util/box: introduce wlr_fbox_transform()

A floating-point version of wlr_box_transform().

include/wlr/util/box.h

@@ -78,4 +78,9 @@ bool wlr_box_empty(const struct wlr_box *box);
 void wlr_box_transform(struct wlr_box *dest, const struct wlr_box *box,
 	enum wl_output_transform transform, int width, int height);
 
+/**
+ * Transforms a floating-point box inside a (0, 0, width, height) box.
+ */
+void wlr_fbox_transform(struct wlr_fbox *dest, const struct wlr_fbox *box,
+	enum wl_output_transform transform, double width, double height);
 #endif

util/box.c

@@ -119,3 +119,51 @@ void wlr_box_transform(struct wlr_box *dest, const struct wlr_box *box,
 		break;
 	}
 }
+
+void wlr_fbox_transform(struct wlr_fbox *dest, const struct wlr_fbox *box,
+		enum wl_output_transform transform, double width, double height) {
+	struct wlr_fbox src = *box;
+
+	if (transform % 2 == 0) {
+		dest->width = src.width;
+		dest->height = src.height;
+	} else {
+		dest->width = src.height;
+		dest->height = src.width;
+	}
+
+	switch (transform) {
+	case WL_OUTPUT_TRANSFORM_NORMAL:
+		dest->x = src.x;
+		dest->y = src.y;
+		break;
+	case WL_OUTPUT_TRANSFORM_90:
+		dest->x = height - src.y - src.height;
+		dest->y = src.x;
+		break;
+	case WL_OUTPUT_TRANSFORM_180:
+		dest->x = width - src.x - src.width;
+		dest->y = height - src.y - src.height;
+		break;
+	case WL_OUTPUT_TRANSFORM_270:
+		dest->x = src.y;
+		dest->y = width - src.x - src.width;
+		break;
+	case WL_OUTPUT_TRANSFORM_FLIPPED:
+		dest->x = width - src.x - src.width;
+		dest->y = src.y;
+		break;
+	case WL_OUTPUT_TRANSFORM_FLIPPED_90:
+		dest->x = src.y;
+		dest->y = src.x;
+		break;
+	case WL_OUTPUT_TRANSFORM_FLIPPED_180:
+		dest->x = src.x;
+		dest->y = height - src.y - src.height;
+		break;
+	case WL_OUTPUT_TRANSFORM_FLIPPED_270:
+		dest->x = height - src.y - src.height;
+		dest->y = width - src.x - src.width;
+		break;
+	}
+}