Replace deprecated function wlc_output_get_pixels.

This makes IPC GET_PIXELS use the new `wlc_pixels_read` call instead of
the deprecated `wlc_output_get_pixels`.

The old version worked by passing a callback function to wlc which would
grab the pixels and send them to the IPC client.
The new version works by maintaining a list of clients who have
requested the pixels of some output and then grap and send the pixels in
the output_post_render hook of the `wlc_interface`.

include/ipc-server.h

@@ -1,6 +1,8 @@
 #ifndef _SWAY_IPC_SERVER_H
 #define _SWAY_IPC_SERVER_H
 
+#include <wlc/wlc.h>
+
 #include "container.h"
 #include "config.h"
 #include "ipc.h"
@@ -27,4 +29,9 @@ void ipc_event_modifier(uint32_t modifier, const char *state);
 void ipc_event_binding_keyboard(struct sway_binding *sb);
 const char *swayc_type_string(enum swayc_types type);
 
+/**
+ * Send pixel data to registered clients.
+ */
+void ipc_get_pixels(wlc_handle output);
+
 #endif

sway/handlers.c

@@ -150,6 +150,10 @@ static void handle_output_pre_render(wlc_handle output) {
 	}
 }
 
+static void handle_output_post_render(wlc_handle output) {
+	ipc_get_pixels(output);
+}
+
 static void handle_output_resolution_change(wlc_handle output, const struct wlc_size *from, const struct wlc_size *to) {
 	sway_log(L_DEBUG, "Output %u resolution changed to %d x %d", (unsigned int)output, to->w, to->h);
 	swayc_t *c = swayc_by_handle(output);
@@ -675,7 +679,8 @@ struct wlc_interface interface = {
 		.resolution = handle_output_resolution_change,
 		.focus = handle_output_focused,
 		.render = {
-			.pre = handle_output_pre_render
+			.pre = handle_output_pre_render,
+			.post = handle_output_post_render
 		}
 	},
 	.view = {

sway/ipc-server.c

@@ -5,7 +5,7 @@
 #include <sys/socket.h>
 #include <sys/un.h>
 #include <stdbool.h>
-#include <wlc/wlc.h>
+#include <wlc/wlc-render.h>
 #include <unistd.h>
 #include <stdlib.h>
 #include <sys/ioctl.h>
@@ -38,6 +38,13 @@ struct ipc_client {
 	enum ipc_command_type subscribed_events;
 };
 
+static list_t *ipc_get_pixel_requests = NULL;
+
+struct get_pixels_request {
+	struct ipc_client *client;
+	wlc_handle output;
+};
+
 struct sockaddr_un *ipc_user_sockaddr(void);
 int ipc_handle_connection(int fd, uint32_t mask, void *data);
 int ipc_client_handle_readable(int client_fd, uint32_t mask, void *data);
@@ -75,6 +82,7 @@ void ipc_init(void) {
 	setenv("SWAYSOCK", ipc_sockaddr->sun_path, 1);
 
 	ipc_client_list = create_list();
+	ipc_get_pixel_requests = create_list();
 
 	ipc_event_source = wlc_event_loop_add_fd(ipc_socket, WLC_EVENT_READABLE, ipc_handle_connection, NULL);
 }
@@ -231,21 +239,49 @@ bool output_by_name_test(swayc_t *view, void *data) {
 	return !strcmp(name, view->name);
 }
 
-bool get_pixels_callback(const struct wlc_size *size, uint8_t *rgba, void *arg) {
-	struct ipc_client *client = (struct ipc_client *)arg;
+void ipc_get_pixels(wlc_handle output) {
+	if (ipc_get_pixel_requests->length == 0) {
+		return;
+	}
+
+	list_t *unhandled = create_list();
+
+	struct get_pixels_request *req;
+	int i;
+	for (i = 0; i < ipc_get_pixel_requests->length; ++i) {
+		req = ipc_get_pixel_requests->items[i];
+		if (req->output != output) {
+			list_add(unhandled, req);
+			continue;
+		}
+
+		const struct wlc_size *size = wlc_output_get_resolution(req->output);
+		struct wlc_geometry g = {
+			.size = *size,
+			.origin = { 0, 0 },
+		};
+		struct wlc_geometry g_out;
 		char response_header[9];
 		memset(response_header, 0, sizeof(response_header));
+		char *data = malloc(sizeof(response_header) + size->w * size->h * 4);
+		wlc_pixels_read(WLC_RGBA8888, &g, &g_out, data + sizeof(response_header));
+
 		response_header[0] = 1;
 		uint32_t *_size = (uint32_t *)(response_header + 1);
-	_size[0] = size->w;
-	_size[1] = size->h;
-	size_t len = sizeof(response_header) + (size->w * size->h * 4);
-	char *payload = malloc(len);
-	memcpy(payload, response_header, sizeof(response_header));
-	memcpy(payload + sizeof(response_header), rgba, len - sizeof(response_header));
-	ipc_send_reply(client, payload, len);
-	free(payload);
-	return false;
+		_size[0] = g_out.size.w;
+		_size[1] = g_out.size.h;
+		size_t len = sizeof(response_header) + (g_out.size.w * g_out.size.h * 4);
+		memcpy(data, response_header, sizeof(response_header));
+		ipc_send_reply(req->client, data, len);
+		free(data);
+		// free the request since it has been handled
+		free(req);
+	}
+
+	// free old list of pixel requests and set new list to all unhandled
+	// requests (request for another output).
+	list_free(ipc_get_pixel_requests);
+	ipc_get_pixel_requests = unhandled;
 }
 
 void ipc_client_handle_command(struct ipc_client *client) {
@@ -394,7 +430,11 @@ void ipc_client_handle_command(struct ipc_client *client) {
 			ipc_send_reply(client, response_header, sizeof(response_header));
 			break;
 		}
-		wlc_output_get_pixels(output->handle, get_pixels_callback, client);
+		struct get_pixels_request *req = malloc(sizeof(struct get_pixels_request));
+		req->client = client;
+		req->output = output->handle;
+		list_add(ipc_get_pixel_requests, req);
+		wlc_output_schedule_render(output->handle);
 		break;
 	}
 	case IPC_GET_BAR_CONFIG: