scrollbar.java

源码为Eclipse开源开发平台桌面开发工具SWT的源代码,

	* 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 amount that the receiver's value will be
 * modified by when the page increment/decrement areas
 * are selected to the argument, which must be at least
 * one.
 *
 * @param value the page 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 setPageIncrement (int value) {
	checkWidget();
	if (value < 1) return;
	pageIncrement = value;
}

/**
 * Sets the single <em>selection</em> that is the receiver's
 * value to the argument which must be greater than or equal
 * to zero.
 *
 * @param selection the new selection (must be zero or greater)
 *
 * @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 setSelection (int selection) {
	checkWidget();
	SCROLLINFO info = new SCROLLINFO ();
	info.cbSize = SCROLLINFO.sizeof;
	int hwnd = hwndScrollBar (), type = scrollBarType ();
	info.fMask = OS.SIF_POS;
	info.nPos = selection;
	OS.SetScrollInfo (hwnd, type, info, true);
}

/**
 * Sets the size of the receiver's thumb relative to the
 * difference between its maximum and minimum values.  This new
 * value will be ignored if it is less than one, and will be
 * clamped if it exceeds the receiver's current range.
 *
 * @param value the new thumb value, which must be at least one and not
 * larger than the size of the current range
 *
 * @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 setThumb (int value) {
	checkWidget();

	/* Position the thumb */
	if (value < 1) return;
	SCROLLINFO info = new SCROLLINFO ();
	info.cbSize = SCROLLINFO.sizeof;
	int hwnd = hwndScrollBar (), type = scrollBarType ();
	info.fMask = OS.SIF_PAGE | OS.SIF_RANGE | OS.SIF_DISABLENOSCROLL;
	OS.GetScrollInfo (hwnd, type, info);
	info.nPage = value;
	if (info.nPage != 0) info.nPage++;
	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,
	* 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 receiver's selection, minimum value, maximum
 * value, thumb, increment and page increment all at once.
 * <p>
 * Note: This is equivalent to setting the values individually
 * using the appropriate methods, but may be implemented in a 
 * more efficient fashion on some platforms.
 * </p>
 *
 * @param selection the new selection value
 * @param minimum the new minimum value
 * @param maximum the new maximum value
 * @param thumb the new thumb value
 * @param increment the new increment value
 * @param pageIncrement the new pageIncrement 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>
 */
public void setValues (int selection, int minimum, int maximum, int thumb, int increment, int pageIncrement) {
	checkWidget();
	if (minimum < 0) return;
	if (maximum < 0) return;
	if (thumb < 1) return;
	if (increment < 1) return;
	if (pageIncrement < 1) return;
	this.increment = increment;	
	this.pageIncrement = pageIncrement;
	SCROLLINFO info = new SCROLLINFO ();
	info.cbSize = SCROLLINFO.sizeof;
	info.fMask = OS.SIF_POS | OS.SIF_PAGE | OS.SIF_RANGE | OS.SIF_DISABLENOSCROLL;
	info.nPos = selection;
	info.nMin = minimum;
	info.nMax = maximum;
	info.nPage = thumb;
	if (info.nPage != 0) info.nPage++;
	int hwnd = hwndScrollBar (), type = scrollBarType ();
	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,
	* 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);
		}
	}
}

/**
 * Marks the receiver as visible if the argument is <code>true</code>,
 * and marks it invisible otherwise. 
 * <p>
 * If one of the receiver's ancestors is not visible or some
 * other condition makes the receiver not visible, marking
 * it visible may not actually cause it to be displayed.
 * </p>
 *
 * @param visible the new 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 void setVisible (boolean visible) {
	checkWidget();
	boolean isVisible = (state & HIDDEN) == 0;
	if (isVisible == visible) return;
	
	/*
	* On Windows CE, use SIF_DISABLENOSCROLL to show and
	* hide the scroll bar when the page size is equal to
	* the range.
	*/
	if (OS.IsWinCE) {
		SCROLLINFO info = new SCROLLINFO ();
		info.cbSize = SCROLLINFO.sizeof;
		int hwnd = hwndScrollBar (), type = scrollBarType ();
		info.fMask = OS.SIF_RANGE | OS.SIF_PAGE;
		if (visible) info.fMask |= OS.SIF_DISABLENOSCROLL;
		OS.GetScrollInfo (hwnd, type, info);
		if (info.nPage == info.nMax - info.nMin + 1) {
			/*
			* Bug in Windows.  When the only changed flag to
			* SetScrollInfo () is OS.SIF_DISABLENOSCROLL, 
			* Windows does not update the scroll bar state.
			* The fix is to increase and then decrease the
			* maximum, causing Windows to honour the flag.
			*/  
			int max = info.nMax;
			info.nMax++;
			OS.SetScrollInfo (hwnd, type, info, false);
			info.nMax = max;
			OS.SetScrollInfo (hwnd, type, info, true);
		} else {
        	/*
        	* This line is intentionally commented.  Currently
        	* always show scrollbar as being enabled and visible.
        	*/
//			if (OS.IsWinCE) error (SWT.ERROR_NOT_IMPLEMENTED);
		}
		return;
	}
	
	/*
	* Set the state bits before calling ShowScrollBar ()
	* because hiding and showing the scroll bar can cause
	* WM_SIZE messages when the client area is resized.
	* Setting the state before the call means that code
	* that runs during WM_SIZE that queries the visibility
	* of the scroll bar will get the correct value.
	*/
	state = visible ? state & ~HIDDEN : state | HIDDEN;
	int hwnd = hwndScrollBar (), type = scrollBarType ();
	if (OS.ShowScrollBar (hwnd, type, visible)) {
		/*
		* Bug in Windows.  For some reason, when the widget
		* is a standard scroll bar, and SetScrollInfo () is
		* called with SIF_RANGE or SIF_PAGE while the widget
		* is not visible, the widget is incorrectly disabled
		* even though the values for SIF_RANGE and SIF_PAGE,
		* when set for a visible scroll bar would not disable
		* the scroll bar.  The fix is to enable the scroll bar
		* when not disabled by the application and the current
		* scroll bar ranges would cause the scroll bar to be
		* enabled had they been set when the scroll bar was
		* visible.
		*/
		if ((state & DISABLED) == 0) {
			SCROLLINFO info = new SCROLLINFO ();
			info.cbSize = SCROLLINFO.sizeof;
			info.fMask = OS.SIF_RANGE | OS.SIF_PAGE;
			OS.GetScrollInfo (hwnd, type, info);
			if (info.nMax - info.nMin - info.nPage >= 0) {
				OS.EnableScrollBar (hwnd, type, OS.ESB_ENABLE_BOTH);
			}
		}
		sendEvent (visible ? SWT.Show : SWT.Hide);
		// widget could be disposed at this point
	}
}

LRESULT wmScrollChild (int wParam, int lParam) {

	/* Do nothing when scrolling is ending */
	int code = wParam & 0xFFFF;
	if (code == OS.SB_ENDSCROLL) return null;

	/*
	* Send the event because WM_HSCROLL and
	* WM_VSCROLL are sent from a modal message
	* loop in Windows that is active when the
	* user is scrolling.
	*/
	Event event = new Event ();
	switch (code) {
		/*
		* This line is intentionally commented.  Do not set the detail
		* field to DRAG to indicate that the dragging has ended when the
		* scroll bar is finally positioned in SB_THUMBPOSITION.
		*/
//		case OS.SB_THUMBPOSITION:	break;
		case OS.SB_THUMBTRACK:		event.detail = SWT.DRAG;  break;
		case OS.SB_TOP: 			event.detail = SWT.HOME;  break;
		case OS.SB_BOTTOM:			event.detail = SWT.END;  break;
		case OS.SB_LINEDOWN:		event.detail = SWT.ARROW_DOWN;  break;
		case OS.SB_LINEUP: 		event.detail = SWT.ARROW_UP;  break;
		case OS.SB_PAGEDOWN:		event.detail = SWT.PAGE_DOWN;  break;
		case OS.SB_PAGEUP:			event.detail = SWT.PAGE_UP;  break;
	}
	sendEvent (SWT.Selection, event);
	// the widget could be destroyed at this point
	return null;
}

}