+(in-package :gtk)
+
+(defstruct ui-d class props children expansion var initform initializer)
+
+(defstruct ui-prop name value)
+
+(defstruct ui-child v props)
+
+(defun parse-ui-props (list)
+ ;; list is ({:prop value}* rest)
+ (iter (for x first list then (cddr x))
+ (while (keywordp (first x)))
+ (for (name value) = x)
+ (collect (make-ui-prop :name name :value value) into props)
+ (finally (return (values props x)))))
+
+(defun parse-ui-children (list)
+ ;; list is (child*)
+ ;; child is {ui {:prop value}*}
+ (iter (while list)
+ (for child = (if (eq :expr (first (first list)))
+ (make-ui-d :var (second (first list)))
+ (parse-ui-description (first list))))
+ (for (values props rest) = (parse-ui-props (rest list)))
+ (setf list rest)
+ (collect (make-ui-child :v child :props props))))
+
+(defun parse-ui-description (description)
+ ;; description is (class {:prop value}* child*)
+ ;; child is {ui {:prop value}*}
+ (let ((class (first description)))
+ (multiple-value-bind (props rest) (parse-ui-props (rest description))
+ (let ((children (parse-ui-children rest)))
+ (make-ui-d :class class :props props :children children)))))
+
+(defun get-ui-d-var (d)
+ (let ((prop (find :var (ui-d-props d) :key #'ui-prop-name)))
+ (if prop
+ (ui-prop-value prop)
+ (gensym (format nil "~A-" (symbol-name (ui-d-class d)))))))
+
+(defun get-ui-d-initform (d)
+ `(make-instance ',(ui-d-class d)
+ ,@(iter (for prop in (ui-d-props d))
+ (unless (eq (ui-prop-name prop) :var)
+ (appending (list (ui-prop-name prop) (ui-prop-value prop)))))))
+
+(defvar *ui-child-packers* (make-hash-table))
+
+(defmacro def-ui-child-packer (class (var child-def child) &body body)
+ `(setf (gethash ',class *ui-child-packers*)
+ (lambda (,var ,child-def ,child) ,@body)))
+
+(def-ui-child-packer container (w d child)
+ (declare (ignore d))
+ `(container-add ,w ,child))
+
+(defun get-ui-child-prop-value (d name required-p context)
+ (let ((prop (find name (ui-child-props d) :key #'ui-prop-name)))
+ (if (and required-p (null prop))
+ (error "~A is a mandatory child property for ~A" name context)
+ (when prop (ui-prop-value prop)))))
+
+(def-ui-child-packer box (b d child)
+ (let ((expand-prop (find :expand (ui-child-props d) :key #'ui-prop-name))
+ (fill-prop (find :fill (ui-child-props d) :key #'ui-prop-name))
+ (padding-prop (find :padding (ui-child-props d) :key #'ui-prop-name)))
+ `(box-pack-start ,b ,child
+ ,@(when expand-prop (list :expand (ui-prop-value expand-prop)))
+ ,@(when fill-prop (list :fill (ui-prop-value fill-prop)))
+ ,@(when padding-prop (list :padding (ui-prop-value padding-prop))))))
+
+(def-ui-child-packer paned (p d child)
+ (let ((resize-prop (find :resize (ui-child-props d) :key #'ui-prop-name))
+ (shrink-prop (find :shrink (ui-child-props d) :key #'ui-prop-name)))
+ `(if (null (paned-child-1 ,p))
+ (paned-pack-1 ,p ,child
+ ,@(when resize-prop (list :resize (ui-prop-value resize-prop)))
+ ,@(when shrink-prop (list :shrink (ui-prop-value shrink-prop))))
+ (paned-pack-2 ,p ,child
+ ,@(when resize-prop (list :resize (ui-prop-value resize-prop)))
+ ,@(when shrink-prop (list :shrink (ui-prop-value shrink-prop)))))))
+
+(def-ui-child-packer table (table d child)
+ `(table-attach ,table ,child
+ ,(get-ui-child-prop-value d :left t "table packing")
+ ,(get-ui-child-prop-value d :right t "table packing")
+ ,(get-ui-child-prop-value d :top t "table packing")
+ ,(get-ui-child-prop-value d :bottom t "table packing")
+ ,@(let ((x-options (get-ui-child-prop-value d :x-options nil nil)))
+ (when x-options
+ (list :x-options x-options)))
+ ,@(let ((y-options (get-ui-child-prop-value d :y-options nil nil)))
+ (when y-options
+ (list :y-options y-options)))
+ ,@(let ((x-padding (get-ui-child-prop-value d :x-padding nil nil)))
+ (when x-padding
+ (list :x-padding x-padding)))
+ ,@(let ((y-padding (get-ui-child-prop-value d :y-padding nil nil)))
+ (when y-padding
+ (list :y-padding y-padding)))))
+
+(defun get-child-packer-fn (d)
+ (iter (for class first (find-class (ui-d-class d)) then (first (c2mop:class-direct-superclasses class)))
+ (while class)
+ (for packer = (gethash (class-name class) *ui-child-packers*))
+ (when packer (return packer))))
+
+(defun get-child-packer (d var)
+ (let ((fn (get-child-packer-fn d)))
+ (when fn
+ (let ((forms (iter (for child in (ui-d-children d))
+ (for child-var = (ui-d-var (ui-child-v child)))
+ (collect (funcall fn var child child-var)))))
+ (when forms (cons 'progn forms))))))
+
+(defun get-ui-d-initializer (d var)
+ (get-child-packer d var))
+
+(defun set-ui-expansion-1 (d)
+ (when (ui-d-class d)
+ ;; only direct-vars do not have class
+ (setf (ui-d-var d) (get-ui-d-var d)
+ (ui-d-initform d) (get-ui-d-initform d))
+ (setf (ui-d-initializer d) (get-ui-d-initializer d (ui-d-var d)))))
+
+(defun set-ui-expansion (description)
+ (iter (for child in (ui-d-children description))
+ (set-ui-expansion (ui-child-v child)))
+ (set-ui-expansion-1 description))
+
+(defun flattened-ui-descriptions (d)
+ (cons d
+ (iter (for child in (ui-d-children d))
+ (when (ui-d-class (ui-child-v child))
+ (appending (flattened-ui-descriptions (ui-child-v child)))))))
+
+(defmacro let-ui (ui-description &body body)
+ (let* ((description (parse-ui-description ui-description))
+ (items (flattened-ui-descriptions description)))
+ (set-ui-expansion description)
+ `(let (,@(iter (for i in items)
+ (collect (list (ui-d-var i)
+ (ui-d-initform i)))))
+ ,@(iter (for i in items)
+ (when (ui-d-initializer i)
+ (collect (ui-d-initializer i))))
+ ,@body)))