xwayland: support multiple wayland → xwayland selection transfers

This fixes drag'n'drop support for Chromium.

3 files changed, 237 insertions, 204 deletions

diff --git a/include/xwayland/xwm.h b/include/xwayland/xwm.h
index 63ee5894..c83dd7c6 100644
--- a/include/xwayland/xwm.h
+++ b/include/xwayland/xwm.h
@@ -47,6 +47,7 @@ enum atom_name {
 	INCR,
 	TEXT,
 	TIMESTAMP,
+	DELETE,
 	NET_WM_WINDOW_TYPE_UTILITY,
 	NET_WM_WINDOW_TYPE_TOOLTIP,
 	NET_WM_WINDOW_TYPE_DND,
@@ -80,22 +81,33 @@ enum net_wm_state_action {
 
 #define XDND_VERSION 5
 
+struct wlr_xwm_selection;
+
+struct wlr_xwm_selection_transfer {
+	struct wlr_xwm_selection *selection;
+	bool incr;
+	bool flush_property_on_delete;
+	bool property_set;
+	struct wl_array source_data;
+	int source_fd;
+	struct wl_event_source *source;
+
+	// when sending to x11
+	xcb_selection_request_event_t request;
+
+	// when receiving from x11
+	int property_start;
+	xcb_get_property_reply_t *property_reply;
+};
+
 struct wlr_xwm_selection {
 	struct wlr_xwm *xwm;
 	xcb_atom_t atom;
 	xcb_window_t window;
-	xcb_selection_request_event_t request;
 	xcb_window_t owner;
 	xcb_timestamp_t timestamp;
-	int incr;
-	int source_fd;
-	int property_start;
-	xcb_get_property_reply_t *property_reply;
-	struct wl_event_source *property_source;
-	int flush_property_on_delete;
-	struct wl_array source_data;
-	xcb_atom_t target;
-	bool property_set;
+
+	struct wlr_xwm_selection_transfer incoming;
 };
 
 struct wlr_xwm {
diff --git a/xwayland/selection.c b/xwayland/selection.c
index 272c10cd..0905870b 100644
--- a/xwayland/selection.c
+++ b/xwayland/selection.c
@@ -38,144 +38,143 @@ static enum wl_data_device_manager_dnd_action
 	return WL_DATA_DEVICE_MANAGER_DND_ACTION_NONE;
 }
 
-static void xwm_selection_send_notify(struct wlr_xwm_selection *selection,
-		xcb_atom_t property) {
+static void xwm_selection_send_notify(struct wlr_xwm *xwm,
+		xcb_selection_request_event_t *req, xcb_atom_t property) {
 	xcb_selection_notify_event_t selection_notify = {
 		.response_type = XCB_SELECTION_NOTIFY,
 		.sequence = 0,
-		.time = selection->request.time,
-		.requestor = selection->request.requestor,
-		.selection = selection->request.selection,
-		.target = selection->request.target,
+		.time = req->time,
+		.requestor = req->requestor,
+		.selection = req->selection,
+		.target = req->target,
 		.property = property,
 	};
 
 	wlr_log(L_DEBUG, "SendEvent destination=%d SelectionNotify(31) time=%d "
-		"requestor=%d selection=%d target=%d property=%d",
-		selection->request.requestor,
-		selection->request.time,
-		selection->request.requestor,
-		selection->request.selection,
-		selection->request.target,
-		property);
-	xcb_send_event(selection->xwm->xcb_conn,
+		"requestor=%d selection=%d target=%d property=%d", req->requestor,
+		req->time, req->requestor, req->selection, req->target, property);
+	xcb_send_event(xwm->xcb_conn,
 		0, // propagate
-		selection->request.requestor,
+		req->requestor,
 		XCB_EVENT_MASK_NO_EVENT,
 		(const char *)&selection_notify);
-	xcb_flush(selection->xwm->xcb_conn);
+	xcb_flush(xwm->xcb_conn);
 }
 
-static int xwm_selection_flush_source_data(struct wlr_xwm_selection *selection) {
-	xcb_change_property(selection->xwm->xcb_conn,
+static int xwm_selection_flush_source_data(
+		struct wlr_xwm_selection_transfer *transfer) {
+	xcb_change_property(transfer->selection->xwm->xcb_conn,
 		XCB_PROP_MODE_REPLACE,
-		selection->request.requestor,
-		selection->request.property,
-		selection->target,
+		transfer->request.requestor,
+		transfer->request.property,
+		transfer->request.target,
 		8, // format
-		selection->source_data.size,
-		selection->source_data.data);
-	selection->property_set = true;
-	int length = selection->source_data.size;
-	selection->source_data.size = 0;
-
+		transfer->source_data.size,
+		transfer->source_data.data);
+	transfer->property_set = true;
+	size_t length = transfer->source_data.size;
+	transfer->source_data.size = 0;
 	return length;
 }
 
-static void xwm_data_source_remove_property_source(
-		struct wlr_xwm_selection *selection) {
-	if (selection->property_source) {
-		wl_event_source_remove(selection->property_source);
+static void xwm_data_source_remove_source(
+		struct wlr_xwm_selection_transfer *transfer) {
+	if (transfer->source != NULL) {
+		wl_event_source_remove(transfer->source);
+		transfer->source = NULL;
 	}
-	selection->property_source = NULL;
 }
 
 static void xwm_data_source_close_source_fd(
-		struct wlr_xwm_selection *selection) {
-	close(selection->source_fd);
-	selection->source_fd = -1;
+		struct wlr_xwm_selection_transfer *transfer) {
+	if (transfer->source_fd >= 0) {
+		close(transfer->source_fd);
+		transfer->source_fd = -1;
+	}
 }
 
 static int xwm_data_source_read(int fd, uint32_t mask, void *data) {
-	struct wlr_xwm_selection *selection = data;
-	struct wlr_xwm *xwm = selection->xwm;
+	struct wlr_xwm_selection_transfer *transfer = data;
+	struct wlr_xwm *xwm = transfer->selection->xwm;
 
 	void *p;
-	int current = selection->source_data.size;
-	if (selection->source_data.size < incr_chunk_size) {
-		p = wl_array_add(&selection->source_data, incr_chunk_size);
-		if (!p){
+	size_t current = transfer->source_data.size;
+	if (transfer->source_data.size < incr_chunk_size) {
+		p = wl_array_add(&transfer->source_data, incr_chunk_size);
+		if (p == NULL) {
 			wlr_log(L_ERROR, "Could not allocate selection source_data");
 			goto error_out;
 		}
 	} else {
-		p = (char *) selection->source_data.data + selection->source_data.size;
+		p = (char *)transfer->source_data.data + transfer->source_data.size;
 	}
 
-	int available = selection->source_data.alloc - current;
-
-	int len = read(fd, p, available);
+	size_t available = transfer->source_data.alloc - current;
+	ssize_t len = read(fd, p, available);
 	if (len == -1) {
 		wlr_log(L_ERROR, "read error from data source: %m");
 		goto error_out;
 	}
 
-	wlr_log(L_DEBUG, "read %d (available %d, mask 0x%x) bytes: \"%.*s\"",
-		len, available, mask, len, (char *) p);
+	wlr_log(L_DEBUG, "read %ld (available %zu, mask 0x%x) bytes: \"%.*s\"",
+		len, available, mask, (int)len, (char *)p);
 
-	selection->source_data.size = current + len;
-	if (selection->source_data.size >= incr_chunk_size) {
-		if (!selection->incr) {
+	transfer->source_data.size = current + len;
+	if (transfer->source_data.size >= incr_chunk_size) {
+		if (!transfer->incr) {
 			wlr_log(L_DEBUG, "got %zu bytes, starting incr",
-				selection->source_data.size);
-			selection->incr = 1;
+				transfer->source_data.size);
+
 			xcb_change_property(xwm->xcb_conn,
-					XCB_PROP_MODE_REPLACE,
-					selection->request.requestor,
-					selection->request.property,
-					xwm->atoms[INCR],
-					32, /* format */
-					1, &incr_chunk_size);
-			selection->property_set = true;
-			selection->flush_property_on_delete = 1;
-			xwm_data_source_remove_property_source(selection);
-			xwm_selection_send_notify(selection, selection->request.property);
-		} else if (selection->property_set) {
+				XCB_PROP_MODE_REPLACE,
+				transfer->request.requestor,
+				transfer->request.property,
+				xwm->atoms[INCR],
+				32, /* format */
+				1, &incr_chunk_size);
+			transfer->incr = true;
+			transfer->property_set = true;
+			transfer->flush_property_on_delete = true;
+			xwm_data_source_remove_source(transfer);
+			xwm_selection_send_notify(xwm, &transfer->request,
+				transfer->request.property);
+		} else if (transfer->property_set) {
 			wlr_log(L_DEBUG, "got %zu bytes, waiting for property delete",
-				selection->source_data.size);
+				transfer->source_data.size);
 
-			selection->flush_property_on_delete = 1;
-			xwm_data_source_remove_property_source(selection);
+			transfer->flush_property_on_delete = true;
+			xwm_data_source_remove_source(transfer);
 		} else {
 			wlr_log(L_DEBUG, "got %zu bytes, property deleted, setting new "
-				"property", selection->source_data.size);
-			xwm_selection_flush_source_data(selection);
+				"property", transfer->source_data.size);
+			xwm_selection_flush_source_data(transfer);
 		}
-	} else if (len == 0 && !selection->incr) {
+	} else if (len == 0 && !transfer->incr) {
 		wlr_log(L_DEBUG, "non-incr transfer complete");
 		/* Non-incr transfer all done. */
-		xwm_selection_flush_source_data(selection);
-		xwm_selection_send_notify(selection, selection->request.property);
+		xwm_selection_flush_source_data(transfer);
+		xwm_selection_send_notify(xwm, &transfer->request,
+			transfer->request.property);
 		xcb_flush(xwm->xcb_conn);
-		xwm_data_source_remove_property_source(selection);
-		xwm_data_source_close_source_fd(selection);
-		wl_array_release(&selection->source_data);
-		selection->request.requestor = XCB_NONE;
-	} else if (len == 0 && selection->incr) {
+		xwm_data_source_remove_source(transfer);
+		xwm_data_source_close_source_fd(transfer);
+		wl_array_release(&transfer->source_data);
+		transfer->request.requestor = XCB_NONE;
+	} else if (len == 0 && transfer->incr) {
 		wlr_log(L_DEBUG, "incr transfer complete");
 
-		selection->flush_property_on_delete = 1;
-		if (selection->property_set) {
+		transfer->flush_property_on_delete = true;
+		if (transfer->property_set) {
 			wlr_log(L_DEBUG, "got %zu bytes, waiting for property delete",
-				selection->source_data.size);
+				transfer->source_data.size);
 		} else {
 			wlr_log(L_DEBUG, "got %zu bytes, property deleted, setting new "
-				"property", selection->source_data.size);
-			xwm_selection_flush_source_data(selection);
+				"property", transfer->source_data.size);
+			xwm_selection_flush_source_data(transfer);
 		}
 		xcb_flush(xwm->xcb_conn);
-		xwm_data_source_remove_property_source(selection);
-		xwm_data_source_close_source_fd(selection);
+		xwm_data_source_remove_source(transfer);
+		xwm_data_source_close_source_fd(transfer);
 	} else {
 		wlr_log(L_DEBUG, "nothing happened, buffered the bytes");
 	}
@@ -183,10 +182,10 @@ static int xwm_data_source_read(int fd, uint32_t mask, void *data) {
 	return 1;
 
 error_out:
-	xwm_selection_send_notify(selection, XCB_ATOM_NONE);
-	xwm_data_source_remove_property_source(selection);
-	xwm_data_source_close_source_fd(selection);
-	wl_array_release(&selection->source_data);
+	xwm_selection_send_notify(xwm, &transfer->request, XCB_ATOM_NONE);
+	xwm_data_source_remove_source(transfer);
+	xwm_data_source_close_source_fd(transfer);
+	wl_array_release(&transfer->source_data);
 	return 0;
 }
 
@@ -242,14 +241,17 @@ static struct wl_array *xwm_selection_source_get_mime_types(
 	return NULL;
 }
 
+/**
+ * Read the Wayland selection and send it to an Xwayland client.
+ */
 static void xwm_selection_send_data(struct wlr_xwm_selection *selection,
-		xcb_atom_t target, const char *mime_type) {
+		xcb_selection_request_event_t *req, const char *mime_type) {
 	// Check MIME type
 	struct wl_array *mime_types =
 		xwm_selection_source_get_mime_types(selection);
 	if (mime_types == NULL) {
 		wlr_log(L_ERROR, "not sending selection: no MIME type list available");
-		xwm_selection_send_notify(selection, XCB_ATOM_NONE);
+		xwm_selection_send_notify(selection->xwm, req, XCB_ATOM_NONE);
 		return;
 	}
 
@@ -265,50 +267,45 @@ static void xwm_selection_send_data(struct wlr_xwm_selection *selection,
 	if (!found) {
 		wlr_log(L_ERROR, "not sending selection: "
 			"requested an unsupported MIME type %s", mime_type);
-		xwm_selection_send_notify(selection, XCB_ATOM_NONE);
+		xwm_selection_send_notify(selection->xwm, req, XCB_ATOM_NONE);
+		return;
+	}
+
+	struct wlr_xwm_selection_transfer *transfer =
+		calloc(1, sizeof(struct wlr_xwm_selection_transfer));
+	if (transfer == NULL) {
+		wlr_log(L_ERROR, "Allocation failed");
 		return;
 	}
+	transfer->selection = selection;
+	transfer->request = *req;
+	wl_array_init(&transfer->source_data);
 
 	int p[2];
 	if (pipe(p) == -1) {
-		wlr_log(L_ERROR, "pipe failed: %m");
-		xwm_selection_send_notify(selection, XCB_ATOM_NONE);
+		wlr_log(L_ERROR, "pipe() failed: %m");
+		xwm_selection_send_notify(selection->xwm, req, XCB_ATOM_NONE);
 		return;
 	}
-
 	fcntl(p[0], F_SETFD, FD_CLOEXEC);
 	fcntl(p[0], F_SETFL, O_NONBLOCK);
 	fcntl(p[1], F_SETFD, FD_CLOEXEC);
 	fcntl(p[1], F_SETFL, O_NONBLOCK);
 
-	wl_array_init(&selection->source_data);
-	selection->target = target;
-	selection->source_fd = p[0];
+	transfer->source_fd = p[0];
+
 	struct wl_event_loop *loop =
 		wl_display_get_event_loop(selection->xwm->xwayland->wl_display);
-	selection->property_source = wl_event_loop_add_fd(loop,
-		selection->source_fd, WL_EVENT_READABLE, xwm_data_source_read,
-		selection);
+	transfer->source = wl_event_loop_add_fd(loop, transfer->source_fd,
+		WL_EVENT_READABLE, xwm_data_source_read, transfer);
 
-	wlr_log(L_DEBUG, "Sending Wayland selection to Xwayland window with "
-		"MIME type %s", mime_type);
+	wlr_log(L_DEBUG, "Sending Wayland selection %u to Xwayland window with "
+		"MIME type %s", req->target, mime_type);
 	xwm_selection_source_send(selection, mime_type, p[1]);
-	close(p[1]);
+	// TODO close(p[1]);
 }
 
-static void xwm_selection_send_timestamp(struct wlr_xwm_selection *selection) {
-	xcb_change_property(selection->xwm->xcb_conn,
-		XCB_PROP_MODE_REPLACE,
-		selection->request.requestor,
-		selection->request.property,
-		XCB_ATOM_INTEGER,
-		32, // format
-		1, &selection->timestamp);
-
-	xwm_selection_send_notify(selection, selection->request.property);
-}
-
-static xcb_atom_t xwm_get_mime_type_atom(struct wlr_xwm *xwm, char *mime_type) {
+static xcb_atom_t xwm_mime_type_to_atom(struct wlr_xwm *xwm, char *mime_type) {
 	if (strcmp(mime_type, "text/plain;charset=utf-8") == 0) {
 		return xwm->atoms[UTF8_STRING];
 	} else if (strcmp(mime_type, "text/plain") == 0) {
@@ -366,7 +363,7 @@ static void xwm_dnd_send_enter(struct wlr_xwm *xwm) {
 		char **mime_type_ptr;
 		wl_array_for_each(mime_type_ptr, mime_types) {
 			char *mime_type = *mime_type_ptr;
-			data.data32[2+i] = xwm_get_mime_type_atom(xwm, mime_type);
+			data.data32[2+i] = xwm_mime_type_to_atom(xwm, mime_type);
 			++i;
 		}
 	} else {
@@ -379,7 +376,7 @@ static void xwm_dnd_send_enter(struct wlr_xwm *xwm) {
 		char **mime_type_ptr;
 		wl_array_for_each(mime_type_ptr, mime_types) {
 			char *mime_type = *mime_type_ptr;
-			targets[i] = xwm_get_mime_type_atom(xwm, mime_type);
+			targets[i] = xwm_mime_type_to_atom(xwm, mime_type);
 			++i;
 		}
 
@@ -453,14 +450,16 @@ static void xwm_dnd_send_leave(struct wlr_xwm *xwm) {
 	xwm_dnd_send_event(xwm, xwm->atoms[DND_FINISHED], &data);
 }*/
 
-static void xwm_selection_send_targets(struct wlr_xwm_selection *selection) {
+static void xwm_selection_send_targets(struct wlr_xwm_selection *selection,
+		xcb_selection_request_event_t *req) {
 	struct wlr_xwm *xwm = selection->xwm;
 
-	struct wl_array *mime_types = xwm_selection_source_get_mime_types(selection);
+	struct wl_array *mime_types =
+		xwm_selection_source_get_mime_types(selection);
 	if (mime_types == NULL) {
 		wlr_log(L_ERROR, "not sending selection targets: "
 			"no selection source available");
-		xwm_selection_send_notify(selection, XCB_ATOM_NONE);
+		xwm_selection_send_notify(selection->xwm, req, XCB_ATOM_NONE);
 		return;
 	}
 
@@ -473,19 +472,32 @@ static void xwm_selection_send_targets(struct wlr_xwm_selection *selection) {
 	char **mime_type_ptr;
 	wl_array_for_each(mime_type_ptr, mime_types) {
 		char *mime_type = *mime_type_ptr;
-		targets[2+i] = xwm_get_mime_type_atom(xwm, mime_type);
+		targets[2+i] = xwm_mime_type_to_atom(xwm, mime_type);
 		++i;
 	}
 
 	xcb_change_property(xwm->xcb_conn,
 		XCB_PROP_MODE_REPLACE,
-		selection->request.requestor,
-		selection->request.property,
+		req->requestor,
+		req->property,
 		XCB_ATOM_ATOM,
 		32, // format
 		n, targets);
 
-	xwm_selection_send_notify(selection, selection->request.property);
+	xwm_selection_send_notify(selection->xwm, req, req->property);
+}
+
+static void xwm_selection_send_timestamp(struct wlr_xwm_selection *selection,
+		xcb_selection_request_event_t *req) {
+	xcb_change_property(selection->xwm->xcb_conn,
+		XCB_PROP_MODE_REPLACE,
+		req->requestor,
+		req->property,
+		XCB_ATOM_INTEGER,
+		32, // format
+		1, &selection->timestamp);
+
+	xwm_selection_send_notify(selection->xwm, req, req->property);
 }
 
 static struct wlr_xwm_selection *xwm_get_selection(struct wlr_xwm *xwm,
@@ -501,134 +513,138 @@ static struct wlr_xwm_selection *xwm_get_selection(struct wlr_xwm *xwm,
 	}
 }
 
+static char *xwm_mime_type_from_atom(struct wlr_xwm *xwm, xcb_atom_t atom) {
+	if (atom == xwm->atoms[UTF8_STRING]) {
+		return strdup("text/plain;charset=utf-8");
+	} else if (atom == xwm->atoms[TEXT]) {
+		return strdup("text/plain");
+	} else {
+		return xwm_get_atom_name(xwm, atom);
+	}
+}
+
 static void xwm_handle_selection_request(struct wlr_xwm *xwm,
 		xcb_generic_event_t *event) {
-	xcb_selection_request_event_t *selection_request =
+	xcb_selection_request_event_t *req =
 		(xcb_selection_request_event_t *) event;
 
 	wlr_log(L_DEBUG, "XCB_SELECTION_REQUEST (time=%u owner=%u, requestor=%u "
 		"selection=%u, target=%u, property=%u)",
-		selection_request->time, selection_request->owner,
-		selection_request->requestor, selection_request->selection,
-		selection_request->target, selection_request->property);
+		req->time, req->owner, req->requestor, req->selection, req->target,
+		req->property);
 
-	if (selection_request->selection == xwm->atoms[CLIPBOARD_MANAGER]) {
+	if (req->selection == xwm->atoms[CLIPBOARD_MANAGER]) {
 		// The wlroots clipboard should already have grabbed the first target,
 		// so just send selection notify now. This isn't synchronized with the
 		// clipboard finishing getting the data, so there's a race here.
-		struct wlr_xwm_selection *selection = &xwm->clipboard_selection;
-		selection->request = *selection_request;
-		selection->incr = 0;
-		selection->flush_property_on_delete = 0;
-		xwm_selection_send_notify(selection, selection->request.property);
+		xwm_selection_send_notify(xwm, req, req->property);
 		return;
 	}
 
 	struct wlr_xwm_selection *selection =
-		xwm_get_selection(xwm, selection_request->selection);
+		xwm_get_selection(xwm, req->selection);
 	if (selection == NULL) {
 		wlr_log(L_DEBUG, "received selection request for unknown selection");
 		return;
 	}
 
-	if (selection->window != selection_request->owner) {
+	if (selection->window != req->owner) {
 		wlr_log(L_DEBUG, "received selection request with invalid owner");
 		return;
 	}
 
-	selection->request = *selection_request;
-	selection->incr = 0;
-	selection->flush_property_on_delete = 0;
-
 	// No xwayland surface focused, deny access to clipboard
 	if (xwm->focus_surface == NULL && xwm->drag_focus == NULL) {
 		char *selection_name = xwm_get_atom_name(xwm, selection->atom);
 		wlr_log(L_DEBUG, "denying read access to selection %u (%s): "
 			"no xwayland surface focused", selection->atom, selection_name);
 		free(selection_name);
-		xwm_selection_send_notify(selection, XCB_ATOM_NONE);
+		xwm_selection_send_notify(xwm, req, XCB_ATOM_NONE);
 		return;
 	}
 
-	if (selection_request->target == xwm->atoms[TARGETS]) {
-		xwm_selection_send_targets(selection);
-	} else if (selection_request->target == xwm->atoms[TIMESTAMP]) {
-		xwm_selection_send_timestamp(selection);
-	} else if (selection_request->target == xwm->atoms[UTF8_STRING]) {
-		xwm_selection_send_data(selection, selection_request->target,
-			"text/plain;charset=utf-8");
-	} else if (selection_request->target == xwm->atoms[TEXT]) {
-		xwm_selection_send_data(selection, selection_request->target,
-			"text/plain");
+	if (req->target == xwm->atoms[TARGETS]) {
+		xwm_selection_send_targets(selection, req);
+	} else if (req->target == xwm->atoms[TIMESTAMP]) {
+		xwm_selection_send_timestamp(selection, req);
+	} else if (req->target == xwm->atoms[DELETE]) {
+		xwm_selection_send_notify(selection->xwm, req, req->property);
 	} else {
-		char *mime_type = xwm_get_atom_name(xwm, selection_request->target);
+		// Send data
+		char *mime_type = xwm_mime_type_from_atom(xwm, req->target);
 		if (mime_type == NULL) {
-			wlr_log(L_ERROR, "ignoring selection request: unknown atom");
-			xwm_selection_send_notify(selection, XCB_ATOM_NONE);
+			wlr_log(L_ERROR, "ignoring selection request: unknown atom %u",
+				req->target);
+			xwm_selection_send_notify(xwm, req, XCB_ATOM_NONE);
 			return;
 		}
-		xwm_selection_send_data(selection, selection_request->target,
-			mime_type);
+		xwm_selection_send_data(selection, req, mime_type);
 		free(mime_type);
 	}
 }
 
 static void xwm_data_source_destroy_property_reply(
-		struct wlr_xwm_selection *selection) {
-	free(selection->property_reply);
-	selection->property_reply = NULL;
+		struct wlr_xwm_selection_transfer *transfer) {
+	free(transfer->property_reply);
+	transfer->property_reply = NULL;
 }
 
+/**
+ * Write the X11 selection to a Wayland client.
+ */
 static int xwm_data_source_write(int fd, uint32_t mask, void *data) {
-	struct wlr_xwm_selection *selection = data;
-	struct wlr_xwm *xwm = selection->xwm;
+	struct wlr_xwm_selection_transfer *transfer = data;
+	struct wlr_xwm *xwm = transfer->selection->xwm;
 
-	unsigned char *property = xcb_get_property_value(selection->property_reply);
-	int remainder = xcb_get_property_value_length(selection->property_reply) -
-		selection->property_start;
+	char *property = xcb_get_property_value(transfer->property_reply);
+	int remainder = xcb_get_property_value_length(transfer->property_reply) -
+		transfer->property_start;
 
-	int len = write(fd, property + selection->property_start, remainder);
+	ssize_t len = write(fd, property + transfer->property_start, remainder);
 	if (len == -1) {
-		xwm_data_source_destroy_property_reply(selection);
-		xwm_data_source_remove_property_source(selection);
-		xwm_data_source_close_source_fd(selection);
+		xwm_data_source_destroy_property_reply(transfer);
+		xwm_data_source_remove_source(transfer);
+		xwm_data_source_close_source_fd(transfer);
 		wlr_log(L_ERROR, "write error to target fd: %m");
 		return 1;
 	}
 
-	wlr_log(L_DEBUG, "wrote %d (chunk size %d) of %d bytes",
-		selection->property_start + len,
-		len, xcb_get_property_value_length(selection->property_reply));
+	wlr_log(L_DEBUG, "wrote %ld (chunk size %ld) of %d bytes",
+		transfer->property_start + len,
+		len, xcb_get_property_value_length(transfer->property_reply));
 
-	selection->property_start += len;
+	transfer->property_start += len;
 	if (len == remainder) {
-		xwm_data_source_destroy_property_reply(selection);
-		xwm_data_source_remove_property_source(selection);
+		xwm_data_source_destroy_property_reply(transfer);
+		xwm_data_source_remove_source(transfer);
 
-		if (selection->incr) {
-			xcb_delete_property(xwm->xcb_conn, selection->window,
+		if (transfer->incr) {
+			xcb_delete_property(xwm->xcb_conn, transfer->selection->window,
 				xwm->atoms[WL_SELECTION]);
 		} else {
 			wlr_log(L_DEBUG, "transfer complete");
-			xwm_data_source_close_source_fd(selection);
+			xwm_data_source_close_source_fd(transfer);
 		}
 	}
 
 	return 1;
 }
 
-static void xwm_write_property(struct wlr_xwm_selection *selection,
+static void xwm_write_property(struct wlr_xwm_selection_transfer *transfer,
 		xcb_get_property_reply_t *reply) {
-	selection->property_start = 0;
-	selection->property_reply = reply;
-	xwm_data_source_write(selection->source_fd, WL_EVENT_WRITABLE, selection);
+	struct wlr_xwm *xwm = transfer->selection->xwm;
+
+	transfer->property_start = 0;
+	transfer->property_reply = reply;
 
-	if (selection->property_reply) {
+	xwm_data_source_write(transfer->source_fd, WL_EVENT_WRITABLE, transfer);
+
+	if (transfer->property_reply != NULL) {
 		struct wl_event_loop *loop =
-			wl_display_get_event_loop(selection->xwm->xwayland->wl_display);
-		selection->property_source = wl_event_loop_add_fd(loop,
-			selection->source_fd, WL_EVENT_WRITABLE, xwm_data_source_write,
-			selection);
+			wl_display_get_event_loop(xwm->xwayland->wl_display);
+		transfer->source = wl_event_loop_add_fd(loop,
+			transfer->source_fd, WL_EVENT_WRITABLE, xwm_data_source_write,
+			transfer);
 	}
 }
 
@@ -647,17 +663,19 @@ static void xwm_selection_get_data(struct wlr_xwm_selection *selection) {
 	xcb_get_property_reply_t *reply =
 		xcb_get_property_reply(xwm->xcb_conn, cookie, NULL);
 	if (reply == NULL) {
+		wlr_log(L_ERROR, "Cannot get selection property");
 		return;
 	}
 
+	struct wlr_xwm_selection_transfer *transfer = &selection->incoming;
 	if (reply->type == xwm->atoms[INCR]) {
-		selection->incr = 1;
+		transfer->incr = true;
 		free(reply);
 	} else {
-		selection->incr = 0;
+		transfer->incr = false;
 		// reply's ownership is transferred to wm, which is responsible
 		// for freeing it
-		xwm_write_property(selection, reply);
+		xwm_write_property(transfer, reply);
 	}
 }
 
@@ -665,6 +683,7 @@ static void source_send(struct wlr_xwm_selection *selection,
 		struct wl_array *mime_types, struct wl_array *mime_types_atoms,
 		const char *requested_mime_type, int32_t fd) {
 	struct wlr_xwm *xwm = selection->xwm;
+	struct wlr_xwm_selection_transfer *transfer = &selection->incoming;
 
 	xcb_atom_t *atoms = mime_types_atoms->data;
 	bool found = false;
@@ -681,7 +700,8 @@ static void source_send(struct wlr_xwm_selection *selection,
 		++i;
 	}
 	if (!found) {
-		wlr_log(L_DEBUG, "cannot send X11 selection: unsupported MIME type");
+		wlr_log(L_DEBUG, "Cannot send X11 selection to Wayland: "
+			"unsupported MIME type");
 		return;
 	}
 
@@ -695,7 +715,7 @@ static void source_send(struct wlr_xwm_selection *selection,
 	xcb_flush(xwm->xcb_conn);
 
 	fcntl(fd, F_SETFL, O_WRONLY | O_NONBLOCK);
-	selection->source_fd = fd;
+	transfer->source_fd = fd;
 }
 
 struct x11_data_source {
@@ -964,14 +984,14 @@ static int xwm_handle_xfixes_selection_notify(struct wlr_xwm *xwm,
 		return 1;
 	}
 
-	selection->incr = 0;
+	struct wlr_xwm_selection_transfer *transfer = &selection->incoming;
+	transfer->incr = false;
 	// doing this will give a selection notify where we actually handle the sync
 	xcb_convert_selection(xwm->xcb_conn, selection->window,
 		selection->atom,
 		xwm->atoms[TARGETS],
 		xwm->atoms[WL_SELECTION],
 		xfixes_selection_notify->timestamp);
-
 	xcb_flush(xwm->xcb_conn);
 
 	return 1;
@@ -1080,7 +1100,7 @@ static void selection_init(struct wlr_xwm *xwm,
 	selection->xwm = xwm;
 	selection->atom = atom;
 	selection->window = xwm->selection_window;
-	selection->request.requestor = XCB_NONE;
+	selection->incoming.selection = selection;
 
 	uint32_t mask =
 		XCB_XFIXES_SELECTION_EVENT_MASK_SET_SELECTION_OWNER |
diff --git a/xwayland/xwm.c b/xwayland/xwm.c
index d5501a0a..0b7c62b4 100644
--- a/xwayland/xwm.c
+++ b/xwayland/xwm.c
@@ -50,6 +50,7 @@ const char *atom_map[ATOM_LAST] = {
 	"INCR",
 	"TEXT",
 	"TIMESTAMP",
+	"DELETE",
 	"_NET_WM_WINDOW_TYPE_UTILITY",
 	"_NET_WM_WINDOW_TYPE_TOOLTIP",
 	"_NET_WM_WINDOW_TYPE_DND",