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Codechange: [OpenGL] Use a vertex buffer object to store the vertex data for the video buffer.

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This commit is contained in:
Michael Lutz 2021-01-16 16:43:13 +01:00
parent 8706c36fc0
commit acf2ce35f7
2 changed files with 58 additions and 5 deletions
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62
src/video/opengl.cpp
View File

@ -34,6 +34,19 @@
static PFNGLDEBUGMESSAGECONTROLPROC _glDebugMessageControl;
static PFNGLDEBUGMESSAGECALLBACKPROC _glDebugMessageCallback;
static PFNGLGENBUFFERSPROC _glGenBuffers;
static PFNGLDELETEBUFFERSPROC _glDeleteBuffers;
static PFNGLBINDBUFFERPROC _glBindBuffer;
static PFNGLBUFFERDATAPROC _glBufferData;
static PFNGLMAPBUFFERPROC _glMapBuffer;
static PFNGLUNMAPBUFFERPROC _glUnmapBuffer;
/** A simple 2D vertex with just position and texture. */
struct Simple2DVertex {
float x, y;
float u, v;
};
/* static */ OpenGLBackend *OpenGLBackend::instance = nullptr;
GetOGLProcAddressProc GetOGLProcAddress;
@ -113,6 +126,28 @@ bool IsOpenGLVersionAtLeast(byte major, byte minor)
return (_gl_major_ver > major) || (_gl_major_ver == major && _gl_minor_ver >= minor);
}
/** Bind vertex buffer object extension functions. */
static bool BindVBOExtension()
{
if (IsOpenGLVersionAtLeast(1, 5)) {
_glGenBuffers = (PFNGLGENBUFFERSPROC)GetOGLProcAddress("glGenBuffers");
_glDeleteBuffers = (PFNGLDELETEBUFFERSPROC)GetOGLProcAddress("glDeleteBuffers");
_glBindBuffer = (PFNGLBINDBUFFERPROC)GetOGLProcAddress("glBindBuffer");
_glBufferData = (PFNGLBUFFERDATAPROC)GetOGLProcAddress("glBufferData");
_glMapBuffer = (PFNGLMAPBUFFERPROC)GetOGLProcAddress("glMapBuffer");
_glUnmapBuffer = (PFNGLUNMAPBUFFERPROC)GetOGLProcAddress("glUnmapBuffer");
} else {
_glGenBuffers = (PFNGLGENBUFFERSPROC)GetOGLProcAddress("glGenBuffersARB");
_glDeleteBuffers = (PFNGLDELETEBUFFERSPROC)GetOGLProcAddress("glDeleteBuffersARB");
_glBindBuffer = (PFNGLBINDBUFFERPROC)GetOGLProcAddress("glBindBufferARB");
_glBufferData = (PFNGLBUFFERDATAPROC)GetOGLProcAddress("glBufferDataARB");
_glMapBuffer = (PFNGLMAPBUFFERPROC)GetOGLProcAddress("glMapBufferARB");
_glUnmapBuffer = (PFNGLUNMAPBUFFERPROC)GetOGLProcAddress("glUnmapBufferARB");
}
return _glGenBuffers != nullptr && _glDeleteBuffers != nullptr && _glBindBuffer != nullptr && _glBufferData != nullptr && _glMapBuffer != nullptr && _glUnmapBuffer != nullptr;
}
/** Callback to receive OpenGL debug messages. */
void APIENTRY DebugOutputCallback(GLenum source, GLenum type, GLuint id, GLenum severity, GLsizei length, const GLchar *message, const void *userParam)
{
@ -203,6 +238,9 @@ OpenGLBackend::OpenGLBackend()
*/
OpenGLBackend::~OpenGLBackend()
{
if (_glDeleteBuffers != nullptr) {
_glDeleteBuffers(1, &this->vbo_quad);
}
glDeleteTextures(1, &this->vid_texture);
free(this->vid_buffer);
}
@ -232,6 +270,9 @@ const char *OpenGLBackend::Init()
if (!IsOpenGLVersionAtLeast(1, 3)) return "OpenGL version >= 1.3 required";
/* Check for non-power-of-two texture support. */
if (!IsOpenGLVersionAtLeast(2, 0) && !IsOpenGLExtensionSupported("GL_ARB_texture_non_power_of_two")) return "Non-power-of-two textures not supported";
/* Check for vertex buffer objects. */
if (!IsOpenGLVersionAtLeast(1, 5) && !IsOpenGLExtensionSupported("ARB_vertex_buffer_object")) return "Vertex buffer objects not supported";
if (!BindVBOExtension()) return "Failed to bind VBO extension functions";
/* Setup video buffer texture. */
glGenTextures(1, &this->vid_texture);
@ -244,12 +285,20 @@ const char *OpenGLBackend::Init()
glBindTexture(GL_TEXTURE_2D, 0);
if (glGetError() != GL_NO_ERROR) return "Can't generate video buffer texture";
/* Prime vertex array with a full-screen quad. */
static const float vert_array[] = { 1.f, -1.f, 1.f, 1.f, -1.f, -1.f, -1.f, 1.f };
static const float tex_array[] = { 1.f, 1.f, 1.f, 0.f, 0.f, 1.f, 0.f, 0.f };
/* Prime vertex buffer with a full-screen quad. */
static const Simple2DVertex vert_array[] = {
// x y u v
{ 1.f, -1.f, 1.f, 1.f },
{ 1.f, 1.f, 1.f, 0.f },
{ -1.f, -1.f, 0.f, 1.f },
{ -1.f, 1.f, 0.f, 0.f },
};
_glGenBuffers(1, &this->vbo_quad);
_glBindBuffer(GL_ARRAY_BUFFER, this->vbo_quad);
_glBufferData(GL_ARRAY_BUFFER, sizeof(vert_array), vert_array, GL_STATIC_DRAW);
if (glGetError() != GL_NO_ERROR) return "Can't generate VBO for fullscreen quad";
glVertexPointer(2, GL_FLOAT, 0, vert_array);
glTexCoordPointer(2, GL_FLOAT, 0, tex_array);
glEnableClientState(GL_VERTEX_ARRAY);
glEnableClientState(GL_TEXTURE_COORD_ARRAY);
@ -309,6 +358,9 @@ void OpenGLBackend::Paint(Rect update_rect)
}
/* Blit video buffer to screen. */
_glBindBuffer(GL_ARRAY_BUFFER, this->vbo_quad);
glVertexPointer(2, GL_FLOAT, sizeof(Simple2DVertex), (GLvoid *)offsetof(Simple2DVertex, x));
glTexCoordPointer(2, GL_FLOAT, sizeof(Simple2DVertex), (GLvoid *)offsetof(Simple2DVertex, u));
glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
}

1
src/video/opengl.h
View File

@ -27,6 +27,7 @@ private:
void *vid_buffer; ///< Pointer to the memory used for the video driver to draw to.
GLuint vid_texture; ///< Texture handle for the video buffer texture.
GLuint vbo_quad; ///< Vertex buffer with a fullscreen quad.
OpenGLBackend();
~OpenGLBackend();