[vlc-devel] [PATCH] opengl: use buffer objects instead of host memory with glVertexAttribPointer.

[Felix Abecassis]

2014-03-26 21:35 GMT+01:00 Rémi Denis-Courmont <remi at remlab.net>:
> Le mercredi 26 mars 2014, 18:33:56 Felix Abecassis a écrit :
>> Previously, glVertexAttribPointer was called in function
>> DrawWithShaders using an host array (textureCoord) allocated on the
>> stack inside a loop. This caused stack buffer overflow afterwards.
>>
>> See http://www.opengl.org/wiki/Synchronization#Asynchronous_action
>>
>> Array definition could have been hoisted out of the loop but using
>> buffer objects is a better solution since it is now the only option
>> with recent OpenGL versions.
>> ---
>>  modules/video_output/opengl.c | 40 ++++++++++++++++++++++++++++++++++++++--
>> 1 file changed, 38 insertions(+), 2 deletions(-)
>>
>> diff --git a/modules/video_output/opengl.c b/modules/video_output/opengl.c
>> index 512429e..a5abdc3 100644
>> --- a/modules/video_output/opengl.c
>> +++ b/modules/video_output/opengl.c
>> @@ -62,6 +62,10 @@
>>  #   define PFNGLUSEPROGRAMPROC               typeof(glUseProgram)*
>>  #   define PFNGLDELETEPROGRAMPROC            typeof(glDeleteProgram)*
>>  #   define PFNGLATTACHSHADERPROC             typeof(glAttachShader)*
>> +#   define PFNGLGENBUFFERSPROC               typeof(glGenBuffers)*
>> +#   define PFNGLBINDBUFFERPROC               typeof(glBindBuffer)*
>> +#   define PFNGLBUFFERDATAPROC               typeof(glBufferData)*
>> +#   define PFNGLDELETEBUFFERSPROC            typeof(glDeleteBuffers)*
>>  #if defined(__APPLE__) && USE_OPENGL_ES
>>  #   import <CoreFoundation/CoreFoundation.h>
>>  #endif
>> @@ -140,6 +144,9 @@ struct vout_display_opengl_t {
>>      int        local_count;
>>      GLfloat    local_value[16];
>>
>> +    GLuint vertex_buffer_object;
>> +    GLuint texture_buffer_object[PICTURE_PLANE_MAX];
>> +
>>      /* Shader variables commands*/
>>  #ifdef SUPPORTS_SHADERS
>>      PFNGLGETUNIFORMLOCATIONPROC      GetUniformLocation;
>> @@ -170,6 +177,11 @@ struct vout_display_opengl_t {
>>      PFNGLGETPROGRAMINFOLOGPROC GetProgramInfoLog;
>>      PFNGLGETSHADERIVPROC   GetShaderiv;
>>      PFNGLGETSHADERINFOLOGPROC GetShaderInfoLog;
>> +
>> +    PFNGLGENBUFFERSPROC    GenBuffers;
>> +    PFNGLBINDBUFFERPROC    BindBuffer;
>> +    PFNGLBUFFERDATAPROC    BufferData;
>> +    PFNGLDELETEBUFFERSPROC DeleteBuffers;
>>  #endif
>>
>>  #if defined(_WIN32)
>> @@ -444,6 +456,12 @@ vout_display_opengl_t
>> *vout_display_opengl_New(video_format_t *fmt, vgl->LinkProgram   =
>> glLinkProgram;
>>      vgl->UseProgram    = glUseProgram;
>>      vgl->DeleteProgram = glDeleteProgram;
>> +
>> +    vgl->GenBuffers    = glGenBuffers;
>> +    vgl->BindBuffer    = glBindBuffer;
>> +    vgl->BufferData    = glBufferData;
>> +    vgl->DeleteBuffers = glDeleteBuffers;
>> +
>>      supports_shaders = true;
>>  #elif defined(SUPPORTS_SHADERS)
>>      vgl->CreateShader  =
>> (PFNGLCREATESHADERPROC)vlc_gl_GetProcAddress(vgl->gl, "glCreateShader"); @@
>> -472,6 +490,11 @@ vout_display_opengl_t
>> *vout_display_opengl_New(video_format_t *fmt, vgl->UseProgram    =
>> (PFNGLUSEPROGRAMPROC)vlc_gl_GetProcAddress(vgl->gl, "glUseProgram");
>> vgl->DeleteProgram = (PFNGLDELETEPROGRAMPROC)vlc_gl_GetProcAddress(vgl->gl,
>> "glDeleteProgram");
>>
>> +    vgl->GenBuffers    =
>> (PFNGLGENBUFFERSPROC)vlc_gl_GetProcAddress(vgl->gl, "glGenBuffers"); +
>> vgl->BindBuffer    = (PFNGLBINDBUFFERPROC)vlc_gl_GetProcAddress(vgl->gl,
>> "glBindBuffer"); +    vgl->BufferData    =
>> (PFNGLBUFFERDATAPROC)vlc_gl_GetProcAddress(vgl->gl, "glBufferData"); +
>> vgl->DeleteBuffers = (PFNGLDELETEBUFFERSPROC)vlc_gl_GetProcAddress(vgl->gl,
>> "glDeleteBuffers"); +
>>      if (!vgl->CreateShader || !vgl->ShaderSource || !vgl->CreateProgram)
>>          supports_shaders = false;
>>  #endif
>> @@ -657,6 +680,11 @@ vout_display_opengl_t
>> *vout_display_opengl_New(video_format_t *fmt, glClearColor(0.0f, 0.0f,
>> 0.0f, 1.0f);
>>      glClear(GL_COLOR_BUFFER_BIT);
>>
>> +#ifdef SUPPORTS_SHADERS
>> +    vgl->GenBuffers(1, &vgl->vertex_buffer_object);
>> +    vgl->GenBuffers(vgl->chroma->plane_count, vgl->texture_buffer_object);
>> +#endif
>
> I suspect this jump to NULL if the OpenGL version is less than 1.5...

You mean the function pointers? Isn't that also true for the GLSL functions?

-- 
Félix Abecassis
http://felix.abecassis.me