On 14.09.2015 18:00, Max Reitz wrote:
> On 09.09.2015 13:20, Gerd Hoffmann wrote:
>> Create a buffer for the vertex data and place vertexes
>> there at initialization time. Then just use the buffer
>> for each texture blit.
>>
>> Signed-off-by: Gerd Hoffmann <kra...@redhat.com>
>> ---
>> include/ui/shader.h | 4 +++-
>> ui/console-gl.c | 7 ++++++-
>> ui/shader.c | 32 +++++++++++++++++++++++++++-----
>> 3 files changed, 36 insertions(+), 7 deletions(-)
>>
>> diff --git a/include/ui/shader.h b/include/ui/shader.h
>> index 8509596..f7d8618 100644
>> --- a/include/ui/shader.h
>> +++ b/include/ui/shader.h
>> @@ -3,7 +3,9 @@
>>
>> #include <epoxy/gl.h>
>>
>> -void qemu_gl_run_texture_blit(GLint texture_blit_prog);
>> +GLuint qemu_gl_init_texture_blit(GLint texture_blit_prog);
>> +void qemu_gl_run_texture_blit(GLint texture_blit_prog,
>> + GLint texture_blit_vao);
>>
>> GLuint qemu_gl_create_compile_shader(GLenum type, const GLchar *src);
>> GLuint qemu_gl_create_link_program(GLuint vert, GLuint frag);
>> diff --git a/ui/console-gl.c b/ui/console-gl.c
>> index cb45cf8..baf397b 100644
>> --- a/ui/console-gl.c
>> +++ b/ui/console-gl.c
>> @@ -33,6 +33,7 @@
>>
>> struct ConsoleGLState {
>> GLint texture_blit_prog;
>> + GLint texture_blit_vao;
>> };
>>
>> /* ---------------------------------------------------------------------- */
>> @@ -47,6 +48,9 @@ ConsoleGLState *console_gl_init_context(void)
>> exit(1);
>> }
>>
>> + gls->texture_blit_vao =
>> + qemu_gl_init_texture_blit(gls->texture_blit_prog);
>> +
>> return gls;
>> }
>>
>> @@ -131,7 +135,8 @@ void surface_gl_render_texture(ConsoleGLState *gls,
>> glClearColor(0.1f, 0.1f, 0.1f, 0.0f);
>> glClear(GL_COLOR_BUFFER_BIT);
>>
>> - qemu_gl_run_texture_blit(gls->texture_blit_prog);
>> + qemu_gl_run_texture_blit(gls->texture_blit_prog,
>> + gls->texture_blit_vao);
>> }
>>
>> void surface_gl_destroy_texture(ConsoleGLState *gls,
>> diff --git a/ui/shader.c b/ui/shader.c
>> index 52a4632..ada1c4c 100644
>> --- a/ui/shader.c
>> +++ b/ui/shader.c
>> @@ -29,21 +29,43 @@
>>
>> /* ---------------------------------------------------------------------- */
>>
>> -void qemu_gl_run_texture_blit(GLint texture_blit_prog)
>> +GLuint qemu_gl_init_texture_blit(GLint texture_blit_prog)
>> {
>> - GLfloat in_position[] = {
>> + static const GLfloat in_position[] = {
>> -1, -1,
>> 1, -1,
>> -1, 1,
>> 1, 1,
>> };
>> GLint l_position;
>> + GLuint vao, buffer;
>> +
>> + glGenVertexArrays(1, &vao);
>> + glBindVertexArray(vao);
>> +
>> + /* this is the VBO that holds the vertex data */
>> + glGenBuffers(1, &buffer);
>> + glBindBuffer(GL_ARRAY_BUFFER, buffer);
>> + glBufferData(GL_ARRAY_BUFFER, sizeof(in_position), in_position,
>> + GL_STATIC_DRAW);
>>
>> - glUseProgram(texture_blit_prog);
>> l_position = glGetAttribLocation(texture_blit_prog, "in_position");
>> - glVertexAttribPointer(l_position, 2, GL_FLOAT, GL_FALSE, 0,
>> in_position);
>> + glVertexAttribPointer(l_position, 2, GL_FLOAT, GL_FALSE, 0, 0);
>> glEnableVertexAttribArray(l_position);
>> - glDrawArrays(GL_TRIANGLE_STRIP, l_position, 4);
>> +
>> + glBindBuffer (GL_ARRAY_BUFFER, 0);
>> + glBindVertexArray (0);
>> + glDeleteBuffers (1, &buffer);
>
> Although I may be wrong, I don't think glVertexAttribPointer() loads the
> buffer data into the given vertex attribute.
>
> As far as I can see from the specification regarding vertex array
> objects, they only represent which data is to be used for vertex
> attributes ("All state related to the definition of data used by the
> vertex processor is encapsulated in a vertex array object.").
>
> glVertexAttribPointer():
> (1) determines the attribute's format,
> (2) binds a vertex attribute index to a shader attribute index,
> (3) binds the data to the vertex attribute.
>
> Step (3) (glBindVertexBuffer()) does not appear to load the data, but
> only define its origin ("The source of data for a generic vertex
> attribute may be determined by attaching a buffer object to a vertex
> array object with [glBindVertexBuffer()]").
>
> Therefore, I'm not sure whether deleting the buffer is right here. Maybe
> OpenGL uses reference counting here, too, so it remembers that the
> buffer is still in use by the VAO, and so the glDeleteBuffers()
> operation will only decrease its refcount, but not actually end up
> deleting it. But I don't think so (compare the documentation of
> glDeleteBuffers() with glDeleteShader(); the former says it will delete
> the buffer, whereas the latter explicitly mentions that the shader will
> not be deleted as long as it is attached to a program).
>
> All in all I don't think we should delete the buffer as long as it is in
> use by the VAO.
Oh, and I just noticed: With glDeleteBuffers(), I get a segmentation
fault when qemu exits (somewhere deep in fglrx_dri.so). Without, the
segfault disappears.
Max
>> +
>> + return vao;
>> +}
>> +
>> +void qemu_gl_run_texture_blit(GLint texture_blit_prog,
>> + GLint texture_blit_vao)
>> +{
>> + glUseProgram(texture_blit_prog);
>> + glBindVertexArray(texture_blit_vao);
>> + glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
>> }
>>
>> /* ---------------------------------------------------------------------- */
>>
>
>
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