Revert "libobs-opengl: Use PBO in device_stage_texture on macOS"

This reverts commit 76f7a0c1c06687ac5970cea95eeb4935be2f1fa9.

Unfortunately, the performance issue is still present with PBOs even on
Monterey. During the 27.2 beta, macOS users even on Monterey have been
reporting a performance regression, and when the profiler data for those
users was looked at, major performance loss was noted in the
stage_output_texture function. This commit was the only probable cause.

libobs-opengl/gl-stagesurf.c

@@ -107,6 +107,58 @@ static bool can_stage(struct gs_stage_surface *dst, struct gs_texture_2d *src)
 	return true;
 }
 
+#ifdef __APPLE__
+
+/* Apparently for mac, PBOs won't do an asynchronous transfer unless you use
+ * FBOs along with glReadPixels, which is really dumb. */
+void device_stage_texture(gs_device_t *device, gs_stagesurf_t *dst,
+			  gs_texture_t *src)
+{
+	struct gs_texture_2d *tex2d = (struct gs_texture_2d *)src;
+	struct fbo_info *fbo;
+	GLint last_fbo;
+	bool success = false;
+
+	if (!can_stage(dst, tex2d))
+		goto failed;
+
+	if (!gl_bind_buffer(GL_PIXEL_PACK_BUFFER, dst->pack_buffer))
+		goto failed;
+
+	fbo = get_fbo(src, dst->width, dst->height);
+
+	if (!gl_get_integer_v(GL_READ_FRAMEBUFFER_BINDING, &last_fbo))
+		goto failed_unbind_buffer;
+	if (!gl_bind_framebuffer(GL_READ_FRAMEBUFFER, fbo->fbo))
+		goto failed_unbind_buffer;
+
+	glFramebufferTexture2D(GL_READ_FRAMEBUFFER, GL_COLOR_ATTACHMENT0 + 0,
+			       src->gl_target, src->texture, 0);
+	if (!gl_success("glFrameBufferTexture2D"))
+		goto failed_unbind_all;
+
+	glReadPixels(0, 0, dst->width, dst->height, dst->gl_format,
+		     dst->gl_type, 0);
+	if (!gl_success("glReadPixels"))
+		goto failed_unbind_all;
+
+	success = true;
+
+failed_unbind_all:
+	gl_bind_framebuffer(GL_READ_FRAMEBUFFER, last_fbo);
+
+failed_unbind_buffer:
+	gl_bind_buffer(GL_PIXEL_PACK_BUFFER, 0);
+
+failed:
+	if (!success)
+		blog(LOG_ERROR, "device_stage_texture (GL) failed");
+
+	UNUSED_PARAMETER(device);
+}
+
+#else
+
 void device_stage_texture(gs_device_t *device, gs_stagesurf_t *dst,
 			  gs_texture_t *src)
 {
@@ -135,6 +187,8 @@ failed:
 	UNUSED_PARAMETER(device);
 }
 
+#endif
+
 uint32_t gs_stagesurface_get_width(const gs_stagesurf_t *stagesurf)
 {
 	return stagesurf->width;