x11

x11 enables java and other jvm languages to talk directly to a x11 server without binding to a C library. The client is similar to X11lib for C but uses objects to represent the protocol resulting in a simplified client. It supports the core protocol and all extensions. The client follows the same pattern as X11lib by queuing one-way requests before sending them to the server. The x11-protocol project enables reading and writing the entire protocol and can be used to help write a x11 server.

Users

The x11-client library can be added to your project using maven or gradle.

Maven

<dependency>
 <groupId>com.github.moaxcp.x11</groupId>
 <artifactId>x11-client</artifactId>
 <version>0.18.0</version>
 <type>module</type>
</dependency>

Gradle

implementation 'com.github.moaxcp.x11:x11-client:0.18.0'

Usage

Users build requests using the builder pattern.

CreateWindow window = CreateWindow.builder()
        .depth(x11Client.getDepth(0))
        .wid(x11Client.nextResourceId())
        .parent(x11Client.getRoot(0))
        .x((short) 10)
        .y((short) 10)
        .width((short) 600)
        .height((short) 480)
        .borderWidth((short) 5)
        .clazz(COPY_FROM_PARENT)
        .visual(x11Client.getVisualId(0))
        .backgroundPixel(x11Client.getWhitePixel(0))
        .borderPixel(x11Client.getBlackPixel(0))
        .eventMaskEnable(EXPOSURE, KEY_PRESS)
        .build();

All protocol objects use the builder pattern. All fields using a value_mask will automatically set the bit in the value_mask when the builder method is called. An example of this is shown above when eventMaskEnable is called.

...
        .eventMaskEnable(EXPOSURE, KEY_PRESS)
...

This enables the value_mask bit for eventMask and turns on the eventMask bits for EXPOSURE and KEY_PRESS.

A client is a resource and should be managed in a try-with-resources block. The try-with-resources block will close the socket connection correctly.

try(X11Client client = X11Client.connect(new DisplayName(":1"))) {

}

In this block requests can be sent through the client.

client.send(window);

Creating a window is a one-way request. These requests do not receive a response from the server. Similar to X11lib, the client queues one-way requests until a two-way request is sent. This queue can be inspected and flushed to the server.

client.flush();

This project converts the x11 protocol to classes which implement core interfaces (XError, XEvent, XRequest, XReply, etc). The client can read and write these objects using the read and write methods defined in each object’s class.

X11ProtocolExceptions may be thrown when there are IOExceptions with the socket. X11ClientExceptions are thrown with client issues such as connection issues or api issues. X11ErrorExceptions represent Errors from the X11 Server. Errors can be handled using the standard try/catch method rather than using an error handler callback as is done with X11lib.

try {
  client.send(request);
} catch(X11ErrorException e) {
  LOG.error(e);
}

All supported x11 extensions are automatically loaded by the client on startup. Users can check if an extension is loaded or activated by calling

client.loadedPlugin("BIG-REQUESTS");
client.activePlugin("BIG-REQUESTS");

If an extension is supported, then XRequests for that extension can be sent to the client.

client.send(Enable.builder().build());

Otherwise, sending an unsupported request will result in an exception.

could not find plugin for request

Examples

These examples are conversions of a X11lib example written in C.

Hello World

This is an example of a simple window. In this example none of the helper methods are used. Raw requests are built and sent directly to the server.

try(X11Client x11Client = X11Client.connect()) {
  CreateWindow window = CreateWindow.builder()
    .depth(x11Client.getDepth(0))
    .wid(x11Client.nextResourceId())
    .parent(x11Client.getRoot(0))
    .x((short) 10)
    .y((short) 10)
    .width((short) 600)
    .height((short) 480)
    .borderWidth((short) 5)
    .clazz(WindowClass.COPY_FROM_PARENT)
    .visual(x11Client.getVisualId(0))
    .backgroundPixel(x11Client.getWhitePixel(0))
    .borderPixel(x11Client.getBlackPixel(0))
    .eventMaskEnable(EventMask.EXPOSURE, EventMask.KEY_PRESS)
    .build();
  x11Client.send(window);
  x11Client.send(MapWindow.builder()
    .window(window.getWid())
    .build());
  CreateGC gc = CreateGC.builder()
    .cid(x11Client.nextResourceId())
    .drawable(window.getWid())
    .background(x11Client.getWhitePixel(0))
    .foreground(x11Client.getBlackPixel(0))
    .build();
  x11Client.send(gc);
  while(true) {
    XEvent event = x11Client.getNextEvent();
    if(event instanceof ExposeEvent) {
      List<Rectangle> rectangles = new ArrayList<>();
      rectangles.add(Rectangle.builder()
        .x((short) 20)
        .y((short) 20)
        .width((short) 10)
        .height((short) 10)
        .build());
      x11Client.send(PolyFillRectangle.builder()
        .drawable(window.getWid())
        .gc(gc.getCid())
        .rectangles(rectangles)
        .build());
      x11Client.send(ImageText8.builder()
        .drawable(window.getWid())
        .gc(gc.getCid())
        .string(stringToByteList("Hello World!"))
        .x((short) 10)
        .y((short) 50)
        .build());
    } else if(event instanceof KeyPressEvent) {
      break;
    }
  }
}

The next example is the same window but uses helper methods in the client.

try(X11Client client = X11Client.connect()) {
  int wid = client.createSimpleWindow((short) 10, (short) 10, (short) 600, (short) 480, EventMask.EXPOSURE, EventMask.KEY_PRESS);
  client.storeName(wid, "Hello World!");
  int deleteAtom = client.getAtom("WM_DELETE_WINDOW");
  client.setWMProtocols(wid, deleteAtom);
  client.mapWindow(wid);
  int gc = client.createGC(0, wid);
  while(true) {
    XEvent event = client.getNextEvent();
    if(event instanceof ExposeEvent) {
      client.fillRectangle(wid, gc, (short) 20, (short) 20, (short) 10, (short) 10);
      client.drawString(wid, gc, (short) 10, (short) 50, "Hello World!");
    } else if(event instanceof KeyPressEvent) {
      break;
    } else if(event instanceof ClientMessageEvent) {
      ClientMessageEvent clientMessage = (ClientMessageEvent) event;
      if(clientMessage.getFormat() == 32) {
        ClientMessageData32 data = (ClientMessageData32) clientMessage.getData();
        if(data.getData32().get(0) == deleteAtom) {
          break;
        }
      }
    }
  }
}

TinyWM

TinyWM is a famous small window manager written in around 50 lines of code. This example is the implementation in java.

try(X11Client client = X11Client.connect(new DisplayName(":1"))) {
  int wid = client.createSimpleWindow(10, 10, 200, 200);
  client.mapWindow(wid);
  client.send(GrabKey.builder()
    .key((byte) client.keySymToKeyCode(KeySym.getByName("F1").get().getValue()))
    .modifiersEnable(ModMask.ONE)
    .grabWindow(client.getRoot(0))
    .ownerEvents(true)
    .keyboardMode(GrabMode.ASYNC)
    .pointerMode(GrabMode.ASYNC)
    .build());
  client.send(GrabButton.builder()
    .button(ButtonIndex.ONE)
    .modifiersEnable(ModMask.ONE)
    .grabWindow(client.getRoot(0))
    .ownerEvents(true)
    .eventMaskEnable(BUTTON_PRESS, BUTTON_RELEASE, POINTER_MOTION)
    .keyboardMode(GrabMode.ASYNC)
    .pointerMode(GrabMode.ASYNC)
    .build());
  client.send(GrabButton.builder()
    .button(ButtonIndex.THREE)
    .modifiersEnable(ModMask.ONE)
    .grabWindow(client.getRoot(0))
    .ownerEvents(true)
    .eventMaskEnable(BUTTON_PRESS, BUTTON_RELEASE, POINTER_MOTION)
    .keyboardMode(GrabMode.ASYNC)
    .pointerMode(GrabMode.ASYNC)
    .build());

  GetGeometryReply geometry = null;
  ButtonPressEvent start = null;

  while(true) {
    XEvent event = client.getNextEvent();
    if(event instanceof KeyPressEvent) {
      KeyPressEvent keyPress = (KeyPressEvent) event;
      int child = keyPress.getChild();
      if(child != Window.NONE.getValue()) {
        client.raiseWindow(child);
      }
    } else if(event instanceof ButtonPressEvent) {
      ButtonPressEvent buttonPress = (ButtonPressEvent) event;
      int child = buttonPress.getChild();
      if(child != Window.NONE.getValue()) {
        geometry = client.send(GetGeometry.builder()
          .drawable(child)
          .build());
        start = buttonPress;
      }
    } else if(event instanceof MotionNotifyEvent) {
      MotionNotifyEvent motionNotify = (MotionNotifyEvent) event;
      int child = motionNotify.getChild();
      if(child != Window.NONE.getValue()) {
        int xdiff = motionNotify.getRootX() - start.getRootX();
        int ydiff = motionNotify.getRootY() - start.getRootY();
        client.send(ConfigureWindow.builder()
          .window(child)
          .x(geometry.getX() + (start.getDetail() == ButtonIndex.ONE.getValue() ? xdiff : 0))
          .y(geometry.getY() + (start.getDetail() == ButtonIndex.ONE.getValue() ? ydiff : 0))
          .width(Math.max(1, geometry.getWidth() + (start.getDetail() == ButtonIndex.THREE.getValue() ? xdiff : 0)))
          .height(Math.max(1, geometry.getHeight() + (start.getDetail() == ButtonIndex.THREE.getValue() ? ydiff : 0)))
          .build());
      }
    } else if(event instanceof ButtonReleaseEvent) {
      start = null;
    }
  }
}

The java version is a bit longer due to the builder pattern being a little more verbose.

Design

Request Prossesing

OneWayRequests are requests which the client expects no response from the server. `OneWayRequests are queued and are only sent when the client is flushed. There are 3 ways in which the client will be flushed.

1. Manually by calling the flush() method
2. sending a TwoWayRequest
3. When the event queue is empty and getNextEvent() is called

TwoWayRequests are requests where the client expects a response from the server. These requests cause the client to flush the OneWayRequest queue and send the TwoWayRequest. Next the client reads input from the server and attempts to find the corresponding XReply and return it. The protocol object read from the server can be a XEvent or XError rather than an XReply. The client needs to handle these before it can find and return the XReply.When a XEvent is read it is stored in the event queue.

When an XError is read it may be for the current request or any of the previous OneWayRequests. Anytime an XError is found an exception will be thrown.

Error Handling

NOTE: error handling per request has not been implemented. This could be in the form of providing an error handler when sending requests.

Event Prossesing

Events can be sent by the server at any time, so they are stored in an event queue when processing TwoWayRequests. This allows the user to receive events by calling client.getNextEvent().

The event queue is an internal queue containing events which are deferred while processing a TwoWayRequest. client.getNextEvent() will empty this queue before reading events from the server. When the queue is empty getNextEvent() will flush the OneWayRequest queue and attempt to find and return a XEvent from the server.

When reading events from the server an error can be read. These errors can only be a result of OneWayRequests that are sent after flush() is called. These errors will be thrown as an exception.

Note: Receiving an XReply while processing events should not be expected since sending TwoWayRequests clears the stream of replies.

Concurrency

The client is not thread safe and invocations from one thread must be isolated from invocations of another thread. The connection socket, one-way request queue, and event queue are shared mutable data. All invocations must be synchronized in some way. Protocol objects are immutable, which allows them to be shared without synchronization.

Contributors

Support is most needed for example code. Other x11 libraries have tons of examples that prove the library works. So far this project only has a few basic examples.

I am not an x11 programmer but I find the protocol to be an interesting challenge and learning experience. The only other x11 client implementation for java that I have found is escher. Escher is very hand written and has many issues. The goal of this client is to automate the generation of the protocol and make a clear distinction between the client and any framework that may provide things like resource management and event dispatch.

This project uses the xcb xmls to generate protocol classes for the core protocol and extensions. It uses a custom gradle plugin to generate the classes. Be sure to check the javadoc to view supported protocol objects.

All protocol objects support read and write methods regardless of type. This means that these objects can also be used to build an x11 server and are not tied specifically to the client.

Xlib and XCB provides convenient methods rather than directly using the protocol. I have avoided adding convenience methods to the client but may do so in the future. Methods such as createSimpleWindow can be added. If you have any suggestions on methods that can be added feel free to submit an issue or PR.

The core protocol and every supported extension implements a plugin which enables the client to figure out which class to use when reading errors and events from the server. These plugins are generated durring the build process. Plugins are discovered and loaded using the ServiceLoader pattern.

Frameworks

There is a need for higher levels of abstraction such as Window, Pixmap, and GraphicsContext. As well as managing the creation and destruction of these objects. There is also a need for dispatching events in a consistent way. These abstractions will be needed for any application and can be implemented in a framework. I would like to consider this the job of a Display class and possibly a Toolkit. Currently there is a Display class which manages Resources and event dispatch. A framework is not the primary goal of the client project and will likely move into a new project.

Other X11 Clients

https://github.com/psychon/x11rb

https://github.com/sidorares/node-x11

https://github.com/BurntSushi/xgb

Learning x11

https://cgit.freedesktop.org/xorg/proto/x11proto/plain/XF86keysym.h

https://tronche.com/gui/x/xlib/input/keyboard-encoding.html

https://jichu4n.com/posts/how-x-window-managers-work-and-how-to-write-one-part-i/

https://www.geeks3d.com/20120102/programming-tutorial-simple-x11-x-window-code-sample-for-linux-and-mac-os-x/

https://wiki.tcl-lang.org/page/Disable+autorepeat+under+X11

https://p.janouch.name/article-xgb.html

https://jamey.thesharps.us/2021/03/25/xcb-protocol-specifications-data/

https://www.x.org/releases/X11R7.6/doc/libXtst/recordlib.html

versions

0.18.0

• Switched to a multimodule project
• Switched to jdk 21
• Added java module system support
• Removed delombok due to issues with modules. This results in javadoc no longer being generated.
• Removed dependency on junixsocket and switched to the jdk UnixDomainSocket.
• Removed jbang
• Moved all integration tests to the examples project with a main method.

0.17.0

• Adding generated protocol sources to git

0.16.0

• Renaming project to x11
• Switching to a multiproject build.
• Change integration tests into examples in example project.

0.15.0

• Adding RecordApi which provides a higher level api for reading records with parsed XObjects so the user does not need to parse the data.
• Each XObject now has a static PLUGIN_NAME assigned to the plugin name and an instance getter method.
• Plugins now use the header as the plugin name.
• Added all plugin info from the xml file (extensionName, extensionXName, extensionMultiword)
• added methods to client for reading protocol from any X11Input. This is used for reading data from the record extension and for testing read/write for any object.
• Fixed issues with list lengths which need to be unsigned.

0.14.0

• Fixed issue where WILD XAuthority entries do not have an address
• Fixed major bug when writing requests. For xproto the header should start with the OPCODE then 1 pad. For extensions the header should start with the majorOpcode then OPCODE. BigRequest and all QueryVersion requests worked because their OPCODE is 0 but everything else in extensions failed. This should be fixed for all extensions and has been tested with the RECORD extension.

0.13.0

ProtocolPluginService now sets majorOpcode on XProtocolPlugins and uses it instead of majorVersion as the base opcode for requests. This fixes a bug in loading plugins and sending requests.

0.12.0

Adding jbang examples Upgrading dependencies Removing rekon gradle plugin

0.11.0

Adding support for xkb except for GetKbdByName

0.10.0

[x] Made DeviceStateAbs_area and DeviceStateAbs_calib names DeviceStateAbsArea and DeviceStateAbsCalib [x] Adding other KeySyms from x11lib.

0.9.0

• Added support for resolving enums directly. In xinput.xml there is an Event Property which has the same name as the enum Property from xproto.xml. The current solution is to use resolveXTypeEnum(String) when resolving enums.

• Added support for <eventstruct> tags.

[x] plugin name constant is needed for checking the <allowed> tag within <eventstruct> [x] offset is required to check if an event is supported by a specific <eventstruct>

• Added support for readParams which are not part of the protocol for the object but passed in from another object's protocol. This is needed for xinput DeviceTimeCoord.

[x] Found bug with reading and writing events and errors for extensions. The offset must be subtracted from the number not added.

[x] Writing events is not possible without passing in the extension offset. The server will treat extension events like xproto events.

[x] Added support for <case> tags within a <switch>. This creates an interface and implementing classes for each case.

0.8.0

Adding support for glx and dri3 extensions

0.7.0

• Adding support for generic events
• Adding support for the Present extension
• Added ProtocolPluginService to handle plugins for the XProtocolService

0.6.0

• Implementing sync() method based on XSync but without a discard parameter.
• Adding discard() method to clear the event queue.
• Added keyCodeToKeySym() methods.
• Added keySymToKeyCodes() method.
• Added getKeySym() method.
• getAtom(int) now returns an AtomValue which contains the id and name.
• Added getWMProtocols(int) to returns the supported protocols for a window.
• Added killClient(int) and inputFocus(int).
• Added Generator for KeySym enum.
• Added KeyboardService to handle the keyboard for the client.
• Added BasicWindowManager to example tests.

0.5.0

Adding hasResponse() method which checks for an available XEvent or XError on the socket.

Since DisplayName can set the default screen methods have been added to return default settings from the connection setup response.

0.4.0

Removing length properties from protocol objects where it is simply the list size. The length still needs to be set for properties involving complex expressions. This results in not having to set the length of lists on most objects. For example drawing a string no longer requires the size.

client.send(ImageText8.builder()
  .drawable(window.getWid())
  .gc(gc.getCid())
  .string(stringToByteList("Hello World!"))
  .x((short) 10)
  .y((short) 50)
  .build());

Adding exclude to x11protocol plugin.

Fixing issues with objects missing padding for the first field. This enables the sync extension to work.

Added support for file descriptors. They are simply treated as an int.

Added extensions shm, sync xrandr, xv, and xvmc

Added defaultGC cache for root windows and method to automatically create them.

0.3.0

Adding TinyWM example.

Added keySymToKeyCode which can be used to grab keys.

Moving XDisplay methods to main client. Removing XDisplay.

Moved DisplayName, KeySym, KeySystem, ParametersCheck, and XAuthority to protocol package.

Adding ResourceIdService which will switch to XC_MISC extension once ids run out.

Adding AtomService which will cache InternAtoms.

0.2.1

Adding github actions build. The workflow will build the library and run a sonar scan.

Adding keysymdef.h support for some of the keys.

0.2.0

Fixed issue where the size of a padalign is returned as 0 rather than calculated.

Updating javadoc and adding tests. Refactoring classes for better package encapsulation.

• Each plugin is now in its extension package
• XProtocolService is in the client package and package private
• Utilities, X11InputStream, and X11OutputStream is in the protocol package
• Made ParametersCheck package private
• ConnectionFailureException, X11ClientException, and X11ErrorException constructors are package private
• X11ClientException is now used for IOExceptions thrown while connecting to the x11 server
• X11Connection is now private

0.1.0

Initial release of x11-client. The client generates classes for bigreq, composite, damage, dpms, dri2, ge, record, res, screensaver, shape, xc_misc, xevie, xf86dri, xf86vidmode, xfixes, xinerama, xproto, xselinux, and xtest.

License

Copyright 2020 John Mercier

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.