Add support for manually setting subpixel hinting on outputs.

Many laptop screens report unknown subpixel order. Allow users to manually set subpixel hinting to work around this.

Addresses https://github.com/swaywm/sway/issues/3163

include/sway/commands.h

@@ -261,6 +261,7 @@ sway_cmd output_cmd_enable;
 sway_cmd output_cmd_mode;
 sway_cmd output_cmd_position;
 sway_cmd output_cmd_scale;
+sway_cmd output_cmd_subpixel;
 sway_cmd output_cmd_transform;
 
 sway_cmd seat_cmd_attach;

include/sway/config.h

@@ -184,6 +184,7 @@ struct output_config {
 	int x, y;
 	float scale;
 	int32_t transform;
+	enum wl_output_subpixel subpixel;
 
 	char *background;
 	char *background_option;

include/sway/output.h

@@ -31,6 +31,7 @@ struct sway_output {
 
 	int lx, ly; // layout coords
 	int width, height; // transformed buffer size
+	enum wl_output_subpixel detected_subpixel;
 
 	bool enabled, configured;
 	list_t *workspaces;

include/util.h

@@ -3,6 +3,7 @@
 
 #include <stdint.h>
 #include <stdbool.h>
+#include <wayland-server-protocol.h>
 
 /**
  * Wrap i into the range [0, max[
@@ -29,4 +30,6 @@ bool parse_boolean(const char *boolean, bool current);
  */
 float parse_float(const char *value);
 
+const char *sway_wl_output_subpixel_to_string(enum wl_output_subpixel subpixel);
+
 #endif