--- /dev/null
+// 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;
+}