The FAQ was clearly written a very long time ago, when user sessions were a pipe dream, session compositors were the important thing, and we had a lot more questions than answers.
Now things have solidified a bit, and I'm writing this from a native Wayland client inside a native Wayland-on-KMS desktop, rewrite good chunks of the FAQ to reflect today's reality a little better. Signed-off-by: Daniel Stone <dani...@collabora.com> --- faq.html | 115 ++++++++++++++++++++++++--------------------------------------- 1 file changed, 43 insertions(+), 72 deletions(-) diff --git a/faq.html b/faq.html index 58b6fc9..edcd6df 100644 --- a/faq.html +++ b/faq.html @@ -52,45 +52,30 @@ behalf of the clients, it expects the clients to use whatever means they prefer to render into a shareable buffer. When the client is done, it informs the Wayland server of the new contents. The - current test clients use either cairo software rendering, cairo on - OpenGL or hardware accelerated OpenGL directly. As long as you have - a userspace driver library that will let you render into a sharable - buffer, you're good to go. + current test clients use either Cairo software rendering, Cairo on + OpenGL or hardware-accelerated OpenGL directly. Additionally, media + frameworks can share their buffers directly with the server. As + long as you have a userspace driver library that will let you render + into a shareable buffer, you're good to go. </p> <h3>Is wayland replacing the X server?</h3> <p> - It could replace X as the native Linux graphics server, but I'm sure - X will always be there on the side. I imagine that Wayland and X - will coexist in two ways on a Linux desktop: Wayland is a graphics - multiplexer for a number of X servers. Linux today typically only - uses one X server for GDM and the user session, but we'll probably - see that move to a dedicated GDM X server, an X server for user - sessions (spawning more on the fly as more users log in) and maybe a - dedicated screensaver/unlock X server. Right now we rely on VT - switching to move between X servers, and it's horrible. We have no - control over what the transitions look like and the VT ioctls are - pretty bad. Wayland provides a solution here, in that it can host - several X servers as they push their root window to Wayland as - surfaces. The compositor in this case will be a dedicated session - switcher that will cross-fade between X servers or spin them on a - cube. -</p> - -<p> - Further down the road we run a user session natively under - Wayland with clients written for Wayland. There will still (always) - be X applications to run, but we now run these under a root-less X - server that is itself a client of the Wayland server. This will - inject the X windows into the Wayland session as native looking - clients. The session Wayland server can run as a nested Wayland - server under the system Wayland server described above, maybe even - side by side with X sessions. There's a number of intermediate - steps, such as running the GNOME screen saver as a native wayland - client, for example, or running a composited X desktop, where the - compositor is a Wayland client, pushing the composited desktop to - Wayland. + Mostly, yes. User sessions are able to run under Wayland today, via + a number of compositors: Weston itself as well as Enlightenment, + GNOME Shell, KDE, and a number of others under development. With + most toolkits having Wayland ports, as well as frameworks such as + GStreamer and SDL, it's perfectly possible to run a purely native + Wayland session as your desktop. +</p> + +<p> + That being said, there are some clients which rely on X11, and + always will be. To that end, XWayland provides a plugin for Wayland + compositors, running a real X server. This gives legacy clients a + real and compliant X11 platform to run on, displayed side by side + with native Wayland clients in your Wayland session. </p> <h3>Why not extend the X server?</h3> @@ -101,15 +86,11 @@ exchange and update models that Wayland is built on into X. However, we have an option here of pushing X out of the hotpath between clients and the hardware and making it a compatibility - option. I'm not deluding myself that any general purpose desktop - Linux distribution will stop shipping X as we know it or as a - Wayland client anytime soon. Nor should they, there will still be X - applications to run and people expect that from a Linux desktop. - What's different now is that a lot of infrastructure has moved from - the X server into the kernel (memory management, command scheduling, - mode setting) or libraries (cairo, pixman, freetype, fontconfig, - pango, etc) and there is very little left that has to happen in a - central server process. + option. What's different now is that a lot of infrastructure has + moved from the X server into the kernel (memory management, command + scheduling, mode setting) or libraries (cairo, pixman, freetype, + fontconfig, pango, etc) and there is very little left that has to + happen in a central server process. </p> <h3>What is wrong with X?</h3> @@ -129,25 +110,18 @@ useful extensions. But we can't ever get rid of the core rendering API and much other complexity that is rarely used in a modern desktop. With Wayland we can move the X server and all its legacy - technology to an optional code path. Getting to a point where the X - server is a compatibility option instead of the core rendering - system will take a while, but we'll never get there if don't plan - for it. + technology to an optional code path. </p> <h3>What about the overhead of running X on wayland?</h3> <p> - If you're running a fullscreen X server, which pushes its root - window buffer to Wayland there is little overhead. If the X server - root window is transformed (i.e. scaled down or spinning on the side - of a cube) the Wayland compositor will have to do an extra copy to - get the pixels on screen. But once the animation finishes and the X - server buffer fills the entire screen, the Wayland compositor can - change the video scanout to source from the X server buffer and - retreat into the background. The X server uses the standard X.org - DDX drivers, renders directly to its pixmaps and its root window, - and the path from X to hardware is exactly as a native X.org server. + Most modern desktops already use an external compositing manager: + when the X server decides it needs to update content, it informs + this external process (usually your window manager), and allows it to + control the rendering entirely. Using XWayland is just the same as + this, but more efficient because the compositing manager doesn't have + to go back through the X server to display the content it rendered. </p> <h3>Is Wayland network transparent / does it support remote rendering?</h3> @@ -210,21 +184,13 @@ manager and compositor into one process. You can think of Wayland as a toolkit for creating clients and compositors. It is not a specific single compositor or window manager. If you want a - different window manager, you can write a new one. + different window manager, you can write a new one. A 'libweston' + effort is underway in order to allow new environments to reuse + Weston's codebase and mechanics, whilst providing their own look + and feel. </p> -<p> - This may sound like a lot of work, but one of the key points about - Wayland is that the boilerplate code to a Wayland compositor is - comparable or less than the X boilerplate involved in becoming an X - window manager and compositor. Bringing up EGL and GLES2 on the - Linux KMS framebuffer and reading input from evdev can be done in - less than a thousand lines of code. The Wayland server side library - provides the protocol implementation and makes it easy to put the - pieces together. -</p> - -<h3>Why does Wayland use EGL and GLES2?</h3> +<h3>Why does Wayland use EGL?</h3> <p> EGL is the only GL binding API that lets us avoid dependencies on @@ -238,8 +204,13 @@ A more subtle point is that libGL.so includes the GLX symbols, so linking to that library will pull in all the X dependencies. This means that we can't link to full GL without pulling in the client - side of X, so we're using GLES2 for now. Longer term, we'll need a - way to use full GL under Wayland. + side of X, so Weston uses OpenGL ES to render. This also enables + Weston to run on GPUs which don't support the full OpenGL API. +</p> + +<p> + As detailed above, clients are however free to use whichever + rendering API they like. </p> </body> -- 2.7.4 _______________________________________________ wayland-devel mailing list wayland-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/wayland-devel
