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//------------------------------------------------------------------------------
// <copyright file="ToolStripDropTargetManager.cs" company="Microsoft">
// Copyright (c) Microsoft Corporation. All rights reserved.
// </copyright>
//------------------------------------------------------------------------------
namespace System.Windows.Forms {
using System;
using System.ComponentModel;
using System.Drawing;
using System.Diagnostics;
using System.Threading;
using System.Runtime.InteropServices;
using System.Security;
using System.Globalization;
/// <devdoc>
/// Why do we have this class? Well it seems that RegisterDropTarget
/// requires an HWND to back it's IDropTargets. Since some ToolStripItems
/// do not have HWNDS, this guy's got to figure out who the event was
/// really supposed to go to and pass it on to it.
/// </devdoc>
internal class ToolStripDropTargetManager : IDropTarget {
private IDropTarget lastDropTarget;
private ToolStrip owner;
#if DEBUG
private bool dropTargetIsEntered;
#endif
#if DEBUG
internal static readonly TraceSwitch DragDropDebug = new TraceSwitch("DragDropDebug", "Debug ToolStrip DragDrop code");
#else
internal static readonly TraceSwitch DragDropDebug;
#endif
/// <devdoc>
/// Summary of ToolStripDropTargetManager.
/// </devdoc>
/// <param name=owner></param>
public ToolStripDropTargetManager(ToolStrip owner) {
this.owner = owner;
if (owner == null) {
throw new ArgumentNullException("owner");
}
}
/// <devdoc>
/// Summary of EnsureRegistered.
/// </devdoc>
/// <param name=dropTarget></param>
public void EnsureRegistered(IDropTarget dropTarget) {
Debug.WriteLineIf(DragDropDebug.TraceVerbose, "Ensuring drop target registered");
SetAcceptDrops(true);
}
/// <devdoc>
/// Summary of EnsureUnRegistered.
/// </devdoc>
/// <param name=dropTarget></param>
public void EnsureUnRegistered(IDropTarget dropTarget) {
Debug.WriteLineIf(DragDropDebug.TraceVerbose, "Attempting to unregister droptarget");
for (int i = 0; i < owner.Items.Count; i++) {
if (owner.Items[i].AllowDrop) {
Debug.WriteLineIf(DragDropDebug.TraceVerbose, "An item still has allowdrop set to true - cant unregister");
return; // can't unregister this as a drop target unless everyone is done.
}
}
if (owner.AllowDrop || owner.AllowItemReorder) {
Debug.WriteLineIf(DragDropDebug.TraceVerbose, "The ToolStrip has AllowDrop or AllowItemReorder set to true - cant unregister");
return; // can't unregister this as a drop target if ToolStrip is still accepting drops
}
SetAcceptDrops(false);
owner.DropTargetManager = null;
}
/// <devdoc>
/// Takes a screen point and converts it into an item. May return null.
/// </devdoc>
/// <param name=x></param>
/// <param name=y></param>
private ToolStripItem FindItemAtPoint(int x, int y) {
return owner.GetItemAt(owner.PointToClient(new Point(x,y)));
}
/// <devdoc>
/// Summary of OnDragEnter.
/// </devdoc>
/// <param name=e></param>
public void OnDragEnter(DragEventArgs e) {
Debug.WriteLineIf(DragDropDebug.TraceVerbose, "[DRAG ENTER] ==============");
// If we are supporting Item Reordering
// and this is a ToolStripItem - snitch it.
if (owner.AllowItemReorder && e.Data.GetDataPresent(typeof(ToolStripItem))) {
Debug.WriteLineIf(DragDropDebug.TraceVerbose, "ItemReorderTarget taking this...");
lastDropTarget = owner.ItemReorderDropTarget;
}
else {
ToolStripItem item = FindItemAtPoint(e.X, e.Y);
if ((item != null) && (item.AllowDrop)) {
// the item wants this event
Debug.WriteLineIf(DragDropDebug.TraceVerbose, "ToolStripItem taking this: " + item.ToString());
lastDropTarget = ((IDropTarget)item);
}
else if (owner.AllowDrop) {
// the winbar wants this event
Debug.WriteLineIf(DragDropDebug.TraceVerbose, "ToolStrip taking this because AllowDrop set to true.");
lastDropTarget = ((IDropTarget)owner);
}
else {
// There could be one item that says "AllowDrop == true" which would turn
// on this drop target manager. If we're not over that particular item - then
// just null out the last drop target manager.
// the other valid reason for being here is that we've done an AllowItemReorder
// and we dont have a ToolStripItem contain within the data (say someone drags a link
// from IE over the ToolStrip)
Debug.WriteLineIf(DragDropDebug.TraceVerbose, "No one wanted it.");
lastDropTarget = null;
}
}
if (lastDropTarget != null) {
Debug.WriteLineIf(DragDropDebug.TraceVerbose, "Calling OnDragEnter on target...");
#if DEBUG
dropTargetIsEntered=true;
#endif
lastDropTarget.OnDragEnter(e);
}
}
/// <devdoc>
/// Summary of OnDragOver.
/// </devdoc>
/// <param name=e></param>
public void OnDragOver(DragEventArgs e) {
Debug.WriteLineIf(DragDropDebug.TraceVerbose, "[DRAG OVER] ==============");
IDropTarget newDropTarget = null;
// If we are supporting Item Reordering
// and this is a ToolStripItem - snitch it.
if (owner.AllowItemReorder && e.Data.GetDataPresent(typeof(ToolStripItem))) {
Debug.WriteLineIf(DragDropDebug.TraceVerbose, "ItemReorderTarget taking this...");
newDropTarget = owner.ItemReorderDropTarget;
}
else {
ToolStripItem item = FindItemAtPoint(e.X, e.Y);
if ((item != null) && (item.AllowDrop)) {
// the item wants this event
Debug.WriteLineIf(DragDropDebug.TraceVerbose, "ToolStripItem taking this: " + item.ToString());
newDropTarget = ((IDropTarget)item);
}
else if (owner.AllowDrop) {
// the winbar wants this event
Debug.WriteLineIf(DragDropDebug.TraceVerbose, "ToolStrip taking this because AllowDrop set to true.");
newDropTarget = ((IDropTarget)owner);
}
else {
Debug.WriteLineIf(DragDropDebug.TraceVerbose, "No one wanted it.");
newDropTarget = null;
}
}
// if we've switched drop targets - then
// we need to create drag enter and leave events
if (newDropTarget != lastDropTarget) {
Debug.WriteLineIf(DragDropDebug.TraceVerbose, "NEW DROP TARGET!");
UpdateDropTarget(newDropTarget, e);
}
// now call drag over
if (lastDropTarget != null) {
Debug.WriteLineIf(DragDropDebug.TraceVerbose, "Calling OnDragOver on target...");
lastDropTarget.OnDragOver(e);
}
}
/// <devdoc>
/// Summary of OnDragLeave.
/// </devdoc>
/// <param name=e></param>
public void OnDragLeave(System.EventArgs e) {
Debug.WriteLineIf(DragDropDebug.TraceVerbose, "[DRAG LEAVE] ==============");
if (lastDropTarget != null) {
Debug.WriteLineIf(DragDropDebug.TraceVerbose, "Calling OnDragLeave on current target...");
#if DEBUG
dropTargetIsEntered=false;
#endif
lastDropTarget.OnDragLeave(e);
}
#if DEBUG
else {
Debug.Assert(!dropTargetIsEntered, "Why do we have an entered droptarget and NO lastDropTarget?");
}
#endif
lastDropTarget = null;
}
/// <devdoc>
/// Summary of OnDragDrop.
/// </devdoc>
/// <param name=e></param>
public void OnDragDrop(DragEventArgs e) {
Debug.WriteLineIf(DragDropDebug.TraceVerbose, "[DRAG DROP] ==============");
if (lastDropTarget != null) {
Debug.WriteLineIf(DragDropDebug.TraceVerbose, "Calling OnDragDrop on current target...");
lastDropTarget.OnDragDrop(e);
}
else {
Debug.Assert(false, "Why is lastDropTarget null?");
}
lastDropTarget = null;
}
/// <devdoc>
/// Used to actually register the control as a drop target.
/// </devdoc>
/// <internalonly/>
/// <param name=accept></param>
private void SetAcceptDrops(bool accept) {
if (owner.AllowDrop && accept) {
// if the owner has set AllowDrop to true then demand Clipboard permissions.
// else its us, and we can assert them.
IntSecurity.ClipboardRead.Demand();
}
if (accept && owner.IsHandleCreated) {
try
{
if (Application.OleRequired() != System.Threading.ApartmentState.STA)
{
throw new ThreadStateException(SR.GetString(SR.ThreadMustBeSTA));
}
if (accept)
{
Debug.WriteLineIf(CompModSwitches.DragDrop.TraceInfo, "Registering as drop target: " + owner.Handle.ToString());
// Register
int n = UnsafeNativeMethods.RegisterDragDrop(new HandleRef(owner, owner.Handle), (UnsafeNativeMethods.IOleDropTarget)(new DropTarget(this)));
Debug.WriteLineIf(CompModSwitches.DragDrop.TraceInfo, " ret:" + n.ToString(CultureInfo.InvariantCulture));
if (n != 0 && n != NativeMethods.DRAGDROP_E_ALREADYREGISTERED)
{
throw new Win32Exception(n);
}
}
else
{
IntSecurity.ClipboardRead.Assert();
try
{
Debug.WriteLineIf(CompModSwitches.DragDrop.TraceInfo, "Revoking drop target: " + owner.Handle.ToString());
// Revoke
int n = UnsafeNativeMethods.RevokeDragDrop(new HandleRef(owner, owner.Handle));
Debug.WriteLineIf(CompModSwitches.DragDrop.TraceInfo, " ret:" + n.ToString(CultureInfo.InvariantCulture));
if (n != 0 && n != NativeMethods.DRAGDROP_E_NOTREGISTERED)
{
throw new Win32Exception(n);
}
}
finally
{
CodeAccessPermission.RevertAssert();
}
}
}
catch (Exception e)
{
throw new InvalidOperationException(SR.GetString(SR.DragDropRegFailed), e);
}
}
}
/// <devdoc>
/// if we have a new active item, fire drag leave and
/// enter. This corresponds to the case where you
/// are dragging between items and havent actually
/// left the ToolStrip's client area.
/// </devdoc>
/// <param name=newTarget></param>
/// <param name=e></param>
private void UpdateDropTarget(IDropTarget newTarget, DragEventArgs e) {
if (newTarget != lastDropTarget) {
// tell the last drag target you've left
if (lastDropTarget != null) {
OnDragLeave(new EventArgs());
}
lastDropTarget = newTarget;
if (newTarget != null) {
DragEventArgs dragEnterArgs = new DragEventArgs(e.Data, e.KeyState, e.X, e.Y, e.AllowedEffect, e.Effect);
dragEnterArgs.Effect = DragDropEffects.None;
// tell the next drag target you've entered
OnDragEnter(dragEnterArgs);
}
}
}
}
}
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