From 3aad9fd6a96aa7c7d0fcf0dfa421c49caae83625 Mon Sep 17 00:00:00 2001
From: emersion <contact@emersion.fr>
Date: Sat, 29 Sep 2018 15:38:06 +0200
Subject: [PATCH 01/11] presentation-time: add protocol implementation

---
 include/wlr/types/meson.build             |   9 +-
 include/wlr/types/wlr_presentation_time.h |  56 ++++++
 protocol/meson.build                      |   1 +
 types/meson.build                         |  25 +--
 types/wlr_presentation_time.c             | 222 ++++++++++++++++++++++
 5 files changed, 297 insertions(+), 16 deletions(-)
 create mode 100644 include/wlr/types/wlr_presentation_time.h
 create mode 100644 types/wlr_presentation_time.c

diff --git a/include/wlr/types/meson.build b/include/wlr/types/meson.build
index 6a8955c3..7a02c3da 100644
--- a/include/wlr/types/meson.build
+++ b/include/wlr/types/meson.build
@@ -5,10 +5,10 @@ install_headers(
 	'wlr_cursor.h',
 	'wlr_data_device.h',
 	'wlr_export_dmabuf_v1.h',
-	'wlr_gamma_control.h',
 	'wlr_gamma_control_v1.h',
-	'wlr_idle.h',
+	'wlr_gamma_control.h',
 	'wlr_idle_inhibit_v1.h',
+	'wlr_idle.h',
 	'wlr_input_device.h',
 	'wlr_input_inhibitor.h',
 	'wlr_keyboard.h',
@@ -16,10 +16,11 @@ install_headers(
 	'wlr_linux_dmabuf_v1.h',
 	'wlr_list.h',
 	'wlr_matrix.h',
-	'wlr_output.h',
 	'wlr_output_damage.h',
 	'wlr_output_layout.h',
+	'wlr_output.h',
 	'wlr_pointer.h',
+	'wlr_presentation_time.h',
 	'wlr_primary_selection.h',
 	'wlr_region.h',
 	'wlr_screencopy_v1.h',
@@ -36,7 +37,7 @@ install_headers(
 	'wlr_xcursor_manager.h',
 	'wlr_xdg_decoration_v1.h',
 	'wlr_xdg_output_v1.h',
-	'wlr_xdg_shell.h',
 	'wlr_xdg_shell_v6.h',
+	'wlr_xdg_shell.h',
 	subdir: 'wlr/types',
 )
diff --git a/include/wlr/types/wlr_presentation_time.h b/include/wlr/types/wlr_presentation_time.h
new file mode 100644
index 00000000..71bf5977
--- /dev/null
+++ b/include/wlr/types/wlr_presentation_time.h
@@ -0,0 +1,56 @@
+/*
+ * This an unstable interface of wlroots. No guarantees are made regarding the
+ * future consistency of this API.
+ */
+#ifndef WLR_USE_UNSTABLE
+#error "Add -DWLR_USE_UNSTABLE to enable unstable wlroots features"
+#endif
+
+#ifndef WLR_TYPES_WLR_PRESENTATION_TIME_H
+#define WLR_TYPES_WLR_PRESENTATION_TIME_H
+
+#include <stdbool.h>
+#include <stddef.h>
+#include <time.h>
+#include <wayland-server.h>
+
+struct wlr_presentation {
+	struct wl_global *global;
+	struct wl_list resources; // wl_resource_get_link
+	struct wl_list feedbacks; // wlr_presentation_feedback::link
+	clockid_t clock;
+
+	struct {
+		struct wl_signal destroy;
+	} events;
+
+	struct wl_listener display_destroy;
+};
+
+struct wlr_presentation_feedback {
+	struct wl_resource *resource;
+	struct wlr_presentation *presentation;
+	struct wlr_surface *surface;
+	bool committed;
+	struct wl_list link; // wlr_presentation::feedbacks
+
+	struct wl_listener surface_commit;
+	struct wl_listener surface_destroy;
+};
+
+struct wlr_presentation_event {
+	struct wlr_output *output;
+	uint64_t tv_sec;
+	uint32_t tv_nsec;
+	uint32_t refresh;
+	uint64_t seq;
+	uint32_t flags; // wp_presentation_feedback_kind
+};
+
+struct wlr_presentation *wlr_presentation_create(struct wl_display *display);
+void wlr_presentation_destroy(struct wlr_presentation *presentation);
+void wlr_presentation_send_surface_presented(
+	struct wlr_presentation *presentation, struct wlr_surface *surface,
+	struct wlr_presentation_event *event);
+
+#endif
diff --git a/protocol/meson.build b/protocol/meson.build
index e03b88e8..82131ff6 100644
--- a/protocol/meson.build
+++ b/protocol/meson.build
@@ -11,6 +11,7 @@ else
 endif
 
 protocols = [
+	[wl_protocol_dir, 'stable/presentation-time/presentation-time.xml'],
 	[wl_protocol_dir, 'stable/xdg-shell/xdg-shell.xml'],
 	[wl_protocol_dir, 'unstable/idle-inhibit/idle-inhibit-unstable-v1.xml'],
 	[wl_protocol_dir, 'unstable/linux-dmabuf/linux-dmabuf-unstable-v1.xml'],
diff --git a/types/meson.build b/types/meson.build
index 038f7de4..9e2e74a8 100644
--- a/types/meson.build
+++ b/types/meson.build
@@ -9,23 +9,27 @@ lib_wlr_types = static_library(
 		'seat/wlr_seat_pointer.c',
 		'seat/wlr_seat_touch.c',
 		'seat/wlr_seat.c',
-		'xdg_shell/wlr_xdg_popup.c',
-		'xdg_shell/wlr_xdg_positioner.c',
-		'xdg_shell/wlr_xdg_shell.c',
-		'xdg_shell/wlr_xdg_surface.c',
-		'xdg_shell/wlr_xdg_toplevel.c',
+		'tablet_v2/wlr_tablet_v2_pad.c',
+		'tablet_v2/wlr_tablet_v2_tablet.c',
+		'tablet_v2/wlr_tablet_v2_tool.c',
+		'tablet_v2/wlr_tablet_v2.c',
 		'xdg_shell_v6/wlr_xdg_popup_v6.c',
 		'xdg_shell_v6/wlr_xdg_positioner_v6.c',
 		'xdg_shell_v6/wlr_xdg_shell_v6.c',
 		'xdg_shell_v6/wlr_xdg_surface_v6.c',
 		'xdg_shell_v6/wlr_xdg_toplevel_v6.c',
+		'xdg_shell/wlr_xdg_popup.c',
+		'xdg_shell/wlr_xdg_positioner.c',
+		'xdg_shell/wlr_xdg_shell.c',
+		'xdg_shell/wlr_xdg_surface.c',
+		'xdg_shell/wlr_xdg_toplevel.c',
 		'wlr_box.c',
 		'wlr_buffer.c',
 		'wlr_compositor.c',
 		'wlr_cursor.c',
 		'wlr_export_dmabuf_v1.c',
-		'wlr_gamma_control.c',
 		'wlr_gamma_control_v1.c',
+		'wlr_gamma_control.c',
 		'wlr_idle_inhibit_v1.c',
 		'wlr_idle.c',
 		'wlr_input_device.c',
@@ -38,17 +42,15 @@ lib_wlr_types = static_library(
 		'wlr_output_damage.c',
 		'wlr_output_layout.c',
 		'wlr_output.c',
-		'wlr_pointer.c',
 		'wlr_pointer_constraints_v1.c',
+		'wlr_pointer.c',
+		'wlr_presentation_time.c',
 		'wlr_primary_selection.c',
 		'wlr_region.c',
+		'wlr_screencopy_v1.c',
 		'wlr_screenshooter.c',
 		'wlr_server_decoration.c',
 		'wlr_surface.c',
-		'tablet_v2/wlr_tablet_v2.c',
-		'tablet_v2/wlr_tablet_v2_pad.c',
-		'tablet_v2/wlr_tablet_v2_tablet.c',
-		'tablet_v2/wlr_tablet_v2_tool.c',
 		'wlr_tablet_pad.c',
 		'wlr_tablet_tool.c',
 		'wlr_touch.c',
@@ -57,7 +59,6 @@ lib_wlr_types = static_library(
 		'wlr_xcursor_manager.c',
 		'wlr_xdg_decoration_v1.c',
 		'wlr_xdg_output_v1.c',
-		'wlr_screencopy_v1.c',
 	),
 	include_directories: wlr_inc,
 	dependencies: [pixman, xkbcommon, wayland_server, wlr_protos, libinput],
diff --git a/types/wlr_presentation_time.c b/types/wlr_presentation_time.c
new file mode 100644
index 00000000..710aa4b9
--- /dev/null
+++ b/types/wlr_presentation_time.c
@@ -0,0 +1,222 @@
+#define _POSIX_C_SOURCE 199309L
+#include <assert.h>
+#include <stdlib.h>
+#include <wlr/types/wlr_presentation_time.h>
+#include <wlr/types/wlr_surface.h>
+#include "presentation-time-protocol.h"
+#include "util/signal.h"
+
+#define PRESENTATION_VERSION 1
+
+static struct wlr_presentation_feedback *presentation_feedback_from_resource(
+		struct wl_resource *resource) {
+	assert(wl_resource_instance_of(resource,
+		&wp_presentation_feedback_interface, NULL));
+	return wl_resource_get_user_data(resource);
+}
+
+static void feedback_handle_resource_destroy(struct wl_resource *resource) {
+	struct wlr_presentation_feedback *feedback =
+		presentation_feedback_from_resource(resource);
+	wl_list_remove(&feedback->surface_commit.link);
+	wl_list_remove(&feedback->surface_destroy.link);
+	wl_list_remove(&feedback->link);
+	free(feedback);
+}
+
+// Destroys the feedback
+static void feedback_send_presented(struct wlr_presentation_feedback *feedback,
+		struct wlr_presentation_event *event) {
+	struct wl_client *client = wl_resource_get_client(feedback->resource);
+	struct wl_resource *resource;
+	wl_resource_for_each(resource, &event->output->resources) {
+		if (wl_resource_get_client(resource) == client) {
+			wp_presentation_feedback_send_sync_output(feedback->resource,
+				resource);
+		}
+	}
+
+	uint32_t tv_sec_hi = event->tv_sec >> 32;
+	uint32_t tv_sec_lo = event->tv_sec & 0xFFFFFFFF;
+	uint32_t seq_hi = event->seq >> 32;
+	uint32_t seq_lo = event->seq & 0xFFFFFFFF;
+	wp_presentation_feedback_send_presented(feedback->resource,
+		tv_sec_hi, tv_sec_lo, event->tv_nsec, event->refresh, seq_hi, seq_lo,
+		event->flags);
+
+	wl_resource_destroy(feedback->resource);
+}
+
+// Destroys the feedback
+static void feedback_send_discarded(
+		struct wlr_presentation_feedback *feedback) {
+	wp_presentation_feedback_send_discarded(feedback->resource);
+	wl_resource_destroy(feedback->resource);
+}
+
+static void feedback_handle_surface_commit(struct wl_listener *listener,
+		void *data) {
+	struct wlr_presentation_feedback *feedback =
+		wl_container_of(listener, feedback, surface_commit);
+
+	if (feedback->committed) {
+		// The content update has been superseded
+		feedback_send_discarded(feedback);
+	} else {
+		feedback->committed = true;
+	}
+}
+
+static void feedback_handle_surface_destroy(struct wl_listener *listener,
+		void *data) {
+	struct wlr_presentation_feedback *feedback =
+		wl_container_of(listener, feedback, surface_destroy);
+	feedback_send_discarded(feedback);
+}
+
+static const struct wp_presentation_interface presentation_impl;
+
+static struct wlr_presentation *presentation_from_resource(
+		struct wl_resource *resource) {
+	assert(wl_resource_instance_of(resource, &wp_presentation_interface,
+		&presentation_impl));
+	return wl_resource_get_user_data(resource);
+}
+
+static void presentation_handle_feedback(struct wl_client *client,
+		struct wl_resource *resource, struct wl_resource *surface_resource,
+		uint32_t id) {
+	struct wlr_presentation *presentation =
+		presentation_from_resource(resource);
+	struct wlr_surface *surface = wlr_surface_from_resource(surface_resource);
+
+	struct wlr_presentation_feedback *feedback =
+		calloc(1, sizeof(struct wlr_presentation_feedback));
+	if (feedback == NULL) {
+		wl_client_post_no_memory(client);
+		return;
+	}
+
+	uint32_t version = wl_resource_get_version(resource);
+	feedback->resource = wl_resource_create(client,
+		&wp_presentation_feedback_interface, version, id);
+	if (feedback->resource == NULL) {
+		free(feedback);
+		wl_client_post_no_memory(client);
+		return;
+	}
+	wl_resource_set_implementation(feedback->resource, NULL, feedback,
+		feedback_handle_resource_destroy);
+
+	feedback->surface = surface;
+
+	feedback->surface_commit.notify = feedback_handle_surface_commit;
+	wl_signal_add(&surface->events.commit, &feedback->surface_commit);
+
+	feedback->surface_destroy.notify = feedback_handle_surface_destroy;
+	wl_signal_add(&surface->events.destroy, &feedback->surface_destroy);
+
+	wl_list_insert(&presentation->feedbacks, &feedback->link);
+}
+
+static void presentation_handle_destroy(struct wl_client *client,
+		struct wl_resource *resource) {
+	wl_resource_destroy(resource);
+}
+
+static const struct wp_presentation_interface presentation_impl = {
+	.feedback = presentation_handle_feedback,
+	.destroy = presentation_handle_destroy,
+};
+
+static void presentation_handle_resource_destroy(struct wl_resource *resource) {
+	wl_list_remove(wl_resource_get_link(resource));
+}
+
+static void presentation_bind(struct wl_client *client, void *data,
+		uint32_t version, uint32_t id) {
+	struct wlr_presentation *presentation = data;
+
+	struct wl_resource *resource = wl_resource_create(client,
+		&wp_presentation_interface, version, id);
+	if (resource == NULL) {
+		wl_client_post_no_memory(client);
+		return;
+	}
+	wl_resource_set_implementation(resource, &presentation_impl, presentation,
+		presentation_handle_resource_destroy);
+	wl_list_insert(&presentation->resources, wl_resource_get_link(resource));
+
+	wp_presentation_send_clock_id(resource, presentation->clock);
+}
+
+static void handle_display_destroy(struct wl_listener *listener, void *data) {
+	struct wlr_presentation *presentation =
+		wl_container_of(listener, presentation, display_destroy);
+	wlr_presentation_destroy(presentation);
+}
+
+struct wlr_presentation *wlr_presentation_create(struct wl_display *display) {
+	struct wlr_presentation *presentation =
+		calloc(1, sizeof(struct wlr_presentation));
+	if (presentation == NULL) {
+		return NULL;
+	}
+
+	presentation->global = wl_global_create(display, &wp_presentation_interface,
+		PRESENTATION_VERSION, presentation, presentation_bind);
+	if (presentation->global == NULL) {
+		free(presentation);
+		return NULL;
+	}
+
+	// TODO: get clock from backend
+	presentation->clock = CLOCK_MONOTONIC;
+
+	wl_list_init(&presentation->resources);
+	wl_list_init(&presentation->feedbacks);
+	wl_signal_init(&presentation->events.destroy);
+
+	presentation->display_destroy.notify = handle_display_destroy;
+	wl_display_add_destroy_listener(display, &presentation->display_destroy);
+
+	return presentation;
+}
+
+void wlr_presentation_destroy(struct wlr_presentation *presentation) {
+	if (presentation == NULL) {
+		return;
+	}
+
+	wlr_signal_emit_safe(&presentation->events.destroy, presentation);
+
+	wl_global_destroy(presentation->global);
+
+	struct wlr_presentation_feedback *feedback, *feedback_tmp;
+	wl_list_for_each_safe(feedback, feedback_tmp, &presentation->feedbacks,
+			link) {
+		wl_resource_destroy(feedback->resource);
+	}
+
+	struct wl_resource *resource, *resource_tmp;
+	wl_resource_for_each_safe(resource, resource_tmp,
+			&presentation->resources) {
+		wl_resource_destroy(resource);
+	}
+
+	wl_list_remove(&presentation->display_destroy.link);
+	free(presentation);
+}
+
+void wlr_presentation_send_surface_presented(
+		struct wlr_presentation *presentation, struct wlr_surface *surface,
+		struct wlr_presentation_event *event) {
+	// TODO: maybe use a hashtable to optimize this function
+	struct wlr_presentation_feedback *feedback, *feedback_tmp;
+	wl_list_for_each_safe(feedback, feedback_tmp,
+			&presentation->feedbacks, link) {
+		if (feedback->surface == surface && feedback->committed) {
+			feedback_send_presented(feedback, event);
+		}
+	}
+}

From 78389fe72225f9baf7def744825323f54ac4ee8e Mon Sep 17 00:00:00 2001
From: emersion <contact@emersion.fr>
Date: Sat, 29 Sep 2018 22:38:13 +0200
Subject: [PATCH 02/11] output: add present event

---
 backend/drm/drm.c                   | 12 ++++++++++--
 include/wlr/interfaces/wlr_output.h |  2 ++
 include/wlr/types/wlr_output.h      | 14 ++++++++++++++
 types/wlr_output.c                  | 11 +++++++++++
 4 files changed, 37 insertions(+), 2 deletions(-)

diff --git a/backend/drm/drm.c b/backend/drm/drm.c
index fa9a95ae..ace0835e 100644
--- a/backend/drm/drm.c
+++ b/backend/drm/drm.c
@@ -1149,8 +1149,8 @@ void scan_drm_connectors(struct wlr_drm_backend *drm) {
 }
 
 static void page_flip_handler(int fd, unsigned seq,
-		unsigned tv_sec, unsigned tv_usec, void *user) {
-	struct wlr_drm_connector *conn = user;
+		unsigned tv_sec, unsigned tv_usec, void *data) {
+	struct wlr_drm_connector *conn = data;
 	struct wlr_drm_backend *drm =
 		get_drm_backend_from_backend(conn->output.backend);
 
@@ -1170,6 +1170,14 @@ static void page_flip_handler(int fd, unsigned seq,
 		post_drm_surface(&conn->crtc->primary->mgpu_surf);
 	}
 
+	struct timespec present_time = {
+		.tv_sec = tv_sec,
+		.tv_nsec = tv_usec * 1000,
+	};
+	uint32_t present_flags = WLR_OUTPUT_PRESENT_VSYNC |
+		WLR_OUTPUT_PRESENT_HW_CLOCK | WLR_OUTPUT_PRESENT_HW_COMPLETION;
+	wlr_output_send_present(&conn->output, &present_time, seq, present_flags);
+
 	if (drm->session->active) {
 		wlr_output_send_frame(&conn->output);
 	}
diff --git a/include/wlr/interfaces/wlr_output.h b/include/wlr/interfaces/wlr_output.h
index bfb3bc9d..b06c5db0 100644
--- a/include/wlr/interfaces/wlr_output.h
+++ b/include/wlr/interfaces/wlr_output.h
@@ -45,5 +45,7 @@ void wlr_output_update_enabled(struct wlr_output *output, bool enabled);
 void wlr_output_update_needs_swap(struct wlr_output *output);
 void wlr_output_damage_whole(struct wlr_output *output);
 void wlr_output_send_frame(struct wlr_output *output);
+void wlr_output_send_present(struct wlr_output *output, struct timespec *when,
+	unsigned seq, uint32_t flags);
 
 #endif
diff --git a/include/wlr/types/wlr_output.h b/include/wlr/types/wlr_output.h
index 96394ba4..a794d4b2 100644
--- a/include/wlr/types/wlr_output.h
+++ b/include/wlr/types/wlr_output.h
@@ -91,6 +91,7 @@ struct wlr_output {
 		struct wl_signal frame;
 		struct wl_signal needs_swap;
 		struct wl_signal swap_buffers; // wlr_output_event_swap_buffers
+		struct wl_signal present; // wlr_output_event_present
 		struct wl_signal enable;
 		struct wl_signal mode;
 		struct wl_signal scale;
@@ -123,6 +124,19 @@ struct wlr_output_event_swap_buffers {
 	pixman_region32_t *damage;
 };
 
+enum wlr_output_present_flag {
+	WLR_OUTPUT_PRESENT_VSYNC = 0x1,
+	WLR_OUTPUT_PRESENT_HW_CLOCK = 0x2,
+	WLR_OUTPUT_PRESENT_HW_COMPLETION = 0x4,
+};
+
+struct wlr_output_event_present {
+	struct wlr_output *output;
+	struct timespec *when;
+	unsigned seq;
+	uint32_t flags; // enum wlr_output_present_flag
+};
+
 struct wlr_surface;
 
 /**
diff --git a/types/wlr_output.c b/types/wlr_output.c
index ac10cf7e..99d769e3 100644
--- a/types/wlr_output.c
+++ b/types/wlr_output.c
@@ -560,6 +560,17 @@ void wlr_output_schedule_frame(struct wlr_output *output) {
 		wl_event_loop_add_idle(ev, schedule_frame_handle_idle_timer, output);
 }
 
+void wlr_output_send_present(struct wlr_output *output, struct timespec *when,
+		unsigned seq, uint32_t flags) {
+	struct wlr_output_event_present event = {
+		.output = output,
+		.when = when,
+		.seq = seq,
+		.flags = flags,
+	};
+	wlr_signal_emit_safe(&output->events.present, &event);
+}
+
 bool wlr_output_set_gamma(struct wlr_output *output, size_t size,
 		const uint16_t *r, const uint16_t *g, const uint16_t *b) {
 	if (!output->impl->set_gamma) {

From 26b9d6dbb1f060405c02b6b66527b0272f79d495 Mon Sep 17 00:00:00 2001
From: emersion <contact@emersion.fr>
Date: Mon, 1 Oct 2018 11:07:58 +0200
Subject: [PATCH 03/11] output: send present event from all backends

---
 backend/headless/output.c |  1 +
 backend/wayland/output.c  | 10 ++++++++--
 backend/x11/output.c      |  7 ++++++-
 types/wlr_output.c        | 12 ++++++++++++
 4 files changed, 27 insertions(+), 3 deletions(-)

diff --git a/backend/headless/output.c b/backend/headless/output.c
index 143900d4..ad0050d8 100644
--- a/backend/headless/output.c
+++ b/backend/headless/output.c
@@ -67,6 +67,7 @@ static bool output_make_current(struct wlr_output *wlr_output, int *buffer_age)
 
 static bool output_swap_buffers(struct wlr_output *wlr_output,
 		pixman_region32_t *damage) {
+	wlr_output_send_present(wlr_output, NULL, 0, 0);
 	return true; // No-op
 }
 
diff --git a/backend/wayland/output.c b/backend/wayland/output.c
index 4eb99a3b..4fbfe9d2 100644
--- a/backend/wayland/output.c
+++ b/backend/wayland/output.c
@@ -66,8 +66,14 @@ static bool output_swap_buffers(struct wlr_output *wlr_output,
 	output->frame_callback = wl_surface_frame(output->surface);
 	wl_callback_add_listener(output->frame_callback, &frame_listener, output);
 
-	return wlr_egl_swap_buffers(&output->backend->egl, output->egl_surface,
-		damage);
+	if (!wlr_egl_swap_buffers(&output->backend->egl,
+			output->egl_surface, damage)) {
+		return false;
+	}
+
+	// TODO: if available, use the presentation-time protocol
+	wlr_output_send_present(wlr_output, NULL, 0, 0);
+	return true;
 }
 
 static void output_transform(struct wlr_output *wlr_output,
diff --git a/backend/x11/output.c b/backend/x11/output.c
index e0210b1a..8cd8ee33 100644
--- a/backend/x11/output.c
+++ b/backend/x11/output.c
@@ -102,7 +102,12 @@ static bool output_swap_buffers(struct wlr_output *wlr_output,
 	struct wlr_x11_output *output = (struct wlr_x11_output *)wlr_output;
 	struct wlr_x11_backend *x11 = output->x11;
 
-	return wlr_egl_swap_buffers(&x11->egl, output->surf, damage);
+	if (!wlr_egl_swap_buffers(&x11->egl, output->surf, damage)) {
+		return false;
+	}
+
+	wlr_output_send_present(wlr_output, NULL, 0, 0);
+	return true;
 }
 
 static const struct wlr_output_impl output_impl = {
diff --git a/types/wlr_output.c b/types/wlr_output.c
index 99d769e3..4ffe561a 100644
--- a/types/wlr_output.c
+++ b/types/wlr_output.c
@@ -18,6 +18,8 @@
 
 #define OUTPUT_VERSION 3
 
+#define DEFAULT_PRESENT_CLOCK CLOCK_MONOTONIC
+
 static void output_send_to_resource(struct wl_resource *resource) {
 	struct wlr_output *output = wlr_output_from_resource(resource);
 	const uint32_t version = wl_resource_get_version(resource);
@@ -562,6 +564,16 @@ void wlr_output_schedule_frame(struct wlr_output *output) {
 
 void wlr_output_send_present(struct wlr_output *output, struct timespec *when,
 		unsigned seq, uint32_t flags) {
+	struct timespec now;
+	if (when == NULL) {
+		if (!clock_gettime(DEFAULT_PRESENT_CLOCK, &now)) {
+			wlr_log_errno(WLR_ERROR, "failed to send output present event: "
+				"failed to read clock");
+			return;
+		}
+		when = &now;
+	}
+
 	struct wlr_output_event_present event = {
 		.output = output,
 		.when = when,

From 9203bfdd4fd0257174cd03c34ee02c6138e604b8 Mon Sep 17 00:00:00 2001
From: emersion <contact@emersion.fr>
Date: Mon, 1 Oct 2018 14:08:07 +0200
Subject: [PATCH 04/11] output: document signals

---
 include/wlr/types/wlr_output.h | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/include/wlr/types/wlr_output.h b/include/wlr/types/wlr_output.h
index a794d4b2..fb3becd1 100644
--- a/include/wlr/types/wlr_output.h
+++ b/include/wlr/types/wlr_output.h
@@ -88,9 +88,14 @@ struct wlr_output {
 	float transform_matrix[9];
 
 	struct {
+		// Request to render a frame
 		struct wl_signal frame;
+		// Emitted when buffers need to be swapped (because software cursors or
+		// fullscreen damage or because of backend-specific logic)
 		struct wl_signal needs_swap;
+		// Emitted right before buffer swap
 		struct wl_signal swap_buffers; // wlr_output_event_swap_buffers
+		// Emitted right after the buffer has been presented to the user
 		struct wl_signal present; // wlr_output_event_present
 		struct wl_signal enable;
 		struct wl_signal mode;

From 54e1287f307d13566deaf51683da373f3524d1d9 Mon Sep 17 00:00:00 2001
From: emersion <contact@emersion.fr>
Date: Mon, 1 Oct 2018 22:44:33 +0200
Subject: [PATCH 05/11] backend: add get_present_clock

---
 backend/backend.c               |  7 +++++++
 backend/drm/backend.c           |  6 ++++++
 backend/drm/drm.c               | 12 +++++++++---
 include/backend/drm/drm.h       |  2 ++
 include/wlr/backend.h           |  4 ++++
 include/wlr/backend/interface.h |  2 ++
 types/wlr_output.c              |  6 +++---
 7 files changed, 33 insertions(+), 6 deletions(-)

diff --git a/backend/backend.c b/backend/backend.c
index 2d6464b7..b8cf8797 100644
--- a/backend/backend.c
+++ b/backend/backend.c
@@ -64,6 +64,13 @@ struct wlr_session *wlr_backend_get_session(struct wlr_backend *backend) {
 	return NULL;
 }
 
+clockid_t wlr_backend_get_present_clock(struct wlr_backend *backend) {
+	if (backend->impl->get_present_clock) {
+		return backend->impl->get_present_clock(backend);
+	}
+	return CLOCK_MONOTONIC;
+}
+
 static size_t parse_outputs_env(const char *name) {
 	const char *outputs_str = getenv(name);
 	if (outputs_str == NULL) {
diff --git a/backend/drm/backend.c b/backend/drm/backend.c
index b298365e..b230613d 100644
--- a/backend/drm/backend.c
+++ b/backend/drm/backend.c
@@ -65,10 +65,16 @@ static struct wlr_renderer *backend_get_renderer(
 	}
 }
 
+static clockid_t backend_get_present_clock(struct wlr_backend *backend) {
+	struct wlr_drm_backend *drm = get_drm_backend_from_backend(backend);
+	return drm->clock;
+}
+
 static struct wlr_backend_impl backend_impl = {
 	.start = backend_start,
 	.destroy = backend_destroy,
 	.get_renderer = backend_get_renderer,
+	.get_present_clock = backend_get_present_clock,
 };
 
 bool wlr_backend_is_drm(struct wlr_backend *b) {
diff --git a/backend/drm/drm.c b/backend/drm/drm.c
index ace0835e..753b6ab8 100644
--- a/backend/drm/drm.c
+++ b/backend/drm/drm.c
@@ -1,3 +1,4 @@
+#define _POSIX_C_SOURCE 199309L
 #include <assert.h>
 #include <drm_mode.h>
 #include <EGL/egl.h>
@@ -27,8 +28,8 @@
 #include "util/signal.h"
 
 bool check_drm_features(struct wlr_drm_backend *drm) {
+	uint64_t cap;
 	if (drm->parent) {
-		uint64_t cap;
 		if (drmGetCap(drm->fd, DRM_CAP_PRIME, &cap) ||
 				!(cap & DRM_PRIME_CAP_IMPORT)) {
 			wlr_log(WLR_ERROR,
@@ -51,16 +52,21 @@ bool check_drm_features(struct wlr_drm_backend *drm) {
 
 	const char *no_atomic = getenv("WLR_DRM_NO_ATOMIC");
 	if (no_atomic && strcmp(no_atomic, "1") == 0) {
-		wlr_log(WLR_DEBUG, "WLR_DRM_NO_ATOMIC set, forcing legacy DRM interface");
+		wlr_log(WLR_DEBUG,
+			"WLR_DRM_NO_ATOMIC set, forcing legacy DRM interface");
 		drm->iface = &legacy_iface;
 	} else if (drmSetClientCap(drm->fd, DRM_CLIENT_CAP_ATOMIC, 1)) {
-		wlr_log(WLR_DEBUG, "Atomic modesetting unsupported, using legacy DRM interface");
+		wlr_log(WLR_DEBUG,
+			"Atomic modesetting unsupported, using legacy DRM interface");
 		drm->iface = &legacy_iface;
 	} else {
 		wlr_log(WLR_DEBUG, "Using atomic DRM interface");
 		drm->iface = &atomic_iface;
 	}
 
+	int ret = drmGetCap(drm->fd, DRM_CAP_TIMESTAMP_MONOTONIC, &cap);
+	drm->clock = (ret == 0 && cap == 1) ? CLOCK_MONOTONIC : CLOCK_REALTIME;
+
 	return true;
 }
 
diff --git a/include/backend/drm/drm.h b/include/backend/drm/drm.h
index 3c728808..de5212d3 100644
--- a/include/backend/drm/drm.h
+++ b/include/backend/drm/drm.h
@@ -6,6 +6,7 @@
 #include <stdbool.h>
 #include <stddef.h>
 #include <stdint.h>
+#include <time.h>
 #include <wayland-server.h>
 #include <wayland-util.h>
 #include <wlr/backend/drm.h>
@@ -67,6 +68,7 @@ struct wlr_drm_backend {
 
 	struct wlr_drm_backend *parent;
 	const struct wlr_drm_interface *iface;
+	clockid_t clock;
 
 	int fd;
 
diff --git a/include/wlr/backend.h b/include/wlr/backend.h
index dfb8d2a8..aee45b73 100644
--- a/include/wlr/backend.h
+++ b/include/wlr/backend.h
@@ -62,5 +62,9 @@ struct wlr_renderer *wlr_backend_get_renderer(struct wlr_backend *backend);
  * Might return NULL for backends that don't use a session.
  */
 struct wlr_session *wlr_backend_get_session(struct wlr_backend *backend);
+/**
+ * Returns the clock used by the backend for presentation feedback.
+ */
+clockid_t wlr_backend_get_present_clock(struct wlr_backend *backend);
 
 #endif
diff --git a/include/wlr/backend/interface.h b/include/wlr/backend/interface.h
index 2c300709..a930c241 100644
--- a/include/wlr/backend/interface.h
+++ b/include/wlr/backend/interface.h
@@ -10,6 +10,7 @@
 #define WLR_BACKEND_INTERFACE_H
 
 #include <stdbool.h>
+#include <time.h>
 #include <wlr/backend.h>
 #include <wlr/render/egl.h>
 
@@ -18,6 +19,7 @@ struct wlr_backend_impl {
 	void (*destroy)(struct wlr_backend *backend);
 	struct wlr_renderer *(*get_renderer)(struct wlr_backend *backend);
 	struct wlr_session *(*get_session)(struct wlr_backend *backend);
+	clockid_t (*get_present_clock)(struct wlr_backend *backend);
 };
 
 /**
diff --git a/types/wlr_output.c b/types/wlr_output.c
index 4ffe561a..1baa5027 100644
--- a/types/wlr_output.c
+++ b/types/wlr_output.c
@@ -18,8 +18,6 @@
 
 #define OUTPUT_VERSION 3
 
-#define DEFAULT_PRESENT_CLOCK CLOCK_MONOTONIC
-
 static void output_send_to_resource(struct wl_resource *resource) {
 	struct wlr_output *output = wlr_output_from_resource(resource);
 	const uint32_t version = wl_resource_get_version(resource);
@@ -268,6 +266,7 @@ void wlr_output_init(struct wlr_output *output, struct wlr_backend *backend,
 	wl_signal_init(&output->events.frame);
 	wl_signal_init(&output->events.needs_swap);
 	wl_signal_init(&output->events.swap_buffers);
+	wl_signal_init(&output->events.present);
 	wl_signal_init(&output->events.enable);
 	wl_signal_init(&output->events.mode);
 	wl_signal_init(&output->events.scale);
@@ -566,7 +565,8 @@ void wlr_output_send_present(struct wlr_output *output, struct timespec *when,
 		unsigned seq, uint32_t flags) {
 	struct timespec now;
 	if (when == NULL) {
-		if (!clock_gettime(DEFAULT_PRESENT_CLOCK, &now)) {
+		clockid_t clock = wlr_backend_get_present_clock(output->backend);
+		if (!clock_gettime(clock, &now)) {
 			wlr_log_errno(WLR_ERROR, "failed to send output present event: "
 				"failed to read clock");
 			return;

From abddfc99f2a0fb4f61292e3ac1c0b142effa28c2 Mon Sep 17 00:00:00 2001
From: emersion <contact@emersion.fr>
Date: Mon, 1 Oct 2018 22:46:22 +0200
Subject: [PATCH 06/11] output: fix clock_gettime return value handling

---
 types/wlr_output.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/types/wlr_output.c b/types/wlr_output.c
index 1baa5027..6ff06fd6 100644
--- a/types/wlr_output.c
+++ b/types/wlr_output.c
@@ -566,7 +566,8 @@ void wlr_output_send_present(struct wlr_output *output, struct timespec *when,
 	struct timespec now;
 	if (when == NULL) {
 		clockid_t clock = wlr_backend_get_present_clock(output->backend);
-		if (!clock_gettime(clock, &now)) {
+		errno = 0;
+		if (clock_gettime(clock, &now) != 0) {
 			wlr_log_errno(WLR_ERROR, "failed to send output present event: "
 				"failed to read clock");
 			return;

From b0635bf3e7f0de7c641ffafb0e8962d62ee88c73 Mon Sep 17 00:00:00 2001
From: emersion <contact@emersion.fr>
Date: Mon, 1 Oct 2018 22:57:36 +0200
Subject: [PATCH 07/11] Rename get_present_clock to get_presentation clock, use
 it

---
 backend/backend.c                         |  6 +++---
 backend/drm/backend.c                     |  4 ++--
 backend/multi/backend.c                   | 17 +++++++++++++++++
 include/wlr/backend.h                     |  2 +-
 include/wlr/backend/interface.h           |  2 +-
 include/wlr/types/wlr_presentation_time.h |  5 ++++-
 types/wlr_output.c                        |  2 +-
 types/wlr_presentation_time.c             |  9 +++++----
 8 files changed, 34 insertions(+), 13 deletions(-)

diff --git a/backend/backend.c b/backend/backend.c
index b8cf8797..4b186767 100644
--- a/backend/backend.c
+++ b/backend/backend.c
@@ -64,9 +64,9 @@ struct wlr_session *wlr_backend_get_session(struct wlr_backend *backend) {
 	return NULL;
 }
 
-clockid_t wlr_backend_get_present_clock(struct wlr_backend *backend) {
-	if (backend->impl->get_present_clock) {
-		return backend->impl->get_present_clock(backend);
+clockid_t wlr_backend_get_presentation_clock(struct wlr_backend *backend) {
+	if (backend->impl->get_presentation_clock) {
+		return backend->impl->get_presentation_clock(backend);
 	}
 	return CLOCK_MONOTONIC;
 }
diff --git a/backend/drm/backend.c b/backend/drm/backend.c
index b230613d..a9082077 100644
--- a/backend/drm/backend.c
+++ b/backend/drm/backend.c
@@ -65,7 +65,7 @@ static struct wlr_renderer *backend_get_renderer(
 	}
 }
 
-static clockid_t backend_get_present_clock(struct wlr_backend *backend) {
+static clockid_t backend_get_presentation_clock(struct wlr_backend *backend) {
 	struct wlr_drm_backend *drm = get_drm_backend_from_backend(backend);
 	return drm->clock;
 }
@@ -74,7 +74,7 @@ static struct wlr_backend_impl backend_impl = {
 	.start = backend_start,
 	.destroy = backend_destroy,
 	.get_renderer = backend_get_renderer,
-	.get_present_clock = backend_get_present_clock,
+	.get_presentation_clock = backend_get_presentation_clock,
 };
 
 bool wlr_backend_is_drm(struct wlr_backend *b) {
diff --git a/backend/multi/backend.c b/backend/multi/backend.c
index 2f4b929f..cefaa361 100644
--- a/backend/multi/backend.c
+++ b/backend/multi/backend.c
@@ -1,6 +1,8 @@
+#define _POSIX_C_SOURCE 199309L
 #include <assert.h>
 #include <stdbool.h>
 #include <stdlib.h>
+#include <time.h>
 #include <wlr/backend/interface.h>
 #include <wlr/backend/session.h>
 #include <wlr/util/log.h>
@@ -77,11 +79,26 @@ static struct wlr_session *multi_backend_get_session(
 	return backend->session;
 }
 
+static clockid_t multi_backend_get_presentation_clock(
+		struct wlr_backend *backend) {
+	struct wlr_multi_backend *multi = multi_backend_from_backend(backend);
+
+	struct subbackend_state *sub;
+	wl_list_for_each(sub, &multi->backends, link) {
+		if (sub->backend->impl->get_presentation_clock) {
+			return wlr_backend_get_presentation_clock(sub->backend);
+		}
+	}
+
+	return CLOCK_MONOTONIC;
+}
+
 struct wlr_backend_impl backend_impl = {
 	.start = multi_backend_start,
 	.destroy = multi_backend_destroy,
 	.get_renderer = multi_backend_get_renderer,
 	.get_session = multi_backend_get_session,
+	.get_presentation_clock = multi_backend_get_presentation_clock,
 };
 
 static void handle_display_destroy(struct wl_listener *listener, void *data) {
diff --git a/include/wlr/backend.h b/include/wlr/backend.h
index aee45b73..54f2b5e8 100644
--- a/include/wlr/backend.h
+++ b/include/wlr/backend.h
@@ -65,6 +65,6 @@ struct wlr_session *wlr_backend_get_session(struct wlr_backend *backend);
 /**
  * Returns the clock used by the backend for presentation feedback.
  */
-clockid_t wlr_backend_get_present_clock(struct wlr_backend *backend);
+clockid_t wlr_backend_get_presentation_clock(struct wlr_backend *backend);
 
 #endif
diff --git a/include/wlr/backend/interface.h b/include/wlr/backend/interface.h
index a930c241..4a6a5cbb 100644
--- a/include/wlr/backend/interface.h
+++ b/include/wlr/backend/interface.h
@@ -19,7 +19,7 @@ struct wlr_backend_impl {
 	void (*destroy)(struct wlr_backend *backend);
 	struct wlr_renderer *(*get_renderer)(struct wlr_backend *backend);
 	struct wlr_session *(*get_session)(struct wlr_backend *backend);
-	clockid_t (*get_present_clock)(struct wlr_backend *backend);
+	clockid_t (*get_presentation_clock)(struct wlr_backend *backend);
 };
 
 /**
diff --git a/include/wlr/types/wlr_presentation_time.h b/include/wlr/types/wlr_presentation_time.h
index 71bf5977..9f9f0e87 100644
--- a/include/wlr/types/wlr_presentation_time.h
+++ b/include/wlr/types/wlr_presentation_time.h
@@ -47,7 +47,10 @@ struct wlr_presentation_event {
 	uint32_t flags; // wp_presentation_feedback_kind
 };
 
-struct wlr_presentation *wlr_presentation_create(struct wl_display *display);
+struct wlr_backend;
+
+struct wlr_presentation *wlr_presentation_create(struct wl_display *display,
+	struct wlr_backend *backend);
 void wlr_presentation_destroy(struct wlr_presentation *presentation);
 void wlr_presentation_send_surface_presented(
 	struct wlr_presentation *presentation, struct wlr_surface *surface,
diff --git a/types/wlr_output.c b/types/wlr_output.c
index 6ff06fd6..25cd0734 100644
--- a/types/wlr_output.c
+++ b/types/wlr_output.c
@@ -565,7 +565,7 @@ void wlr_output_send_present(struct wlr_output *output, struct timespec *when,
 		unsigned seq, uint32_t flags) {
 	struct timespec now;
 	if (when == NULL) {
-		clockid_t clock = wlr_backend_get_present_clock(output->backend);
+		clockid_t clock = wlr_backend_get_presentation_clock(output->backend);
 		errno = 0;
 		if (clock_gettime(clock, &now) != 0) {
 			wlr_log_errno(WLR_ERROR, "failed to send output present event: "
diff --git a/types/wlr_presentation_time.c b/types/wlr_presentation_time.c
index 710aa4b9..c83b5e99 100644
--- a/types/wlr_presentation_time.c
+++ b/types/wlr_presentation_time.c
@@ -3,6 +3,7 @@
 #include <stdlib.h>
 #include <wlr/types/wlr_presentation_time.h>
 #include <wlr/types/wlr_surface.h>
+#include <wlr/backend.h>
 #include "presentation-time-protocol.h"
 #include "util/signal.h"
 
@@ -147,7 +148,7 @@ static void presentation_bind(struct wl_client *client, void *data,
 		presentation_handle_resource_destroy);
 	wl_list_insert(&presentation->resources, wl_resource_get_link(resource));
 
-	wp_presentation_send_clock_id(resource, presentation->clock);
+	wp_presentation_send_clock_id(resource, (uint32_t)presentation->clock);
 }
 
 static void handle_display_destroy(struct wl_listener *listener, void *data) {
@@ -156,7 +157,8 @@ static void handle_display_destroy(struct wl_listener *listener, void *data) {
 	wlr_presentation_destroy(presentation);
 }
 
-struct wlr_presentation *wlr_presentation_create(struct wl_display *display) {
+struct wlr_presentation *wlr_presentation_create(struct wl_display *display,
+		struct wlr_backend *backend) {
 	struct wlr_presentation *presentation =
 		calloc(1, sizeof(struct wlr_presentation));
 	if (presentation == NULL) {
@@ -170,8 +172,7 @@ struct wlr_presentation *wlr_presentation_create(struct wl_display *display) {
 		return NULL;
 	}
 
-	// TODO: get clock from backend
-	presentation->clock = CLOCK_MONOTONIC;
+	presentation->clock = wlr_backend_get_presentation_clock(backend);
 
 	wl_list_init(&presentation->resources);
 	wl_list_init(&presentation->feedbacks);

From 0aafd6e234ff921e2b41126e22c426f928877cc4 Mon Sep 17 00:00:00 2001
From: emersion <contact@emersion.fr>
Date: Tue, 2 Oct 2018 11:19:20 +0200
Subject: [PATCH 08/11] rootston: add layer_for_each_surface

---
 rootston/output.c | 64 +++++++++++++++++++++++------------------------
 1 file changed, 31 insertions(+), 33 deletions(-)

diff --git a/rootston/output.c b/rootston/output.c
index e85612fa..e8a1b60f 100644
--- a/rootston/output.c
+++ b/rootston/output.c
@@ -127,6 +127,23 @@ static void drag_icons_for_each_surface(struct roots_input *input,
 	}
 }
 
+static void layer_for_each_surface(struct wl_list *layer,
+		const struct wlr_box *output_layout_box,
+		 wlr_surface_iterator_func_t iterator, struct layout_data *layout_data,
+		void *user_data) {
+	struct roots_layer_surface *roots_surface;
+	wl_list_for_each(roots_surface, layer, link) {
+		struct wlr_layer_surface_v1 *layer = roots_surface->layer_surface;
+
+		layout_data->x = roots_surface->geo.x + output_layout_box->x;
+		layout_data->y = roots_surface->geo.y + output_layout_box->y;
+		layout_data->width = roots_surface->geo.width;
+		layout_data->height = roots_surface->geo.height;
+		layout_data->rotation = 0;
+		wlr_layer_surface_v1_for_each_surface(layer, iterator, user_data);
+	}
+}
+
 
 struct render_data {
 	struct layout_data layout;
@@ -320,6 +337,14 @@ static void render_view(struct roots_view *view, struct render_data *data) {
 	view_for_each_surface(view, &data->layout, render_surface, data);
 }
 
+static void render_layer(struct roots_output *output,
+		const struct wlr_box *output_layout_box, struct render_data *data,
+		struct wl_list *layer) {
+	data->alpha = 1;
+	layer_for_each_surface(layer, output_layout_box, render_surface,
+		&data->layout, data);
+}
+
 static bool has_standalone_surface(struct roots_view *view) {
 	if (!wl_list_empty(&view->wlr_surface->subsurfaces)) {
 		return false;
@@ -358,38 +383,6 @@ static void surface_send_frame_done(struct wlr_surface *surface, int sx, int sy,
 	wlr_surface_send_frame_done(surface, when);
 }
 
-static void render_layer(struct roots_output *output,
-		const struct wlr_box *output_layout_box, struct render_data *data,
-		struct wl_list *layer) {
-	struct roots_layer_surface *roots_surface;
-	wl_list_for_each(roots_surface, layer, link) {
-		struct wlr_layer_surface_v1 *layer = roots_surface->layer_surface;
-
-		surface_for_each_surface(layer->surface,
-			roots_surface->geo.x + output_layout_box->x,
-			roots_surface->geo.y + output_layout_box->y,
-			0, &data->layout, render_surface, data);
-
-		wlr_layer_surface_v1_for_each_surface(layer, render_surface, data);
-	}
-}
-
-static void layers_send_done(
-		struct roots_output *output, struct timespec *when) {
-	size_t len = sizeof(output->layers) / sizeof(output->layers[0]);
-	for (size_t i = 0; i < len; ++i) {
-		struct roots_layer_surface *roots_surface;
-		wl_list_for_each(roots_surface, &output->layers[i], link) {
-			struct wlr_layer_surface_v1 *layer = roots_surface->layer_surface;
-			wlr_surface_send_frame_done(layer->surface, when);
-			struct wlr_xdg_popup *popup;
-			wl_list_for_each(popup, &roots_surface->layer_surface->popups, link) {
-				wlr_surface_send_frame_done(popup->base->surface, when);
-			}
-		}
-	}
-}
-
 static void render_output(struct roots_output *output) {
 	struct wlr_output *wlr_output = output->wlr_output;
 	struct roots_desktop *desktop = output->desktop;
@@ -563,7 +556,12 @@ damage_finish:
 		drag_icons_for_each_surface(server->input, surface_send_frame_done,
 			&data.layout, &data);
 	}
-	layers_send_done(output, data.when);
+
+	size_t len = sizeof(output->layers) / sizeof(output->layers[0]);
+	for (size_t i = 0; i < len; ++i) {
+		layer_for_each_surface(&output->layers[i], output_box,
+			surface_send_frame_done, &data.layout, &data);
+	}
 }
 
 void output_damage_whole(struct roots_output *output) {

From ba63d77ec19b84c9bf9be24cc4d91f3bfa856dba Mon Sep 17 00:00:00 2001
From: emersion <contact@emersion.fr>
Date: Tue, 2 Oct 2018 11:26:40 +0200
Subject: [PATCH 09/11] rootston: add output_for_each_surface

---
 rootston/output.c | 78 +++++++++++++++++++++++++++--------------------
 1 file changed, 45 insertions(+), 33 deletions(-)

diff --git a/rootston/output.c b/rootston/output.c
index e8a1b60f..1707be3a 100644
--- a/rootston/output.c
+++ b/rootston/output.c
@@ -129,7 +129,7 @@ static void drag_icons_for_each_surface(struct roots_input *input,
 
 static void layer_for_each_surface(struct wl_list *layer,
 		const struct wlr_box *output_layout_box,
-		 wlr_surface_iterator_func_t iterator, struct layout_data *layout_data,
+		wlr_surface_iterator_func_t iterator, struct layout_data *layout_data,
 		void *user_data) {
 	struct roots_layer_surface *roots_surface;
 	wl_list_for_each(roots_surface, layer, link) {
@@ -144,6 +144,48 @@ static void layer_for_each_surface(struct wl_list *layer,
 	}
 }
 
+static void output_for_each_surface(struct roots_output *output,
+		wlr_surface_iterator_func_t iterator, struct layout_data *layout_data,
+		void *user_data) {
+	struct wlr_output *wlr_output = output->wlr_output;
+	struct roots_desktop *desktop = output->desktop;
+	struct roots_server *server = desktop->server;
+
+	const struct wlr_box *output_box =
+		wlr_output_layout_get_box(desktop->layout, wlr_output);
+
+	if (output->fullscreen_view != NULL) {
+		struct roots_view *view = output->fullscreen_view;
+		if (wlr_output->fullscreen_surface == view->wlr_surface) {
+			// The surface is managed by the wlr_output
+			return;
+		}
+
+		view_for_each_surface(view, layout_data, iterator, user_data);
+
+#ifdef WLR_HAS_XWAYLAND
+		if (view->type == ROOTS_XWAYLAND_VIEW) {
+			xwayland_children_for_each_surface(view->xwayland_surface,
+				iterator, layout_data, user_data);
+		}
+#endif
+	} else {
+		struct roots_view *view;
+		wl_list_for_each_reverse(view, &desktop->views, link) {
+			view_for_each_surface(view, layout_data, iterator, user_data);
+		}
+
+		drag_icons_for_each_surface(server->input, iterator,
+			layout_data, user_data);
+	}
+
+	size_t len = sizeof(output->layers) / sizeof(output->layers[0]);
+	for (size_t i = 0; i < len; ++i) {
+		layer_for_each_surface(&output->layers[i], output_box,
+			iterator, layout_data, user_data);
+	}
+}
+
 
 struct render_data {
 	struct layout_data layout;
@@ -530,38 +572,8 @@ damage_finish:
 	pixman_region32_fini(&damage);
 
 	// Send frame done events to all surfaces
-	if (output->fullscreen_view != NULL) {
-		struct roots_view *view = output->fullscreen_view;
-		if (wlr_output->fullscreen_surface == view->wlr_surface) {
-			// The surface is managed by the wlr_output
-			return;
-		}
-
-		view_for_each_surface(view, &data.layout, surface_send_frame_done,
-			&data);
-
-#ifdef WLR_HAS_XWAYLAND
-		if (view->type == ROOTS_XWAYLAND_VIEW) {
-			xwayland_children_for_each_surface(view->xwayland_surface,
-				surface_send_frame_done, &data.layout, &data);
-		}
-#endif
-	} else {
-		struct roots_view *view;
-		wl_list_for_each_reverse(view, &desktop->views, link) {
-			view_for_each_surface(view, &data.layout, surface_send_frame_done,
-				&data);
-		}
-
-		drag_icons_for_each_surface(server->input, surface_send_frame_done,
-			&data.layout, &data);
-	}
-
-	size_t len = sizeof(output->layers) / sizeof(output->layers[0]);
-	for (size_t i = 0; i < len; ++i) {
-		layer_for_each_surface(&output->layers[i], output_box,
-			surface_send_frame_done, &data.layout, &data);
-	}
+	output_for_each_surface(output, surface_send_frame_done,
+		&data.layout, &data);
 }
 
 void output_damage_whole(struct roots_output *output) {

From abd3e995ab446b5487f4d2ff16d9e2c3f1baade1 Mon Sep 17 00:00:00 2001
From: emersion <contact@emersion.fr>
Date: Tue, 2 Oct 2018 11:46:28 +0200
Subject: [PATCH 10/11] rootston: send presentation events

---
 include/rootston/desktop.h |  2 ++
 include/rootston/output.h  |  1 +
 rootston/desktop.c         |  3 +++
 rootston/output.c          | 52 +++++++++++++++++++++++++++++++++++++-
 4 files changed, 57 insertions(+), 1 deletion(-)

diff --git a/include/rootston/desktop.h b/include/rootston/desktop.h
index 90851a17..8cee170f 100644
--- a/include/rootston/desktop.h
+++ b/include/rootston/desktop.h
@@ -13,6 +13,7 @@
 #include <wlr/types/wlr_list.h>
 #include <wlr/types/wlr_output_layout.h>
 #include <wlr/types/wlr_output.h>
+#include <wlr/types/wlr_presentation_time.h>
 #include <wlr/types/wlr_primary_selection.h>
 #include <wlr/types/wlr_screencopy_v1.h>
 #include <wlr/types/wlr_screenshooter.h>
@@ -57,6 +58,7 @@ struct roots_desktop {
 	struct wlr_screencopy_manager_v1 *screencopy;
 	struct wlr_tablet_manager_v2 *tablet_v2;
 	struct wlr_pointer_constraints_v1 *pointer_constraints;
+	struct wlr_presentation *presentation;
 
 	struct wl_listener new_output;
 	struct wl_listener layout_change;
diff --git a/include/rootston/output.h b/include/rootston/output.h
index 69bc5126..3f07ab6f 100644
--- a/include/rootston/output.h
+++ b/include/rootston/output.h
@@ -24,6 +24,7 @@ struct roots_output {
 	struct wl_listener destroy;
 	struct wl_listener mode;
 	struct wl_listener transform;
+	struct wl_listener present;
 	struct wl_listener damage_frame;
 	struct wl_listener damage_destroy;
 };
diff --git a/rootston/desktop.c b/rootston/desktop.c
index c180c839..7f749050 100644
--- a/rootston/desktop.c
+++ b/rootston/desktop.c
@@ -969,6 +969,9 @@ struct roots_desktop *desktop_create(struct roots_server *server,
 	wl_signal_add(&desktop->pointer_constraints->events.new_constraint,
 		&desktop->pointer_constraint);
 
+	desktop->presentation =
+		wlr_presentation_create(server->wl_display, server->backend);
+
 	return desktop;
 }
 
diff --git a/rootston/output.c b/rootston/output.c
index 1707be3a..8168a0c3 100644
--- a/rootston/output.c
+++ b/rootston/output.c
@@ -5,9 +5,10 @@
 #include <time.h>
 #include <wlr/backend/drm.h>
 #include <wlr/config.h>
-#include <wlr/types/wlr_matrix.h>
 #include <wlr/types/wlr_compositor.h>
+#include <wlr/types/wlr_matrix.h>
 #include <wlr/types/wlr_output_layout.h>
+#include <wlr/types/wlr_presentation_time.h>
 #include <wlr/types/wlr_wl_shell.h>
 #include <wlr/types/wlr_xdg_shell_v6.h>
 #include <wlr/types/wlr_xdg_shell.h>
@@ -784,6 +785,7 @@ static void output_destroy(struct roots_output *output) {
 	wl_list_remove(&output->destroy.link);
 	wl_list_remove(&output->mode.link);
 	wl_list_remove(&output->transform.link);
+	wl_list_remove(&output->present.link);
 	wl_list_remove(&output->damage_frame.link);
 	wl_list_remove(&output->damage_destroy.link);
 	free(output);
@@ -820,6 +822,52 @@ static void output_handle_transform(struct wl_listener *listener, void *data) {
 	arrange_layers(output);
 }
 
+struct presentation_data {
+	struct layout_data layout;
+	struct roots_output *output;
+	struct wlr_presentation_event *event;
+};
+
+static void surface_send_presented(struct wlr_surface *surface, int sx, int sy,
+		void *_data) {
+	struct presentation_data *data = _data;
+	struct roots_output *output = data->output;
+	float rotation = data->layout.rotation;
+
+	double lx, ly;
+	get_layout_position(&data->layout, &lx, &ly, surface, sx, sy);
+
+	if (!surface_intersect_output(surface, output->desktop->layout,
+			output->wlr_output, lx, ly, rotation, NULL)) {
+		return;
+	}
+
+	wlr_presentation_send_surface_presented(output->desktop->presentation,
+		surface, data->event);
+}
+
+static void output_handle_present(struct wl_listener *listener, void *data) {
+	struct roots_output *output =
+		wl_container_of(listener, output, present);
+	struct wlr_output_event_present *output_event = data;
+
+	struct wlr_presentation_event event = {
+		.output = output->wlr_output,
+		.tv_sec = (uint64_t)output_event->when->tv_sec,
+		.tv_nsec = (uint32_t)output_event->when->tv_nsec,
+		.refresh = 0, // TODO: predict next output vsync delay
+		.seq = (uint64_t)output_event->seq,
+		.flags = output_event->flags,
+	};
+
+	struct presentation_data presentation_data = {
+		.output = output,
+		.event = &event,
+	};
+	output_for_each_surface(output, surface_send_presented,
+		&presentation_data.layout, &presentation_data);
+}
+
 void handle_new_output(struct wl_listener *listener, void *data) {
 	struct roots_desktop *desktop = wl_container_of(listener, desktop,
 		new_output);
@@ -847,6 +895,8 @@ void handle_new_output(struct wl_listener *listener, void *data) {
 	wl_signal_add(&wlr_output->events.mode, &output->mode);
 	output->transform.notify = output_handle_transform;
 	wl_signal_add(&wlr_output->events.transform, &output->transform);
+	output->present.notify = output_handle_present;
+	wl_signal_add(&wlr_output->events.present, &output->present);
 
 	output->damage_frame.notify = output_damage_handle_frame;
 	wl_signal_add(&output->damage->events.frame, &output->damage_frame);

From eac7c2ad2faf49084342d9f805cf06b773723fdd Mon Sep 17 00:00:00 2001
From: emersion <contact@emersion.fr>
Date: Tue, 2 Oct 2018 12:11:09 +0200
Subject: [PATCH 11/11] output: add presentation refresh prediction

---
 backend/drm/drm.c                   | 15 ++++++++++++---
 backend/headless/output.c           |  5 +++--
 backend/wayland/output.c            |  2 +-
 backend/x11/output.c                |  2 +-
 include/wlr/interfaces/wlr_output.h |  4 ++--
 include/wlr/types/wlr_output.h      | 13 +++++++++++++
 rootston/output.c                   |  2 +-
 types/wlr_output.c                  | 23 ++++++++++++-----------
 types/wlr_presentation_time.c       |  4 ++--
 9 files changed, 47 insertions(+), 23 deletions(-)

diff --git a/backend/drm/drm.c b/backend/drm/drm.c
index 753b6ab8..0187e5d0 100644
--- a/backend/drm/drm.c
+++ b/backend/drm/drm.c
@@ -1154,6 +1154,10 @@ void scan_drm_connectors(struct wlr_drm_backend *drm) {
 	attempt_enable_needs_modeset(drm);
 }
 
+static int mhz_to_nsec(int mhz) {
+	return 1000000000000LL / mhz;
+}
+
 static void page_flip_handler(int fd, unsigned seq,
 		unsigned tv_sec, unsigned tv_usec, void *data) {
 	struct wlr_drm_connector *conn = data;
@@ -1180,9 +1184,14 @@ static void page_flip_handler(int fd, unsigned seq,
 		.tv_sec = tv_sec,
 		.tv_nsec = tv_usec * 1000,
 	};
-	uint32_t present_flags = WLR_OUTPUT_PRESENT_VSYNC |
-		WLR_OUTPUT_PRESENT_HW_CLOCK | WLR_OUTPUT_PRESENT_HW_COMPLETION;
-	wlr_output_send_present(&conn->output, &present_time, seq, present_flags);
+	struct wlr_output_event_present present_event = {
+		.when = &present_time,
+		.seq = seq,
+		.refresh = mhz_to_nsec(conn->output.refresh),
+		.flags = WLR_OUTPUT_PRESENT_VSYNC | WLR_OUTPUT_PRESENT_HW_CLOCK |
+			WLR_OUTPUT_PRESENT_HW_COMPLETION,
+	};
+	wlr_output_send_present(&conn->output, &present_event);
 
 	if (drm->session->active) {
 		wlr_output_send_frame(&conn->output);
diff --git a/backend/headless/output.c b/backend/headless/output.c
index ad0050d8..3cb35dce 100644
--- a/backend/headless/output.c
+++ b/backend/headless/output.c
@@ -67,8 +67,9 @@ static bool output_make_current(struct wlr_output *wlr_output, int *buffer_age)
 
 static bool output_swap_buffers(struct wlr_output *wlr_output,
 		pixman_region32_t *damage) {
-	wlr_output_send_present(wlr_output, NULL, 0, 0);
-	return true; // No-op
+	// Nothing needs to be done for pbuffers
+	wlr_output_send_present(wlr_output, NULL);
+	return true;
 }
 
 static void output_destroy(struct wlr_output *wlr_output) {
diff --git a/backend/wayland/output.c b/backend/wayland/output.c
index 4fbfe9d2..bc7a9f05 100644
--- a/backend/wayland/output.c
+++ b/backend/wayland/output.c
@@ -72,7 +72,7 @@ static bool output_swap_buffers(struct wlr_output *wlr_output,
 	}
 
 	// TODO: if available, use the presentation-time protocol
-	wlr_output_send_present(wlr_output, NULL, 0, 0);
+	wlr_output_send_present(wlr_output, NULL);
 	return true;
 }
 
diff --git a/backend/x11/output.c b/backend/x11/output.c
index 8cd8ee33..1ac12a8d 100644
--- a/backend/x11/output.c
+++ b/backend/x11/output.c
@@ -106,7 +106,7 @@ static bool output_swap_buffers(struct wlr_output *wlr_output,
 		return false;
 	}
 
-	wlr_output_send_present(wlr_output, NULL, 0, 0);
+	wlr_output_send_present(wlr_output, NULL);
 	return true;
 }
 
diff --git a/include/wlr/interfaces/wlr_output.h b/include/wlr/interfaces/wlr_output.h
index b06c5db0..52581768 100644
--- a/include/wlr/interfaces/wlr_output.h
+++ b/include/wlr/interfaces/wlr_output.h
@@ -45,7 +45,7 @@ void wlr_output_update_enabled(struct wlr_output *output, bool enabled);
 void wlr_output_update_needs_swap(struct wlr_output *output);
 void wlr_output_damage_whole(struct wlr_output *output);
 void wlr_output_send_frame(struct wlr_output *output);
-void wlr_output_send_present(struct wlr_output *output, struct timespec *when,
-	unsigned seq, uint32_t flags);
+void wlr_output_send_present(struct wlr_output *output,
+	struct wlr_output_event_present *event);
 
 #endif
diff --git a/include/wlr/types/wlr_output.h b/include/wlr/types/wlr_output.h
index fb3becd1..9ccfbbb5 100644
--- a/include/wlr/types/wlr_output.h
+++ b/include/wlr/types/wlr_output.h
@@ -130,15 +130,28 @@ struct wlr_output_event_swap_buffers {
 };
 
 enum wlr_output_present_flag {
+	// The presentation was synchronized to the "vertical retrace" by the
+	// display hardware such that tearing does not happen.
 	WLR_OUTPUT_PRESENT_VSYNC = 0x1,
+	// The display hardware provided measurements that the hardware driver
+	// converted into a presentation timestamp.
 	WLR_OUTPUT_PRESENT_HW_CLOCK = 0x2,
+	// The display hardware signalled that it started using the new image
+	// content.
 	WLR_OUTPUT_PRESENT_HW_COMPLETION = 0x4,
+	// The presentation of this update was done zero-copy.
+	WLR_OUTPUT_PRESENT_ZERO_COPY = 0x8,
 };
 
 struct wlr_output_event_present {
 	struct wlr_output *output;
+	// Time when the content update turned into light the first time.
 	struct timespec *when;
+	// Vertical retrace counter. Zero if unavailable.
 	unsigned seq;
+	// Prediction of how many nanoseconds after `when` the very next output
+	// refresh may occur. Zero if unknown.
+	int refresh; // nsec
 	uint32_t flags; // enum wlr_output_present_flag
 };
 
diff --git a/rootston/output.c b/rootston/output.c
index 8168a0c3..9d376f8e 100644
--- a/rootston/output.c
+++ b/rootston/output.c
@@ -855,7 +855,7 @@ static void output_handle_present(struct wl_listener *listener, void *data) {
 		.output = output->wlr_output,
 		.tv_sec = (uint64_t)output_event->when->tv_sec,
 		.tv_nsec = (uint32_t)output_event->when->tv_nsec,
-		.refresh = 0, // TODO: predict next output vsync delay
+		.refresh = (uint32_t)output_event->refresh,
 		.seq = (uint64_t)output_event->seq,
 		.flags = output_event->flags,
 	};
diff --git a/types/wlr_output.c b/types/wlr_output.c
index 25cd0734..b3840415 100644
--- a/types/wlr_output.c
+++ b/types/wlr_output.c
@@ -561,10 +561,17 @@ void wlr_output_schedule_frame(struct wlr_output *output) {
 		wl_event_loop_add_idle(ev, schedule_frame_handle_idle_timer, output);
 }
 
-void wlr_output_send_present(struct wlr_output *output, struct timespec *when,
-		unsigned seq, uint32_t flags) {
+void wlr_output_send_present(struct wlr_output *output,
+		struct wlr_output_event_present *event) {
+	struct wlr_output_event_present _event = {0};
+	if (event == NULL) {
+		event = &_event;
+	}
+
+	event->output = output;
+
 	struct timespec now;
-	if (when == NULL) {
+	if (event->when == NULL) {
 		clockid_t clock = wlr_backend_get_presentation_clock(output->backend);
 		errno = 0;
 		if (clock_gettime(clock, &now) != 0) {
@@ -572,16 +579,10 @@ void wlr_output_send_present(struct wlr_output *output, struct timespec *when,
 				"failed to read clock");
 			return;
 		}
-		when = &now;
+		event->when = &now;
 	}
 
-	struct wlr_output_event_present event = {
-		.output = output,
-		.when = when,
-		.seq = seq,
-		.flags = flags,
-	};
-	wlr_signal_emit_safe(&output->events.present, &event);
+	wlr_signal_emit_safe(&output->events.present, event);
 }
 
 bool wlr_output_set_gamma(struct wlr_output *output, size_t size,
diff --git a/types/wlr_presentation_time.c b/types/wlr_presentation_time.c
index c83b5e99..eeba47b6 100644
--- a/types/wlr_presentation_time.c
+++ b/types/wlr_presentation_time.c
@@ -42,8 +42,8 @@ static void feedback_send_presented(struct wlr_presentation_feedback *feedback,
 	uint32_t seq_hi = event->seq >> 32;
 	uint32_t seq_lo = event->seq & 0xFFFFFFFF;
 	wp_presentation_feedback_send_presented(feedback->resource,
-		tv_sec_hi, tv_sec_lo, event->tv_nsec, event->refresh, seq_hi, seq_lo,
-		event->flags);
+		tv_sec_hi, tv_sec_lo, event->tv_nsec, event->refresh,
+		seq_hi, seq_lo, event->flags);
 
 	wl_resource_destroy(feedback->resource);
 }