Duilib Edit占位提示文本实现

源码下载地址：https://gitee.com/Ailsc/Duilib

在实际过程中我们经常需要实现edit的占位文本提示，如下

实现原理：当edit为空的时候，则展示占位文本。

DWORD m_dwPlaceholderTexeColor;
  CDuiString m_sPlaceholderText;

void CEditUI::SetPlaceholderText(LPCTSTR pstrText)
  {
    if (m_sPlaceholderText == pstrText) return;
    m_sPlaceholderText = pstrText;
    if (m_sText.IsEmpty())
    {
      Invalidate();
    }
  }

  void CEditUI::SetPlaceholderTextColor(DWORD dwColor)
  {
    if (m_dwPlaceholderTexeColor == dwColor) return;
    m_dwPlaceholderTexeColor = dwColor;
    if (m_sText.IsEmpty())
    {
      Invalidate();
    }
  }

重写paintText实现：

void CEditUI::PaintText(HDC hDC)
  {
    if( m_dwTextColor == 0 ) m_dwTextColor = m_pManager->GetDefaultFontColor();
    if( m_dwDisabledTextColor == 0 ) m_dwDisabledTextColor = m_pManager->GetDefaultDisabledColor();

    if (m_sText.IsEmpty() && m_sPlaceholderText.IsEmpty()) return;
    
    DWORD dwTextColor = m_sText.IsEmpty() ? m_dwDisabledTextColor : m_dwTextColor;
    CDuiString drawText = m_sText.IsEmpty() ? m_sPlaceholderText : m_sText;
    CDuiString sText = drawText;
    if (m_bPasswordMode && !m_sText.IsEmpty()) {
      sText.Empty();
      LPCTSTR p = drawText.GetData();
      while( *p != _T('\0') ) {
        sText += m_cPasswordChar;
        p = ::CharNext(p);
      }
    }

    RECT rc = m_rcItem;
    rc.left += m_rcTextPadding.left;
    rc.right -= m_rcTextPadding.right;
    rc.top += m_rcTextPadding.top;
    rc.bottom -= m_rcTextPadding.bottom;
    if( IsEnabled() ) {
      CRenderEngine::DrawText(hDC, m_pManager, rc, sText, dwTextColor, \
        m_iFont, DT_SINGLELINE | m_uTextStyle);
    }
    else {
      CRenderEngine::DrawText(hDC, m_pManager, rc, sText, m_dwDisabledTextColor, \
        m_iFont, DT_SINGLELINE | m_uTextStyle);

    }
  }

实现属性设置：SetAttribute

else if (_tcscmp(pstrName, _T("placeholdertext")) == 0) SetPlaceholderText(pstrValue);
    else if (_tcscmp(pstrName, _T("placeholdertextcolor")) == 0) {
      if (*pstrValue == _T('#')) pstrValue = ::CharNext(pstrValue);
      LPTSTR pstr = NULL;
      DWORD clrColor = _tcstoul(pstrValue, &pstr, 16);
      SetPlaceholderTextColor(clrColor);
    }
    else CLabelUI::SetAttribute(pstrName, pstrValue);

使用：

<Edit name="pass_word" font="6" placeholdertextcolor="#ff9999a9" placeholdertext="请输入身份证号码" bkcolor="#fff2f2f4" nativebkcolor="#fff2f2f4" maxchar="64" padding="3,3,3,3"/>