output: atomic mode, enabled, scale and transform

This commit makes more output properties (mode, enabled, scale and transform)
atomic. This means that they are double-buffered and only applied on commit.

Compositors now need to call wlr_output_commit after setting any of those
properties.

Internally, backends still apply properties sequentially. The behaviour should
be exactly the same as before. Future commits will update some backends to take
advantage of the atomic interface. Some backends are non-atomic by design, e.g.
the X11 backend or the legacy DRM backend.

Updates: https://github.com/swaywm/wlroots/issues/1640

6 files changed, 155 insertions, 42 deletions

diff --git a/backend/drm/drm.c b/backend/drm/drm.c
index eef7beb5..730240c8 100644
--- a/backend/drm/drm.c
+++ b/backend/drm/drm.c
@@ -328,12 +328,9 @@ static bool drm_connector_attach_render(struct wlr_output *output,
 	return make_drm_surface_current(&conn->crtc->primary->surf, buffer_age);
 }
 
-static bool drm_connector_commit(struct wlr_output *output) {
+static bool drm_connector_commit_buffer(struct wlr_output *output) {
 	struct wlr_drm_connector *conn = get_drm_connector_from_output(output);
 	struct wlr_drm_backend *drm = get_drm_backend_from_backend(output->backend);
-	if (!drm->session->active) {
-		return false;
-	}
 
 	struct wlr_drm_crtc *crtc = conn->crtc;
 	if (!crtc) {
@@ -404,6 +401,37 @@ static bool drm_connector_commit(struct wlr_output *output) {
 	return true;
 }
 
+static bool drm_connector_commit(struct wlr_output *output) {
+	struct wlr_drm_backend *drm = get_drm_backend_from_backend(output->backend);
+
+	if (!drm->session->active) {
+		return false;
+	}
+
+	if (output->pending.committed & WLR_OUTPUT_STATE_ENABLED) {
+		if (!enable_drm_connector(output, output->pending.enabled)) {
+			return false;
+		}
+	}
+
+	if (output->pending.committed & WLR_OUTPUT_STATE_MODE) {
+		if (output->pending.mode_type != WLR_OUTPUT_STATE_MODE_FIXED) {
+			return false;
+		}
+		if (!drm_connector_set_mode(output, output->pending.mode)) {
+			return false;
+		}
+	}
+
+	if (output->pending.committed & WLR_OUTPUT_STATE_BUFFER) {
+		if (!drm_connector_commit_buffer(output)) {
+			return false;
+		}
+	}
+
+	return true;
+}
+
 static void fill_empty_gamma_table(size_t size,
 		uint16_t *r, uint16_t *g, uint16_t *b) {
 	for (uint32_t i = 0; i < size; ++i) {
@@ -922,8 +950,6 @@ static void drm_connector_destroy(struct wlr_output *output) {
 }
 
 static const struct wlr_output_impl output_impl = {
-	.enable = enable_drm_connector,
-	.set_mode = drm_connector_set_mode,
 	.set_cursor = drm_connector_set_cursor,
 	.move_cursor = drm_connector_move_cursor,
 	.destroy = drm_connector_destroy,
diff --git a/backend/headless/output.c b/backend/headless/output.c
index 992a4883..1916b525 100644
--- a/backend/headless/output.c
+++ b/backend/headless/output.c
@@ -58,8 +58,26 @@ static bool output_attach_render(struct wlr_output *wlr_output,
 }
 
 static bool output_commit(struct wlr_output *wlr_output) {
-	// Nothing needs to be done for pbuffers
-	wlr_output_send_present(wlr_output, NULL);
+	if (wlr_output->pending.committed & WLR_OUTPUT_STATE_ENABLED) {
+		wlr_log(WLR_DEBUG, "Cannot disable a headless output");
+		return false;
+	}
+
+	if (wlr_output->pending.committed & WLR_OUTPUT_STATE_MODE) {
+		assert(wlr_output->pending.mode_type == WLR_OUTPUT_STATE_MODE_CUSTOM);
+		if (!output_set_custom_mode(wlr_output,
+				wlr_output->pending.custom_mode.width,
+				wlr_output->pending.custom_mode.height,
+				wlr_output->pending.custom_mode.refresh)) {
+			return false;
+		}
+	}
+
+	if (wlr_output->pending.committed & WLR_OUTPUT_STATE_BUFFER) {
+		// Nothing needs to be done for pbuffers
+		wlr_output_send_present(wlr_output, NULL);
+	}
+
 	return true;
 }
 
@@ -76,7 +94,6 @@ static void output_destroy(struct wlr_output *wlr_output) {
 }
 
 static const struct wlr_output_impl output_impl = {
-	.set_custom_mode = output_set_custom_mode,
 	.destroy = output_destroy,
 	.attach_render = output_attach_render,
 	.commit = output_commit,
diff --git a/backend/noop/output.c b/backend/noop/output.c
index 1022ac6f..15c84941 100644
--- a/backend/noop/output.c
+++ b/backend/noop/output.c
@@ -12,19 +12,30 @@ static struct wlr_noop_output *noop_output_from_output(
 	return (struct wlr_noop_output *)wlr_output;
 }
 
-static bool output_set_custom_mode(struct wlr_output *wlr_output,
-		int32_t width, int32_t height, int32_t refresh) {
-	wlr_output_update_custom_mode(wlr_output, width, height, refresh);
-	return true;
-}
-
 static bool output_attach_render(struct wlr_output *wlr_output,
 		int *buffer_age) {
 	return false;
 }
 
 static bool output_commit(struct wlr_output *wlr_output) {
-	return false;
+	if (wlr_output->pending.committed & WLR_OUTPUT_STATE_ENABLED) {
+		wlr_log(WLR_DEBUG, "Cannot disable a noop output");
+		return false;
+	}
+
+	if (wlr_output->pending.committed & WLR_OUTPUT_STATE_MODE) {
+		assert(wlr_output->pending.mode_type == WLR_OUTPUT_STATE_MODE_CUSTOM);
+		wlr_output_update_custom_mode(wlr_output,
+			wlr_output->pending.custom_mode.width,
+			wlr_output->pending.custom_mode.height,
+			wlr_output->pending.custom_mode.refresh);
+	}
+
+	if (wlr_output->pending.committed & WLR_OUTPUT_STATE_BUFFER) {
+		return false;
+	}
+
+	return true;
 }
 
 static void output_destroy(struct wlr_output *wlr_output) {
@@ -37,7 +48,6 @@ static void output_destroy(struct wlr_output *wlr_output) {
 }
 
 static const struct wlr_output_impl output_impl = {
-	.set_custom_mode = output_set_custom_mode,
 	.destroy = output_destroy,
 	.attach_render = output_attach_render,
 	.commit = output_commit,
diff --git a/backend/rdp/output.c b/backend/rdp/output.c
index 45eba3aa..68d2ed17 100644
--- a/backend/rdp/output.c
+++ b/backend/rdp/output.c
@@ -166,9 +166,9 @@ static bool nsc_swap_buffers(
 	return true;
 }
 
-static bool output_commit(struct wlr_output *wlr_output) {
-	struct wlr_rdp_output *output =
-		rdp_output_from_output(wlr_output);
+static bool output_commit_buffer(struct wlr_rdp_output *output) {
+	struct wlr_output *wlr_output = &output->wlr_output;
+
 	bool ret = false;
 
 	pixman_region32_t output_region;
@@ -220,6 +220,33 @@ out:
 	return ret;
 }
 
+static bool output_commit(struct wlr_output *wlr_output) {
+	struct wlr_rdp_output *output = rdp_output_from_output(wlr_output);
+
+	if (wlr_output->pending.committed & WLR_OUTPUT_STATE_ENABLED) {
+		wlr_log(WLR_DEBUG, "Cannot disable an RDP output");
+		return false;
+	}
+
+	if (wlr_output->pending.committed & WLR_OUTPUT_STATE_MODE) {
+		assert(wlr_output->pending.mode_type == WLR_OUTPUT_STATE_MODE_CUSTOM);
+		if (!output_set_custom_mode(wlr_output,
+				wlr_output->pending.custom_mode.width,
+				wlr_output->pending.custom_mode.height,
+				wlr_output->pending.custom_mode.refresh)) {
+			return false;
+		}
+	}
+
+	if (wlr_output->pending.committed & WLR_OUTPUT_STATE_BUFFER) {
+		if (!output_commit_buffer(output)) {
+			return false;
+		}
+	}
+
+	return true;
+}
+
 static void output_destroy(struct wlr_output *wlr_output) {
 	struct wlr_rdp_output *output =
 		rdp_output_from_output(wlr_output);
@@ -234,7 +261,6 @@ static void output_destroy(struct wlr_output *wlr_output) {
 }
 
 static const struct wlr_output_impl output_impl = {
-	.set_custom_mode = output_set_custom_mode,
 	.destroy = output_destroy,
 	.attach_render = output_attach_render,
 	.commit = output_commit,
diff --git a/backend/wayland/output.c b/backend/wayland/output.c
index b179a5f6..7074b830 100644
--- a/backend/wayland/output.c
+++ b/backend/wayland/output.c
@@ -63,26 +63,44 @@ static bool output_commit(struct wlr_output *wlr_output) {
 	struct wlr_wl_output *output =
 		get_wl_output_from_output(wlr_output);
 
-	if (output->frame_callback != NULL) {
-		wlr_log(WLR_ERROR, "Skipping buffer swap");
+	if (wlr_output->pending.committed & WLR_OUTPUT_STATE_ENABLED) {
+		wlr_log(WLR_DEBUG, "Cannot disable a Wayland output");
 		return false;
 	}
 
-	output->frame_callback = wl_surface_frame(output->surface);
-	wl_callback_add_listener(output->frame_callback, &frame_listener, output);
-
-	pixman_region32_t *damage = NULL;
-	if (wlr_output->pending.committed & WLR_OUTPUT_STATE_DAMAGE) {
-		damage = &wlr_output->pending.damage;
+	if (wlr_output->pending.committed & WLR_OUTPUT_STATE_MODE) {
+		assert(wlr_output->pending.mode_type == WLR_OUTPUT_STATE_MODE_CUSTOM);
+		if (!output_set_custom_mode(wlr_output,
+				wlr_output->pending.custom_mode.width,
+				wlr_output->pending.custom_mode.height,
+				wlr_output->pending.custom_mode.refresh)) {
+			return false;
+		}
 	}
 
-	if (!wlr_egl_swap_buffers(&output->backend->egl,
-			output->egl_surface, damage)) {
-		return false;
+	if (wlr_output->pending.committed & WLR_OUTPUT_STATE_BUFFER) {
+		if (output->frame_callback != NULL) {
+			wlr_log(WLR_ERROR, "Skipping buffer swap");
+			return false;
+		}
+
+		output->frame_callback = wl_surface_frame(output->surface);
+		wl_callback_add_listener(output->frame_callback, &frame_listener, output);
+
+		pixman_region32_t *damage = NULL;
+		if (wlr_output->pending.committed & WLR_OUTPUT_STATE_DAMAGE) {
+			damage = &wlr_output->pending.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);
 	}
 
-	// TODO: if available, use the presentation-time protocol
-	wlr_output_send_present(wlr_output, NULL);
 	return true;
 }
 
@@ -219,7 +237,6 @@ static bool output_schedule_frame(struct wlr_output *wlr_output) {
 }
 
 static const struct wlr_output_impl output_impl = {
-	.set_custom_mode = output_set_custom_mode,
 	.destroy = output_destroy,
 	.attach_render = output_attach_render,
 	.commit = output_commit,
diff --git a/backend/x11/output.c b/backend/x11/output.c
index 1307f785..7194d7fb 100644
--- a/backend/x11/output.c
+++ b/backend/x11/output.c
@@ -103,21 +103,38 @@ static bool output_commit(struct wlr_output *wlr_output) {
 	struct wlr_x11_output *output = get_x11_output_from_output(wlr_output);
 	struct wlr_x11_backend *x11 = output->x11;
 
-	pixman_region32_t *damage = NULL;
-	if (wlr_output->pending.committed & WLR_OUTPUT_STATE_DAMAGE) {
-		damage = &wlr_output->pending.damage;
+	if (wlr_output->pending.committed & WLR_OUTPUT_STATE_ENABLED) {
+		wlr_log(WLR_DEBUG, "Cannot disable an X11 output");
+		return false;
 	}
 
-	if (!wlr_egl_swap_buffers(&x11->egl, output->surf, damage)) {
-		return false;
+	if (wlr_output->pending.committed & WLR_OUTPUT_STATE_MODE) {
+		assert(wlr_output->pending.mode_type == WLR_OUTPUT_STATE_MODE_CUSTOM);
+		if (!output_set_custom_mode(wlr_output,
+				wlr_output->pending.custom_mode.width,
+				wlr_output->pending.custom_mode.height,
+				wlr_output->pending.custom_mode.refresh)) {
+			return false;
+		}
+	}
+
+	if (wlr_output->pending.committed & WLR_OUTPUT_STATE_BUFFER) {
+		pixman_region32_t *damage = NULL;
+		if (wlr_output->pending.committed & WLR_OUTPUT_STATE_DAMAGE) {
+			damage = &wlr_output->pending.damage;
+		}
+
+		if (!wlr_egl_swap_buffers(&x11->egl, output->surf, damage)) {
+			return false;
+		}
+
+		wlr_output_send_present(wlr_output, NULL);
 	}
 
-	wlr_output_send_present(wlr_output, NULL);
 	return true;
 }
 
 static const struct wlr_output_impl output_impl = {
-	.set_custom_mode = output_set_custom_mode,
 	.destroy = output_destroy,
 	.attach_render = output_attach_render,
 	.commit = output_commit,