backend/wayland: add scaling support for output layers

Use the viewporter protocol to scale output layers.

backend/wayland/backend.c

@@ -29,6 +29,7 @@
 #include "xdg-shell-client-protocol.h"
 #include "tablet-unstable-v2-client-protocol.h"
 #include "relative-pointer-unstable-v1-client-protocol.h"
+#include "viewporter-client-protocol.h"
 
 struct wlr_wl_linux_dmabuf_feedback_v1 {
 	struct wlr_wl_backend *backend;
@@ -396,6 +397,9 @@ static void registry_global(void *data, struct wl_registry *registry,
 	} else if (strcmp(iface, wl_subcompositor_interface.name) == 0) {
 		wl->subcompositor = wl_registry_bind(registry, name,
 			&wl_subcompositor_interface, 1);
+	} else if (strcmp(iface, wp_viewporter_interface.name) == 0) {
+		wl->viewporter = wl_registry_bind(registry, name,
+			&wp_viewporter_interface, 1);
 	}
 }
 
@@ -515,6 +519,9 @@ static void backend_destroy(struct wlr_backend *backend) {
 	if (wl->subcompositor) {
 		wl_subcompositor_destroy(wl->subcompositor);
 	}
+	if (wl->viewporter) {
+		wp_viewporter_destroy(wl->viewporter);
+	}
 	free(wl->drm_render_name);
 	free(wl->activation_token);
 	xdg_wm_base_destroy(wl->xdg_wm_base);

backend/wayland/meson.build

@@ -19,6 +19,7 @@ client_protos = [
 	'presentation-time',
 	'relative-pointer-unstable-v1',
 	'tablet-unstable-v2',
+	'viewporter',
 	'xdg-activation-v1',
 	'xdg-decoration-unstable-v1',
 	'xdg-shell',

backend/wayland/output.c

@@ -22,6 +22,7 @@
 
 #include "linux-dmabuf-unstable-v1-client-protocol.h"
 #include "presentation-time-client-protocol.h"
+#include "viewporter-client-protocol.h"
 #include "xdg-activation-v1-client-protocol.h"
 #include "xdg-decoration-unstable-v1-client-protocol.h"
 #include "xdg-shell-client-protocol.h"
@@ -287,11 +288,12 @@ static bool output_test(struct wlr_output *wlr_output,
 				int y = layer_state->dst_box.y;
 				int width = layer_state->dst_box.width;
 				int height = layer_state->dst_box.height;
+				bool needs_viewport = width != layer_state->buffer->width ||
+					height != layer_state->buffer->height;
 				if (x < 0 || y < 0 ||
 						x + width > wlr_output->width ||
 						y + height > wlr_output->height ||
-						width != layer_state->buffer->width ||
-						height != layer_state->dst_box.height) {
+						(output->backend->viewporter == NULL && needs_viewport)) {
 					supported = false;
 				}
 				if (!wlr_fbox_empty(&layer_state->src_box)) {
@@ -315,6 +317,9 @@ static void output_layer_handle_addon_destroy(struct wlr_addon *addon) {
 	struct wlr_wl_output_layer *layer = wl_container_of(addon, layer, addon);
 
 	wlr_addon_finish(&layer->addon);
+	if (layer->viewport != NULL) {
+		wp_viewport_destroy(layer->viewport);
+	}
 	wl_subsurface_destroy(layer->subsurface);
 	wl_surface_destroy(layer->surface);
 	free(layer);
@@ -355,6 +360,10 @@ static struct wlr_wl_output_layer *get_or_create_output_layer(
 	wl_surface_set_input_region(layer->surface, region);
 	wl_region_destroy(region);
 
+	if (output->backend->viewporter != NULL) {
+		layer->viewport = wp_viewporter_get_viewport(output->backend->viewporter, layer->surface);
+	}
+
 	return layer;
 }
 
@@ -405,6 +414,12 @@ static bool output_layer_commit(struct wlr_wl_output *output,
 		return false;
 	}
 
+	if (layer->viewport != NULL &&
+			(state->layer->dst_box.width != state->dst_box.width ||
+			state->layer->dst_box.height != state->dst_box.height)) {
+		wp_viewport_set_destination(layer->viewport, state->dst_box.width, state->dst_box.height);
+	}
+
 	wl_surface_attach(layer->surface, buffer->wl_buffer, 0, 0);
 	wl_surface_damage_buffer(layer->surface, 0, 0, INT32_MAX, INT32_MAX);
 	wl_surface_commit(layer->surface);

include/backend/wayland.h

@@ -48,6 +48,7 @@ struct wlr_wl_backend {
 	struct wl_drm *legacy_drm;
 	struct xdg_activation_v1 *activation_v1;
 	struct wl_subcompositor *subcompositor;
+	struct wp_viewporter *viewporter;
 	char *drm_render_name;
 };
 
@@ -71,6 +72,7 @@ struct wlr_wl_output_layer {
 
 	struct wl_surface *surface;
 	struct wl_subsurface *subsurface;
+	struct wp_viewport *viewport;
 	bool mapped;
 };