output: document gamma functions

include/wlr/types/wlr_output.h

@@ -174,9 +174,17 @@ bool wlr_output_swap_buffers(struct wlr_output *output, struct timespec *when,
  * it is a no-op.
  */
 void wlr_output_schedule_frame(struct wlr_output *output);
+/**
+ * Returns the maximum length of each gamma ramp, or 0 if unsupported.
+ */
+uint32_t wlr_output_get_gamma_size(struct wlr_output *output);
+/**
+ * Sets the gamma table for this output. `r`, `g` and `b` are gamma ramps for
+ * red, green and blue. `size` is the length of the ramps and must not exceed
+ * the value returned by `wlr_output_get_gamma_size`.
+ */
 bool wlr_output_set_gamma(struct wlr_output *output,
 	uint32_t size, uint16_t *r, uint16_t *g, uint16_t *b);
-uint32_t wlr_output_get_gamma_size(struct wlr_output *output);
 bool wlr_output_export_dmabuf(struct wlr_output *output,
 	struct wlr_dmabuf_attributes *attribs);
 void wlr_output_set_fullscreen_surface(struct wlr_output *output,