x11

x11 protocol probes

The repository aim is to creat a template for a code. By the code I mean some, possibly graphical, application that uses epoll syscall to wait for events.

** STRUCTURE **

aux_* files represent auxiliary modules. prob_* files are templates.

opencv_image2poly.cpp is a command line tool to convert raster image polygon contours to JSON format.

===========================================================================

aux_xcb

• module that does a communication with X11 by means of XCB. all functionality are done as much synchronous as possible. that is done deliberately, to ease debugging.

aux_raster

• module that carry almost no use, except to creat image buffer that will be sent to X11 for display.

aux_drm

• module that wraps libDRM functionality.

aux_egl

• module that wraps libEGL.

aux_gl

• module that wraps libGL.

===========================================================================

prob_xcb

• simplest application that creates XCB window and listens for events.

prob_xcb_dri

• same as prob_xcb. new thing is that application enqueues messages for screen refresh updates and gets update events.

prob_egl

• enumerate GPUs via EGL. no display server(X11) required. map EGL "devices" to DRM ones.
• mapping done through comparison of EGL EGL_DRM_DEVICE_FILE_EXT device string <=> with DRM /dev/dri/card{0} filesystem path.
• OpenGL context can be created w/o XCB, or X11 connection.

** PREREQUISITES **

Debian.

Debian packages required

libx11-dev, libx11-xcb-dev, libxcb1-dev, libxcb-keysyms1-dev, libxcb-util-dev, libxcb-image0-dev, libxcb-present-dev, libxcb-randr0-dev

prob_xcb_dri needs: libdrm-dev

prob_egl needs: libglu1-mesa-dev, libegl-dev, libgl-dev

img2poly needs: libopencv-dev, libjson-c-dev

** COMPILE && INSTALL **

• make

** RUN **

• ./bin/<binary name>

** LYRICS **

/* possible source of latency */

• user => compositing WM => X server => DRM => GPU

/* possible source of latency */

• user => compositing WM => X server => compositing WM => X server => DRM => GPU

/* X11 and GPU driver */

• X11, or GPU driver should distribute and sync a FB to monitors.

/* do compositing WM always have one big FB? */

• many FBs with a different scaling and whatelse is left behind. for now.

/* VBLANK event for a window? */

• it is really NOT a question of getting VBLANK for a CRTC. it is a question, which VBLANK events will window receive?

/* window and CRTC interop */

• window <=> CRTC

  • if it moves.

  • if it power-offs and switches to another CRTC.

  • if the window is visible on many physical monitors.

    • xfce4-wm chooses a strategy so, that window receives VBLANKS of a monitor that the window is most part visible on.