scrollbar.java

源码为Eclipse开源开发平台桌面开发工具SWT的源代码,

 */
public int getSelection () {
	checkWidget();
	SCROLLINFO info = new SCROLLINFO ();
	info.cbSize = SCROLLINFO.sizeof;
	info.fMask = OS.SIF_POS;
	int hwnd = hwndScrollBar ();
	int type = scrollBarType ();
	OS.GetScrollInfo (hwnd, type, info);
	return info.nPos;
}

/**
 * Returns a point describing the receiver's size. The
 * x coordinate of the result is the width of the receiver.
 * The y coordinate of the result is the height of the
 * receiver.
 *
 * @return the receiver's size
 *
 * @exception SWTException <ul>
 *    <li>ERROR_WIDGET_DISPOSED - if the receiver has been disposed</li>
 *    <li>ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver</li>
 * </ul>
 */
public Point getSize () {
	checkWidget();
	parent.forceResize ();
	RECT rect = new RECT ();
	OS.GetClientRect (parent.handle, rect);
	int width, height;
	if ((style & SWT.HORIZONTAL) != 0) {
		width = rect.right - rect.left;
		height = OS.GetSystemMetrics (OS.SM_CYHSCROLL);
	} else {
		width = OS.GetSystemMetrics (OS.SM_CXVSCROLL);
		height = rect.bottom - rect.top;
	}
	return new Point (width, height);
}

/**
 * Answers the size of the receiver's thumb relative to the
 * difference between its maximum and minimum values.
 *
 * @return the thumb value
 *
 * @exception SWTException <ul>
 *    <li>ERROR_WIDGET_DISPOSED - if the receiver has been disposed</li>
 *    <li>ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver</li>
 * </ul>
 *
 * @see ScrollBar
 */
public int getThumb () {
	checkWidget();
	SCROLLINFO info = new SCROLLINFO ();
	info.cbSize = SCROLLINFO.sizeof;
	info.fMask = OS.SIF_PAGE;
	int hwnd = hwndScrollBar ();
	int type = scrollBarType ();
	OS.GetScrollInfo (hwnd, type, info);
	if (info.nPage != 0) --info.nPage;
	return info.nPage;
}

/**
 * Returns <code>true</code> if the receiver is visible, and
 * <code>false</code> otherwise.
 * <p>
 * If one of the receiver's ancestors is not visible or some
 * other condition makes the receiver not visible, this method
 * may still indicate that it is considered visible even though
 * it may not actually be showing.
 * </p>
 *
 * @return the receiver's visibility state
 *
 * @exception SWTException <ul>
 *    <li>ERROR_WIDGET_DISPOSED - if the receiver has been disposed</li>
 *    <li>ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver</li>
 * </ul>
 */
public boolean getVisible () {
	checkWidget();
	return (state & HIDDEN) == 0;
}

int hwndScrollBar () {
	return parent.handle;
}

/**
 * Returns <code>true</code> if the receiver is enabled and all
 * of the receiver's ancestors are enabled, and <code>false</code>
 * otherwise. A disabled control is typically not selectable from the
 * user interface and draws with an inactive or "grayed" look.
 *
 * @return the receiver's enabled state
 *
 * @exception SWTException <ul>
 *    <li>ERROR_WIDGET_DISPOSED - if the receiver has been disposed</li>
 *    <li>ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver</li>
 * </ul>
 * 
 * @see #getEnabled
 */
public boolean isEnabled () {
	checkWidget();
	return getEnabled () && parent.isEnabled ();
}

/**
 * Returns <code>true</code> if the receiver is visible and all
 * of the receiver's ancestors are visible and <code>false</code>
 * otherwise.
 *
 * @return the receiver's visibility state
 *
 * @exception SWTException <ul>
 *    <li>ERROR_WIDGET_DISPOSED - if the receiver has been disposed</li>
 *    <li>ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver</li>
 * </ul>
 *
 * @see #getVisible
 */
public boolean isVisible () {
	checkWidget();
	return getVisible () && parent.isVisible ();
}

void releaseChild () {
	super.releaseChild ();
	if (parent.horizontalBar == this) parent.horizontalBar = null;
	if (parent.verticalBar == this) parent.verticalBar = null;
}

void releaseWidget () {
	super.releaseWidget ();
	parent = null;
}

/**
 * Removes the listener from the collection of listeners who will
 * be notified when the receiver's value changes.
 *
 * @param listener the listener which should no longer be notified
 *
 * @exception IllegalArgumentException <ul>
 *    <li>ERROR_NULL_ARGUMENT - if the listener is null</li>
 * </ul>
 * @exception SWTException <ul>
 *    <li>ERROR_WIDGET_DISPOSED - if the receiver has been disposed</li>
 *    <li>ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver</li>
 * </ul>
 *
 * @see SelectionListener
 * @see #addSelectionListener
 */
public void removeSelectionListener (SelectionListener listener) {
	checkWidget();
	if (listener == null) error (SWT.ERROR_NULL_ARGUMENT);
	if (eventTable == null) return;
	eventTable.unhook (SWT.Selection, listener);
	eventTable.unhook (SWT.DefaultSelection,listener);	
}

int scrollBarType () {
	if ((style & SWT.VERTICAL) != 0) return OS.SB_VERT;
	/*
	* This line is intentionally commented.  There should
	* only ever be HORIZONTAL and VERTICAL scroll bars.
	* The commented code reminds us that this is the case
	* and that the default style is HORIZONTAL.
	*/	
//	if ((style & SWT.HORIZONTAL) != 0) return OS.SB_HORZ;
	return OS.SB_HORZ;
}

/**
 * Enables the receiver if the argument is <code>true</code>,
 * and disables it otherwise. A disabled control is typically
 * not selectable from the user interface and draws with an
 * inactive or "grayed" look.
 *
 * @param enabled the new enabled state
 *
 * @exception SWTException <ul>
 *    <li>ERROR_WIDGET_DISPOSED - if the receiver has been disposed</li>
 *    <li>ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver</li>
 * </ul>
 */
public void setEnabled (boolean enabled) {
	checkWidget();
	/*
	* This line is intentionally commented.  Currently
	* always show scrollbar as being enabled and visible.
	*/
//	if (OS.IsWinCE) error (SWT.ERROR_NOT_IMPLEMENTED);
	if (!OS.IsWinCE) {
		int hwnd = hwndScrollBar (), type = scrollBarType ();
		int flags = enabled ? OS.ESB_ENABLE_BOTH : OS.ESB_DISABLE_BOTH;
		OS.EnableScrollBar (hwnd, type, flags);
		state &= ~DISABLED;
		if (!enabled) state |= DISABLED;
	}
}

/**
 * Sets the amount that the receiver's value will be
 * modified by when the up/down (or right/left) arrows
 * are pressed to the argument, which must be at least 
 * one.
 *
 * @param value the new increment (must be greater than zero)
 *
 * @exception SWTException <ul>
 *    <li>ERROR_WIDGET_DISPOSED - if the receiver has been disposed</li>
 *    <li>ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver</li>
 * </ul>
 */
public void setIncrement (int value) {
	checkWidget();
	if (value < 1) return;
	increment = value;
}

/**
 * Sets the maximum. If this value is negative or less than or
 * equal to the minimum, the value is ignored. If necessary, first
 * the thumb and then the selection are adjusted to fit within the
 * new range.
 *
 * @param value the new maximum
 *
 * @exception SWTException <ul>
 *    <li>ERROR_WIDGET_DISPOSED - if the receiver has been disposed</li>
 *    <li>ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver</li>
 * </ul>
 */
public void setMaximum (int value) {
	checkWidget();
	if (value < 0) return;
	SCROLLINFO info = new SCROLLINFO ();
	info.cbSize = SCROLLINFO.sizeof;
	int hwnd = hwndScrollBar (), type = scrollBarType ();
	info.fMask = OS.SIF_RANGE | OS.SIF_DISABLENOSCROLL;
	OS.GetScrollInfo (hwnd, type, info);
	if (value - info.nMin - info.nPage < 1) return;
	info.nMax = value;
	OS.SetScrollInfo (hwnd, type, info, (state & DISABLED) == 0);
	
	/*
	* Bug in Windows.  For some reason, when the widget
	* is a standard scroll bar, and SetScrollInfo () is
	* called with SIF_RANGE or SIF_PAGE, the widget is
	* incorrectly made visible so that the next time the
	* widget is resized (or another scroll bar operation
	* is performed), the scroll bar draws.  The fix is
	* to hide the scroll bar (again) when already hidden.
	*/
	if ((state & HIDDEN) != 0) {
		/*
		* This line is intentionally commented.  Currently
		* always show scrollbar as being enabled and visible.
		*/
//		if (OS.IsWinCE) error (SWT.ERROR_NOT_IMPLEMENTED);
		if (!OS.IsWinCE) {
			OS.ShowScrollBar (hwnd, type, false);
		}
	}
		
	/*
	* Feature in Windows.  Using SIF_DISABLENOSCROLL,
	* SetScrollInfo () can change enabled and disabled
	* state of the scroll bar causing a scroll bar that
	* was disabled by the application to become enabled.
	* The fix is to disable the scroll bar (again) when
	* the application has disabled the scroll bar.
	*/
	if ((state & DISABLED) != 0) {
		/*
		* This line is intentionally commented.  Currently
		* always show scrollbar as being enabled and visible.
		*/
//		if (OS.IsWinCE) error (SWT.ERROR_NOT_IMPLEMENTED);
		if (!OS.IsWinCE) {
			OS.EnableScrollBar (hwnd, type, OS.ESB_DISABLE_BOTH);
		}
	}
}

/**
 * Sets the minimum value. If this value is negative or greater
 * than or equal to the maximum, the value is ignored. If necessary,
 * first the thumb and then the selection are adjusted to fit within
 * the new range.
 *
 * @param value the new minimum
 *
 * @exception SWTException <ul>
 *    <li>ERROR_WIDGET_DISPOSED - if the receiver has been disposed</li>
 *    <li>ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver</li>
 * </ul>
 */
public void setMinimum (int value) {
	checkWidget();
	if (value < 0) return;
	SCROLLINFO info = new SCROLLINFO ();
	info.cbSize = SCROLLINFO.sizeof;
	int hwnd = hwndScrollBar (), type = scrollBarType ();
	info.fMask = OS.SIF_RANGE | OS.SIF_DISABLENOSCROLL;
	OS.GetScrollInfo (hwnd, type, info);
	if (info.nMax - value - info.nPage < 1) return;
	info.nMin = value;
	OS.SetScrollInfo (hwnd, type, info, true);
	
	/*
	* Bug in Windows.  For some reason, when the widget
	* is a standard scroll bar, and SetScrollInfo () is
	* called with SIF_RANGE or SIF_PAGE, the widget is
	* incorrectly made visible so that the next time the
	* widget is resized (or another scroll bar operation
	* is performed), the scroll bar draws.  The fix is
	* to hide the scroll bar (again) when already hidden.
	*/
	if ((state & HIDDEN) != 0) {
		/*
		* This line is intentionally commented.  Currently
		* always show scrollbar as being enabled and visible.
		*/
//		if (OS.IsWinCE) error (SWT.ERROR_NOT_IMPLEMENTED);
		if (!OS.IsWinCE) {
			OS.ShowScrollBar (hwnd, type, false);
		}
	}
		
	/*
	* Feature in Windows.  Using SIF_DISABLENOSCROLL,