Adding upstream version 0.7.0+dfsg.

Signed-off-by: Daniel Baumann <daniel@debian.org>

clipboard.go

@@ -0,0 +1,154 @@
+// Copyright 2021 The golang.design Initiative Authors.
+// All rights reserved. Use of this source code is governed
+// by a MIT license that can be found in the LICENSE file.
+//
+// Written by Changkun Ou <changkun.de>
+
+/*
+Package clipboard provides cross platform clipboard access and supports
+macOS/Linux/Windows/Android/iOS platform. Before interacting with the
+clipboard, one must call Init to assert if it is possible to use this
+package:
+
+	err := clipboard.Init()
+	if err != nil {
+		panic(err)
+	}
+
+The most common operations are `Read` and `Write`. To use them:
+
+	// write/read text format data of the clipboard, and
+	// the byte buffer regarding the text are UTF8 encoded.
+	clipboard.Write(clipboard.FmtText, []byte("text data"))
+	clipboard.Read(clipboard.FmtText)
+
+	// write/read image format data of the clipboard, and
+	// the byte buffer regarding the image are PNG encoded.
+	clipboard.Write(clipboard.FmtImage, []byte("image data"))
+	clipboard.Read(clipboard.FmtImage)
+
+Note that read/write regarding image format assumes that the bytes are
+PNG encoded since it serves the alpha blending purpose that might be
+used in other graphical software.
+
+In addition, `clipboard.Write` returns a channel that can receive an
+empty struct as a signal, which indicates the corresponding write call
+to the clipboard is outdated, meaning the clipboard has been overwritten
+by others and the previously written data is lost. For instance:
+
+	changed := clipboard.Write(clipboard.FmtText, []byte("text data"))
+
+	select {
+	case <-changed:
+		println(`"text data" is no longer available from clipboard.`)
+	}
+
+You can ignore the returning channel if you don't need this type of
+notification. Furthermore, when you need more than just knowing whether
+clipboard data is changed, use the watcher API:
+
+	ch := clipboard.Watch(context.TODO(), clipboard.FmtText)
+	for data := range ch {
+		// print out clipboard data whenever it is changed
+		println(string(data))
+	}
+*/
+package clipboard // import "golang.design/x/clipboard"
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"os"
+	"sync"
+)
+
+var (
+	// activate only for running tests.
+	debug          = false
+	errUnavailable = errors.New("clipboard unavailable")
+	errUnsupported = errors.New("unsupported format")
+)
+
+// Format represents the format of clipboard data.
+type Format int
+
+// All sorts of supported clipboard data
+const (
+	// FmtText indicates plain text clipboard format
+	FmtText Format = iota
+	// FmtImage indicates image/png clipboard format
+	FmtImage
+)
+
+var (
+	// Due to the limitation on operating systems (such as darwin),
+	// concurrent read can even cause panic, use a global lock to
+	// guarantee one read at a time.
+	lock = sync.Mutex{}
+	initOnce sync.Once
+	initError error
+)
+
+// Init initializes the clipboard package. It returns an error
+// if the clipboard is not available to use. This may happen if the
+// target system lacks required dependency, such as libx11-dev in X11
+// environment. For example,
+//
+// 	err := clipboard.Init()
+// 	if err != nil {
+// 		panic(err)
+// 	}
+//
+// If Init returns an error, any subsequent Read/Write/Watch call
+// may result in an unrecoverable panic.
+func Init() error {
+	initOnce.Do(func() {
+		initError = initialize()
+	})
+	return initError
+}
+
+// Read returns a chunk of bytes of the clipboard data if it presents
+// in the desired format t presents. Otherwise, it returns nil.
+func Read(t Format) []byte {
+	lock.Lock()
+	defer lock.Unlock()
+
+	buf, err := read(t)
+	if err != nil {
+		if debug {
+			fmt.Fprintf(os.Stderr, "read clipboard err: %v\n", err)
+		}
+		return nil
+	}
+	return buf
+}
+
+// Write writes a given buffer to the clipboard in a specified format.
+// Write returned a receive-only channel can receive an empty struct
+// as a signal, which indicates the clipboard has been overwritten from
+// this write.
+// If format t indicates an image, then the given buf assumes
+// the image data is PNG encoded.
+func Write(t Format, buf []byte) <-chan struct{} {
+	lock.Lock()
+	defer lock.Unlock()
+
+	changed, err := write(t, buf)
+	if err != nil {
+		if debug {
+			fmt.Fprintf(os.Stderr, "write to clipboard err: %v\n", err)
+		}
+		return nil
+	}
+	return changed
+}
+
+// Watch returns a receive-only channel that received the clipboard data
+// whenever any change of clipboard data in the desired format happens.
+//
+// The returned channel will be closed if the given context is canceled.
+func Watch(ctx context.Context, t Format) <-chan []byte {
+	return watch(ctx, t)
+}