CHScrollbarListBox

原创于 2014-09-26 16:20:30 发布 · 614 阅读

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本文介绍了一个自定义的滚动条列表框控件，该控件能够根据内容自动调整水平滚动条的显示与隐藏，并确保所有项目都能完整显示。文章详细展示了如何通过重写AddString和DeleteString方法来实现这一功能。

重点几个函数

参考 http://blog.youkuaiyun.com/god00/article/details/6783947

int CHScrollbarListBox::AddString( LPCTSTR lpszItem )
{
int nRet = CListBox::AddString(lpszItem);

SCROLLINFO scrollInfo;
memset(&scrollInfo, 0, sizeof(SCROLLINFO));
scrollInfo.cbSize = sizeof(SCROLLINFO);
scrollInfo.fMask = SIF_ALL;
GetScrollInfo(SB_VERT, &scrollInfo, SIF_ALL);

int nScrollWidth = 0; //vScrollwidth
if(GetCount() > 1 && ((int)scrollInfo.nMax >= (int)scrollInfo.nPage))
{
nScrollWidth = GetSystemMetrics(SM_CXVSCROLL);
//Metrics 分辨率宽度以分辨率为单位
}

RECT lRect;
GetWindowRect(&lRect);
int nBoxWidth = lRect.right - lRect.left - nScrollWidth;

SIZE sSize;
CClientDC myDC(this);
CFont* pListBoxFont = GetFont();
if(pListBoxFont == NULL)
{
}

CFont* pOldFont =
myDC.SelectObject(pListBoxFont);
GetTextExtentPoint32(myDC.m_hDC, lpszItem, _tcslen(lpszItem), &sSize);
m_nMaxWidth = max(m_nMaxWidth, (int)sSize.cx);
if (m_nMaxWidth+5 > nBoxWidth)
{
SetHorizontalExtent(m_nMaxWidth + 4);
}
myDC.SelectObject(pOldFont);

return nRet;

}

int CHScrollbarListBox::DeleteString( UINT nIndex )
{
int nRet = CListBox::DeleteString(nIndex);

RECT lRect;
GetWindowRect(&lRect);
SCROLLINFO scrollInfo;
memset(&scrollInfo, 0, sizeof(SCROLLINFO));
scrollInfo.cbSize = sizeof(SCROLLINFO);
scrollInfo.fMask = SIF_ALL;
GetScrollInfo(SB_VERT, &scrollInfo, SIF_ALL);

int nScrollWidth = 0; //vScrollwidth
if(GetCount() > 1 && ((int)scrollInfo.nMax
>= (int)scrollInfo.nPage))
{
nScrollWidth = GetSystemMetrics(SM_CXVSCROLL);
}

SIZE sSize;
CClientDC myDC(this);
CString lpszItem;
CFont* pListFont = GetFont();
CFont* pOldFont = myDC.SelectObject(pListFont);

int nBoxWidth = lRect.right - lRect.left - nScrollWidth;
m_nMaxWidth = 0;
for (int i = 0 ; i < GetCount(); i ++)
{
CListBox::GetText(i,lpszItem);
GetTextExtentPoint32(myDC.m_hDC,lpszItem,_tcslen(lpszItem.GetBuffer()),&sSize);
lpszItem.ReleaseBuffer();
m_nMaxWidth = max(m_nMaxWidth, (int)sSize.cx);
}
myDC.SelectObject(pOldFont);

if(nBoxWidth < m_nMaxWidth +5)
{
SetHorizontalExtent(m_nMaxWidth + 4);
}else
{
ShowScrollBar(SB_HORZ,FALSE);
SetHorizontalExtent(0);
}
return nRet;
}

void CHScrollbarListBox::ResetContent()
{
CListBox::ResetContent();
m_nMaxWidth = 0 ;
SetHorizontalExtent(0);
}