/// <summary>
/// lock window draw if thumb drag in process
/// </summary>
public void LockWindowDrawOnThumbDrag()
{
if (_isThumbDrag)
{
NativeWindowCommon.LockWindowUpdate(this.Handle);
}
}
/// <summary>
/// unlock window draw if thumb drag in process or has ended
/// </summary>
/// <returns></returns>
public bool UnlockWindowDrawOnThumbDrag()
{
if (_isThumbDrag)
{
NativeWindowCommon.LockWindowUpdate(IntPtr.Zero);
return(true);
}
else
{
return(false);
}
}
/// <summary>
/// Update vertical scroll bar
/// </summary>
/// <param name="calculateRowsInPage">Calculate rows in page before updating scroll bar</param>
protected override void updateVScroll(bool calculateRowsInPage)
{
bool visibleChanged = false;
bool hScrollBarExisted;
bool hScrollBarExists;
if (SuspendPaint)
{
return;
}
if (calculateRowsInPage)
{
ComputeAndSetRowsInPage(false);
}
hScrollBarExisted = isHscrollShown();
if (isVscrollShown())
{
if (isVerticalScrollBarVisible != isVscrollShown())
{
// In case of thumb drag window is already locked, no need to lock again
if (RightToLeft == RightToLeft.Yes && !_isThumbDrag)
{
NativeWindowCommon.LockWindowUpdate(this.Handle);
}
NativeScroll.ShowScrollBar(this.Handle, NativeScroll.SB_VERT, true);
if (RightToLeft == RightToLeft.Yes && !_isThumbDrag)
{
NativeWindowCommon.LockWindowUpdate(IntPtr.Zero);
}
visibleChanged = true;
}
// Unlock window and update
if (UnlockWindowDrawOnThumbDrag())
{
this.Update();
}
NativeScroll.SCROLLINFO sc = ScrollInfo(NativeScroll.SB_VERT);
sc.nPos = _vScrollThumbPos;
sc.nMax = _virtualItemsCount;
sc.nPage = PageSize;
sc.fMask = NativeScroll.SIF_PAGE | NativeScroll.SIF_RANGE | NativeScroll.SIF_POS;
NativeScroll.SetScrollInfo(this.Handle, NativeScroll.SB_VERT, ref sc, true);
// lock drawing on the window
LockWindowDrawOnThumbDrag();
}
else
{
// If the scrollbar was shown earlier (isVerticalScrollBarVisible is true) and is to be removed
// now (isVscrollShown() is false)...
if (isVerticalScrollBarVisible)
{
if (RightToLeft == RightToLeft.Yes && !_isThumbDrag)
{
NativeWindowCommon.LockWindowUpdate(this.Handle);
}
// Also, handle scrollbar animation caused due to bug in Windows theme
HideVerticalScrollbarAnimationForWindowsThemes();
if (RightToLeft == RightToLeft.Yes && !_isThumbDrag)
{
NativeWindowCommon.LockWindowUpdate(IntPtr.Zero);
}
//...end thumb drag.
if (_isThumbDrag)
{
EndThumbDrag();
}
visibleChanged = true;
}
}
hScrollBarExists = isHscrollShown();
if (visibleChanged)
{
OnVScrollBarVisibleChanged(isVscrollShown(), hScrollBarExisted, hScrollBarExists);
}
isVerticalScrollBarVisible = isVscrollShown();
}