skia2/include/gpu/gl/GrGLConfig.h

/*
 * Copyright 2011 Google Inc.
 *
 * Use of this source code is governed by a BSD-style license that can be
 * found in the LICENSE file.
 */



#ifndef GrGLConfig_DEFINED
#define GrGLConfig_DEFINED

#include "GrTypes.h"

/**
 * Optional GL config file.
 */
#ifdef GR_GL_CUSTOM_SETUP_HEADER
    #include GR_GL_CUSTOM_SETUP_HEADER
#endif

#if !defined(GR_GL_FUNCTION_TYPE)
    #define GR_GL_FUNCTION_TYPE
#endif

/**
 * The following are optional defines that can be enabled at the compiler
 * command line, in a IDE project, in a GrUserConfig.h file, or in a GL custom
 * file (if one is in use). If a GR_GL_CUSTOM_SETUP_HEADER is used they can
 * also be placed there.
 *
 * GR_GL_LOG_CALLS: if 1 Gr can print every GL call using GrPrintf. Defaults to
 * 0. Logging can be enabled and disabled at runtime using a debugger via to
 * global gLogCallsGL. The initial value of gLogCallsGL is controlled by
 * GR_GL_LOG_CALLS_START.
 *
 * GR_GL_LOG_CALLS_START: controls the initial value of gLogCallsGL when
 * GR_GL_LOG_CALLS is 1. Defaults to 0.
 *
 * GR_GL_CHECK_ERROR: if enabled Gr can do a glGetError() after every GL call.
 * Defaults to 1 if GR_DEBUG is set, otherwise 0. When GR_GL_CHECK_ERROR is 1
 * this can be toggled in a debugger using the gCheckErrorGL global. The initial
 * value of gCheckErrorGL is controlled by by GR_GL_CHECK_ERROR_START.
 *
 * GR_GL_CHECK_ERROR_START: controls the initial value of gCheckErrorGL
 * when GR_GL_CHECK_ERROR is 1.  Defaults to 1.
 *
 * GR_GL_NO_CONSTANT_ATTRIBUTES: if this evaluates to true then the GL backend
 * will use uniforms instead of attributes in all cases when there is not
 * per-vertex data. This is important when the underlying GL implementation
 * doesn't actually support immediate style attribute values (e.g. when 
 * the GL stream is converted to DX as in ANGLE on Chrome). Defaults to 0.
 *
 * GR_GL_USE_BUFFER_DATA_NULL_HINT: When specifing new data for a vertex/index
 * buffer that replaces old data Ganesh can give a hint to the driver that the
 * previous data will not be used in future draws like this:
 *  glBufferData(GL_..._BUFFER, size, NULL, usage);       //<--hint, NULL means
 *  glBufferSubData(GL_..._BUFFER, 0, lessThanSize, data) //   old data can't be
 *                                                        //   used again.
 * However, this can be an unoptimization on some platforms, esp. Chrome.
 * Chrome's cmd buffer will create a new allocation and memset the whole thing
 * to zero (for security reasons). Defaults to 1 (enabled).
 *
 * GR_GL_PER_GL_FUNC_CALLBACK: When set to 1 the GrGLInterface object provides
 * a function pointer that is called just before every gl function. The ptr must
 * be valid (i.e. there is no NULL check). However, by default the callback will
 * be set to a function that does nothing. The signature of the function is:
 *    void function(const GrGLInterface*)
 * It is not extern "C".
 * The GrGLInterface field fCallback specifies the function ptr and there is an
 * additional field fCallbackData of type intptr_t for client data.
 *
 * GR_GL_RGBA_8888_PIXEL_OPS_SLOW: Set this to 1 if it is known that performing
 * glReadPixels / glTex(Sub)Image with format=GL_RGBA, type=GL_UNISIGNED_BYTE is
 * significantly slower than format=GL_BGRA, type=GL_UNISIGNED_BYTE.
 *
 * GR_GL_FULL_READPIXELS_FASTER_THAN_PARTIAL: Set this to 1 if calling
 * glReadPixels to read the entire framebuffer is faster than calling it with
 * the same sized rectangle but with a framebuffer bound that is larger than
 * the rectangle read.
 *
 * GR_GL_CHECK_ALLOC_WITH_GET_ERROR: If set to 1 this will then glTexImage,
 * glBufferData, glRenderbufferStorage, etc will be checked for errors. This
 * amounts to ensuring the error is GL_NO_ERROR, calling the allocating
 * function, and then checking that the error is still GL_NO_ERROR. When the
 * value is 0 we will assume no error was generated without checking.
 *
 * GR_GL_CHECK_FBO_STATUS_ONCE_PER_FORMAT: We will normally check the FBO status
 * every time we bind a texture or renderbuffer to an FBO. However, in some
 * environments CheckFrameBufferStatus is very expensive. If this is set we will
 * check the first time we use a color format or a combination of color /
 * stencil formats as attachments. If the FBO is complete we will assume
 * subsequent attachments with the same formats are complete as well.
 */

#if !defined(GR_GL_LOG_CALLS)
    #define GR_GL_LOG_CALLS                             GR_DEBUG
#endif

#if !defined(GR_GL_LOG_CALLS_START)
    #define GR_GL_LOG_CALLS_START                       0
#endif

#if !defined(GR_GL_CHECK_ERROR)
    #define GR_GL_CHECK_ERROR                           GR_DEBUG
#endif

#if !defined(GR_GL_CHECK_ERROR_START)
    #define GR_GL_CHECK_ERROR_START                     1
#endif

#if !defined(GR_GL_NO_CONSTANT_ATTRIBUTES)
    #define GR_GL_NO_CONSTANT_ATTRIBUTES                0
#endif

#if !defined(GR_GL_USE_BUFFER_DATA_NULL_HINT)
    #define GR_GL_USE_BUFFER_DATA_NULL_HINT             1
#endif

#if !defined(GR_GL_PER_GL_FUNC_CALLBACK)
    #define GR_GL_PER_GL_FUNC_CALLBACK                  0
#endif

#if !defined(GR_GL_RGBA_8888_PIXEL_OPS_SLOW)
    #define GR_GL_RGBA_8888_PIXEL_OPS_SLOW              0
#endif

#if !defined(GR_GL_FULL_READPIXELS_FASTER_THAN_PARTIAL)
    #define GR_GL_FULL_READPIXELS_FASTER_THAN_PARTIAL   0
#endif

#if !defined(GR_GL_CHECK_ALLOC_WITH_GET_ERROR)
    #define GR_GL_CHECK_ALLOC_WITH_GET_ERROR            1
#endif

#if !defined(GR_GL_CHECK_FBO_STATUS_ONCE_PER_FORMAT)
    #define GR_GL_CHECK_FBO_STATUS_ONCE_PER_FORMAT      0
#endif

/**
 * There is a strange bug that occurs on Macs with NVIDIA GPUs. We don't
 * fully understand it. When (element) array buffers are continually
 * respecified using glBufferData performance can fall off of a cliff. The
 * driver winds up performing many DMA mapping / unmappings and chews up ~50% of
 * the core. However, it has been observed that occaisonally respecifiying the
 * buffer using glBufferData and then writing data using glBufferSubData
 * prevents the bad behavior.
 *
 * There is a lot of uncertainty around this issue. In Chrome backgrounding
 * the tab somehow initiates this behavior and we don't know what the connection
 * is. Another observation is that Chrome's cmd buffer server will actually
 * create a buffer full of zeros when it sees a NULL data param (for security
 * reasons). If this is disabled and NULL is actually passed all the way to the
 * driver then the workaround doesn't help.
 *
 * The issue is tracked at:
 * http://code.google.com/p/chromium/issues/detail?id=114865
 *
 * When the workaround is enabled we will use the glBufferData / glBufferSubData
 * trick every 128 array buffer uploads.
 *
 * Hopefully we will understand this better and have a cleaner fix or get a
 * OS/driver level fix.
 */
#define GR_GL_MAC_BUFFER_OBJECT_PERFOMANCE_WORKAROUND   \
    (GR_MAC_BUILD &&                                    \
     !GR_GL_USE_BUFFER_DATA_NULL_HINT)

#endif