X-Git-Url: https://git.libre-soc.org/?a=blobdiff_plain;f=docs%2Fegl.html;h=e77c2359dc1f8f04c2e901f13900f79df0809d56;hb=a3b73ccf6db3efe4ce0eed4c60d1e2709b335cac;hp=cdfae044a8ae2a9bfbc33e0898c66d5c6ce37c45;hpb=5f08eff2a769e27df37fc00e46797e70a54727bb;p=mesa.git diff --git a/docs/egl.html b/docs/egl.html index cdfae044a8a..e77c2359dc1 100644 --- a/docs/egl.html +++ b/docs/egl.html @@ -1,16 +1,24 @@ - - -Mesa EGL + + + + + Mesa EGL + + + - +
+

The Mesa 3D Graphics Library

+
- + +

Mesa EGL

The current version of EGL in Mesa implements EGL 1.4. More information about EGL can be found at - + http://www.khronos.org/egl/.

The Mesa's implementation of EGL uses a driver architecture. The main @@ -19,114 +27,115 @@ API entry points and helper functions for use by the drivers. Drivers are dynamically loaded by the main library and most of the EGL API calls are directly dispatched to the drivers.

-

The driver in use decides the window system to support. For drivers that -support hardware rendering, there are usually multiple drivers supporting the -same window system. Each one of of them supports a certain range of graphics -cards.

+

The driver in use decides the window system to support.

Build EGL

  1. -

    Run configure with the desired state trackers and and enable -the Gallium driver for your hardware. For example

    +

    Run configure with the desired client APIs and enable +the driver for your hardware. For example

    -  $ ./configure --with-state-trackers=egl,es,vega --enable-gallium-{swrast,intel}
+  $ ./configure --enable-gles1 --enable-gles2 \
+                --with-dri-drivers=... \
+                --with-gallium-drivers=...
    -

    The main library will be enabled by default. The egl state -tracker is needed by a number of EGL drivers. EGL drivers will be covered -later. The es state tracker provides OpenGL ES 1.x -and 2.x and the vega state tracker provides OpenVG -1.x.

    +

    The main library and OpenGL is enabled by default. The first two options +above enables OpenGL ES 1.x and 2.x. The last two +options enables the listed classic and and Gallium drivers respectively.

    +
  2. Build and install Mesa as usual.

In the given example, it will build and install libEGL, -libGLESv1_CM, libGLESv2, libOpenVG, and -one or more EGL drivers.

+libGL, libGLESv1_CM, libGLESv2, and one +or more EGL drivers.

Configure Options

There are several options that control the build of EGL at configuration time

- +

By default, libGL has its own copy of libglapi. +This options makes libGL use the shared libglapi. This +is required if applications mix OpenGL and OpenGL ES.

+ + -

OpenGL

+
--enable-openvg
+
-

The OpenGL state tracker is not built in the above example. It should be -noted that the classic libGL is not a state tracker and cannot be -used with EGL (unless the EGL driver in use is egl_glx). To build -the OpenGL state tracker, one may append glx to ---with-state-trackers and manually build -src/gallium/winsys/xlib/.

+

OpenVG must be explicitly enabled by this option.

+ +
+ +

Use EGL

-

The demos for OpenGL ES and OpenVG can be found in progs/es1/, -progs/es2/ and progs/openvg/. You can use them to -test your build. For example,

+

Demos

-
-  $ cd progs/es1/xegl
-  $ make
-  $ ./torus
-
+

There are demos for the client APIs supported by EGL. They can be found in +mesa/demos repository.

Environment Variables

There are several environment variables that control the behavior of EGL at runtime

- + +

EGL Drivers

-

There are two categories of EGL drivers: Gallium and classic.

- -

Gallium EGL drivers supports all rendering APIs specified in EGL 1.4. The -support for optional EGL functions and EGL extensions is usually more complete -than the classic ones. These drivers depend on the egl state -tracker to build. The available drivers are

- - - -

<dpy> is given by --with-egl-displays at -configuration time. There will be one EGL driver for each combination of the -displays listed and the hardware drivers enabled.

- -

Classic EGL drivers, on the other hand, supports only OpenGL as its -rendering API. They can be found under src/egl/drivers/. There -are 3 of them

- - +

This driver is based on Gallium3D. It supports all rendering APIs and +hardware supported by Gallium3D. It is the only driver that supports OpenVG. +The supported platforms are X11, DRM, FBDEV, and GDI.

+ +

This driver comes with its own hardware drivers +(pipe_<hw>) and client API modules +(st_<api>).

+ + + +

Packaging

+ +

The ABI between the main library and its drivers are not stable. Nor is +there a plan to stabilize it at the moment. Of the EGL drivers, +egl_gallium has its own hardware drivers and client API modules. +They are considered internal to egl_gallium and there is also no +stable ABI between them. These should be kept in mind when packaging for +distribution.

-

To use the classic drivers, one must manually set EGL_DRIVER at -runtime.

+

Generally, egl_dri2 is preferred over egl_gallium +when the system already has DRI drivers. As egl_gallium is loaded +before egl_dri2 when both are available, egl_gallium +is disabled by default.

Developers

@@ -233,10 +245,6 @@ runtime.

src/egl/. The sources of the egl state tracker can be found at src/gallium/state_trackers/egl/.

-

The suggested way to learn to write a EGL driver is to see how other drivers -are written. egl_glx should be a good reference. It works in any -environment that has GLX support, and it is simpler than most drivers.

-

Lifetime of Display Resources

Contexts and surfaces are examples of display resources. They might live @@ -244,8 +252,8 @@ longer than the display that creates them.

In EGL, when a display is terminated through eglTerminate, all display resources should be destroyed. Similarly, when a thread is released -throught eglReleaseThread, all current display resources should be -released. Another way to destory or release resources is through functions +through eglReleaseThread, all current display resources should be +released. Another way to destroy or release resources is through functions such as eglDestroySurface or eglMakeCurrent.

When a resource that is current to some thread is destroyed, the resource @@ -267,16 +275,50 @@ uninitialized display.

resources. The drivers are responsible to the correct behavior as defined by EGL.

-

TODOs

- - - +

EGL_RENDER_BUFFER

+ +

In EGL, the color buffer a context should try to render to is decided by the +binding surface. It should try to render to the front buffer if the binding +surface has EGL_RENDER_BUFFER set to +EGL_SINGLE_BUFFER; If the same context is later bound to a +surface with EGL_RENDER_BUFFER set to +EGL_BACK_BUFFER, the context should try to render to the back +buffer. However, the context is allowed to make the final decision as to which +color buffer it wants to or is able to render to.

+ +

For pbuffer surfaces, the render buffer is always +EGL_BACK_BUFFER. And for pixmap surfaces, the render buffer is +always EGL_SINGLE_BUFFER. Unlike window surfaces, EGL spec +requires their EGL_RENDER_BUFFER values to be honored. As a +result, a driver should never set EGL_PIXMAP_BIT or +EGL_PBUFFER_BIT bits of a config if the contexts created with the +config won't be able to honor the EGL_RENDER_BUFFER of pixmap or +pbuffer surfaces.

+ +

It should also be noted that pixmap and pbuffer surfaces are assumed to be +single-buffered, in that eglSwapBuffers has no effect on them. It +is desirable that a driver allocates a private color buffer for each pbuffer +surface created. If the window system the driver supports has native pbuffers, +or if the native pixmaps have more than one color buffers, the driver should +carefully attach the native color buffers to the EGL surfaces, re-route them if +required.

+ +

There is no defined behavior as to, for example, how +glDrawBuffer interacts with EGL_RENDER_BUFFER. Right +now, it is desired that the draw buffer in a client API be fixed for pixmap and +pbuffer surfaces. Therefore, the driver is responsible to guarantee that the +client API renders to the specified render buffer for pixmap and pbuffer +surfaces.

+ +

EGLDisplay Mutex

+ +The EGLDisplay will be locked before calling any of the dispatch +functions (well, except for GetProcAddress which does not take an +EGLDisplay). This guarantees that the same dispatch function will +not be called with the sample display at the same time. If a driver has access +to an EGLDisplay without going through the EGL APIs, the driver +should as well lock the display before using it. + +