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      3 Notes about the EGL library:
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      5 
      6 The EGL code here basically consists of two things:
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      8 1. An EGL API dispatcher.  This directly routes all the eglFooBar() API
      9    calls into driver-specific functions.
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     11 2. Fallbacks for EGL API functions.  A driver _could_ implement all the
     12    EGL API calls from scratch.  But in many cases, the fallbacks provided
     13    in libEGL (such as eglChooseConfig()) will do the job.
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     15 
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     17 Bootstrapping:
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     19 When the apps calls eglOpenDisplay() a device driver is selected and loaded
     20 (look for dlsym() or LoadLibrary() in egldriver.c).
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     22 The driver's _eglMain() function is then called.  This driver function
     23 allocates, initializes and returns a new _EGLDriver object (usually a
     24 subclass of that type).
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     26 As part of initialization, the dispatch table in _EGLDriver->API must be
     27 populated with all the EGL entrypoints.  Typically, _eglInitDriverFallbacks()
     28 can be used to plug in default/fallback functions.  Some functions like
     29 driver->API.Initialize and driver->API.Terminate _must_ be implemented
     30 with driver-specific code (no default/fallback function is possible).
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     32 
     33 A bit later, the app will call eglInitialize().  This will get routed
     34 to the driver->API.Initialize() function.  Any additional driver
     35 initialization that wasn't done in _eglMain() should be done at this
     36 point.  Typically, this will involve setting up visual configs, etc.
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     38 
     39 
     40 Special Functions:
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     42 Certain EGL functions _must_ be implemented by the driver.  This includes:
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     44 eglCreateContext
     45 eglCreateWindowSurface
     46 eglCreatePixmapSurface
     47 eglCreatePBufferSurface
     48 eglMakeCurrent
     49 eglSwapBuffers
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     51 Most of the EGLConfig-related functions can be implemented with the
     52 defaults/fallbacks.  Same thing for the eglGet/Query functions.
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     57 Teardown:
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     59 When eglTerminate() is called, the driver->API.Terminate() function is
     60 called.  The driver should clean up after itself.  eglTerminate() will
     61 then close/unload the driver (shared library).
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     66 Subclassing:
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     68 The internal libEGL data structures such as _EGLDisplay, _EGLContext,
     69 _EGLSurface, etc should be considered base classes from which drivers
     70 will derive subclasses.
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