package draw9 import (	"fmt"	"io"	"io/ioutil"	"os"	"sync") type Display struct {	// debugging	debug bool	// sync	mu      sync.Mutex	locking bool 	dirno int 	// control files	fd    *os.File	reffd *os.File	ctlfd *os.File 	// image ids	imageid uint32	qmask   *Image 	local    bool	devdir   string	windir   string	oldlabel string 	// colors	White       *Image	Black       *Image	Opaque      *Image	Transparent *Image 	Image       *Image	Screen      *Screen	ScreenImage *Image	Windows     *Image 	// devdraw message buffering	bufsize int	buf     []byte 	// fonts	DefaultFont    *Font	DefaultSubfont *Subfont} func (d *Display) OpenFont(name string) (*Font, error) {	// nil display is allowed, for querying font metrics	// in non-draw program.	if d != nil {		d.mu.Lock()		defer d.mu.Unlock()	}	return d.openFont(name)} func (d *Display) openFont(name string) (*Font, error) {	data, err := ioutil.ReadFile(name) 	if err != nil {		return nil, err	} 	return d.buildFont(data, name)} func (d *Display) readSubfont(name string, fd io.Reader, ai *Image) (*Subfont, error) {	hdr := make([]byte, 3*12+4)	i := ai	if i == nil {		var err error		i, err = d.readImage(fd)		if err != nil {			return nil, err		}	}	var (		n   int		p   []byte		fc  []Fontchar		f   *Subfont		err error	)	// Release lock for the I/O - could take a long time.	if d != nil {		//d.mu.Unlock()	}	_, err = io.ReadFull(fd, hdr[:3*12])	if d != nil {		//d.mu.Lock()	}	//defer d.mu.Unlock()	if err != nil {		err = fmt.Errorf("rdsubfontfile: header read error: %v", err)		goto Err	}	n = atoi(hdr)	p = make([]byte, 6*(n+1))	if _, err = io.ReadFull(fd, p); err != nil {		err = fmt.Errorf("rdsubfontfile: fontchar read error: %v", err)		goto Err	}	fc = make([]Fontchar, n+1)	unpackinfo(fc, p, n)	f = d.allocSubfont(name, atoi(hdr[12:]), atoi(hdr[24:]), fc, i)	return f, nil Err:	if ai == nil {		i.free()	}	return nil, err} func (d *Display) ReadSubfont(name string, fd io.Reader) (*Subfont, error) {	d.mu.Lock()	defer d.mu.Unlock()	return d.readSubfont(name, fd, nil)} func unpackinfo(fc []Fontchar, p []byte, n int) {	for j := 0; j <= n; j++ {		fc[j].X = int(p[0]) | int(p[1])<<8		fc[j].Top = uint8(p[2])		fc[j].Bottom = uint8(p[3])		fc[j].Left = int8(p[4])		fc[j].Width = uint8(p[5])		p = p[6:]	}} //func (d *Display)func (d *Display) Close() error {	d.mu.Lock()	defer d.mu.Unlock()	return d.close()} func (d *Display) close() error {	if d.oldlabel != "" {		if f, err := os.OpenFile(d.windir+"/label", os.O_WRONLY, 0); err == nil {			io.WriteString(f, d.oldlabel)			f.Close()		}	} 	return nil 	d.White.free()	d.Black.free() 	err1 := d.fd.Close()	err2 := d.ctlfd.Close()	err3 := d.reffd.Close() 	if err1 != nil {		return err1	}	if err2 != nil {		return err2	}	if err3 != nil {		return err3	}	return nil} func (d *Display) readctl() ([]byte, error) {	buf := make([]byte, 12*12+1)	d.ctlfd.Seek(0, 0)	_, err := d.ctlfd.Read(buf)	return buf, err} func (d *Display) bufimage(n int) []byte {	if d == nil || n < 0 || n > d.bufsize {		panic("bad count in bufimage")	} 	if len(d.buf)+n > d.bufsize {		if err := d.doflush(); err != nil {			panic("bufimage flush: " + err.Error())		}	} 	i := len(d.buf)	d.buf = d.buf[:i+n]	return d.buf[i:]} // Flush writes any pending data to the screen.func (d *Display) Flush() error {	d.mu.Lock()	defer d.mu.Unlock()	return d.flush(true)} // flush data, maybe make visiblefunc (d *Display) flush(vis bool) error {	if vis {		d.bufsize++		a := d.bufimage(1)		d.bufsize--		a[0] = 'v'	} 	return d.doflush()} // write out any buffered data to the devdraw data fdfunc (d *Display) doflush() error {	if len(d.buf) == 0 {		return nil	} 	if d.debug {		fmt.Fprintf(os.Stderr, "flushing %d %c %x\n", len(d.buf), rune(d.buf[0]), d.buf[1:len(d.buf)])	} 	_, err := d.fd.Write(d.buf)	d.buf = d.buf[:0] 	if err != nil {		if d.debug {			fmt.Fprintf(os.Stderr, "doflush: %s\n", err)		}		return fmt.Errorf("doflush: %s", err)	} 	return nil}