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Codechange: [OpenGL] Use a pixel buffer object to store the video buffer.

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This commit is contained in:
Michael Lutz
2021-01-16 16:43:16 +01:00
parent 5af0cfd902
commit a990c497b5
4 changed files with 89 additions and 35 deletions
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62
src/video/opengl.cpp
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@@ -264,9 +264,9 @@ OpenGLBackend::~OpenGLBackend()
if (_glDeleteVertexArrays != nullptr) _glDeleteVertexArrays(1, &this->vao_quad);
if (_glDeleteBuffers != nullptr) {
_glDeleteBuffers(1, &this->vbo_quad);
_glDeleteBuffers(1, &this->vid_pbo);
}
glDeleteTextures(1, &this->vid_texture);
free(this->vid_buffer);
}
/**
@@ -297,6 +297,8 @@ 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 pixel buffer objects. */
if (!IsOpenGLVersionAtLeast(2, 1) && !IsOpenGLExtensionSupported("GL_ARB_pixel_buffer_object")) return "Pixel buffer objects not supported";
/* 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";
@@ -312,6 +314,11 @@ const char *OpenGLBackend::Init()
glBindTexture(GL_TEXTURE_2D, 0);
if (glGetError() != GL_NO_ERROR) return "Can't generate video buffer texture";
/* Create pixel buffer object as video buffer storage. */
_glGenBuffers(1, &this->vid_pbo);
_glBindBuffer(GL_PIXEL_UNPACK_BUFFER, this->vid_pbo);
if (glGetError() != GL_NO_ERROR) return "Can't allocate pixel buffer for video buffer";
/* Prime vertex buffer with a full-screen quad and store
* the corresponding state in a vertex array object. */
static const Simple2DVertex vert_array[] = {
@@ -355,13 +362,14 @@ const char *OpenGLBackend::Init()
*/
bool OpenGLBackend::Resize(int w, int h, bool force)
{
if (!force && _screen.width == w && _screen.height == h && this->vid_buffer != nullptr) return false;
if (!force && _screen.width == w && _screen.height == h) return false;
glViewport(0, 0, w, h);
/* Re-allocate video buffer texture. */
free(this->vid_buffer);
this->vid_buffer = CallocT<uint32>(w * h); // 32bpp
/* Re-allocate video buffer texture and backing store. */
_glBindBuffer(GL_PIXEL_UNPACK_BUFFER, this->vid_pbo);
_glBufferData(GL_PIXEL_UNPACK_BUFFER, w * h * 4, nullptr, GL_DYNAMIC_READ); // Buffer content has to persist from frame to frame and is read back by the blitter, which means a READ usage hint.
_glBindBuffer(GL_PIXEL_UNPACK_BUFFER, 0);
glBindTexture(GL_TEXTURE_2D, this->vid_texture);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA8, w, h, 0, GL_BGRA, GL_UNSIGNED_INT_8_8_8_8_REV, nullptr);
@@ -371,30 +379,50 @@ bool OpenGLBackend::Resize(int w, int h, bool force)
_screen.height = h;
_screen.width = w;
_screen.pitch = w;
_screen.dst_ptr = this->GetVideoBuffer();
_screen.dst_ptr = nullptr;
return true;
}
/**
* Render video buffer to the screen.
* @param update_rect Rectangle encompassing the dirty region of the video buffer.
*/
void OpenGLBackend::Paint(Rect update_rect)
void OpenGLBackend::Paint()
{
assert(this->vid_buffer != nullptr);
glClear(GL_COLOR_BUFFER_BIT);
/* Update changed rect of the video buffer texture. */
glBindTexture(GL_TEXTURE_2D, this->vid_texture);
if (!IsEmptyRect(update_rect)) {
glPixelStorei(GL_UNPACK_ROW_LENGTH, _screen.pitch);
glTexSubImage2D(GL_TEXTURE_2D, 0, update_rect.left, update_rect.top, update_rect.right - update_rect.left, update_rect.bottom - update_rect.top, GL_BGRA, GL_UNSIGNED_INT_8_8_8_8_REV, (uint32 *)this->vid_buffer + update_rect.top * _screen.pitch + update_rect.left);
}
/* Blit video buffer to screen. */
glBindTexture(GL_TEXTURE_2D, this->vid_texture);
_glBindVertexArray(this->vao_quad);
glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
}
/**
* Get a pointer to the memory for the video driver to draw to.
* @return Pointer to draw on.
*/
void *OpenGLBackend::GetVideoBuffer()
{
_glBindBuffer(GL_PIXEL_UNPACK_BUFFER, this->vid_pbo);
return _glMapBuffer(GL_PIXEL_UNPACK_BUFFER, GL_READ_WRITE);
}
/**
* Update video buffer texture after the video buffer was filled.
* @param update_rect Rectangle encompassing the dirty region of the video buffer.
*/
void OpenGLBackend::ReleaseVideoBuffer(const Rect &update_rect)
{
assert(this->vid_pbo != 0);
_glBindBuffer(GL_PIXEL_UNPACK_BUFFER, this->vid_pbo);
_glUnmapBuffer(GL_PIXEL_UNPACK_BUFFER);
/* Update changed rect of the video buffer texture. */
if (!IsEmptyRect(update_rect)) {
glBindTexture(GL_TEXTURE_2D, this->vid_texture);
glPixelStorei(GL_UNPACK_ROW_LENGTH, _screen.pitch);
glTexSubImage2D(GL_TEXTURE_2D, 0, update_rect.left, update_rect.top, update_rect.right - update_rect.left, update_rect.bottom - update_rect.top, GL_BGRA, GL_UNSIGNED_INT_8_8_8_8_REV, (GLvoid *)(size_t)(update_rect.top * _screen.pitch * 4 + update_rect.left * 4));
}
}