output: Introduce wlr_output_state_copy()

include/wlr/types/wlr_output.h

@@ -690,12 +690,24 @@ void wlr_output_state_set_damage(struct wlr_output_state *state,
  * advantage of backend features that may reduce the amount of things that
  * need to be composited.
  *
- * The array must be kept valid by the caller until wlr_output_state_finish().
+ * The array must be kept valid by the caller until wlr_output_state_finish()
+ * and all copies of the state have been finished as well.
  * This state will be applied once wlr_output_commit_state() is called.
  */
 void wlr_output_state_set_layers(struct wlr_output_state *state,
 	struct wlr_output_layer_state *layers, size_t layers_len);
 
+/**
+ * Copies the output state from src to dst. It is safe to then
+ * wlr_output_state_finish() src and have dst still be valid.
+ *
+ * Note: The lifetime of the output layers inside the state are not managed. It
+ * is the responsibility of the constructor of the output layers to make sure
+ * they remain valid for the output state and all copies made.
+ */
+bool wlr_output_state_copy(struct wlr_output_state *dst,
+	const struct wlr_output_state *src);
+
 
 /**
  * Re-configure the swapchain as required for the output's primary buffer.

types/output/state.c

@@ -129,3 +129,39 @@ void wlr_output_state_set_layers(struct wlr_output_state *state,
 	state->layers = layers;
 	state->layers_len = layers_len;
 }
+
+bool wlr_output_state_copy(struct wlr_output_state *dst,
+		const struct wlr_output_state *src) {
+	struct wlr_output_state copy = *src;
+	copy.committed &= ~(WLR_OUTPUT_STATE_BUFFER |
+		WLR_OUTPUT_STATE_DAMAGE |
+		WLR_OUTPUT_STATE_GAMMA_LUT);
+
+	if (src->committed & WLR_OUTPUT_STATE_BUFFER) {
+		wlr_output_state_set_buffer(&copy, src->buffer);
+	}
+
+	if (src->committed & WLR_OUTPUT_STATE_DAMAGE) {
+		wlr_output_state_set_damage(&copy, &src->damage);
+	}
+
+	if (src->committed & WLR_OUTPUT_STATE_GAMMA_LUT) {
+		size_t gamma_buffer_size = 3 * src->gamma_lut_size * sizeof(uint16_t);
+		copy.gamma_lut = malloc(gamma_buffer_size);
+		if (!copy.gamma_lut) {
+			wlr_log_errno(WLR_ERROR, "Allocation failed");
+			goto err;
+		}
+
+		copy.committed |= WLR_OUTPUT_STATE_GAMMA_LUT;
+		memcpy(copy.gamma_lut, src->gamma_lut, gamma_buffer_size);
+		copy.gamma_lut_size = src->gamma_lut_size;
+	}
+
+	wlr_output_state_finish(dst);
+	*dst = copy;
+	return true;
+err:
+	wlr_output_state_finish(&copy);
+	return false;
+}