backend/x11: Give X11 a real rendering loop

Makes use of the present extension to get notified of vsync, and not
require any stupid timer hacks. Also make use of the present version of
ConfigureNotify, because why not?

3 files changed, 90 insertions, 61 deletions

diff --git a/backend/x11/backend.c b/backend/x11/backend.c
index 26c56cab..9a7387ce 100644
--- a/backend/x11/backend.c
+++ b/backend/x11/backend.c
@@ -12,6 +12,7 @@
 #include <X11/Xlib-xcb.h>
 #include <wayland-server-core.h>
 #include <xcb/xcb.h>
+#include <xcb/present.h>
 #include <xcb/xfixes.h>
 #include <xcb/xinput.h>
 
@@ -50,16 +51,6 @@ static void handle_x11_event(struct wlr_x11_backend *x11,
 		}
 		break;
 	}
-	case XCB_CONFIGURE_NOTIFY: {
-		xcb_configure_notify_event_t *ev =
-			(xcb_configure_notify_event_t *)event;
-		struct wlr_x11_output *output =
-			get_x11_output_from_window_id(x11, ev->window);
-		if (output != NULL) {
-			handle_x11_configure_notify(output, ev);
-		}
-		break;
-	}
 	case XCB_CLIENT_MESSAGE: {
 		xcb_client_message_event_t *ev = (xcb_client_message_event_t *)event;
 		if (ev->data.data32[0] == x11->atoms.wm_delete_window) {
@@ -73,7 +64,10 @@ static void handle_x11_event(struct wlr_x11_backend *x11,
 	}
 	case XCB_GE_GENERIC: {
 		xcb_ge_generic_event_t *ev = (xcb_ge_generic_event_t *)event;
-		if (ev->extension == x11->xinput_opcode) {
+		if (ev->extension == x11->present_opcode) {
+			handle_x11_present_event(x11,
+				(xcb_present_generic_event_t *)ev);
+		} else if (ev->extension == x11->xinput_opcode) {
 			handle_x11_xinput_event(x11, ev);
 		}
 	}
@@ -224,6 +218,30 @@ struct wlr_backend *wlr_x11_backend_create(struct wl_display *display,
 
 	const xcb_query_extension_reply_t *ext;
 
+	/* Present extension */
+
+	ext = xcb_get_extension_data(x11->xcb, &xcb_present_id);
+	if (!ext || !ext->present) {
+		wlr_log(WLR_ERROR, "X11 does not support Present extension");
+		goto error_display;
+	}
+	x11->present_opcode = ext->major_opcode;
+
+	xcb_present_query_version_cookie_t present_cookie =
+		xcb_present_query_version(x11->xcb, 1, 2);
+	xcb_present_query_version_reply_t *present_reply =
+		xcb_present_query_version_reply(x11->xcb, present_cookie, NULL);
+
+	if (!present_reply || (present_reply->major_version <= 1 &&
+			present_reply->minor_version < 2)) {
+		wlr_log(WLR_ERROR, "X11 does not support required Present version");
+		free(present_reply);
+		goto error_display;
+	}
+	free(present_reply);
+
+	/* Xfixes extension */
+
 	ext = xcb_get_extension_data(x11->xcb, &xcb_xfixes_id);
 	if (!ext || !ext->present) {
 		wlr_log(WLR_ERROR, "X11 does not support Xfixes extension");
@@ -242,6 +260,8 @@ struct wlr_backend *wlr_x11_backend_create(struct wl_display *display,
 	}
 	free(fixes_reply);
 
+	/* Xinput extension */
+
 	ext = xcb_get_extension_data(x11->xcb, &xcb_input_id);
 	if (!ext || !ext->present) {
 		wlr_log(WLR_ERROR, "X11 does not support Xinput extension");
diff --git a/backend/x11/meson.build b/backend/x11/meson.build
index 19e873ab..62b280e5 100644
--- a/backend/x11/meson.build
+++ b/backend/x11/meson.build
@@ -2,8 +2,9 @@ x11_libs = []
 x11_required = [
 	'x11-xcb',
 	'xcb',
-	'xcb-xinput',
+	'xcb-present',
 	'xcb-xfixes',
+	'xcb-xinput',
 ]
 
 foreach lib : x11_required
diff --git a/backend/x11/output.c b/backend/x11/output.c
index 1307f785..c65e39cc 100644
--- a/backend/x11/output.c
+++ b/backend/x11/output.c
@@ -5,6 +5,7 @@
 #include <string.h>
 
 #include <xcb/xcb.h>
+#include <xcb/present.h>
 #include <xcb/xinput.h>
 
 #include <wlr/interfaces/wlr_output.h>
@@ -15,13 +16,6 @@
 #include "backend/x11.h"
 #include "util/signal.h"
 
-static int signal_frame(void *data) {
-	struct wlr_x11_output *output = data;
-	wlr_output_send_frame(&output->wlr_output);
-	wl_event_source_timer_update(output->frame_timer, output->frame_delay);
-	return 0;
-}
-
 static void parse_xcb_setup(struct wlr_output *output,
 		xcb_connection_t *xcb) {
 	const xcb_setup_t *xcb_setup = xcb_get_setup(xcb);
@@ -40,26 +34,11 @@ static struct wlr_x11_output *get_x11_output_from_output(
 	return (struct wlr_x11_output *)wlr_output;
 }
 
-static void output_set_refresh(struct wlr_output *wlr_output, int32_t refresh) {
-	struct wlr_x11_output *output = get_x11_output_from_output(wlr_output);
-
-	if (refresh <= 0) {
-		refresh = X11_DEFAULT_REFRESH;
-	}
-
-	wlr_output_update_custom_mode(&output->wlr_output, wlr_output->width,
-		wlr_output->height, refresh);
-
-	output->frame_delay = 1000000 / refresh;
-}
-
 static bool output_set_custom_mode(struct wlr_output *wlr_output,
 		int32_t width, int32_t height, int32_t refresh) {
 	struct wlr_x11_output *output = get_x11_output_from_output(wlr_output);
 	struct wlr_x11_backend *x11 = output->x11;
 
-	output_set_refresh(&output->wlr_output, refresh);
-
 	const uint32_t values[] = { width, height };
 	xcb_void_cookie_t cookie = xcb_configure_window_checked(
 		x11->xcb, output->win,
@@ -84,7 +63,6 @@ static void output_destroy(struct wlr_output *wlr_output) {
 	wlr_input_device_destroy(&output->touch_dev);
 
 	wl_list_remove(&output->link);
-	wl_event_source_remove(output->frame_timer);
 	wlr_egl_destroy_surface(&x11->egl, output->surf);
 	xcb_destroy_window(x11->xcb, output->win);
 	xcb_flush(x11->xcb);
@@ -140,19 +118,15 @@ struct wlr_output *wlr_x11_output_create(struct wlr_backend *backend) {
 	struct wlr_output *wlr_output = &output->wlr_output;
 	wlr_output_init(wlr_output, &x11->backend, &output_impl, x11->wl_display);
 
-	wlr_output->width = 1024;
-	wlr_output->height = 768;
-
-	output_set_refresh(&output->wlr_output, 0);
+	wlr_output_update_custom_mode(&output->wlr_output, 1024, 768, 0);
+	wlr_output_update_enabled(wlr_output, true);
 
 	snprintf(wlr_output->name, sizeof(wlr_output->name), "X11-%zd",
 		++x11->last_output_num);
 	parse_xcb_setup(wlr_output, x11->xcb);
 
 	uint32_t mask = XCB_CW_EVENT_MASK;
-	uint32_t values[] = {
-		XCB_EVENT_MASK_EXPOSURE | XCB_EVENT_MASK_STRUCTURE_NOTIFY
-	};
+	uint32_t values[] = { XCB_EVENT_MASK_EXPOSURE };
 	output->win = xcb_generate_id(x11->xcb);
 	xcb_create_window(x11->xcb, XCB_COPY_FROM_PARENT, output->win,
 		x11->screen->root, 0, 0, wlr_output->width, wlr_output->height, 1,
@@ -176,6 +150,11 @@ struct wlr_output *wlr_x11_output_create(struct wlr_backend *backend) {
 	};
 	xcb_input_xi_select_events(x11->xcb, output->win, 1, &xinput_mask.head);
 
+	output->present_context = xcb_generate_id(x11->xcb);
+	xcb_present_select_input(x11->xcb, output->present_context, output->win,
+		XCB_PRESENT_EVENT_MASK_CONFIGURE_NOTIFY |
+		XCB_PRESENT_EVENT_MASK_COMPLETE_NOTIFY);
+
 	output->surf = wlr_egl_create_surface(&x11->egl, &output->win);
 	if (!output->surf) {
 		wlr_log(WLR_ERROR, "Failed to create EGL surface");
@@ -189,17 +168,8 @@ struct wlr_output *wlr_x11_output_create(struct wlr_backend *backend) {
 
 	wlr_x11_output_set_title(wlr_output, NULL);
 
-	xcb_map_window(x11->xcb, output->win);
-	xcb_flush(x11->xcb);
-
-	struct wl_event_loop *ev = wl_display_get_event_loop(x11->wl_display);
-	output->frame_timer = wl_event_loop_add_timer(ev, signal_frame, output);
-
 	wl_list_insert(&x11->outputs, &output->link);
 
-	wl_event_source_timer_update(output->frame_timer, output->frame_delay);
-	wlr_output_update_enabled(wlr_output, true);
-
 	wlr_input_device_init(&output->pointer_dev, WLR_INPUT_DEVICE_POINTER,
 		&input_device_impl, "X11 pointer", 0, 0);
 	wlr_pointer_init(&output->pointer, &pointer_impl);
@@ -217,22 +187,60 @@ struct wlr_output *wlr_x11_output_create(struct wlr_backend *backend) {
 	wlr_signal_emit_safe(&x11->backend.events.new_input, &output->pointer_dev);
 	wlr_signal_emit_safe(&x11->backend.events.new_input, &output->touch_dev);
 
+	// Start the vsync loop
+	xcb_present_notify_msc(x11->xcb, output->win, 0, 0, 1, 0);
+	xcb_map_window(x11->xcb, output->win);
+	xcb_flush(x11->xcb);
+
 	return wlr_output;
 }
 
-void handle_x11_configure_notify(struct wlr_x11_output *output,
-		xcb_configure_notify_event_t *ev) {
-	// ignore events that set an invalid size:
-	if (ev->width > 0 && ev->height > 0) {
-		wlr_output_update_custom_mode(&output->wlr_output, ev->width,
-			ev->height, output->wlr_output.refresh);
+void handle_x11_present_event(struct wlr_x11_backend *x11,
+		xcb_present_generic_event_t *base) {
+	struct wlr_x11_output *output;
+
+	switch (base->evtype) {
+	case XCB_PRESENT_CONFIGURE_NOTIFY: {
+		xcb_present_configure_notify_event_t *ev =
+			(xcb_present_configure_notify_event_t *)base;
+
+		output = get_x11_output_from_window_id(x11, ev->window);
+		if (!output || output->present_context != ev->event) {
+			break;
+		}
+
+		if (ev->width <= 0 || ev->height <= 0) {
+			break;
+		}
+
+		/*
+		 * We don't need to resize anything here ourselves.
+		 * The EGL/OpenGL driver does that automatically.
+		 */
+		wlr_output_update_custom_mode(&output->wlr_output,
+			ev->width, ev->height, 0);
 
 		// Move the pointer to its new location
 		update_x11_pointer_position(output, output->x11->time);
-	} else {
-		wlr_log(WLR_DEBUG,
-			"Ignoring X11 configure event for height=%d, width=%d",
-			ev->width, ev->height);
+
+		break;
+	}
+	case XCB_PRESENT_COMPLETE_NOTIFY: {
+		xcb_present_complete_notify_event_t *ev =
+			(xcb_present_complete_notify_event_t *)base;
+
+		output = get_x11_output_from_window_id(x11, ev->window);
+		if (!output || output->present_context != ev->event) {
+			break;
+		}
+
+		wlr_output_send_frame(&output->wlr_output);
+
+		xcb_present_notify_msc(x11->xcb, output->win, 0, 0, 1, 0);
+		xcb_flush(x11->xcb);
+
+		break;
+	}
 	}
 }