// Copyright 2009 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// This package implements an X11 backend for the exp/draw package.
//
// The X protocol specification is at ftp://ftp.x.org/pub/X11R7.0/doc/PDF/proto.pdf.
// A summary of the wire format can be found in XCB's xproto.xml.
package x11
// BUG(nigeltao): This is a toy library and not ready for production use.
import (
"bufio";
"exp/draw";
"image";
"io";
"net";
"os";
)
type resID uint32 // X resource IDs.
// TODO(nigeltao): Handle window resizes.
const (
windowHeight = 600;
windowWidth = 800;
)
type conn struct {
// TODO(nigeltao): Figure out which goroutine should be responsible for closing c,
// or if there is a race condition if one goroutine calls c.Close whilst another one
// is reading from r, or writing to w.
c io.Closer;
r *bufio.Reader;
w *bufio.Writer;
gc, window, root, visual resID;
img *image.RGBA;
kbd chan int;
mouse chan draw.Mouse;
resize chan bool;
quit chan bool;
mouseState draw.Mouse;
buf [256]byte; // General purpose scratch buffer.
flush chan bool;
flushBuf0 [24]byte;
flushBuf1 [4 * 1024]byte;
}
// flusher runs in its own goroutine, serving both FlushImage calls directly from the exp/draw client
// and indirectly from X expose events. It paints c.img to the X server via PutImage requests.
func (c *conn) flusher() {
for {
_ = <-c.flush;
if closed(c.flush) {
return
}
// Each X request has a 16-bit length (in terms of 4-byte units). To avoid going over
// this limit, we send PutImage for each row of the image, rather than trying to paint
// the entire image in one X request. This approach could easily be optimized (or the
// X protocol may have an escape sequence to delimit very large requests).
// TODO(nigeltao): See what XCB's xcb_put_image does in this situation.
w, h := c.img.Width(), c.img.Height();
units := 6 + w;
if units > 0xffff || h > 0xffff {
// This window is too large for X.
close(c.flush);
return;
}
c.flushBuf0[0] = 0x48; // PutImage opcode.
c.flushBuf0[1] = 0x02; // XCB_IMAGE_FORMAT_Z_PIXMAP.
c.flushBuf0[2] = uint8(units);
c.flushBuf0[3] = uint8(units >> 8);
setU32LE(c.flushBuf0[4:8], uint32(c.window));
setU32LE(c.flushBuf0[8:12], uint32(c.gc));
setU32LE(c.flushBuf0[12:16], 1<<16|uint32(w));
c.flushBuf0[21] = 0x18; // depth = 24 bits.
for y := 0; y < h; y++ {
setU32LE(c.flushBuf0[16:20], uint32(y<<16));
_, err := c.w.Write(c.flushBuf0[0:24]);
if err != nil {
close(c.flush);
return;
}
for x := 0; x < w; {
nx := w - x;
if nx > len(c.flushBuf1)/4 {
nx = len(c.flushBuf1) / 4
}
for i := 0; i < nx; i++ {
r, g, b, _ := c.img.At(x, y).RGBA();
c.flushBuf1[4*i+0] = uint8(b >> 24);
c.flushBuf1[4*i+1] = uint8(g >> 24);
c.flushBuf1[4*i+2] = uint8(r >> 24);
x++;
}
_, err := c.w.Write(c.flushBuf1[0 : 4*nx]);
if err != nil {
close(c.flush);
return;
}
}
}
if c.w.Flush() != nil {
close(c.flush);
return;
}
}
}
func (c *conn) Screen() draw.Image { return c.img }
func (c *conn) FlushImage() {
// We do the send (the <- operator) in an expression context, rather than in
// a statement context, so that it does not block, and fails if the buffered
// channel is full (in which case there already is a flush request pending).
_ = c.flush <- false
}
func (c *conn) KeyboardChan() <-chan int { return c.kbd }
func (c *conn) MouseChan() <-chan draw.Mouse { return c.mouse }
func (c *conn) ResizeChan() <-chan bool { return c.resize }
func (c *conn) QuitChan() <-chan bool { return c.quit }
// pumper runs in its own goroutine, reading X events and demuxing them over the kbd / mouse / resize / quit chans.
func (c *conn) pumper() {
for {
// X events are always 32 bytes long.
_, err := io.ReadFull(c.r, c.buf[0:32]);
if err != nil {
// TODO(nigeltao): should draw.Context expose err?
// TODO(nigeltao): should we do c.quit<-true? Should c.quit be a buffered channel?
// Or is c.quit only for non-exceptional closing (e.g. when the window manager destroys
// our window), and not for e.g. an I/O error?
break
}
switch c.buf[0] {
case 0x02, 0x03: // Key press, key release.
// BUG(nigeltao): Keycode to keysym mapping is not implemented.
// The keycode is in c.buf[1], but as keymaps aren't implemented yet, we'll use the
// space character as a placeholder.
keysym := int(' ');
// TODO(nigeltao): Should we send KeyboardChan ints for Shift/Ctrl/Alt? Should Shift-A send
// the same int down the channel as the sent on just the A key?
// TODO(nigeltao): How should IME events (e.g. key presses that should generate CJK text) work? Or
// is that outside the scope of the draw.Context interface?
if c.buf[0] == 0x03 {
keysym = -keysym
}
c.kbd <- keysym;
case 0x04, 0x05: // Button press, button release.
mask := 1 << (c.buf[1] - 1);
if c.buf[0] == 0x04 {
c.mouseState.Buttons |= mask
} else {
c.mouseState.Buttons &^= mask
}
// TODO(nigeltao): update mouseState's timestamp.
c.mouse <- c.mouseState;
case 0x06: // Motion notify.
c.mouseState.Point.X = int(c.buf[25])<<8 | int(c.buf[24]);
c.mouseState.Point.Y = int(c.buf[27])<<8 | int(c.buf[26]);
// TODO(nigeltao): update mouseState's timestamp.
c.mouse <- c.mouseState;
case 0x0c: // Expose.
// A single user action could trigger multiple expose events (e.g. if moving another
// window with XShape'd rounded corners over our window). In that case, the X server
// will send a count (in bytes 16-17) of the number of additional expose events coming.
// We could parse each event for the (x, y, width, height) and maintain a minimal dirty
// rectangle, but for now, the simplest approach is to paint the entire window, when
// receiving the final event in the series.
count := int(c.buf[17])<<8 | int(c.buf[16]);
if count == 0 {
// TODO(nigeltao): Should we ignore the very first expose event? A freshly mapped window
// will trigger expose, but until the first c.FlushImage call, there's probably nothing to
// paint but black. For an 800x600 window, at 4 bytes per pixel, each repaint writes about
// 2MB over the socket.
c.FlushImage()
}
// TODO(nigeltao): Should we listen to DestroyNotify (0x11) and ResizeRequest (0x19) events?
// What about EnterNotify (0x07) and LeaveNotify (0x08)?
}
}
close(c.flush);
// TODO(nigeltao): Is this the right place for c.c.Close()?
// TODO(nigeltao): Should we explicitly close our kbd/mouse/resize/quit chans?
}
// Authenticate ourselves with the X server.
func (c *conn) authenticate() os.Error {
key, value, err := readAuth(c.buf[0:]);
if err != nil {
return err
}
// Assume that the authentication protocol is "MIT-MAGIC-COOKIE-1".
if len(key) != 18 || len(value) != 16 {
return os.NewError("unsupported Xauth")
}
// 0x006c means little-endian. 0x000b, 0x0000 means X major version 11, minor version 0.
// 0x0012 and 0x0010 means the auth key and value have lenths 18 and 16.
// The final 0x0000 is padding, so that the string length is a multiple of 4.
_, err = io.WriteString(c.w, "\x6c\x00\x0b\x00\x00\x00\x12\x00\x10\x00\x00\x00");
if err != nil {
return err
}
_, err = io.WriteString(c.w, key);
if err != nil {
return err
}
// Again, the 0x0000 is padding.
_, err = io.WriteString(c.w, "\x00\x00");
if err != nil {
return err
}
_, err = io.WriteString(c.w, value);
if err != nil {
return err
}
err = c.w.Flush();
if err != nil {
return err
}
return nil;
}
// Reads a uint8 from r, using b as a scratch buffer.
func readU8(r io.Reader, b []byte) (uint8, os.Error) {
_, err := io.ReadFull(r, b[0:1]);
if err != nil {
return 0, err
}
return uint8(b[0]), nil;
}
// Reads a little-endian uint16 from r, using b as a scratch buffer.
func readU16LE(r io.Reader, b []byte) (uint16, os.Error) {
_, err := io.ReadFull(r, b[0:2]);
if err != nil {
return 0, err
}
return uint16(b[0]) | uint16(b[1])<<8, nil;
}
// Reads a little-endian uint32 from r, using b as a scratch buffer.
func readU32LE(r io.Reader, b []byte) (uint32, os.Error) {
_, err := io.ReadFull(r, b[0:4]);
if err != nil {
return 0, err
}
return uint32(b[0]) | uint32(b[1])<<8 | uint32(b[2])<<16 | uint32(b[3])<<24, nil;
}
// Sets b[0:4] to be the big-endian representation of u.
func setU32LE(b []byte, u uint32) {
b[0] = byte((u >> 0) & 0xff);
b[1] = byte((u >> 8) & 0xff);
b[2] = byte((u >> 16) & 0xff);
b[3] = byte((u >> 24) & 0xff);
}
// Check that we have an agreeable X pixmap Format.
func checkPixmapFormats(r io.Reader, b []byte, n int) (agree bool, err os.Error) {
for i := 0; i < n; i++ {
_, err = io.ReadFull(r, b[0:8]);
if err != nil {
return
}
// Byte 0 is depth, byte 1 is bits-per-pixel, byte 2 is scanline-pad, the rest (5) is padding.
if b[0] == 24 && b[1] == 32 {
agree = true
}
}
return;
}
// Check that we have an agreeable X Depth (i.e. one that has an agreeable X VisualType).
func checkDepths(r io.Reader, b []byte, n int, visual uint32) (agree bool, err os.Error) {
for i := 0; i < n; i++ {
depth, err := readU16LE(r, b);
if err != nil {
return
}
depth &= 0xff;
visualsLen, err := readU16LE(r, b);
if err != nil {
return
}
// Ignore 4 bytes of padding.
_, err = io.ReadFull(r, b[0:4]);
if err != nil {
return
}
for j := 0; j < int(visualsLen); j++ {
// Read 24 bytes: visual(4), class(1), bits per rgb value(1), colormap entries(2),
// red mask(4), green mask(4), blue mask(4), padding(4).
v, err := readU32LE(r, b);
_, err = readU32LE(r, b);
rm, err := readU32LE(r, b);
gm, err := readU32LE(r, b);
bm, err := readU32LE(r, b);
_, err = readU32LE(r, b);
if err != nil {
return
}
if v == visual && rm == 0xff0000 && gm == 0xff00 && bm == 0xff && depth == 24 {
agree = true
}
}
}
return;
}
// Check that we have an agreeable X Screen.
func checkScreens(r io.Reader, b []byte, n int) (root, visual uint32, err os.Error) {
for i := 0; i < n; i++ {
root0, err := readU32LE(r, b);
if err != nil {
return
}
// Ignore the next 7x4 bytes, which is: colormap, whitepixel, blackpixel, current input masks,
// width and height (pixels), width and height (mm), min and max installed maps.
_, err = io.ReadFull(r, b[0:28]);
if err != nil {
return
}
visual0, err := readU32LE(r, b);
if err != nil {
return
}
// Next 4 bytes: backing stores, save unders, root depth, allowed depths length.
x, err := readU32LE(r, b);
if err != nil {
return
}
nDepths := int(x >> 24);
agree, err := checkDepths(r, b, nDepths, visual0);
if err != nil {
return
}
if agree && root == 0 {
root = root0;
visual = visual0;
}
}
return;
}
// Perform the protocol handshake with the X server, and ensure that the server provides a compatible Screen, Depth, etcetera.
func (c *conn) handshake() os.Error {
_, err := io.ReadFull(c.r, c.buf[0:8]);
if err != nil {
return err
}
// Byte 0:1 should be 1 (success), bytes 2:6 should be 0xb0000000 (major/minor version 11.0).
if c.buf[0] != 1 || c.buf[2] != 11 || c.buf[3] != 0 || c.buf[4] != 0 || c.buf[5] != 0 {
return os.NewError("unsupported X version")
}
// Ignore the release number.
_, err = io.ReadFull(c.r, c.buf[0:4]);
if err != nil {
return err
}
// Read the resource ID base.
resourceIdBase, err := readU32LE(c.r, c.buf[0:4]);
if err != nil {
return err
}
// Read the resource ID mask.
resourceIdMask, err := readU32LE(c.r, c.buf[0:4]);
if err != nil {
return err
}
if resourceIdMask < 256 {
return os.NewError("X resource ID mask is too small")
}
// Ignore the motion buffer size.
_, err = io.ReadFull(c.r, c.buf[0:4]);
if err != nil {
return err
}
// Read the vendor length.
vendorLen, err := readU16LE(c.r, c.buf[0:2]);
if err != nil {
return err
}
if vendorLen != 20 {
// For now, assume the vendor is "The X.Org Foundation". Supporting different
// vendors would require figuring out how much padding we need to read.
return os.NewError("unsupported X vendor")
}
// Read the maximum request length.
maxReqLen, err := readU16LE(c.r, c.buf[0:2]);
if err != nil {
return err
}
if maxReqLen != 0xffff {
return os.NewError("unsupported X maximum request length")
}
// Read the roots length.
rootsLen, err := readU8(c.r, c.buf[0:1]);
if err != nil {
return err
}
// Read the pixmap formats length.
pixmapFormatsLen, err := readU8(c.r, c.buf[0:1]);
if err != nil {
return err
}
// Ignore some things that we don't care about (totalling 30 bytes):
// imageByteOrder(1), bitmapFormatBitOrder(1), bitmapFormatScanlineUnit(1) bitmapFormatScanlinePad(1),
// minKeycode(1), maxKeycode(1), padding(4), vendor(20, hard-coded above).
_, err = io.ReadFull(c.r, c.buf[0:30]);
if err != nil {
return err
}
// Check that we have an agreeable pixmap format.
agree, err := checkPixmapFormats(c.r, c.buf[0:8], int(pixmapFormatsLen));
if err != nil {
return err
}
if !agree {
return os.NewError("unsupported X pixmap formats")
}
// Check that we have an agreeable screen.
root, visual, err := checkScreens(c.r, c.buf[0:24], int(rootsLen));
if err != nil {
return err
}
if root == 0 || visual == 0 {
return os.NewError("unsupported X screen")
}
c.gc = resID(resourceIdBase);
c.window = resID(resourceIdBase + 1);
c.root = resID(root);
c.visual = resID(visual);
return nil;
}
// Returns a new draw.Context, backed by a newly created and mapped X11 window.
func NewWindow() (draw.Context, os.Error) {
display := getDisplay();
if len(display) == 0 {
return nil, os.NewError("unsupported DISPLAY")
}
s, err := net.Dial("unix", "", "/tmp/.X11-unix/X"+display);
if err != nil {
return nil, err
}
c := new(conn);
c.c = s;
c.r = bufio.NewReader(s);
c.w = bufio.NewWriter(s);
err = c.authenticate();
if err != nil {
return nil, err
}
err = c.handshake();
if err != nil {
return nil, err
}
// Now that we're connected, show a window, via three X protocol messages.
// First, create a graphics context (GC).
setU32LE(c.buf[0:4], 0x00060037); // 0x37 is the CreateGC opcode, and the message is 6 x 4 bytes long.
setU32LE(c.buf[4:8], uint32(c.gc));
setU32LE(c.buf[8:12], uint32(c.root));
setU32LE(c.buf[12:16], 0x00010004); // Bit 2 is XCB_GC_FOREGROUND, bit 16 is XCB_GC_GRAPHICS_EXPOSURES.
setU32LE(c.buf[16:20], 0x00000000); // The Foreground is black.
setU32LE(c.buf[20:24], 0x00000000); // GraphicsExposures' value is unused.
// Second, create the window.
setU32LE(c.buf[24:28], 0x000a0001); // 0x01 is the CreateWindow opcode, and the message is 10 x 4 bytes long.
setU32LE(c.buf[28:32], uint32(c.window));
setU32LE(c.buf[32:36], uint32(c.root));
setU32LE(c.buf[36:40], 0x00000000); // Initial (x, y) is (0, 0).
setU32LE(c.buf[40:44], windowHeight<<16|windowWidth);
setU32LE(c.buf[44:48], 0x00010000); // Border width is 0, XCB_WINDOW_CLASS_INPUT_OUTPUT is 1.
setU32LE(c.buf[48:52], uint32(c.visual));
setU32LE(c.buf[52:56], 0x00000802); // Bit 1 is XCB_CW_BACK_PIXEL, bit 11 is XCB_CW_EVENT_MASK.
setU32LE(c.buf[56:60], 0x00000000); // The Back-Pixel is black.
setU32LE(c.buf[60:64], 0x0000804f); // Key/button press and release, pointer motion, and expose event masks.
// Third, map the window.
setU32LE(c.buf[64:68], 0x00020008); // 0x08 is the MapWindow opcode, and the message is 2 x 4 bytes long.
setU32LE(c.buf[68:72], uint32(c.window));
// Write the bytes.
_, err = c.w.Write(c.buf[0:72]);
if err != nil {
return nil, err
}
err = c.w.Flush();
if err != nil {
return nil, err
}
c.img = image.NewRGBA(windowWidth, windowHeight);
// TODO(nigeltao): Should these channels be buffered?
c.kbd = make(chan int);
c.mouse = make(chan draw.Mouse);
c.resize = make(chan bool);
c.quit = make(chan bool);
c.flush = make(chan bool, 1);
go c.flusher();
go c.pumper();
return c, nil;
}
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