# The Mesa 3D Graphics Library

# OpenGL ES

Mesa implements OpenGL ES 1.1 and OpenGL ES 2.0. More information about OpenGL ES can be found at https://www.khronos.org/opengles/.

OpenGL ES depends on a working EGL implementation. Please refer to Mesa EGL for more information about EGL.

## Build the Libraries

1. Run `meson configure` with `-D gles1=true -D gles2=true` and enable the Gallium driver for your hardware.
2. Build and install Mesa as usual.

Alternatively, if XCB-DRI2 is installed on the system, one can use `egl_dri2` EGL driver with OpenGL|ES-enabled DRI drivers

1. Run `meson configure` with `-D gles1=true -D gles2=true`.
2. Build and install Mesa as usual.

Both methods will install libGLESv1_CM, libGLESv2, libEGL, and one or more EGL drivers for your hardware.

## Run the Demos

There are some demos in `mesa/demos` repository.

## Developers

### Dispatch Table

OpenGL ES has an additional indirection when dispatching functions

      Mesa:       glFoo() --> _mesa_Foo()
      OpenGL ES:  glFoo() --> _es_Foo() --> _mesa_Foo()

The indirection serves several purposes

- When a function is in Mesa and the type matches, it checks the arguments and calls the Mesa function.
- When a function is in Mesa but the type mismatches, it checks and converts the arguments before calling the Mesa function.
- When a function is not available in Mesa, or accepts arguments that are not available in OpenGL, it provides its own implementation.

Other than the last case, OpenGL ES uses `APIspec.xml` to generate functions to check and/or converts the arguments.