Runtime Editable Control

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Note

This is a simple example developed with VS.NET 2005 Beta 1 codename Whidbey. So, project and solution are not usable with previous versions, while code should run in previous versions without problems.

Introduction and background

Faced with and, as the matter of fact, astonished by user requirement specification for one project, where one of the requirements were that controls (some or all) on the form must be movable (runtime editable in narrower sense).

So after "brainstorming", the decision was made to make a framework to implement a UserControl for runtime movable controls called EditableControl. EditableControl should be super class for any custom made control with arbitrary number and type of controls.

The idea is to allow users to adjust his/hers look and feel through positions of controls, whereby business logic behind the control stays the same (actually, user is not able to change anything except presentation).

The control should be reusable, so it inherits from UserControl, and any other business logic control that inherits from EditableControl will be editable too.

Original control

Control after runtime "editing"

Design

EditableControl has four member variables for layout editing (moving): points for the origin of the moved control, destination, reference to control being moved, and an ArrayList of controls that can be moved (for other controls).

        /// <summary>
        /// Point where from Control will be moved
        /// </summary>
        private
            Point
            _point_begin 
            ;

        /// <summary>
        /// Point where to Control will be moved
        /// </summary>
        private
            Point
            _point_end
            ;

        /// <summary>
        /// Moved Control
        /// </summary>
        private
            Control
            _control_moving
            = null
            ;

        /// <summary>
        /// Container for defining set of movable/editable Controls
        /// <summary>
        public
            System.Collections.ArrayList
            EditableControls
            ;

To accomplish drag&drop of the control, three mouse events must be handled by containing (hosting control, parent) as well as by every contained (child) control. Those events are: MouseDown to detect selection of the control, MouseMove to animate movement, and MouseUp to detect destination point. Actually, only two events are needed: MouseDown and MouseUp, but animation can't hurt. Initialization hooks events to all contained child controls.

        /// <summary>
        /// initialize member function hooks mouse events of all child 
        /// controls to mouse event handlers of the EditableControl
        /// </summary>
        protected
            virtual
            void
            initialize
            (
            )
        {
            foreach (Control ctrl in Controls)
            {
                ctrl.MouseDown += new MouseEventHandler(MouseDownEventHandler);
                ctrl.MouseUp += new MouseEventHandler(MouseUpEventHandler);
                ctrl.MouseMove += new MouseEventHandler(MouseMoveEventHandler);
            }

            return;
        }

And events which are handled for each movable control and do not interfere with control's behavior (events and logic):

        /// <summary>
        /// MouseDownEventHandler detects whether child control was hit and
        /// sets the starting point for the move of the child control
        /// </summary>
        /// <param name="sender">
        /// </param>
        /// <param name="evnt_args_mouse">
        /// </param>
        protected
            virtual
            void
            MouseDownEventHandler
            (
              object sender
            , MouseEventArgs evnt_args_mouse
            )
        {
            int x;
            int y;
            if (
                // while left button pressed (could define other keys)
                evnt_args_mouse.Button == MouseButtons.Left
                &&
                // ignore containing (parent) control
                ! "Core.Windows.Forms.EditableControl"
                .Equals(sender.GetType().ToString())
                &&
                // control is defined as movable
                EditableControls.Contains(sender)
               )
            {
                Point pt;

                pt = Cursor.Position;
                x_offset_on_client_control = evnt_args_mouse.X;
                y_offset_on_client_control = evnt_args_mouse.Y;

                x = x_offset_on_client_control + ((Control)sender).Location.X;
                y = y_offset_on_client_control + ((Control)sender).Location.Y;
                pt = new Point(x, y);

                _point_begin = pt;
            }

            foreach (Control ctrl in Controls)
            {
                if (ctrl.Bounds.Contains(_point_begin))
                {
                    _control_moving = ctrl;
                }
            }
            return;
        }

        /// <summary>
        /// MouseMoveEventHandler moves child control on the screen
        /// </summary>
        /// <param name="sender">
        /// </param>
        /// <param name="evnt_args_mouse">
        /// </param>
        protected
           virtual
           void
           MouseMoveEventHandler
           (
             object sender
           , MouseEventArgs evnt_args_mouse
           )
        {
            if (
                ! "Core.Windows.Forms.EditableControl"
                .Equals(sender.GetType().ToString())
                &&
                _control_moving != null
                &&
                evnt_args_mouse.Button == MouseButtons.Left
               )
            {
                Point pt = Cursor.Position;
                _control_moving.Left =
                                (this.PointToClient(pt)).X
                                - 
                                x_offset_on_client_control
                                ;
                _control_moving.Top =
                                (this.PointToClient(pt)).Y
                                -
                                y_offset_on_client_control
                                ;
            }
        }

        /// <summary>
        /// MouseUpEventHandler detects when and where child control released
        /// and sets the ending point for the move of the child control
        /// </summary>
        /// <param name="sender">
        /// </param>
        /// <param name="evnt_args_mouse">
        /// </param>
        protected
            virtual
            void
            MouseUpEventHandler
            (
              object sender
            , MouseEventArgs evnt_args_mouse
            )
        {
            if (
                _control_moving != null
                &&
                evnt_args_mouse.Button == MouseButtons.Left
               )
            {
                int x;
                int y;

                x = ((Control)sender).Location.X;
                y = ((Control)sender).Location.Y;

                Point pt = new Point(x, y);
                _point_end = pt;
                _control_moving.Location = _point_end;
                _control_moving = null;
            }

            return;
        }

Using the code

To make any control (let's say SomeUserControl) runtime editable, inherit from EditableControl.

    /// <summary>
    /// UserControl with runtime editable layout extends EditableControl
    /// </summary>
    public partial class SomeUserControl 
        : Core.Windows.Forms.EditableControl
    {
        public SomeUserControl()
            :base()
        {
            InitializeComponent();

       // define movable controls
            base.EditableControls.Add(this.textBox1);
            base.EditableControls.Add(this.dataGridView1);
            base.EditableControls.Add(this.checkBox1);
            base.EditableControls.Add(this.checkedListBox1);
            base.EditableControls.Add(this.button1);

            // prepare EditableControl
            base.initialize();

        }
    }

TODOs

• Resizable runtime controls
• Keys to control selection of moving control (Alt, Ctrl)

History

• First version by moljac++ - 2004.12.03.