/src/Core/PdnBaseForm.cs

/////////////////////////////////////////////////////////////////////////////////

// Paint.NET                                                                   //

// Copyright (C) dotPDN LLC, Rick Brewster, Tom Jackson, and contributors.     //

// Portions Copyright (C) Microsoft Corporation. All Rights Reserved.          //

// See src/Resources/Files/License.txt for full licensing and attribution      //

// details.                                                                    //

// .                                                                           //

/////////////////////////////////////////////////////////////////////////////////



using System.Linq;

using PaintDotNet.Base;

using PaintDotNet.SystemLayer;

using System;

using System.Drawing;

using System.Collections.Generic;

using System.ComponentModel;

using System.Resources;

using System.Threading;

using System.Windows.Forms;



namespace PaintDotNet

{

    /// <summary>

    /// This Form class is used to fix a few bugs in Windows Forms, and to add a few performance

    /// enhancements, such as disabling opacity != 1.0 when running in a remote TS/RD session.

    /// We derive from this class instead of Windows.Forms.Form directly.

    /// </summary>

    public class PdnBaseForm 

        : Form,

          ISnapManagerHost

    {

        static PdnBaseForm()

        {

            Application.EnterThreadModal += ApplicationEnterThreadModal;

            Application.LeaveThreadModal += ApplicationLeaveThreadModal;

            ApplicationEnterThreadModal(null, EventArgs.Empty);

        }



        // This set keeps track of forms which cannot be the current modal form.

        private static readonly Stack<List<Form>> ParentModalForms = new Stack<List<Form>>();



        private static bool IsInParentModalForms(Form form)

        {

            return ParentModalForms.Any(formList => formList.Any(parentModalForm => parentModalForm == form));

        }



        private static List<Form> GetAllPeerForms(Form form)

        {

            if (form == null)

            {

                return new List<Form>();

            }



            if (form.Owner != null)

            {

                return GetAllPeerForms(form.Owner);

            }



            var forms = new List<Form> {form};

            forms.AddRange(form.OwnedForms);



            return forms;

        }



        private static void ApplicationEnterThreadModal(object sender, EventArgs e)

        {

            Form activeForm = ActiveForm;

            List<Form> allPeerForms = GetAllPeerForms(activeForm);

            ParentModalForms.Push(allPeerForms);

        }



        private static void ApplicationLeaveThreadModal(object sender, EventArgs e)

        {

            ParentModalForms.Pop();

        }



        protected override void OnShown(EventArgs e)

        {

            IsShown = true;

            Tracing.LogFeature("ShowDialog(" + GetType().FullName + ")");

            base.OnShown(e);

        }



        public bool IsShown { get; private set; }



        private bool _enableOpacity = true;

        private double _ourOpacity = 1.0; // store opacity setting so that when we go from disabled->enabled opacity we can set the correct value

        private SnapManager _snapManager;

        private IContainer components;

        private bool _instanceEnableOpacity = true;

        private static bool _globalEnableOpacity = true;

        private readonly FormEx _formEx;

        private bool _processFormHotKeyMutex; // if we're already processing a form hotkey, don't let other hotkeys execute.



        private static Dictionary<Keys, Function<bool, Keys>> _hotkeyRegistrar;



        /// <summary>

        /// Registers a form-wide hot key, and a callback for when the key is pressed.

        /// The callback must be an instance method on a Control. Whatever Form the Control

        /// is on will process the hotkey, as long as the Form is derived from PdnBaseForm.

        /// </summary>

        public static void RegisterFormHotKey(Keys keys, Function<bool, Keys> callback)

        {

            var targetAsComponent = callback.Target as IComponent;

            var targetAsHotKeyTarget = callback.Target as IHotKeyTarget;



            if (targetAsComponent == null && targetAsHotKeyTarget == null)

            {

                throw new ArgumentException("target instance must implement IComponent or IHotKeyTarget", "callback");

            }



            if (_hotkeyRegistrar == null)

            {

                _hotkeyRegistrar = new Dictionary<Keys, Function<bool, Keys>>();

            }



            Function<bool, Keys> theDelegate;



            if (_hotkeyRegistrar.ContainsKey(keys))

            {

                theDelegate = _hotkeyRegistrar[keys];

                theDelegate += callback;

                _hotkeyRegistrar[keys] = theDelegate;

            }

            else

            {

                theDelegate = new Function<bool, Keys>(callback);

                _hotkeyRegistrar.Add(keys, theDelegate);

            }



            if (targetAsComponent != null)

            {

                targetAsComponent.Disposed += TargetAsComponentDisposed;

            }

            else

            {

                targetAsHotKeyTarget.Disposed += TargetAsHotKeyTargetDisposed;

            }

        }



        private static bool ShouldProcessHotKey(Keys keys)

        {

            Keys keyOnly = keys & ~Keys.Modifiers;



            if (keyOnly == Keys.Back ||

                keyOnly == Keys.Delete ||

                keyOnly == Keys.Left ||

                keyOnly == Keys.Right ||

                keyOnly == Keys.Up ||

                keyOnly == Keys.Down ||

                keys == (Keys.Control | Keys.A) ||        // select all

                keys == (Keys.Control | Keys.Z) ||        // undo

                keys == (Keys.Control | Keys.Y) ||        // redo

                keys == (Keys.Control | Keys.X) ||        // cut

                keys == (Keys.Control | Keys.C) ||        // copy

                keys == (Keys.Control | Keys.V) ||        // paste

                keys == (Keys.Shift | Keys.Delete) ||     // cut (left-handed)

                keys == (Keys.Control | Keys.Insert) ||   // copy (left-handed)

                keys == (Keys.Shift | Keys.Insert)        // paste (left-handed)

                )

            {

                Control focused = Utility.FindFocus();



                if (focused is TextBox || focused is ComboBox || focused is UpDownBase)

                {

                    return false;

                }

            }



            return true;

        }



        private static void TargetAsComponentDisposed(object sender, EventArgs e)

        {

            ((IComponent)sender).Disposed -= TargetAsComponentDisposed;

            RemoveDisposedTarget(sender);

        }



        private static void TargetAsHotKeyTargetDisposed(object sender, EventArgs e)

        {

            ((IHotKeyTarget)sender).Disposed -= TargetAsHotKeyTargetDisposed;

            RemoveDisposedTarget(sender);

        }



        static void RemoveDisposedTarget(object sender)

        {

            // Control was disposed, but it never unregistered for its hotkeys!

            var keysList = new List<Keys>(_hotkeyRegistrar.Keys);



            foreach (Keys keys in keysList)

            {

                Function<bool, Keys> theMultiDelegate = _hotkeyRegistrar[keys];



                foreach (Delegate theDelegate in

                    theMultiDelegate.GetInvocationList().Where(theDelegate => ReferenceEquals(theDelegate.Target, sender)))

                {

                    UnregisterFormHotKey(keys, (Function<bool, Keys>)theDelegate);

                }

            }

        }



        public static void UnregisterFormHotKey(Keys keys, Function<bool, Keys> callback)

        {

            if (_hotkeyRegistrar == null) return;

            Function<bool, Keys> theDelegate = _hotkeyRegistrar[keys];

            theDelegate -= callback;

            _hotkeyRegistrar[keys] = theDelegate;



            var targetAsComponent = callback.Target as IComponent;

            if (targetAsComponent != null)

            {

                targetAsComponent.Disposed -= TargetAsComponentDisposed;

            }



            var targetAsHotKeyTarget = callback.Target as IHotKeyTarget;

            if (targetAsHotKeyTarget != null)

            {

                targetAsHotKeyTarget.Disposed -= TargetAsHotKeyTargetDisposed;

            }



            if (theDelegate.GetInvocationList().Length == 0)

            {

                _hotkeyRegistrar.Remove(keys);

            }



            if (_hotkeyRegistrar.Count == 0)

            {

                _hotkeyRegistrar = null;

            }

        }



        public void Flash()

        {

            UI.FlashForm(this);

        }



        public void RestoreWindow()

        {

            if (WindowState == FormWindowState.Minimized)

            {

                UI.RestoreWindow(this);

            }

        }



        /// <summary>

        /// Returns the currently active modal form if the process is in the foreground and is active.

        /// </summary>

        /// <remarks>

        /// If Form.ActiveForm is modeless, we search up the chain of owner forms

        /// to find its modeless owner form.

        /// </remarks>

        public static Form CurrentModalForm

        {

            get

            {

                Form theForm = ActiveForm;



                while (theForm != null && !theForm.Modal && theForm.Owner != null)

                {

                    theForm = theForm.Owner;

                }



                return theForm;

            }

        }



        /// <summary>

        /// Gets whether the current form is the processes' top level modal form.

        /// </summary>

        public bool IsCurrentModalForm

        {

            get

            {

                if (IsInParentModalForms(this))

                {

                    return false;

                }



                if (ContainsFocus)

                {

                    return true;

                }



                if (OwnedForms.Any(ownedForm => ownedForm.ContainsFocus))

                {

                    return true;

                }



                return (this == CurrentModalForm);

            }

        }



        private static bool IsTargetFormActive(object target)

        {

            Control targetControl = null;



            {

                var asControl = target as Control;



                if (asControl != null)

                {

                    targetControl = asControl;

                }

            }



            if (targetControl == null)

            {

                var asIFormAssociate = target as IFormAssociate;



                if (asIFormAssociate != null)

                {

                    targetControl = asIFormAssociate.AssociatedForm;

                }

            }



            // target is not a control, or a type of non-control that we recognize as hosted by a control

            if (targetControl == null)

            {

                return false;

            }



            Form targetForm = targetControl.FindForm();



            // target is not on a form

            if (targetForm == null)

            {

                return false;

            }



            // is the target on the currently active form?

            Form activeModalForm = CurrentModalForm;



            return targetForm == activeModalForm;



            // Nope.

        }



        private static object GetConcreteTarget(object target)

        {

            var asDelegate = target as Delegate;



            return asDelegate == null ? target : GetConcreteTarget(asDelegate.Target);

        }



        private bool ProcessFormHotKey(Keys keyData)

        {

            bool processed = false;



            if (_processFormHotKeyMutex)

            {

                processed = true;

            }

            else

            {

                _processFormHotKeyMutex = true;



                try

                {

                    if (_hotkeyRegistrar != null && _hotkeyRegistrar.ContainsKey(keyData))

                    {

                        Function<bool, Keys> theDelegate = _hotkeyRegistrar[keyData];

                        Delegate[] invokeList = theDelegate.GetInvocationList();



                        for (int i = invokeList.Length - 1; i >= 0; --i)

                        {

                            var invokeMe = (Function<bool, Keys>)invokeList[i];

                            object concreteTarget = GetConcreteTarget(invokeMe.Target);



                            if (!IsTargetFormActive(concreteTarget)) continue;

                            bool result = invokeMe(keyData);



                            if (!result) continue;

                            // The callback handled the key.

                            processed = true;

                            break;

                        }

                    }

                }



                finally

                {

                    _processFormHotKeyMutex = false;

                }

            }



            return processed;

        }



        private void OnProcessCmdKeyRelay(object sender, FormEx.ProcessCmdKeyEventArgs e)

        {

            bool handled = e.Handled;



            if (handled) return;

            handled = ProcessCmdKeyData(e.KeyData);

            e.Handled = handled;

        }



        public bool RelayProcessCmdKey(ref Message msg, Keys keyData)

        {

            return ProcessCmdKeyData(keyData);

        }



        protected override bool ProcessCmdKey(ref Message msg, Keys keyData)

        {

            bool processed = ProcessCmdKeyData(keyData);



            if (!processed)

            {

                processed = base.ProcessCmdKey(ref msg, keyData);

            }



            return processed;

        }



        private bool ProcessCmdKeyData(Keys keyData)

        {

            bool shouldHandle = ShouldProcessHotKey(keyData);



            if (shouldHandle)

            {

                bool processed = ProcessFormHotKey(keyData);

                return processed;

            }

            return false;

        }



        public static void UpdateAllForms()

        {

            try

            {

                foreach (Form form in Application.OpenForms)

                {

                    try

                    {

                        form.Update();

                    }



                    catch (Exception)

                    {

                    }

                }

            }



            catch (InvalidOperationException)

            {

            }

        }



        protected override void OnHelpRequested(HelpEventArgs hevent)

        {

            if (!hevent.Handled)

            {

                Utility.ShowHelp(this);

                hevent.Handled = true;

            }



            base.OnHelpRequested(hevent);

        }



        public static EventHandler EnableOpacityChanged;

        private static void OnEnableOpacityChanged()

        {

            if (EnableOpacityChanged != null)

            {

                EnableOpacityChanged(null, EventArgs.Empty);

            }

        }



        public bool EnableInstanceOpacity

        {

            get

            {

                return _instanceEnableOpacity;

            }



            set

            {

                _instanceEnableOpacity = value;

                DecideOpacitySetting();

            }

        }



        /// <summary>

        /// Gets or sets a flag that enables or disables opacity for all PdnBaseForm instances.

        /// If a particular form's EnableInstanceOpacity property is false, that will override

        /// this property being 'true'.

        /// </summary>

        public static bool EnableOpacity

        {

            get

            {

                return _globalEnableOpacity;

            }



            set

            {

                _globalEnableOpacity = value;

                OnEnableOpacityChanged();

            }

        }



        /// <summary>

        /// Gets or sets the titlebar rendering behavior for when the form is deactivated.

        /// </summary>

        /// <remarks>

        /// If this property is false, the titlebar will be rendered in a different color when the form

        /// is inactive as opposed to active. If this property is true, it will always render with the

        /// active style. If the whole application is deactivated, the title bar will still be drawn in

        /// an inactive state.

        /// </remarks>

        public bool ForceActiveTitleBar

        {

            get

            {

                return _formEx.ForceActiveTitleBar;

            }



            set

            {

                _formEx.ForceActiveTitleBar = value;

            }

        }



        private readonly ThreadPriority _originalPriority;



        protected override void OnScroll(ScrollEventArgs se)

        {

            Thread.CurrentThread.Priority = _originalPriority;

            base.OnScroll(se);

        }



        public PdnBaseForm()

        {

            _originalPriority = Thread.CurrentThread.Priority;

            Thread.CurrentThread.Priority = ThreadPriority.AboveNormal;



            UI.InitScaling(this);



            SuspendLayout();

            InitializeComponent();



            _formEx = new FormEx(this, RealWndProc);

            Controls.Add(_formEx);

            _formEx.Visible = false;

            DecideOpacitySetting();

            ResumeLayout(false);



            _formEx.ProcessCmdKeyRelay += OnProcessCmdKeyRelay;

        }



        protected override void OnLoad(EventArgs e)

        {

            if (!DesignMode)

            {

                LoadResources();

            }



            base.OnLoad(e);

        }



        public virtual void LoadResources()

        {

            if (DesignMode) return;

            string stringName = Name + ".Localized";

            string stringValue = StringsResourceManager.GetString(stringName);



            if (stringValue == null)

            {

            }

            else

            {

                try

                {

                    bool boolValue = bool.Parse(stringValue);



                    if (boolValue)

                    {

                        LoadLocalizedResources();

                    }

                }



                catch (Exception)

                {

                }

            }

        }



        protected virtual ResourceManager StringsResourceManager

        {

            get

            {

                return PdnResources.Strings;

            }

        }



        private void LoadLocalizedResources()

        {

            LoadLocalizedResources(Name, this);

        }



        private static void ParsePair(string theString, out int x, out int y)

        {

            string[] split = theString.Split(',');

            x = int.Parse(split[0]);

            y = int.Parse(split[1]);

        }



        private void LoadLocalizedResources(string baseName, Control control)

        {

            // Text

            string textStringName = baseName + ".Text";

            string textString = StringsResourceManager.GetString(textStringName);



            if (textString != null)

            {

                control.Text = textString;

            }



            // Location

            string locationStringName = baseName + ".Location";

            string locationString = StringsResourceManager.GetString(locationStringName);



            if (locationString != null)

            {

                try

                {

                    int x;

                    int y;



                    ParsePair(locationString, out x, out y);

                    control.Location = new Point(x, y);

                }



                catch (Exception ex)

                {

                    Tracing.Ping(locationStringName + " is invalid: " + locationString + ", exception: " + ex.ToString());

                }

            }



            // Size

            string sizeStringName = baseName + ".Size";

            string sizeString = StringsResourceManager.GetString(sizeStringName);



            if (sizeString != null)

            {

                try

                {

                    int width;

                    int height;



                    ParsePair(sizeString, out width, out height);

                    control.Size = new Size(width, height);

                }



                catch (Exception ex)

                {

                    Tracing.Ping(sizeStringName + " is invalid: " + sizeString + ", exception: " + ex.ToString());

                }

            }



            // Recurse

            foreach (Control child in control.Controls)

            {

                if (child.Name == null || child.Name.Length > 0)

                {

                    string newBaseName = baseName + "." + child.Name;

                    LoadLocalizedResources(newBaseName, child);

                }

                else

                {

                    Tracing.Ping("Name property not set for an instance of " + child.GetType().Name + " within " + baseName);

                }

            }

        }



        protected override void OnClosing(CancelEventArgs e)

        {

            base.OnClosing(e);



            if (!e.Cancel)

            {

                ForceActiveTitleBar = false;

            }

        }

        

        private void EnableOpacityChangedHandler(object sender, EventArgs e)

        {

            DecideOpacitySetting();

        }



        protected override void OnHandleCreated(EventArgs e)

        {

            base.OnHandleCreated (e);



            EnableOpacityChanged += EnableOpacityChangedHandler;

            UserSessions.SessionChanged += UserSessionsSessionChanged;

            DecideOpacitySetting();

        }



        protected override void OnHandleDestroyed(EventArgs e)

        {

            base.OnHandleDestroyed(e);



            EnableOpacityChanged -= EnableOpacityChangedHandler;

            UserSessions.SessionChanged -= UserSessionsSessionChanged;

        }



        /// <summary>

        /// Clean up any resources being used.

        /// </summary>

        protected override void Dispose(bool disposing)

        {

            if (disposing)

            {

                if (components != null)

                {

                    components.Dispose();

                    components = null;

                }

            }



            base.Dispose(disposing);

        }



        /// <summary>

        /// Sets the opacity of the form.

        /// </summary>

        /// <param name="newOpacity">The new opacity value.</param>

        /// <remarks>

        /// Depending on the system configuration, this request may be ignored. For example,

        /// when running within a Terminal Service (or Remote Desktop) session, opacity will

        /// always be set to 1.0 for performance reasons.

        /// </remarks>

        public new double Opacity

        {

            get

            {

                return _ourOpacity;

            }



            set

            {

                if (_enableOpacity)

                {

                    // Bypassing Form.Opacity eliminates a "black flickering" that occurs when

                    // the form transitions from Opacity=1.0 to Opacity != 1.0, or vice versa.

                    // It appears to be a result of toggling the WS_EX_LAYERED style, or the

                    // fact that Form.Opacity re-applies visual styles when this value transition

                    // takes place.

                    UI.SetFormOpacity(this, value);

                }



                _ourOpacity = value;

            }

        }



        /// <summary>

        /// Decides whether or not to have opacity be enabled.

        /// </summary>

        private void DecideOpacitySetting()

        {

            if (UserSessions.IsRemote || !_globalEnableOpacity || !EnableInstanceOpacity)

            {

                if (_enableOpacity)

                {

                    try

                    {

                        UI.SetFormOpacity(this, 1.0);

                    }



                    // This fails in certain odd situations (bug #746), so we just eat the exception.

                    catch (Win32Exception)

                    {

                    }

                }



                _enableOpacity = false;

            }

            else

            {

                if (!_enableOpacity)

                {

                    // This fails in certain odd situations (bug #746), so we just eat the exception.

                    try

                    {

                        UI.SetFormOpacity(this, _ourOpacity);

                    }



                    catch (Win32Exception)

                    {

                    }

                }



                _enableOpacity = true;

            }

        }



        public double ScreenAspect

        {

            get

            {

                Rectangle bounds = Screen.FromControl(this).Bounds;

                double aspect = (double)bounds.Width / (double)bounds.Height;

                return aspect;

            }

        }



        #region Windows Form Designer generated code

        /// <summary>

        /// Required method for Designer support - do not modify

        /// the contents of this method with the code editor.

        /// </summary>

        private void InitializeComponent()

        {

            this.components = new System.ComponentModel.Container();

            this.SuspendLayout();

            // 

            // PdnBaseForm

            // 

            this.AutoScaleDimensions = new SizeF(96F, 96F);

            this.AutoScaleMode = AutoScaleMode.Dpi;

            this.ClientSize = new System.Drawing.Size(291, 270);

            this.Name = "PdnBaseForm";

            this.StartPosition = System.Windows.Forms.FormStartPosition.Manual;

            this.Text = "PdnBaseForm";

            this.ResumeLayout(false);



        }

        #endregion



        public event MovingEventHandler Moving;

        protected virtual void OnMoving(MovingEventArgs mea)

        {

            if (Moving != null)

            {

                Moving(this, mea);

            }

        }

        

        public event CancelEventHandler QueryEndSession;

        protected virtual void OnQueryEndSession(CancelEventArgs e)

        {

            if (QueryEndSession != null)

            {

                QueryEndSession(this, e);

            }

        }



        private void UserSessionsSessionChanged(object sender, EventArgs e)

        {

            DecideOpacitySetting();

        }



        void RealWndProc(ref Message m)

        {

            OurWndProc(ref m);

        }



        protected override void WndProc(ref Message m)

        {

            if (_formEx == null)

            {

                base.WndProc(ref m);

            }

            else if (!_formEx.HandleParentWndProc(ref m))

            {

                OurWndProc(ref m);

            }

        }



        private void OurWndProc(ref Message m)

        {

            switch (m.Msg)

            {

                case 0x0216: // WM_MOVING

                    unsafe

                    {

                        var p = (int *)m.LParam;

                        Rectangle rect = Rectangle.FromLTRB(p[0], p[1], p[2], p[3]);

                       

                        var mea = new MovingEventArgs(rect);

                        OnMoving(mea);



                        p[0] = mea.Rectangle.Left;

                        p[1] = mea.Rectangle.Top;

                        p[2] = mea.Rectangle.Right;

                        p[3] = mea.Rectangle.Bottom;



                        m.Result = new IntPtr(1);

                    }

                    break;



                // WinForms doesn't handle this message correctly and wrongly returns 0 instead of 1.

                case 0x0011: // WM_QUERYENDSESSION

                    var e = new CancelEventArgs();

                    OnQueryEndSession(e);

                    m.Result = e.Cancel ? IntPtr.Zero : new IntPtr(1);

                    break;



                default:

                    base.WndProc(ref m);

                    break;

            }

        }

        

        public SnapManager SnapManager

        {

            get { return _snapManager ?? (_snapManager = new SnapManager()); }

        }



        public Size ClientSizeToWindowSize(Size clientSize)

        {

            Size baseClientSize = ClientSize;

            Size baseWindowSize = Size;



            int extraWidth = baseWindowSize.Width - baseClientSize.Width;

            int extraHeight = baseWindowSize.Height - baseClientSize.Height;



            var windowSize = new Size(clientSize.Width + extraWidth, clientSize.Height + extraHeight);

            return windowSize;

        }



        public Size WindowSizeToClientSize(Size windowSize)

        {

            Size baseClientSize = ClientSize;

            Size baseWindowSize = Size;



            int extraWidth = baseWindowSize.Width - baseClientSize.Width;

            int extraHeight = baseWindowSize.Height - baseClientSize.Height;

            var clientSize = new Size(windowSize.Width - extraWidth, windowSize.Height - extraHeight);



            return clientSize;

        }



        public Rectangle ClientBoundsToWindowBounds(Rectangle clientBounds)

        {

            Rectangle currentBounds = Bounds;

            Rectangle currentClientBounds = RectangleToScreen(ClientRectangle);



            var newWindowBounds = new Rectangle(

                clientBounds.Left - (currentClientBounds.Left - currentBounds.Left),

                clientBounds.Top - (currentClientBounds.Top - currentBounds.Top),

                clientBounds.Width + (currentBounds.Width - currentClientBounds.Width),

                clientBounds.Height + (currentBounds.Height - currentClientBounds.Height));



            return newWindowBounds;

        }



        public Rectangle WindowBoundsToClientBounds(Rectangle windowBounds)

        {

            Rectangle currentBounds = Bounds;

            Rectangle currentClientBounds = RectangleToScreen(ClientRectangle);



            var newClientBounds = new Rectangle(

                windowBounds.Left + (currentClientBounds.Left - currentBounds.Left),

                windowBounds.Top + (currentClientBounds.Top - currentBounds.Top),

                windowBounds.Width - (currentBounds.Width - currentClientBounds.Width),

                windowBounds.Height - (currentBounds.Height - currentClientBounds.Height));



            return newClientBounds;

        }



        public void EnsureFormIsOnScreen()

        {

            if (WindowState == FormWindowState.Maximized)

            {

                return;

            }



            if (WindowState == FormWindowState.Minimized)

            {

                return;

            }



            Screen ourScreen;



            try

            {

                ourScreen = Screen.FromControl(this);

            }



            catch (Exception)

            {

                ourScreen = null;

            }



            if (ourScreen == null)

            {

                ourScreen = Screen.PrimaryScreen;

            }



            Rectangle currentBounds = Bounds;

            Rectangle newBounds = EnsureRectIsOnScreen(ourScreen, currentBounds);

            Bounds = newBounds;

        }



        public static Rectangle EnsureRectIsOnScreen(Screen screen, Rectangle bounds)

        {

            Rectangle newBounds = bounds;

            Rectangle screenBounds = screen.WorkingArea;



            // Make sure the bottom and right do not fall off the edge, by moving the bounds

            if (newBounds.Right > screenBounds.Right)

            {

                newBounds.X -= (newBounds.Right - screenBounds.Right);

            }



            if (newBounds.Bottom > screenBounds.Bottom)

            {

                newBounds.Y -= (newBounds.Bottom - screenBounds.Bottom);

            }



            // Make sure the top and left haven't fallen off, by moving

            if (newBounds.Left < screenBounds.Left)

            {

                newBounds.X = screenBounds.Left;

            }



            if (newBounds.Top < screenBounds.Top)

            {

                newBounds.Y = screenBounds.Top;

            }



            // Make sure that we are not too wide / tall, by resizing

            if (newBounds.Right > screenBounds.Right)

            {

                newBounds.Width -= (newBounds.Right - screenBounds.Right);

            }



            if (newBounds.Bottom > screenBounds.Bottom)

            {

                newBounds.Height -= (newBounds.Bottom - screenBounds.Bottom);

            }



            // All done.

            return newBounds;

        }

    }

}