Pileus Git - ~andy/gtk/blob - gtk/gtkviewport.c

   1 /* GTK - The GIMP Toolkit
   2  * Copyright (C) 1995-1997 Peter Mattis, Spencer Kimball and Josh MacDonald
   3  *
   4  * This library is free software; you can redistribute it and/or
   5  * modify it under the terms of the GNU Library General Public
   6  * License as published by the Free Software Foundation; either
   7  * version 2 of the License, or (at your option) any later version.
   8  *
   9  * This library is distributed in the hope that it will be useful,
  10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12  * Library General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU Library General Public
  15  * License along with this library; if not, write to the Free
  16  * Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  17  */
  18 #include "gtksignal.h"
  19 #include "gtkviewport.h"
  20
  21
  22 static void gtk_viewport_class_init               (GtkViewportClass *klass);
  23 static void gtk_viewport_init                     (GtkViewport      *viewport);
  24 static void gtk_viewport_map                      (GtkWidget        *widget);
  25 static void gtk_viewport_unmap                    (GtkWidget        *widget);
  26 static void gtk_viewport_realize                  (GtkWidget        *widget);
  27 static void gtk_viewport_unrealize                (GtkWidget        *widget);
  28 static void gtk_viewport_paint                    (GtkWidget        *widget,
  29                                                    GdkRectangle     *area);
  30 static void gtk_viewport_draw                     (GtkWidget        *widget,
  31                                                    GdkRectangle     *area);
  32 static gint gtk_viewport_expose                   (GtkWidget        *widget,
  33                                                    GdkEventExpose   *event);
  34 static void gtk_viewport_size_request             (GtkWidget        *widget,
  35                                                    GtkRequisition   *requisition);
  36 static void gtk_viewport_size_allocate            (GtkWidget        *widget,
  37                                                    GtkAllocation    *allocation);
  38 static gint gtk_viewport_need_resize              (GtkContainer     *container);
  39 static void gtk_viewport_adjustment_changed       (GtkAdjustment    *adjustment,
  40                                                    gpointer          data);
  41 static void gtk_viewport_adjustment_value_changed (GtkAdjustment    *adjustment,
  42                                                    gpointer          data);
  43
  44
  45 guint
  46 gtk_viewport_get_type ()
  47 {
  48   static guint viewport_type = 0;
  49
  50   if (!viewport_type)
  51     {
  52       GtkTypeInfo viewport_info =
  53       {
  54         "GtkViewport",
  55         sizeof (GtkViewport),
  56         sizeof (GtkViewportClass),
  57         (GtkClassInitFunc) gtk_viewport_class_init,
  58         (GtkObjectInitFunc) gtk_viewport_init,
  59         (GtkArgFunc) NULL,
  60       };
  61
  62       viewport_type = gtk_type_unique (gtk_bin_get_type (), &viewport_info);
  63     }
  64
  65   return viewport_type;
  66 }
  67
  68 static void
  69 gtk_viewport_class_init (GtkViewportClass *class)
  70 {
  71   GtkWidgetClass *widget_class;
  72   GtkContainerClass *container_class;
  73
  74   widget_class = (GtkWidgetClass*) class;
  75   container_class = (GtkContainerClass*) class;
  76
  77   widget_class->map = gtk_viewport_map;
  78   widget_class->unmap = gtk_viewport_unmap;
  79   widget_class->realize = gtk_viewport_realize;
  80   widget_class->unrealize = gtk_viewport_unrealize;
  81   widget_class->draw = gtk_viewport_draw;
  82   widget_class->expose_event = gtk_viewport_expose;
  83   widget_class->size_request = gtk_viewport_size_request;
  84   widget_class->size_allocate = gtk_viewport_size_allocate;
  85
  86   container_class->need_resize = gtk_viewport_need_resize;
  87 }
  88
  89 static void
  90 gtk_viewport_init (GtkViewport *viewport)
  91 {
  92   GTK_WIDGET_UNSET_FLAGS (viewport, GTK_NO_WINDOW);
  93   GTK_WIDGET_SET_FLAGS (viewport, GTK_BASIC);
  94
  95   viewport->shadow_type = GTK_SHADOW_IN;
  96   viewport->main_window = NULL;
  97   viewport->view_window = NULL;
  98   viewport->hadjustment = NULL;
  99   viewport->vadjustment = NULL;
 100 }
 101
 102 GtkWidget*
 103 gtk_viewport_new (GtkAdjustment *hadjustment,
 104                   GtkAdjustment *vadjustment)
 105 {
 106   GtkViewport *viewport;
 107
 108   viewport = gtk_type_new (gtk_viewport_get_type ());
 109
 110   if (!hadjustment)
 111     hadjustment = (GtkAdjustment*) gtk_adjustment_new (0.0, 0.0, 0.0, 0.0, 0.0, 0.0);
 112
 113   if (!vadjustment)
 114     vadjustment = (GtkAdjustment*) gtk_adjustment_new (0.0, 0.0, 0.0, 0.0, 0.0, 0.0);
 115
 116   gtk_viewport_set_hadjustment (viewport, hadjustment);
 117   gtk_viewport_set_vadjustment (viewport, vadjustment);
 118
 119   return GTK_WIDGET (viewport);
 120 }
 121
 122 GtkAdjustment*
 123 gtk_viewport_get_hadjustment (GtkViewport *viewport)
 124 {
 125   g_return_val_if_fail (viewport != NULL, NULL);
 126   g_return_val_if_fail (GTK_IS_VIEWPORT (viewport), NULL);
 127
 128   return viewport->hadjustment;
 129 }
 130
 131 GtkAdjustment*
 132 gtk_viewport_get_vadjustment (GtkViewport *viewport)
 133 {
 134   g_return_val_if_fail (viewport != NULL, NULL);
 135   g_return_val_if_fail (GTK_IS_VIEWPORT (viewport), NULL);
 136
 137   return viewport->vadjustment;
 138 }
 139
 140 void
 141 gtk_viewport_set_hadjustment (GtkViewport   *viewport,
 142                               GtkAdjustment *adjustment)
 143 {
 144   g_return_if_fail (viewport != NULL);
 145   g_return_if_fail (GTK_IS_VIEWPORT (viewport));
 146   g_return_if_fail (adjustment != NULL);
 147
 148   if (viewport->hadjustment)
 149     {
 150       gtk_signal_disconnect_by_data (GTK_OBJECT (viewport->hadjustment), (gpointer) viewport);
 151       gtk_object_unref (GTK_OBJECT (viewport->hadjustment));
 152     }
 153
 154   viewport->hadjustment = adjustment;
 155   gtk_object_ref (GTK_OBJECT (viewport->hadjustment));
 156
 157   gtk_signal_connect (GTK_OBJECT (adjustment), "changed",
 158                       (GtkSignalFunc) gtk_viewport_adjustment_changed,
 159                       (gpointer) viewport);
 160   gtk_signal_connect (GTK_OBJECT (adjustment), "value_changed",
 161                       (GtkSignalFunc) gtk_viewport_adjustment_value_changed,
 162                       (gpointer) viewport);
 163
 164   gtk_viewport_adjustment_changed (adjustment, (gpointer) viewport);
 165 }
 166
 167 void
 168 gtk_viewport_set_vadjustment (GtkViewport   *viewport,
 169                               GtkAdjustment *adjustment)
 170 {
 171   g_return_if_fail (viewport != NULL);
 172   g_return_if_fail (GTK_IS_VIEWPORT (viewport));
 173   g_return_if_fail (adjustment != NULL);
 174
 175   if (viewport->vadjustment)
 176     {
 177       gtk_signal_disconnect_by_data (GTK_OBJECT (viewport->vadjustment), (gpointer) viewport);
 178       gtk_object_unref (GTK_OBJECT (viewport->vadjustment));
 179     }
 180
 181   viewport->vadjustment = adjustment;
 182   gtk_object_ref (GTK_OBJECT (viewport->vadjustment));
 183
 184   gtk_signal_connect (GTK_OBJECT (adjustment), "changed",
 185                       (GtkSignalFunc) gtk_viewport_adjustment_changed,
 186                       (gpointer) viewport);
 187   gtk_signal_connect (GTK_OBJECT (adjustment), "value_changed",
 188                       (GtkSignalFunc) gtk_viewport_adjustment_value_changed,
 189                       (gpointer) viewport);
 190
 191   gtk_viewport_adjustment_changed (adjustment, (gpointer) viewport);
 192 }
 193
 194 void
 195 gtk_viewport_set_shadow_type (GtkViewport   *viewport,
 196                               GtkShadowType  type)
 197 {
 198   g_return_if_fail (viewport != NULL);
 199   g_return_if_fail (GTK_IS_VIEWPORT (viewport));
 200
 201   if ((GtkShadowType) viewport->shadow_type != type)
 202     {
 203       viewport->shadow_type = type;
 204
 205       if (GTK_WIDGET_VISIBLE (viewport))
 206         {
 207           gtk_widget_size_allocate (GTK_WIDGET (viewport), &(GTK_WIDGET (viewport)->allocation));
 208           gtk_widget_queue_draw (GTK_WIDGET (viewport));
 209         }
 210     }
 211 }
 212
 213
 214 static void
 215 gtk_viewport_map (GtkWidget *widget)
 216 {
 217   GtkViewport *viewport;
 218   GtkBin *bin;
 219
 220   g_return_if_fail (widget != NULL);
 221   g_return_if_fail (GTK_IS_VIEWPORT (widget));
 222
 223   GTK_WIDGET_SET_FLAGS (widget, GTK_MAPPED);
 224   viewport = GTK_VIEWPORT (widget);
 225   bin = GTK_BIN (widget);
 226
 227   gdk_window_show (viewport->main_window);
 228
 229   if (bin->child &&
 230       GTK_WIDGET_VISIBLE (bin->child) &&
 231       !GTK_WIDGET_MAPPED (bin->child))
 232     gtk_widget_map (bin->child);
 233 }
 234
 235 static void
 236 gtk_viewport_unmap (GtkWidget *widget)
 237 {
 238   GtkViewport *viewport;
 239
 240   g_return_if_fail (widget != NULL);
 241   g_return_if_fail (GTK_IS_VIEWPORT (widget));
 242
 243   GTK_WIDGET_UNSET_FLAGS (widget, GTK_MAPPED);
 244   viewport = GTK_VIEWPORT (widget);
 245
 246   gdk_window_hide (viewport->main_window);
 247 }
 248
 249 static void
 250 gtk_viewport_realize (GtkWidget *widget)
 251 {
 252   GtkViewport *viewport;
 253   GdkWindowAttr attributes;
 254   GtkRequisition *child_requisition;
 255   gint attributes_mask;
 256
 257   g_return_if_fail (widget != NULL);
 258   g_return_if_fail (GTK_IS_VIEWPORT (widget));
 259
 260   viewport = GTK_VIEWPORT (widget);
 261   GTK_WIDGET_SET_FLAGS (widget, GTK_REALIZED);
 262
 263   attributes.x = widget->allocation.x + GTK_CONTAINER (widget)->border_width;
 264   attributes.y = widget->allocation.y + GTK_CONTAINER (widget)->border_width;
 265   attributes.width = widget->allocation.width - GTK_CONTAINER (widget)->border_width * 2;
 266   attributes.height = widget->allocation.height - GTK_CONTAINER (widget)->border_width * 2;
 267   attributes.window_type = GDK_WINDOW_CHILD;
 268   attributes.wclass = GDK_INPUT_OUTPUT;
 269   attributes.visual = gtk_widget_get_visual (widget);
 270   attributes.colormap = gtk_widget_get_colormap (widget);
 271   attributes.event_mask = gtk_widget_get_events (widget) | GDK_EXPOSURE_MASK;
 272
 273   attributes_mask = GDK_WA_X | GDK_WA_Y | GDK_WA_VISUAL | GDK_WA_COLORMAP;
 274
 275   viewport->main_window = gdk_window_new (widget->parent->window, &attributes, attributes_mask);
 276   gdk_window_set_user_data (viewport->main_window, viewport);
 277
 278   attributes.x += widget->style->klass->xthickness;
 279   attributes.y += widget->style->klass->ythickness;
 280   attributes.width -= widget->style->klass->xthickness * 2;
 281   attributes.height -= widget->style->klass->ythickness * 2;
 282
 283   viewport->view_window = gdk_window_new (viewport->main_window, &attributes, attributes_mask);
 284   gdk_window_set_user_data (viewport->view_window, viewport);
 285
 286   attributes.x = 0;
 287   attributes.y = 0;
 288
 289   if (GTK_BIN (viewport)->child)
 290     {
 291       child_requisition = &GTK_WIDGET (GTK_BIN (viewport)->child)->requisition;
 292       attributes.width = child_requisition->width;
 293       attributes.height = child_requisition->height;
 294     }
 295
 296   widget->window = gdk_window_new (viewport->view_window, &attributes, attributes_mask);
 297   gdk_window_set_user_data (widget->window, viewport);
 298
 299   widget->style = gtk_style_attach (widget->style, viewport->main_window);
 300   gtk_style_set_background (widget->style, viewport->main_window, GTK_STATE_NORMAL);
 301   gtk_style_set_background (widget->style, widget->window, GTK_STATE_NORMAL);
 302
 303   gdk_window_show (widget->window);
 304   gdk_window_show (viewport->view_window);
 305 }
 306
 307 static void
 308 gtk_viewport_unrealize (GtkWidget *widget)
 309 {
 310   GtkViewport *viewport;
 311
 312   g_return_if_fail (widget != NULL);
 313   g_return_if_fail (GTK_IS_VIEWPORT (widget));
 314
 315   viewport = GTK_VIEWPORT (widget);
 316   GTK_WIDGET_UNSET_FLAGS (widget, GTK_REALIZED | GTK_MAPPED);
 317
 318   gtk_style_detach (widget->style);
 319
 320   gdk_window_destroy (widget->window);
 321   gdk_window_destroy (viewport->view_window);
 322   gdk_window_destroy (viewport->main_window);
 323
 324   widget->window = NULL;
 325   viewport->view_window = NULL;
 326   viewport->main_window = NULL;
 327 }
 328
 329 static void
 330 gtk_viewport_paint (GtkWidget    *widget,
 331                     GdkRectangle *area)
 332 {
 333   GtkViewport *viewport;
 334   GtkStateType state;
 335   gint x, y;
 336
 337   g_return_if_fail (widget != NULL);
 338   g_return_if_fail (GTK_IS_VIEWPORT (widget));
 339   g_return_if_fail (area != NULL);
 340
 341   if (GTK_WIDGET_DRAWABLE (widget))
 342     {
 343       viewport = GTK_VIEWPORT (widget);
 344
 345       state = widget->state;
 346       if (!GTK_WIDGET_IS_SENSITIVE (widget))
 347         state = GTK_STATE_INSENSITIVE;
 348
 349       x = GTK_CONTAINER (viewport)->border_width;
 350       y = GTK_CONTAINER (viewport)->border_width;
 351
 352       gtk_draw_shadow (widget->style, viewport->main_window,
 353                        GTK_STATE_NORMAL, viewport->shadow_type,
 354                        0, 0, -1, -1);
 355     }
 356 }
 357
 358 static void
 359 gtk_viewport_draw (GtkWidget    *widget,
 360                    GdkRectangle *area)
 361 {
 362   GtkViewport *viewport;
 363   GtkBin *bin;
 364   GdkRectangle tmp_area;
 365   GdkRectangle child_area;
 366
 367   g_return_if_fail (widget != NULL);
 368   g_return_if_fail (GTK_IS_VIEWPORT (widget));
 369   g_return_if_fail (area != NULL);
 370
 371   if (GTK_WIDGET_DRAWABLE (widget))
 372     {
 373       viewport = GTK_VIEWPORT (widget);
 374       bin = GTK_BIN (widget);
 375
 376       gtk_viewport_paint (widget, area);
 377
 378       if (bin->child)
 379         {
 380           tmp_area = *area;
 381           tmp_area.x += viewport->hadjustment->value;
 382           tmp_area.y += viewport->vadjustment->value;
 383
 384           if (gtk_widget_intersect (bin->child, &tmp_area, &child_area))
 385             gtk_widget_draw (bin->child, &child_area);
 386         }
 387     }
 388 }
 389
 390 static gint
 391 gtk_viewport_expose (GtkWidget      *widget,
 392                      GdkEventExpose *event)
 393 {
 394   GtkViewport *viewport;
 395   GtkBin *bin;
 396   GdkEventExpose child_event;
 397
 398   g_return_val_if_fail (widget != NULL, FALSE);
 399   g_return_val_if_fail (GTK_IS_VIEWPORT (widget), FALSE);
 400   g_return_val_if_fail (event != NULL, FALSE);
 401
 402   if (GTK_WIDGET_DRAWABLE (widget))
 403     {
 404       viewport = GTK_VIEWPORT (widget);
 405       bin = GTK_BIN (widget);
 406
 407       if (event->window == viewport->main_window)
 408         gtk_viewport_paint (widget, &event->area);
 409
 410       child_event = *event;
 411       if (bin->child &&
 412           GTK_WIDGET_NO_WINDOW (bin->child) &&
 413           gtk_widget_intersect (bin->child, &event->area, &child_event.area))
 414         gtk_widget_event (bin->child, (GdkEvent*) &child_event);
 415     }
 416
 417   return FALSE;
 418 }
 419
 420 static void
 421 gtk_viewport_size_request (GtkWidget      *widget,
 422                            GtkRequisition *requisition)
 423 {
 424   GtkViewport *viewport;
 425   GtkBin *bin;
 426
 427   g_return_if_fail (widget != NULL);
 428   g_return_if_fail (GTK_IS_VIEWPORT (widget));
 429   g_return_if_fail (requisition != NULL);
 430
 431   viewport = GTK_VIEWPORT (widget);
 432   bin = GTK_BIN (widget);
 433
 434   requisition->width = (GTK_CONTAINER (widget)->border_width +
 435                         GTK_WIDGET (widget)->style->klass->xthickness) * 2 + 5;
 436
 437   requisition->height = (GTK_CONTAINER (widget)->border_width * 2 +
 438                          GTK_WIDGET (widget)->style->klass->ythickness) * 2 + 5;
 439
 440   if (bin->child && GTK_WIDGET_VISIBLE (bin->child))
 441     gtk_widget_size_request (bin->child, &bin->child->requisition);
 442 }
 443
 444 static void
 445 gtk_viewport_size_allocate (GtkWidget     *widget,
 446                             GtkAllocation *allocation)
 447 {
 448   GtkViewport *viewport;
 449   GtkBin *bin;
 450   GtkAllocation child_allocation;
 451   gint hval, vval;
 452
 453   g_return_if_fail (widget != NULL);
 454   g_return_if_fail (GTK_IS_VIEWPORT (widget));
 455   g_return_if_fail (allocation != NULL);
 456
 457   widget->allocation = *allocation;
 458   viewport = GTK_VIEWPORT (widget);
 459   bin = GTK_BIN (widget);
 460
 461   child_allocation.x = GTK_WIDGET (viewport)->style->klass->xthickness;
 462   child_allocation.width = allocation->width - child_allocation.x * 2;
 463
 464   child_allocation.y = GTK_WIDGET (viewport)->style->klass->ythickness;
 465   child_allocation.height = allocation->height - child_allocation.y * 2;
 466
 467   if (GTK_WIDGET_REALIZED (widget))
 468     {
 469       gdk_window_move_resize (viewport->main_window,
 470                               allocation->x + GTK_CONTAINER (viewport)->border_width,
 471                               allocation->y + GTK_CONTAINER (viewport)->border_width,
 472                               allocation->width - GTK_CONTAINER (viewport)->border_width * 2,
 473                               allocation->height - GTK_CONTAINER (viewport)->border_width * 2);
 474
 475       gdk_window_move_resize (viewport->view_window,
 476                               child_allocation.x,
 477                               child_allocation.y,
 478                               child_allocation.width,
 479                               child_allocation.height);
 480     }
 481
 482   viewport->hadjustment->page_size = child_allocation.width;
 483   viewport->hadjustment->page_increment = viewport->hadjustment->page_size / 2;
 484   viewport->hadjustment->step_increment = 10;
 485
 486   viewport->vadjustment->page_size = child_allocation.height;
 487   viewport->vadjustment->page_increment = viewport->vadjustment->page_size / 2;
 488   viewport->vadjustment->step_increment = 10;
 489
 490   hval = viewport->hadjustment->value;
 491   vval = viewport->vadjustment->value;
 492
 493   if (bin->child && GTK_WIDGET_VISIBLE (bin->child))
 494     {
 495       viewport->hadjustment->lower = 0;
 496       viewport->hadjustment->upper = MAX (bin->child->requisition.width,
 497                                           child_allocation.width);
 498
 499       hval = CLAMP (hval, 0,
 500                     viewport->hadjustment->upper -
 501                     viewport->hadjustment->page_size);
 502
 503       viewport->vadjustment->lower = 0;
 504       viewport->vadjustment->upper = MAX (bin->child->requisition.height,
 505                                           child_allocation.height);
 506
 507       vval = CLAMP (vval, 0,
 508                     viewport->vadjustment->upper -
 509                     viewport->vadjustment->page_size);
 510     }
 511
 512   if (bin->child && GTK_WIDGET_VISIBLE (bin->child))
 513     {
 514       child_allocation.x = 0;
 515       child_allocation.y = 0;
 516
 517       child_allocation.width = viewport->hadjustment->upper;
 518       child_allocation.height = viewport->vadjustment->upper;
 519
 520       if (!GTK_WIDGET_REALIZED (widget))
 521         gtk_widget_realize (widget);
 522
 523       gdk_window_resize (widget->window,
 524                          child_allocation.width,
 525                          child_allocation.height);
 526
 527       child_allocation.x = 0;
 528       child_allocation.y = 0;
 529       gtk_widget_size_allocate (bin->child, &child_allocation);
 530     }
 531
 532   gtk_signal_emit_by_name (GTK_OBJECT (viewport->hadjustment), "changed");
 533   gtk_signal_emit_by_name (GTK_OBJECT (viewport->vadjustment), "changed");
 534   if (viewport->hadjustment->value != hval)
 535     {
 536       viewport->hadjustment->value = hval;
 537       gtk_signal_emit_by_name (GTK_OBJECT (viewport->hadjustment), "value_changed");
 538     }
 539   if (viewport->vadjustment->value != vval)
 540     {
 541       viewport->vadjustment->value = vval;
 542       gtk_signal_emit_by_name (GTK_OBJECT (viewport->vadjustment), "value_changed");
 543     }
 544 }
 545
 546 static gint
 547 gtk_viewport_need_resize (GtkContainer *container)
 548 {
 549   GtkBin *bin;
 550
 551   g_return_val_if_fail (container != NULL, FALSE);
 552   g_return_val_if_fail (GTK_IS_VIEWPORT (container), FALSE);
 553
 554   if (GTK_WIDGET_REALIZED (container))
 555     {
 556       bin = GTK_BIN (container);
 557
 558       gtk_widget_size_request (bin->child, &bin->child->requisition);
 559
 560       gtk_widget_size_allocate (GTK_WIDGET (container),
 561                                 &(GTK_WIDGET (container)->allocation));
 562     }
 563
 564   return FALSE;
 565 }
 566
 567 static void
 568 gtk_viewport_adjustment_changed (GtkAdjustment *adjustment,
 569                                  gpointer       data)
 570 {
 571   GtkViewport *viewport;
 572
 573   g_return_if_fail (adjustment != NULL);
 574   g_return_if_fail (data != NULL);
 575   g_return_if_fail (GTK_IS_VIEWPORT (data));
 576
 577   viewport = GTK_VIEWPORT (data);
 578 }
 579
 580 static void
 581 gtk_viewport_adjustment_value_changed (GtkAdjustment *adjustment,
 582                                        gpointer       data)
 583 {
 584   GtkViewport *viewport;
 585   GtkBin *bin;
 586   GtkAllocation child_allocation;
 587   gint width, height;
 588
 589   g_return_if_fail (adjustment != NULL);
 590   g_return_if_fail (data != NULL);
 591   g_return_if_fail (GTK_IS_VIEWPORT (data));
 592
 593   viewport = GTK_VIEWPORT (data);
 594   bin = GTK_BIN (data);
 595
 596   if (bin->child && GTK_WIDGET_VISIBLE (bin->child))
 597     {
 598       gdk_window_get_size (viewport->view_window, &width, &height);
 599
 600       child_allocation.x = 0;
 601       child_allocation.y = 0;
 602
 603       if (viewport->hadjustment->lower != (viewport->hadjustment->upper -
 604                                            viewport->hadjustment->page_size))
 605         child_allocation.x =  viewport->hadjustment->lower - viewport->hadjustment->value;
 606
 607       if (viewport->vadjustment->lower != (viewport->vadjustment->upper -
 608                                            viewport->vadjustment->page_size))
 609         child_allocation.y = viewport->vadjustment->lower - viewport->vadjustment->value;
 610
 611       if (GTK_WIDGET_REALIZED (viewport))
 612         gdk_window_move (GTK_WIDGET (viewport)->window,
 613                          child_allocation.x,
 614                          child_allocation.y);
 615     }
 616 }