com.trolltech.qt.gui
Class QAbstractScrollArea

java.lang.Object
  extended by com.trolltech.qt.internal.QSignalEmitterInternal
      extended by com.trolltech.qt.QSignalEmitter
          extended by com.trolltech.qt.QtJambiObject
              extended by com.trolltech.qt.core.QObject
                  extended by com.trolltech.qt.gui.QWidget
                      extended by com.trolltech.qt.gui.QFrame
                          extended by com.trolltech.qt.gui.QAbstractScrollArea
All Implemented Interfaces:
QPaintDeviceInterface, QtJambiInterface
Direct Known Subclasses:
QAbstractItemView, QGraphicsView, QMdiArea, QPlainTextEdit, QScrollArea, QTextEdit

public class QAbstractScrollArea
extends QFrame

The QAbstractScrollArea widget provides a scrolling area with on-demand scroll bars. QAbstractScrollArea is a low-level abstraction of a scrolling area. The area provides a central widget called the viewport, in which the contents of the area is to be scrolled (i.e, the visible parts of the contents are rendered in the viewport).

Next to the viewport is a vertical scroll bar, and below is a horizontal scroll bar. When all of the area contents fits in the viewport, each scroll bar can be either visible or hidden depending on the scroll bar's Qt::ScrollBarPolicy . When a scroll bar is hidden, the viewport expands in order to cover all available space. When a scroll bar becomes visible again, the viewport shrinks in order to make room for the scroll bar.

It is possible to reserve a margin area around the viewport, see setViewportMargins(). The feature is mostly used to place a QHeaderView widget above or beside the scrolling area. Subclasses of QAbstractScrollArea should implement margins.

When inheriting QAbstractScrollArea, you need to do the following:

With a scroll bar policy of Qt::ScrollBarAsNeeded (the default), QAbstractScrollArea shows scroll bars when they provide a non-zero scrolling range, and hides them otherwise.

The scroll bars and viewport should be updated whenever the viewport receives a resize event or the size of the contents changes. The viewport also needs to be updated when the scroll bars values change. The initial values of the scroll bars are often set when the area receives new contents.

We give a simple example, in which we have implemented a scroll area that can scroll any QWidget. We make the widget a child of the viewport; this way, we do not have to calculate which part of the widget to draw but can simply move the widget with QWidget::move(). When the area contents or the viewport size changes, we do the following:

        QSize areaSize = viewport().size();
        QSize  widgetSize = widget.size();

        verticalScrollBar().setPageStep(widgetSize.height());
        horizontalScrollBar().setPageStep(widgetSize.width());
        verticalScrollBar().setRange(0, widgetSize.height() - areaSize.height());
        horizontalScrollBar().setRange(0, widgetSize.width() - areaSize.width());
        updateWidgetPosition();
    
When the scroll bars change value, we need to update the widget position, i.e., find the part of the widget that is to be drawn in the viewport:
        int hvalue = horizontalScrollBar().value();
        int vvalue = verticalScrollBar().value();
        QPoint topLeft = viewport().rect().topLeft();

        widget.move(topLeft.x() - hvalue, topLeft.y() - vvalue);
    
In order to track scroll bar movements, reimplement the virtual function scrollContentsBy(). In order to fine-tune scrolling behavior, connect to a scroll bar's QAbstractSlider::actionTriggered() signal and adjust the QAbstractSlider::sliderPosition as you wish.

For convenience, QAbstractScrollArea makes all viewport events available in the virtual viewportEvent() handler. QWidget's specialized handlers are remapped to viewport events in the cases where this makes sense. The remapped specialized handlers are: paintEvent(), mousePressEvent(), mouseReleaseEvent(), mouseDoubleClickEvent(), mouseMoveEvent(), wheelEvent(), dragEnterEvent(), dragMoveEvent(), dragLeaveEvent(), dropEvent(), contextMenuEvent(), and resizeEvent().

QScrollArea, which inherits QAbstractScrollArea, provides smooth scrolling for any QWidget (i.e., the widget is scrolled pixel by pixel). You only need to subclass QAbstractScrollArea if you need more specialized behavior. This is, for instance, true if the entire contents of the area is not suitable for being drawn on a QWidget or if you do not want smooth scrolling.

See also:
QScrollArea.


Nested Class Summary
 
Nested classes/interfaces inherited from class com.trolltech.qt.gui.QFrame
QFrame.Shadow, QFrame.Shape, QFrame.StyleMask
 
Nested classes/interfaces inherited from class com.trolltech.qt.gui.QWidget
QWidget.RenderFlag, QWidget.RenderFlags
 
Nested classes/interfaces inherited from class com.trolltech.qt.QSignalEmitter
QSignalEmitter.AbstractSignal, QSignalEmitter.PrivateSignal0, QSignalEmitter.PrivateSignal1, QSignalEmitter.PrivateSignal2, QSignalEmitter.PrivateSignal3, QSignalEmitter.PrivateSignal4, QSignalEmitter.PrivateSignal5, QSignalEmitter.PrivateSignal6, QSignalEmitter.PrivateSignal7, QSignalEmitter.PrivateSignal8, QSignalEmitter.PrivateSignal9, QSignalEmitter.Signal0, QSignalEmitter.Signal1, QSignalEmitter.Signal2, QSignalEmitter.Signal3, QSignalEmitter.Signal4, QSignalEmitter.Signal5, QSignalEmitter.Signal6, QSignalEmitter.Signal7, QSignalEmitter.Signal8, QSignalEmitter.Signal9
 
Nested classes/interfaces inherited from class com.trolltech.qt.internal.QSignalEmitterInternal
com.trolltech.qt.internal.QSignalEmitterInternal.AbstractSignalInternal
 
Field Summary
 
Fields inherited from class com.trolltech.qt.gui.QWidget
customContextMenuRequested
 
Fields inherited from class com.trolltech.qt.internal.QSignalEmitterInternal
currentSender
 
Constructor Summary
QAbstractScrollArea()
          Constructs a viewport.
QAbstractScrollArea(QWidget parent)
          Constructs a viewport.
 
Method Summary
 void addScrollBarWidget(QWidget widget, Qt.Alignment alignment)
          Adds widget as a scroll bar widget in the location specified by alignment.
 void addScrollBarWidget(QWidget widget, Qt.AlignmentFlag[] alignment)
          This is an overloaded method provided for convenience.
 QWidget cornerWidget()
          Returns the widget in the corner between the two scroll bars.
 QScrollBar horizontalScrollBar()
          Returns the horizontal scroll bar.
 Qt.ScrollBarPolicy horizontalScrollBarPolicy()
          This property holds the policy for the horizontal scroll bar.
 QSize maximumViewportSize()
          Returns the size of the viewport as if the scroll bars had no valid scrolling range.
 java.util.List scrollBarWidgets(Qt.Alignment alignment)
          Returns a list of the currently set scroll bar widgets.
 java.util.List scrollBarWidgets(Qt.AlignmentFlag[] alignment)
          This is an overloaded method provided for convenience.
protected  void scrollContentsBy(int dx, int dy)
          This virtual handler is called when the scroll bars are moved by dx, dy, and consequently the viewport's contents should be scrolled accordingly.
 void setCornerWidget(QWidget widget)
          Sets the widget in the corner between the two scroll bars to be widget.
 void setHorizontalScrollBar(QScrollBar scrollbar)
          Replaces the existing horizontal scroll bar with scrollBar, and sets all the former scroll bar's slider properties on the new scroll bar.
 void setHorizontalScrollBarPolicy(Qt.ScrollBarPolicy arg__1)
          This property holds the policy for the horizontal scroll bar.
protected  void setupViewport(QWidget viewport)
          This slot is called by QAbstractScrollArea after setViewport(viewport) has been called.
 void setVerticalScrollBar(QScrollBar scrollbar)
          Replaces the existing vertical scroll bar with scrollBar, and sets all the former scroll bar's slider properties on the new scroll bar.
 void setVerticalScrollBarPolicy(Qt.ScrollBarPolicy arg__1)
          This property holds the policy for the vertical scroll bar.
 void setViewport(QWidget widget)
          Sets the viewport to be the given widget.
protected  void setViewportMargins(int left, int top, int right, int bottom)
          Sets the margins around the scrolling area to left, top, right and bottom.
 QScrollBar verticalScrollBar()
          Returns the vertical scroll bar.
 Qt.ScrollBarPolicy verticalScrollBarPolicy()
          This property holds the policy for the vertical scroll bar.
 QWidget viewport()
          Returns the viewport widget.
protected  boolean viewportEvent(QEvent arg__1)
          The main event handler for the scrolling area (the viewport() widget).
 
Methods inherited from class com.trolltech.qt.gui.QFrame
frameRect, frameShadow, frameShape, frameStyle, frameWidth, lineWidth, midLineWidth, setFrameRect, setFrameShadow, setFrameShape, setFrameStyle, setLineWidth, setMidLineWidth
 
Methods inherited from class com.trolltech.qt.gui.QWidget
acceptDrops, accessibleDescription, accessibleName, actionEvent, actions, activateWindow, addAction, addActions, adjustSize, autoFillBackground, backgroundRole, baseSize, changeEvent, childAt, childAt, childrenRect, childrenRegion, clearFocus, clearMask, close, closeEvent, contentsRect, contextMenuEvent, contextMenuPolicy, cursor, depth, destroy, destroy, destroy, dragEnterEvent, dragLeaveEvent, dragMoveEvent, dropEvent, effectiveWinId, ensurePolished, enterEvent, focusInEvent, focusNextChild, focusNextPrevChild, focusOutEvent, focusPolicy, focusPreviousChild, focusProxy, focusWidget, font, fontInfo, fontMetrics, foregroundRole, frameGeometry, frameSize, geometry, getContentsMargins, grabKeyboard, grabMouse, grabMouse, grabShortcut, grabShortcut, graphicsProxyWidget, hasFocus, hasMouseTracking, height, heightForWidth, heightMM, hide, hideEvent, inputContext, inputMethodEvent, inputMethodQuery, insertAction, insertActions, isActiveWindow, isAncestorOf, isEnabled, isEnabledTo, isFullScreen, isHidden, isMaximized, isMinimized, isModal, isVisible, isVisibleTo, isWindow, isWindowModified, keyboardGrabber, keyPressEvent, keyReleaseEvent, languageChange, layout, layoutDirection, leaveEvent, locale, logicalDpiX, logicalDpiY, lower, mapFrom, mapFromGlobal, mapFromParent, mapTo, mapToGlobal, mapToParent, mask, maximumHeight, maximumSize, maximumWidth, metric, minimumHeight, minimumSize, minimumSizeHint, minimumWidth, mouseDoubleClickEvent, mouseGrabber, mouseMoveEvent, mousePressEvent, mouseReleaseEvent, move, move, moveEvent, nativeParentWidget, nextInFocusChain, normalGeometry, numColors, overrideWindowFlags, overrideWindowFlags, overrideWindowState, paintEngine, paintEvent, paintingActive, palette, parentWidget, physicalDpiX, physicalDpiY, pos, raise, rect, releaseKeyboard, releaseMouse, releaseShortcut, removeAction, render, render, render, render, render, render, render, render, render, repaint, repaint, repaint, repaint, resetInputContext, resize, resize, resizeEvent, restoreGeometry, saveGeometry, scroll, scroll, setAcceptDrops, setAccessibleDescription, setAccessibleName, setAttribute, setAttribute, setAutoFillBackground, setBackgroundRole, setBaseSize, setBaseSize, setContentsMargins, setContentsMargins, setContextMenuPolicy, setCursor, setDisabled, setEnabled, setFixedHeight, setFixedSize, setFixedSize, setFixedWidth, setFocus, setFocus, setFocusPolicy, setFocusProxy, setFont, setForegroundRole, setGeometry, setGeometry, setHidden, setInputContext, setLayout, setLayoutDirection, setLocale, setMask, setMask, setMaximumHeight, setMaximumSize, setMaximumSize, setMaximumWidth, setMinimumHeight, setMinimumSize, setMinimumSize, setMinimumWidth, setMouseTracking, setPalette, setParent, setParent, setParent, setShortcutAutoRepeat, setShortcutAutoRepeat, setShortcutEnabled, setShortcutEnabled, setSizeIncrement, setSizeIncrement, setSizePolicy, setSizePolicy, setStatusTip, setStyle, setStyleSheet, setTabOrder, setToolTip, setUpdatesEnabled, setVisible, setWhatsThis, setWindowFilePath, setWindowFlags, setWindowFlags, setWindowIcon, setWindowIconText, setWindowModality, setWindowModified, setWindowOpacity, setWindowRole, setWindowState, setWindowState, setWindowTitle, show, showEvent, showFullScreen, showMaximized, showMinimized, showNormal, size, sizeHint, sizeIncrement, sizePolicy, stackUnder, statusTip, style, styleSheet, tabletEvent, testAttribute, toolTip, underMouse, unsetCursor, unsetLayoutDirection, unsetLocale, update, update, update, update, updateGeometry, updateMicroFocus, updatesEnabled, visibleRegion, whatsThis, wheelEvent, width, widthMM, window, windowFilePath, windowFlags, windowIcon, windowIconText, windowModality, windowOpacity, windowRole, windowState, windowTitle, windowType, winId, x, y
 
Methods inherited from class com.trolltech.qt.core.QObject
childEvent, children, connectSlotsByName, customEvent, disposeLater, dumpObjectInfo, dumpObjectTree, dynamicPropertyNames, event, eventFilter, findChild, findChild, findChild, findChildren, findChildren, findChildren, findChildren, indexOfProperty, installEventFilter, isWidgetType, killTimer, moveToThread, objectName, parent, properties, property, removeEventFilter, setObjectName, setParent, setProperty, startTimer, timerEvent, toString, userProperty
 
Methods inherited from class com.trolltech.qt.QtJambiObject
dispose, disposed, equals, finalize, reassignNativeResources, tr, tr, tr
 
Methods inherited from class com.trolltech.qt.QSignalEmitter
blockSignals, disconnect, disconnect, signalsBlocked, signalSender, thread
 
Methods inherited from class com.trolltech.qt.internal.QSignalEmitterInternal
__qt_signalInitialization
 
Methods inherited from class java.lang.Object
clone, getClass, hashCode, notify, notifyAll, wait, wait, wait
 
Methods inherited from interface com.trolltech.qt.QtJambiInterface
disableGarbageCollection, nativeId, nativePointer, reenableGarbageCollection, setJavaOwnership
 

Constructor Detail

QAbstractScrollArea

public QAbstractScrollArea()
Constructs a viewport.

The parent arguments is sent to the QWidget constructor.


QAbstractScrollArea

public QAbstractScrollArea(QWidget parent)
Constructs a viewport.

The parent arguments is sent to the QWidget constructor.

Method Detail

addScrollBarWidget

public final void addScrollBarWidget(QWidget widget,
                                     Qt.AlignmentFlag[] alignment)
This is an overloaded method provided for convenience.


addScrollBarWidget

public final void addScrollBarWidget(QWidget widget,
                                     Qt.Alignment alignment)
Adds widget as a scroll bar widget in the location specified by alignment.

Scroll bar widgets are shown next to the horizontal or vertical scroll bar, and can be placed on either side of it. If you want the scroll bar widgets to be always visible, set the scrollBarPolicy for the corresponding scroll bar to AlwaysOn.

alignment must be one of Qt::Alignleft and Qt::AlignRight , which maps to the horizontal scroll bar, or Qt::AlignTop and Qt::AlignBottom , which maps to the vertical scroll bar.

A scroll bar widget can be removed by either re-parenting the widget or deleting it. It's also possible to hide a widget with QWidget::hide()

The scroll bar widget will be resized to fit the scroll bar geometry for the current style. The following describes the case for scroll bar widgets on the horizontal scroll bar:

The height of the widget will be set to match the height of the scroll bar. To control the width of the widget, use QWidget::setMinimumWidth and QWidget::setMaximumWidth, or implement QWidget::sizeHint() and set a horizontal size policy. If you want a square widget, call QStyle::pixelMetric(QStyle::PM_ScrollBarExtent ) and set the width to this value.

See also:
scrollBarWidgets().


cornerWidget

public final QWidget cornerWidget()
Returns the widget in the corner between the two scroll bars.

By default, no corner widget is present.

See also:
setCornerWidget().


horizontalScrollBar

public final QScrollBar horizontalScrollBar()
Returns the horizontal scroll bar.

See also:
setHorizontalScrollBar(), horizontalScrollBarPolicy, and verticalScrollBar().


horizontalScrollBarPolicy

public final Qt.ScrollBarPolicy horizontalScrollBarPolicy()
This property holds the policy for the horizontal scroll bar. The default policy is Qt::ScrollBarAsNeeded .

See also:
verticalScrollBarPolicy.


maximumViewportSize

public final QSize maximumViewportSize()
Returns the size of the viewport as if the scroll bars had no valid scrolling range.


scrollBarWidgets

public final java.util.List scrollBarWidgets(Qt.AlignmentFlag[] alignment)
This is an overloaded method provided for convenience.


scrollBarWidgets

public final java.util.List scrollBarWidgets(Qt.Alignment alignment)
Returns a list of the currently set scroll bar widgets. alignment can be any combination of the four location flags.

See also:
addScrollBarWidget().


setCornerWidget

public final void setCornerWidget(QWidget widget)
Sets the widget in the corner between the two scroll bars to be widget.

You will probably also want to set at least one of the scroll bar modes to AlwaysOn.

Passing 0 shows no widget in the corner.

Any previous corner widget is hidden.

You may call setCornerWidget() with the same widget at different times.

All widgets set here will be deleted by the scroll area when it is destroyed unless you separately reparent the widget after setting some other corner widget (or 0).

Any newly set widget should have no current parent.

By default, no corner widget is present.

See also:
cornerWidget(), horizontalScrollBarPolicy, and horizontalScrollBarPolicy.


setHorizontalScrollBar

public final void setHorizontalScrollBar(QScrollBar scrollbar)
Replaces the existing horizontal scroll bar with scrollBar, and sets all the former scroll bar's slider properties on the new scroll bar. The former scroll bar is then deleted.

QAbstractScrollArea already provides horizontal and vertical scroll bars by default. You can call this function to replace the default horizontal scroll bar with your own custom scroll bar.

See also:
horizontalScrollBar(), and setVerticalScrollBar().


setHorizontalScrollBarPolicy

public final void setHorizontalScrollBarPolicy(Qt.ScrollBarPolicy arg__1)
This property holds the policy for the horizontal scroll bar. The default policy is Qt::ScrollBarAsNeeded .

See also:
verticalScrollBarPolicy.


setVerticalScrollBar

public final void setVerticalScrollBar(QScrollBar scrollbar)
Replaces the existing vertical scroll bar with scrollBar, and sets all the former scroll bar's slider properties on the new scroll bar. The former scroll bar is then deleted.

QAbstractScrollArea already provides vertical and horizontal scroll bars by default. You can call this function to replace the default vertical scroll bar with your own custom scroll bar.

See also:
verticalScrollBar(), and setHorizontalScrollBar().


setVerticalScrollBarPolicy

public final void setVerticalScrollBarPolicy(Qt.ScrollBarPolicy arg__1)
This property holds the policy for the vertical scroll bar. The default policy is Qt::ScrollBarAsNeeded .

See also:
horizontalScrollBarPolicy.


setViewport

public final void setViewport(QWidget widget)
Sets the viewport to be the given widget. The QAbstractScrollArea will take ownership of the given widget.

If widget is 0, QAbstractScrollArea will assign a new QWidget instance for the viewport.

See also:
viewport().


setViewportMargins

protected final void setViewportMargins(int left,
                                        int top,
                                        int right,
                                        int bottom)
Sets the margins around the scrolling area to left, top, right and bottom. This is useful for applications such as spreadsheets with "locked" rows and columns. The marginal space is is left blank; put widgets in the unused area.

Note that this function is frequently called by QTreeView and QTableView, so margins must be implemented by QAbstractScrollArea subclasses. Also, if the subclasses are to be used in item views, they should not call this function.

By default all margins are zero.


setupViewport

protected void setupViewport(QWidget viewport)
This slot is called by QAbstractScrollArea after setViewport(viewport) has been called. Reimplement this function in a subclass of QAbstractScrollArea to initialize the new viewport before it is used.

See also:
setViewport().


verticalScrollBar

public final QScrollBar verticalScrollBar()
Returns the vertical scroll bar.

See also:
setVerticalScrollBar(), verticalScrollBarPolicy, and horizontalScrollBar().


verticalScrollBarPolicy

public final Qt.ScrollBarPolicy verticalScrollBarPolicy()
This property holds the policy for the vertical scroll bar. The default policy is Qt::ScrollBarAsNeeded .

See also:
horizontalScrollBarPolicy.


viewport

public final QWidget viewport()
Returns the viewport widget.

Use the QScrollArea::widget() function to retrieve the contents of the viewport widget.

See also:
setViewport(), and QScrollArea::widget().


scrollContentsBy

protected void scrollContentsBy(int dx,
                                int dy)
This virtual handler is called when the scroll bars are moved by dx, dy, and consequently the viewport's contents should be scrolled accordingly.

The default implementation simply calls update() on the entire viewport(), subclasses can reimplement this handler for optimization purposes, or - like QScrollArea - to move a contents widget. The parameters dx and dy are there for convenience, so that the class knows how much should be scrolled (useful e.g. when doing pixel-shifts). You may just as well ignore these values and scroll directly to the position the scroll bars indicate.

Calling this function in order to scroll programmatically is an error, use the scroll bars instead (e.g. by calling QScrollBar::setValue() directly).


viewportEvent

protected boolean viewportEvent(QEvent arg__1)
The main event handler for the scrolling area (the viewport() widget). It handles the event specified, and can be called by subclasses to provide reasonable default behavior.

Returns true to indicate to the event system that the event has been handled, and needs no further processing; otherwise returns false to indicate that the event should be propagated further.

You can reimplement this function in a subclass, but we recommend using one of the specialized event handlers instead.

Specialised handlers for viewport events are: paintEvent(), mousePressEvent(), mouseReleaseEvent(), mouseDoubleClickEvent(), mouseMoveEvent(), wheelEvent(), dragEnterEvent(), dragMoveEvent(), dragLeaveEvent(), dropEvent(), contextMenuEvent(), and resizeEvent().