mcs/class/Managed.Windows.Forms/Test/System.Windows.Forms/DragAndDropTest.cs

   1 //
   2 // DragAndDropTest.cs: tests for general drag and drop operations.
   3 //
   4 // Permission is hereby granted, free of charge, to any person obtaining
   5 // a copy of this software and associated documentation files (the
   6 // "Software"), to deal in the Software without restriction, including
   7 // without limitation the rights to use, copy, modify, merge, publish,
   8 // distribute, sublicense, and/or sell copies of the Software, and to
   9 // permit persons to whom the Software is furnished to do so, subject to
  10 // the following conditions:
  11 //
  12 // The above copyright notice and this permission notice shall be
  13 // included in all copies or substantial portions of the Software.
  14 //
  15 // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
  16 // EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  17 // MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
  18 // NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
  19 // LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
  20 // OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
  21 // WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  22 //
  23 // Author:
  24 //   Carlos Alberto Cortez <ccortes@novell.com>
  25 //
  26 // (C) 2008 Novell, Inc. (http://www.novell.com)
  27 //
  28 // NOTE: Since this is an interactive set of tests, I didn't include it as part
  29 // of the MWF test suite build. You will need to build it by yourself and then
  30 // use nunit-console, since the nunit GUI has some problems with DND (basically a COM
  31 // issue).
  32 //
  33
  34 using System;
  35 using System.Drawing;
  36 using System.Reflection;
  37 using System.Windows.Forms;
  38
  39 using NUnit.Framework;
  40
  41 namespace MonoTests.System.Windows.Forms
  42 {
  43         [TestFixture]
  44         public class DragAndDropTest
  45         {
  46                 [Test]
  47                 public void DropCancelledByEsc ()
  48                 {
  49                         DNDForm form = new DNDForm ();
  50                         form.Text = MethodBase.GetCurrentMethod ().Name;
  51                         form.InstructionsText =
  52                                 "Instructions:" + Environment.NewLine + Environment.NewLine +
  53                                 "1. Click with left button on the control on the left, holding it." + Environment.NewLine +
  54                                 "2. Move mouse pointer to the control in the right. " + Environment.NewLine +
  55                                 "3. While still pressing the mouse button, press ESC." + Environment.NewLine +
  56                                 "4. Close the form.";
  57                         form.DragControl.DragData = "hello";
  58                         form.DragControl.AllowedEffects = DragDropEffects.All;
  59                         form.DropControl.DropEffect = DragDropEffects.Copy;
  60
  61                         Application.Run (form);
  62
  63                         Assert.AreEqual (DragDropEffects.None, form.DragControl.PerformedEffect, "A1");
  64                         Assert.AreEqual (1, form.DropControl.EnterFiredCount, "A2");
  65                         Assert.AreEqual (1, form.DropControl.LeaveFiredCount, "A3");
  66                         Assert.AreEqual (0, form.DropControl.DropFiredCount, "A4");
  67                 }
  68
  69                 [Test]
  70                 public void DropCancelledByQuery ()
  71                 {
  72                         DNDForm form = new DNDForm ();
  73                         form.Text = MethodBase.GetCurrentMethod ().Name;
  74                         form.InstructionsText =
  75                                 "Instructions:" + Environment.NewLine + Environment.NewLine +
  76                                 "1. Click with left button on the control on the left, holding it." + Environment.NewLine +
  77                                 "2. Move mouse pointer to the control in the right. " + Environment.NewLine +
  78                                 "3. The drop should be cancelled after some seconds." + Environment.NewLine +
  79                                 "4. Close the form.";
  80                         form.DragControl.DragData = "hello";
  81                         form.DragControl.AllowedEffects = DragDropEffects.All;
  82                         form.DropControl.DropEffect = DragDropEffects.Copy;
  83
  84                         query_counter = 0;
  85                         form.DragControl.QueryContinueDrag += new QueryContinueDragEventHandler (DragControl_QueryContinueDrag);
  86
  87                         Application.Run (form);
  88
  89                         Assert.AreEqual (DragDropEffects.None, form.DragControl.PerformedEffect, "A1");
  90                         Assert.AreEqual (1, form.DropControl.EnterFiredCount, "A2");
  91                         Assert.AreEqual (1, form.DropControl.LeaveFiredCount, "A3");
  92                         Assert.AreEqual (0, form.DropControl.DropFiredCount, "A4");
  93                 }
  94
  95                 int query_counter = 0;
  96
  97                 void DragControl_QueryContinueDrag (object sender, QueryContinueDragEventArgs e)
  98                 {
  99                         DragDropControl c = (DragDropControl)sender;
 100                         DNDForm f = (DNDForm)c.Parent;
 101                         if (f.DropControl.EnterFiredCount == 0)
 102                                 return;
 103
 104                         // Cancel dnd operation AFTER we have reached the drop control
 105                         if (query_counter++ >= 32)
 106                                 e.Action = DragAction.Cancel;
 107                 }
 108
 109                 [Test]
 110                 public void EventsAfterDrop ()
 111                 {
 112                         DNDForm form = new DNDForm ();
 113                         form.Text = MethodBase.GetCurrentMethod ().Name;
 114                         form.InstructionsText =
 115                                 "Instructions:" + Environment.NewLine + Environment.NewLine +
 116                                 "1. Click with left button on the control on the left, holding it." + Environment.NewLine +
 117                                 "2. Move mouse pointer to the control in the right. " + Environment.NewLine +
 118                                 "3. Move the pointer around and then release the mouse button." + Environment.NewLine +
 119                                 "4. Close the form.";
 120                         form.DragControl.DragData = "hello";
 121                         form.DragControl.AllowedEffects = DragDropEffects.All;
 122                         form.DropControl.DropEffect = DragDropEffects.Copy;
 123
 124                         // These should clear the event counters AND
 125                         // thus the event counters should remain at 0 after drop occurred
 126                         // AND we should get any MouseUp event.
 127                         mouse_up_counter = 0;
 128                         form.DropControl.DragDrop += new DragEventHandler (DropControl_DragDrop);
 129                         form.DropControl.MouseUp += new MouseEventHandler (DropControl_MouseUp);
 130
 131                         Application.Run (form);
 132
 133                         Assert.AreEqual (DragDropEffects.Copy, form.DragControl.PerformedEffect, "A1");
 134                         Assert.AreEqual (0, form.DropControl.EnterFiredCount, "A2");
 135                         Assert.AreEqual (0, form.DropControl.LeaveFiredCount, "A3");
 136                         Assert.AreEqual (0, form.DropControl.DropFiredCount, "A4");
 137                         Assert.AreEqual (0, form.DropControl.DragOverFiredCount, "A5");
 138                         Assert.AreEqual (0, mouse_up_counter, "A6");
 139                 }
 140
 141                 void DropControl_DragDrop (object sender, DragEventArgs e)
 142                 {
 143                         DragDropControl c = (DragDropControl)sender;
 144                         c.ResetEventCounters ();
 145                 }
 146
 147                 int mouse_up_counter;
 148
 149                 void DropControl_MouseUp (object sender, MouseEventArgs e)
 150                 {
 151                         mouse_up_counter++;
 152                 }
 153
 154                 [Test]
 155                 public void SimpleDragDrop ()
 156                 {
 157                         DNDForm form = new DNDForm ();
 158                         form.Text = MethodBase.GetCurrentMethod ().Name;
 159                         form.InstructionsText =
 160                                 "Instructions:" + Environment.NewLine + Environment.NewLine +
 161                                 "1. Click with left button on the control on the left, holding it." + Environment.NewLine +
 162                                 "2. Move mouse pointer to the control in the right. " + Environment.NewLine +
 163                                 "3. Drop on the right control." + Environment.NewLine +
 164                                 "4. Close the form.";
 165                         form.DragControl.DragData = "SimpleDragDropMessage";
 166                         form.DragControl.AllowedEffects = DragDropEffects.Copy;
 167                         form.DropControl.DropEffect = DragDropEffects.Copy;
 168
 169                         Application.Run (form);
 170
 171                         Assert.AreEqual (DragDropEffects.Copy, form.DragControl.PerformedEffect, "A1");
 172                         Assert.IsTrue (form.DropControl.Data != null, "A2");
 173                         Assert.AreEqual (true, form.DropControl.Data.GetDataPresent (typeof (string)), "A3");
 174                         Assert.AreEqual ("SimpleDragDropMessage", form.DropControl.Data.GetData (typeof (string)), "A4");
 175                 }
 176
 177                 [Test]
 178                 public void SimpleLeave ()
 179                 {
 180                         DNDForm form = new DNDForm ();
 181                         form.Text = MethodBase.GetCurrentMethod ().Name;
 182                         form.InstructionsText =
 183                                 "Instructions:" + Environment.NewLine + Environment.NewLine +
 184                                 "1. Click with left button on the control on the left, holding it." + Environment.NewLine +
 185                                 "2. Move mouse pointer to the control in the right. " + Environment.NewLine +
 186                                 "3. Move the mouse pointer outside the drop control." + Environment.NewLine +
 187                                 "5. Release mouse button." + Environment.NewLine +
 188                                 "6. Close the form.";
 189                         form.DragControl.DragData = "hello";
 190                         form.DragControl.AllowedEffects = DragDropEffects.All;
 191                         form.DropControl.DropEffect = DragDropEffects.Copy;
 192
 193                         Application.Run (form);
 194
 195                         Assert.AreEqual (DragDropEffects.None, form.DragControl.PerformedEffect, "A1");
 196                         Assert.AreEqual (1, form.DropControl.EnterFiredCount, "A2");
 197                         Assert.AreEqual (1, form.DropControl.LeaveFiredCount, "A3");
 198                         Assert.AreEqual (0, form.DropControl.DropFiredCount, "A4");
 199                 }
 200
 201                 [Test]
 202                 public void NotAllowedDropEffect ()
 203                 {
 204                         DNDForm form = new DNDForm ();
 205                         form.Text = MethodBase.GetCurrentMethod ().Name;
 206                         form.InstructionsText =
 207                                 "Instructions:" + Environment.NewLine + Environment.NewLine +
 208                                 "1. Click with left button on the control on the left, holding it." + Environment.NewLine +
 209                                 "2. Move mouse pointer to the control in the right. " + Environment.NewLine +
 210                                 "3. Drop on the right control." + Environment.NewLine +
 211                                 "4. Close the form.";
 212                         form.DragControl.DragData = "SimpleDragDropMessage";
 213                         form.DragControl.AllowedEffects = DragDropEffects.Copy;
 214                         form.DropControl.DropEffect = DragDropEffects.Move;
 215
 216                         Application.Run (form);
 217
 218                         Assert.AreEqual (DragDropEffects.None, form.DragControl.PerformedEffect, "A1");
 219                         Assert.AreEqual (1, form.DropControl.EnterFiredCount, "A2");
 220                         Assert.AreEqual (0, form.DropControl.DropFiredCount, "A3");
 221                         Assert.AreEqual (1, form.DropControl.LeaveFiredCount, "A4");
 222                 }
 223
 224                 // This test should probably include a 'log' check
 225                 [Test]
 226                 public void SequentialOperations ()
 227                 {
 228                         DNDForm form = new DNDForm ();
 229                         form.Text = MethodBase.GetCurrentMethod ().Name;
 230                         form.InstructionsText =
 231                                 "Instructions:" + Environment.NewLine + Environment.NewLine +
 232                                 "1. Click with left button on the control on the left, holding it." + Environment.NewLine +
 233                                 "2. Drag on the control on the right. " + Environment.NewLine + Environment.NewLine +
 234                                 "3. Click with left button on the control on the left again, holding it." + Environment.NewLine +
 235                                 "4. Move the mouse pointer to the control in the right." + Environment.NewLine +
 236                                 "5. Move the mouse pointer outside the drop control." + Environment.NewLine +
 237                                 "6. Release mouse button." + Environment.NewLine + Environment.NewLine +
 238                                 "7. Click with left button on the control on the left again, holding it." + Environment.NewLine +
 239                                 "8. Drag on the control on the right. " + Environment.NewLine + Environment.NewLine +
 240                                 "9. Close the form.";
 241                         form.DragControl.DragData = "SimpleDragDropMessage";
 242                         form.DragControl.AllowedEffects = DragDropEffects.Move;
 243                         form.DropControl.DropEffect = DragDropEffects.Move;
 244
 245                         Application.Run (form);
 246
 247                         Assert.AreEqual (2, form.DropControl.DropFiredCount, "A1");
 248                         Assert.AreEqual (1, form.DropControl.LeaveFiredCount, "A2");
 249                         Assert.AreEqual (DragDropEffects.Move, form.DragControl.PerformedEffect, "A3");
 250                 }
 251
 252                 [Test]
 253                 public void DropWithoutMovement ()
 254                 {
 255                         DNDForm form = new DNDForm ();
 256                         form.Text = MethodBase.GetCurrentMethod ().Name;
 257                         form.InstructionsText =
 258                                 "Instructions:" + Environment.NewLine + Environment.NewLine +
 259                                 "1. Click with left button on the control on the left, holding it, WITHOUT MOVING IT." + Environment.NewLine +
 260                                 "2. Release the button." + Environment.NewLine +
 261                                 "3. Close the form.";
 262                         form.DragControl.DragData = "no movement";
 263                         form.DragControl.AllowDrop = true;
 264                         form.DragControl.AllowedEffects = DragDropEffects.Move;
 265                         form.DragControl.DropEffect = DragDropEffects.Move;
 266
 267                         // Force to automatically do a dnd operation when mouse is pressed,
 268                         // instead of waiting for movement
 269                         form.DragControl.MouseDown += new MouseEventHandler (DragControl_MouseDown);
 270
 271                         Application.Run (form);
 272
 273                         Assert.AreEqual (1, form.DragControl.EnterFiredCount, "A1");
 274                         Assert.AreEqual (0, form.DragControl.LeaveFiredCount, "A2");
 275                         Assert.AreEqual (1, form.DragControl.DropFiredCount, "A3");
 276                         Assert.AreEqual (0, form.DragControl.DragOverFiredCount, "A4");
 277                         Assert.AreEqual (true, form.DragControl.Data != null, "A5");
 278                         // The assertion below is weird: We had a successfully drop, but the returned value is None
 279                         Assert.AreEqual (DragDropEffects.None, form.DragControl.PerformedEffect, "A6");
 280                 }
 281
 282                 void DragControl_MouseDown (object sender, MouseEventArgs e)
 283                 {
 284                         DragDropControl ctrl = (DragDropControl)sender;
 285                         ctrl.DoDragDrop (ctrl.DragData, ctrl.AllowedEffects);
 286                 }
 287
 288                 [Test]
 289                 public void DragDropInSameControl ()
 290                 {
 291                         DNDForm form = new DNDForm ();
 292                         form.Text = MethodBase.GetCurrentMethod ().Name;
 293                         form.InstructionsText =
 294                                 "Instructions:" + Environment.NewLine + Environment.NewLine +
 295                                 "1. Click with left button on the control on the left, holding it." + Environment.NewLine +
 296                                 "2. Move the mouse inside left control. " + Environment.NewLine +
 297                                 "3. Drop on left control (same)." + Environment.NewLine + Environment.NewLine +
 298                                 "4. Click with left button on the control on the left again, holding it." + Environment.NewLine +
 299                                 "5. Move the mouse inside the left control. " + Environment.NewLine +
 300                                 "6. Press ESC, release mouse button and move mouse pointer outside control." + Environment.NewLine +
 301                                 "7. Close the form.";
 302                         form.DragControl.DragData = "SameControl";
 303                         form.DragControl.AllowDrop = true;
 304                         form.DragControl.AllowedEffects = DragDropEffects.Copy;
 305
 306                         data = null;
 307                         drag_enter_count = drag_leave_count = 0;
 308                         form.DragControl.DragEnter += new DragEventHandler (DragDropInSameControl_DragEnter);
 309                         form.DragControl.DragLeave += new EventHandler (DragDropInSameControl_DragLeave);
 310                         form.DragControl.DragDrop += new DragEventHandler (DragDropInSameControl_DragDrop);
 311
 312                         Application.Run (form);
 313
 314                         Assert.AreEqual (2, drag_enter_count, "A1");
 315                         Assert.AreEqual (1, drag_leave_count, "A2");
 316                         Assert.AreEqual (1, drag_drop_count, "A3");
 317                         Assert.AreEqual ("SameControl", data, "A4");
 318                 }
 319
 320                 int drag_enter_count;
 321                 int drag_leave_count;
 322                 int drag_drop_count;
 323                 object data;
 324
 325                 void DragDropInSameControl_DragDrop (object sender, DragEventArgs e)
 326                 {
 327                         drag_drop_count++;
 328                         data = e.Data.GetData (typeof (string));
 329                 }
 330
 331                 void DragDropInSameControl_DragLeave (object sender, EventArgs e)
 332                 {
 333                         drag_leave_count++;
 334                 }
 335
 336                 void DragDropInSameControl_DragEnter (object sender, DragEventArgs e)
 337                 {
 338                         e.Effect = DragDropEffects.Copy;
 339                         drag_enter_count++;
 340                 }
 341         }
 342
 343         public class DNDForm : Form
 344         {
 345                 DragDropControl drag_control;
 346                 DragDropControl drop_control;
 347                 TextBox instructions_tb;
 348                 Label test_name;
 349
 350                 public DNDForm ()
 351                 {
 352                         test_name = new Label ();
 353                         test_name.Location = new Point (5, 5);
 354                         test_name.AutoSize = true;
 355                         test_name.Font = new Font (Font, FontStyle.Bold | Font.Style);
 356                         test_name.Text = Text;
 357
 358                         instructions_tb = new TextBox ();
 359                         instructions_tb.Multiline = true;
 360                         instructions_tb.ScrollBars = ScrollBars.Vertical;
 361                         instructions_tb.Location = new Point (5, test_name.Bottom + 5);
 362                         instructions_tb.Size = new Size (460, 180);
 363
 364                         drag_control = new DragDropControl ();
 365                         drag_control.Location = new Point (5, instructions_tb.Bottom + 10);
 366                         drag_control.Size = new Size (220, 180);
 367                         drag_control.BackColor = Color.LightYellow;
 368                         drag_control.DragDropColor = Color.Yellow;
 369                         drag_control.Text = "Drag Control";
 370                         drag_control.DoDrag = true;
 371
 372                         drop_control = new DragDropControl ();
 373                         drop_control.Location = new Point (drag_control.Right + 20, instructions_tb.Bottom + 10);
 374                         drop_control.Size = new Size (220, 180);
 375                         drop_control.BackColor = Color.LightGreen;
 376                         drop_control.DragDropColor = Color.Green;
 377                         drop_control.Text = "Drop Control";
 378                         drop_control.AllowDrop = true;
 379
 380                         Controls.AddRange (new Control [] { test_name, instructions_tb, drag_control, drop_control });
 381
 382                         Size = new Size (480, 440);
 383                 }
 384
 385                 public string InstructionsText {
 386                         get {
 387                                 return instructions_tb.Text;
 388                         }
 389                         set {
 390                                 instructions_tb.Text = value;
 391                         }
 392                 }
 393
 394                 public DragDropControl DragControl {
 395                         get {
 396                                 return drag_control;
 397                         }
 398                 }
 399
 400                 public DragDropControl DropControl {
 401                         get {
 402                                 return drop_control;
 403                         }
 404                 }
 405
 406                 protected override void OnTextChanged (EventArgs args)
 407                 {
 408                         base.OnTextChanged (args);
 409                         test_name.Text = Text;
 410                 }
 411         }
 412
 413         public class DragDropControl : Control
 414         {
 415                 DragDropEffects effect;
 416                 DragDropEffects allowed_effects;
 417                 DragDropEffects performed_effect;
 418                 object drag_data;
 419                 IDataObject data;
 420                 Color drop_color;
 421                 Color prev_color;
 422                 Rectangle drag_rect;
 423                 bool do_drag;
 424
 425                 int drop_fired_count;
 426                 int leave_fired_count;
 427                 int drag_over_fired_count;
 428                 int enter_fired_count;
 429
 430                 public DragDropControl ()
 431                 {
 432                         drag_rect = new Rectangle (new Point (-1, -1), SystemInformation.DragSize);
 433                 }
 434
 435                 // to call or not DoDragDrop when mouse movement is detected. Only handle dnd events otherwise.
 436                 public bool DoDrag {
 437                         get {
 438                                 return do_drag;
 439                         }
 440                         set {
 441                                 do_drag = value;
 442                         }
 443                 }
 444
 445                 // Color of the control when an operation is having place
 446                 public Color DragDropColor {
 447                         get {
 448                                 return drop_color;
 449                         }
 450                         set {
 451                                 drop_color = value;
 452                         }
 453                 }
 454
 455                 // Data to pass to Control.DoDragDrop
 456                 public object DragData {
 457                         get {
 458                                 return drag_data;
 459                         }
 460                         set {
 461                                 drag_data = value;
 462                         }
 463                 }
 464
 465                 // Effects passed to Control.DoDragDrop
 466                 public DragDropEffects AllowedEffects {
 467                         get {
 468                                 return allowed_effects;
 469                         }
 470                         set {
 471                                 allowed_effects = value;
 472                         }
 473                 }
 474
 475                 // Effect returned by Control.DoDragDrop
 476                 public DragDropEffects PerformedEffect {
 477                         get {
 478                                 return performed_effect;
 479                         }
 480                 }
 481
 482                 // The value DragEventArgs.Effect gets in DragEnter event
 483                 public DragDropEffects DropEffect {
 484                         get {
 485                                 return effect;
 486                         }
 487                         set {
 488                                 effect = value;
 489                         }
 490                 }
 491
 492                 // The value in DragEventArgs.Data
 493                 public IDataObject Data {
 494                         get {
 495                                 return data;
 496                         }
 497                 }
 498
 499                 public int DropFiredCount {
 500                         get {
 501                                 return drop_fired_count;
 502                         }
 503                 }
 504
 505                 public int EnterFiredCount {
 506                         get {
 507                                 return enter_fired_count;
 508                         }
 509                 }
 510
 511                 public int LeaveFiredCount {
 512                         get {
 513                                 return leave_fired_count;
 514                         }
 515                 }
 516
 517                 public int DragOverFiredCount {
 518                         get {
 519                                 return drag_over_fired_count;
 520                         }
 521                 }
 522
 523                 public void ResetEventCounters ()
 524                 {
 525                         drop_fired_count = enter_fired_count = leave_fired_count = drag_over_fired_count = 0;
 526                 }
 527
 528                 protected override void OnDragEnter (DragEventArgs drgevent)
 529                 {
 530                         if (!do_drag) {
 531                                 prev_color = BackColor;
 532                                 BackColor = drop_color;
 533                         }
 534
 535                         enter_fired_count++;
 536                         drgevent.Effect = effect;
 537
 538                         base.OnDragEnter (drgevent);
 539                 }
 540
 541                 protected override void OnDragOver (DragEventArgs drgevent)
 542                 {
 543                         drag_over_fired_count++;
 544
 545                         base.OnDragOver (drgevent);
 546                 }
 547
 548                 protected override void OnDragLeave (EventArgs e)
 549                 {
 550                         data = null;
 551                         leave_fired_count++;
 552
 553                         if (!do_drag)
 554                                 BackColor = prev_color;
 555
 556                         base.OnDragLeave (e);
 557                 }
 558
 559                 protected override void OnDragDrop (DragEventArgs drgevent)
 560                 {
 561                         data = drgevent.Data;
 562                         drop_fired_count++;
 563
 564                         if (!do_drag)
 565                                 BackColor = prev_color;
 566
 567                         base.OnDragDrop (drgevent);
 568                 }
 569
 570                 protected override void OnMouseMove (MouseEventArgs e)
 571                 {
 572                         base.OnMouseMove (e);
 573
 574                         if (!do_drag)
 575                                 return;
 576
 577                         if (e.Button == MouseButtons.Left || e.Button == MouseButtons.Right) {
 578
 579                                 if (drag_rect.X == -1 && drag_rect.Y == -1)
 580                                         drag_rect.Location = new Point (e.X, e.Y);
 581                                 else {
 582                                         if (!drag_rect.Contains (new Point (e.X, e.Y))) {
 583                                                 Color prev_color = BackColor;
 584                                                 BackColor = drop_color;
 585
 586                                                 performed_effect = DoDragDrop (drag_data, allowed_effects);
 587
 588                                                 drag_rect.Location = new Point (-1, -1);
 589                                                 BackColor = prev_color;
 590                                         }
 591                                 }
 592
 593                         }
 594                 }
 595
 596                 protected override void OnPaint (PaintEventArgs e)
 597                 {
 598                         base.OnPaint (e);
 599
 600                         Graphics g = e.Graphics;
 601
 602                         StringFormat sf = new StringFormat ();
 603                         sf.Alignment = StringAlignment.Center;
 604                         sf.LineAlignment = StringAlignment.Center;
 605
 606                         g.DrawString (Text, SystemFonts.DefaultFont, SystemBrushes.ControlDark,
 607                                 ClientRectangle, sf);
 608
 609                         sf.Dispose ();
 610                 }
 611         }
 612 }
 613