view: send scale notification when the output is known

sway/tree/view.c

@@ -6,6 +6,7 @@
 #include <wlr/types/wlr_buffer.h>
 #include <wlr/types/wlr_ext_foreign_toplevel_list_v1.h>
 #include <wlr/types/wlr_foreign_toplevel_management_v1.h>
+#include <wlr/types/wlr_fractional_scale_v1.h>
 #include <wlr/types/wlr_output_layout.h>
 #include <wlr/types/wlr_server_decoration.h>
 #include <wlr/types/wlr_subcompositor.h>
@@ -741,6 +742,14 @@ void view_map(struct sway_view *view, struct wlr_surface *wlr_surface,
 		ws = select_workspace(view);
 	}
 
+	if (ws && ws->output) {
+		// Once the output is determined, we can notify the client early about
+		// scale to reduce startup jitter.
+		float scale = ws->output->wlr_output->scale;
+		wlr_fractional_scale_v1_notify_scale(wlr_surface, scale);
+		wlr_surface_set_preferred_buffer_scale(wlr_surface, ceil(scale));
+	}
+
 	struct sway_seat *seat = input_manager_current_seat();
 	struct sway_node *node =
 		seat_get_focus_inactive(seat, ws ? &ws->node : &root->node);