Plaster

common-lisp
(in-readtable :qtools) ;;; MIME data containing a Lisp data reference (defvar *mime-data-with-object-type* "application/qtools-mime-data-with-object") (define-widget mime-data-with-object (qmimedata) ((object :accessor object :initarg :object :initform nil))) ;;; Draggable (define-widget draggable (QWidget) ((mime-type :accessor mime-type :initarg :mime-type :initform nil))) (define-override (draggable mouse-press-event) (event) (when (eq (enum-value (q+:button event)) (q+:qt.left-button)) (let ((drag (q+:make-qdrag draggable)) (mime-data (make-instance 'mime-data-with-object :object draggable))) (setf (q+:data mime-data *mime-data-with-object-type*) "" (q+:mime-data drag) mime-data) (let ((drop-action (q+:exec drag))) drop-action))) (stop-overriding)) ;;; Drop target (define-widget drop-target (QWidget) ()) (define-initializer (drop-target initialize-drop-target) (setf (q+:accept-drops drop-target) t)) (define-override (drop-target drag-enter-event) (event) (when (q+:has-format (q+:mime-data event) *mime-data-with-object-type*) (q+:accept-proposed-action event)) (stop-overriding)) (define-override (drop-target drop-event) (event) (let ((mime-data (q+:mime-data event))) (drop mime-data drop-target)) (stop-overriding)) ;; GFs and methods (defgeneric drop (item target)) (defgeneric drop-acceptable-p (item target)) (defmethod drop :around (item target) (when (drop-acceptable-p item target) (call-next-method))) (defmethod drop ((item mime-data-with-object) target) (drop (object item) target)) (defmethod drop-acceptable-p ((item mime-data-with-object) target) T) (defmethod drop ((item draggable) target) (print item)) ;;; Test - drag from top of the window to the bottom of the window (defun test () (with-main-window (layout 'qui:flow-layout) (qui:add-widget (make-instance 'draggable) layout) (qui:add-widget (make-instance 'drop-target) layout)))