:n], slice)
-	f.cursor += int64(n)
-	if f.cursor >= size {
-		return n, io.EOF
-	}
-	return n, nil
-}
-
-func (f *file) Close() error {
-	return nil
-}
-
-type fileInfo struct {
-	v js.Value
-}
-
-func (f *fileInfo) Name() string {
-	return f.v.Get("name").String()
-}
-
-func (f *fileInfo) Size() int64 {
-	return int64(f.v.Get("size").Float())
-}
-
-func (f *fileInfo) Mode() fs.FileMode {
-	return 0400
-}
-
-func (f *fileInfo) ModTime() time.Time {
-	return time.UnixMilli(int64(f.v.Get("lastModified").Float()))
-}
-
-func (f *fileInfo) IsDir() bool {
-	return false
-}
-
-func (f *fileInfo) Sys() any {
-	return nil
-}
-
-type dir struct {
-	entry js.Value
-}
-
-func (d *dir) Stat() (fs.FileInfo, error) {
-	return &dirInfo{entry: d.entry}, nil
-}
-
-func (d *dir) Read(buf []byte) (int, error) {
-	return 0, fmt.Errorf("%s is a directory", d.entry.Get("name").String())
-}
-
-func (d *dir) Close() error {
-	return nil
-}
-
-type dirInfo struct {
-	entry js.Value
-}
-
-func (d *dirInfo) Name() string {
-	return d.entry.Get("name").String()
-}
-
-func (d *dirInfo) Size() int64 {
-	return 0
-}
-
-func (d *dirInfo) Mode() fs.FileMode {
-	return 0400 | fs.ModeDir
-}
-
-func (d *dirInfo) ModTime() time.Time {
-	return time.Time{}
-}
-
-func (d *dirInfo) IsDir() bool {
-	return true
-}
-
-func (d *dirInfo) Sys() any {
-	return nil
-}

run.go

@@ -666,13 +666,12 @@ func toUIRunOptions(options *RunGameOptions) *ui.RunOptions {
 	}
 }
 
-// AppendDroppedFiles appends files, dropped at the time Update is called, to the given slice,
-// and returns the extended buffer.
-// Giving a slice that already has enough capacity works efficiently.
+// DroppedFiles returns a virtual file system that includes only dropped files and/or directories
+// at its root directory, at the time Update is called.
 //
-// AppendDroppedFiles works on desktops and browsers.
+// DroppedFiles works on desktops and browsers.
 //
-// AppendDroppedFiles is concurrent-safe.
-func AppendDroppedFiles(files []fs.File) []fs.File {
-	return theInputState.appendDroppedFiles(files)
+// DroppedFiles is concurrent-safe.
+func DroppedFiles() fs.FS {
+	return theInputState.droppedFiles()
 }