view: Save all buffers associated with view

During the execution of a resize transaction, the buffer associated
with a view's surface is saved and reused until the client acknowledges
the resulting configure event.

However, only one the main buffer of the main surface was stored and
rendered, meaning that subsurfaces disappear during resize.

Iterate over all, store and render buffers from all surfaces in the view
to ensure that correct rendering is preserved.

4 files changed, 77 insertions, 48 deletions

diff --git a/sway/desktop/output.c b/sway/desktop/output.c
index a86622e1..18250ae6 100644
--- a/sway/desktop/output.c
+++ b/sway/desktop/output.c
@@ -511,7 +511,7 @@ static bool scan_out_fullscreen_view(struct sway_output *output,
 		return false;
 	}
 
-	if (view->saved_buffer) {
+	if (!wl_list_empty(&view->saved_buffers)) {
 		return false;
 	}
 
diff --git a/sway/desktop/render.c b/sway/desktop/render.c
index 14753df2..491a9bc0 100644
--- a/sway/desktop/render.c
+++ b/sway/desktop/render.c
@@ -280,37 +280,44 @@ static void render_saved_view(struct sway_view *view,
 		struct sway_output *output, pixman_region32_t *damage, float alpha) {
 	struct wlr_output *wlr_output = output->wlr_output;
 
-	if (!view->saved_buffer || !view->saved_buffer->texture) {
+	if (wl_list_empty(&view->saved_buffers)) {
 		return;
 	}
-	struct wlr_box box = {
-		.x = view->container->surface_x - output->lx -
-			view->saved_geometry.x,
-		.y = view->container->surface_y - output->ly -
-			view->saved_geometry.y,
-		.width = view->saved_buffer_width,
-		.height = view->saved_buffer_height,
-	};
-
-	struct wlr_box output_box = {
-		.width = output->width,
-		.height = output->height,
-	};
+	struct sway_saved_buffer *saved_buf;
+	wl_list_for_each(saved_buf, &view->saved_buffers, link) {
+		if (!saved_buf->buffer->texture) {
+			continue;
+		}
 
-	struct wlr_box intersection;
-	bool intersects = wlr_box_intersection(&intersection, &output_box, &box);
-	if (!intersects) {
-		return;
-	}
+		struct wlr_box box = {
+			.x = view->container->surface_x - output->lx -
+				view->saved_geometry.x + saved_buf->x,
+			.y = view->container->surface_y - output->ly -
+				view->saved_geometry.y + saved_buf->y,
+			.width = saved_buf->width,
+			.height = saved_buf->height,
+		};
+
+		struct wlr_box output_box = {
+			.width = output->width,
+			.height = output->height,
+		};
+
+		struct wlr_box intersection;
+		bool intersects = wlr_box_intersection(&intersection, &output_box, &box);
+		if (!intersects) {
+			continue;
+		}
 
-	scale_box(&box, wlr_output->scale);
+		scale_box(&box, wlr_output->scale);
 
-	float matrix[9];
-	wlr_matrix_project_box(matrix, &box, WL_OUTPUT_TRANSFORM_NORMAL, 0,
-		wlr_output->transform_matrix);
+		float matrix[9];
+		wlr_matrix_project_box(matrix, &box, WL_OUTPUT_TRANSFORM_NORMAL, 0,
+			wlr_output->transform_matrix);
 
-	render_texture(wlr_output, damage, view->saved_buffer->texture,
-			&box, matrix, alpha);
+		render_texture(wlr_output, damage, saved_buf->buffer->texture,
+				&box, matrix, alpha);
+	}
 
 	// FIXME: we should set the surface that this saved buffer originates from
 	// as sampled here.
@@ -323,7 +330,7 @@ static void render_saved_view(struct sway_view *view,
 static void render_view(struct sway_output *output, pixman_region32_t *damage,
 		struct sway_container *con, struct border_colors *colors) {
 	struct sway_view *view = con->view;
-	if (view->saved_buffer) {
+	if (!wl_list_empty(&view->saved_buffers)) {
 		render_saved_view(view, output, damage, view->container->alpha);
 	} else if (view->surface) {
 		render_view_toplevels(view, output, damage, view->container->alpha);
@@ -1020,7 +1027,7 @@ void output_render(struct sway_output *output, struct timespec *when,
 		}
 
 		if (fullscreen_con->view) {
-			if (fullscreen_con->view->saved_buffer) {
+			if (!wl_list_empty(&fullscreen_con->view->saved_buffers)) {
 				render_saved_view(fullscreen_con->view, output, damage, 1.0f);
 			} else if (fullscreen_con->view->surface) {
 				render_view_toplevels(fullscreen_con->view,
diff --git a/sway/desktop/transaction.c b/sway/desktop/transaction.c
index ccf60514..ef656102 100644
--- a/sway/desktop/transaction.c
+++ b/sway/desktop/transaction.c
@@ -210,14 +210,17 @@ static void apply_container_state(struct sway_container *container,
 	struct sway_view *view = container->view;
 	// Damage the old location
 	desktop_damage_whole_container(container);
-	if (view && view->saved_buffer) {
-		struct wlr_box box = {
-			.x = container->current.content_x - view->saved_geometry.x,
-			.y = container->current.content_y - view->saved_geometry.y,
-			.width = view->saved_buffer_width,
-			.height = view->saved_buffer_height,
-		};
-		desktop_damage_box(&box);
+	if (view && !wl_list_empty(&view->saved_buffers)) {
+		struct sway_saved_buffer *saved_buf;
+		wl_list_for_each(saved_buf, &view->saved_buffers, link) {
+			struct wlr_box box = {
+				.x = container->current.content_x - view->saved_geometry.x + saved_buf->x,
+				.y = container->current.content_y - view->saved_geometry.y + saved_buf->y,
+				.width = saved_buf->width,
+				.height = saved_buf->height,
+			};
+			desktop_damage_box(&box);
+		}
 	}
 
 	// There are separate children lists for each instruction state, the
@@ -229,7 +232,7 @@ static void apply_container_state(struct sway_container *container,
 
 	memcpy(&container->current, state, sizeof(struct sway_container_state));
 
-	if (view && view->saved_buffer) {
+	if (view && !wl_list_empty(&view->saved_buffers)) {
 		if (!container->node.destroying || container->node.ntxnrefs == 1) {
 			view_remove_saved_buffer(view);
 		}
@@ -432,7 +435,7 @@ static void transaction_commit(struct sway_transaction *transaction) {
 			wlr_surface_send_frame_done(
 					node->sway_container->view->surface, &now);
 		}
-		if (node_is_view(node) && !node->sway_container->view->saved_buffer) {
+		if (node_is_view(node) && wl_list_empty(&node->sway_container->view->saved_buffers)) {
 			view_save_buffer(node->sway_container->view);
 			memcpy(&node->sway_container->view->saved_geometry,
 					&node->sway_container->view->geometry,
diff --git a/sway/tree/view.c b/sway/tree/view.c
index 8e12a229..25951deb 100644
--- a/sway/tree/view.c
+++ b/sway/tree/view.c
@@ -36,6 +36,7 @@ void view_init(struct sway_view *view, enum sway_view_type type,
 	view->type = type;
 	view->impl = impl;
 	view->executed_criteria = create_list();
+	wl_list_init(&view->saved_buffers);
 	view->allow_request_urgent = true;
 	view->shortcuts_inhibit = SHORTCUTS_INHIBIT_DEFAULT;
 	wl_signal_init(&view->events.unmap);
@@ -54,6 +55,9 @@ void view_destroy(struct sway_view *view) {
 				"(might have a pending transaction?)")) {
 		return;
 	}
+	if (!wl_list_empty(&view->saved_buffers)) {
+		view_remove_saved_buffer(view);
+	}
 	list_free(view->executed_criteria);
 
 	free(view->title_format);
@@ -1176,23 +1180,38 @@ bool view_is_urgent(struct sway_view *view) {
 }
 
 void view_remove_saved_buffer(struct sway_view *view) {
-	if (!sway_assert(view->saved_buffer, "Expected a saved buffer")) {
+	if (!sway_assert(!wl_list_empty(&view->saved_buffers), "Expected a saved buffer")) {
 		return;
 	}
-	wlr_buffer_unlock(&view->saved_buffer->base);
-	view->saved_buffer = NULL;
+	struct sway_saved_buffer *saved_buf, *tmp;
+	wl_list_for_each_safe(saved_buf, tmp, &view->saved_buffers, link) {
+		wlr_buffer_unlock(&saved_buf->buffer->base);
+		wl_list_remove(&saved_buf->link);
+		free(saved_buf);
+	}
+}
+
+static void view_save_buffer_iterator(struct wlr_surface *surface,
+		int sx, int sy, void *data) {
+	struct sway_view *view = data;
+
+	if (surface && wlr_surface_has_buffer(surface)) {
+		wlr_buffer_lock(&surface->buffer->base);
+		struct sway_saved_buffer *saved_buffer = calloc(1, sizeof(struct sway_saved_buffer));
+		saved_buffer->buffer = surface->buffer;
+		saved_buffer->width = surface->current.width;
+		saved_buffer->height = surface->current.height;
+		saved_buffer->x = sx;
+		saved_buffer->y = sy;
+		wl_list_insert(&view->saved_buffers, &saved_buffer->link);
+	}
 }
 
 void view_save_buffer(struct sway_view *view) {
-	if (!sway_assert(!view->saved_buffer, "Didn't expect saved buffer")) {
+	if (!sway_assert(wl_list_empty(&view->saved_buffers), "Didn't expect saved buffer")) {
 		view_remove_saved_buffer(view);
 	}
-	if (view->surface && wlr_surface_has_buffer(view->surface)) {
-		wlr_buffer_lock(&view->surface->buffer->base);
-		view->saved_buffer = view->surface->buffer;
-		view->saved_buffer_width = view->surface->current.width;
-		view->saved_buffer_height = view->surface->current.height;
-	}
+	view_for_each_surface(view, view_save_buffer_iterator, view);
 }
 
 bool view_is_transient_for(struct sway_view *child,