screencast: implement format negotation

wire/jay_render_ctx.txt

@@ -13,3 +13,17 @@ event no_device {
 event device {
     fd: fd,
 }
+
+event read_modifier (since = 7) {
+    format: u32,
+    modifier: pod(u64),
+}
+
+event write_modifier (since = 7) {
+    format: u32,
+    modifier: pod(u64),
+}
+
+event format (since = 7) {
+    format: u32,
+}

wire/jay_screencast.txt

@@ -47,6 +47,13 @@ request set_toplevel {
     id: id(jay_toplevel),
 }
 
+request clear_buffers (since = 7) {
+}
+
+request add_buffer (since = 7) {
+    buffer: id(wl_buffer),
+}
+
 # events
 
 event plane {
@@ -101,3 +108,8 @@ event config_running {
 event config_done {
     serial: u32,
 }
+
+event config_size (since = 7) {
+    width: i32,
+    height: i32,
+}