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

This commit is contained in:
Michael Lutz 2021-01-16 16:43:14 +01:00
parent acf2ce35f7
commit 5af0cfd902
2 changed files with 40 additions and 5 deletions
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44
src/video/opengl.cpp
View File

@ -41,6 +41,10 @@ static PFNGLBUFFERDATAPROC _glBufferData;
static PFNGLMAPBUFFERPROC _glMapBuffer;
static PFNGLUNMAPBUFFERPROC _glUnmapBuffer;
static PFNGLGENVERTEXARRAYSPROC _glGenVertexArrays;
static PFNGLDELETEVERTEXARRAYSPROC _glDeleteVertexArrays;
static PFNGLBINDVERTEXARRAYPROC _glBindVertexArray;
/** A simple 2D vertex with just position and texture. */
struct Simple2DVertex {
float x, y;
@ -148,6 +152,25 @@ static bool BindVBOExtension()
return _glGenBuffers != nullptr && _glDeleteBuffers != nullptr && _glBindBuffer != nullptr && _glBufferData != nullptr && _glMapBuffer != nullptr && _glUnmapBuffer != nullptr;
}
/** Bind vertex array object extension functions. */
static bool BindVBAExtension()
{
/* The APPLE and ARB variants have different semantics (that don't matter for us).
* Successfully getting pointers to one variant doesn't mean it is supported for
* the current context. Always check the extension strings as well. */
if (IsOpenGLVersionAtLeast(3, 0) || IsOpenGLExtensionSupported("GL_ARB_vertex_array_object")) {
_glGenVertexArrays = (PFNGLGENVERTEXARRAYSPROC)GetOGLProcAddress("glGenVertexArrays");
_glDeleteVertexArrays = (PFNGLDELETEVERTEXARRAYSPROC)GetOGLProcAddress("glDeleteVertexArrays");
_glBindVertexArray = (PFNGLBINDVERTEXARRAYPROC)GetOGLProcAddress("glBindVertexArray");
} else if (IsOpenGLExtensionSupported("GL_APPLE_vertex_array_object")) {
_glGenVertexArrays = (PFNGLGENVERTEXARRAYSPROC)GetOGLProcAddress("glGenVertexArraysAPPLE");
_glDeleteVertexArrays = (PFNGLDELETEVERTEXARRAYSPROC)GetOGLProcAddress("glDeleteVertexArraysAPPLE");
_glBindVertexArray = (PFNGLBINDVERTEXARRAYPROC)GetOGLProcAddress("glBindVertexArrayAPPLE");
}
return _glGenVertexArrays != nullptr && _glDeleteVertexArrays != nullptr && _glBindVertexArray != 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)
{
@ -238,6 +261,7 @@ OpenGLBackend::OpenGLBackend()
*/
OpenGLBackend::~OpenGLBackend()
{
if (_glDeleteVertexArrays != nullptr) _glDeleteVertexArrays(1, &this->vao_quad);
if (_glDeleteBuffers != nullptr) {
_glDeleteBuffers(1, &this->vbo_quad);
}
@ -273,6 +297,9 @@ const char *OpenGLBackend::Init()
/* 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";
/* Check for vertex array objects. */
if (!IsOpenGLVersionAtLeast(3, 0) && (!IsOpenGLExtensionSupported("GL_ARB_vertex_array_object") || !IsOpenGLExtensionSupported("GL_APPLE_vertex_array_object"))) return "Vertex array objects not supported";
if (!BindVBAExtension()) return "Failed to bind VBA extension functions";
/* Setup video buffer texture. */
glGenTextures(1, &this->vid_texture);
@ -285,7 +312,8 @@ const char *OpenGLBackend::Init()
glBindTexture(GL_TEXTURE_2D, 0);
if (glGetError() != GL_NO_ERROR) return "Can't generate video buffer texture";
/* Prime vertex buffer with a full-screen quad. */
/* Prime vertex buffer with a full-screen quad and store
* the corresponding state in a vertex array object. */
static const Simple2DVertex vert_array[] = {
// x y u v
{ 1.f, -1.f, 1.f, 1.f },
@ -294,13 +322,21 @@ const char *OpenGLBackend::Init()
{ -1.f, 1.f, 0.f, 0.f },
};
/* Create VAO. */
_glGenVertexArrays(1, &this->vao_quad);
_glBindVertexArray(this->vao_quad);
/* Create and fill VBO. */
_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";
/* Set vertex state. */
glEnableClientState(GL_VERTEX_ARRAY);
glEnableClientState(GL_TEXTURE_COORD_ARRAY);
glVertexPointer(2, GL_FLOAT, sizeof(Simple2DVertex), (GLvoid *)offsetof(Simple2DVertex, x));
glTexCoordPointer(2, GL_FLOAT, sizeof(Simple2DVertex), (GLvoid *)offsetof(Simple2DVertex, u));
_glBindVertexArray(0);
glClearColor(0.0f, 0.0f, 0.0f, 1.0f);
glDisable(GL_DEPTH_TEST);
@ -358,9 +394,7 @@ 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));
_glBindVertexArray(this->vao_quad);
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 vao_quad; ///< Vertex array object storing the rendering state for the fullscreen quad.
GLuint vbo_quad; ///< Vertex buffer with a fullscreen quad.
OpenGLBackend();