First buffer swap takes 20 seconds

prokoprandacek · March 16, 2021, 8:22am

My first glfwSwapBuffers after glfw init takes 20 seconds.
Is this normal? Does anybody know what is causing this?
Any next buffer swap takes <1 ms.

source code:

github.com

ProkopRandacek/rendering/blob/main/src/opengl.c#L98


	glBindVertexArray(gl->VAO);

	dprint("GL DONE");
}

void renderOGL() {
	shdSetFloat(gl->s, "time", (float)glfwGetTime());
	glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_INT, 0);

	// swap buffers
	glfwSwapBuffers(gl->window);
	glfwPollEvents();
}

void screenshot() {
	frameCount++;

	glReadPixels(0, 0, w, h, GL_RGB, GL_UNSIGNED_BYTE, pixels);

	char fname[15];
	sprintf(fname, "%04d", frameCount);

I’m not sure what other info I should provide.

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First buffer swap takes 20 seconds

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