Transparent Edit Using a Pattern Background Brush

While working on a project that needed a transparent edit control, I found an article from Duncan Weir on this Web site about editor background colors. To see the article, click here

In this article, to make an editor transparent, a NULL_BRUSH was created and returned from the OnCtlColor message handler. This idea was very simple, but when I tried to use it, I found that the blue rectangle of text selection remained in the background after the text was unselected.

So, instead of creating a NULL_BRUSH, I created a pattern brush by using a chunk of bitmap from where the edit control is going to be shown. That is, instead of using this:

void CInPlaceEdit::PrepareBackground( CRect pos )
{
   m_Brush.GetStockObject(NULL_BRUSH);
}

I did this instead:

void CInPlaceEdit::PrepareBackground( CRect pos )
{
   CClientDC thisDC( this );
   CClientDC parentDC( GetParent() );
   CDC thisMem;

   INT OldParentMapMode = parentDC.SetMapMode( MM_LOENGLISH );

   CBitmap* pOldThisBmp;

   thisMem.CreateCompatibleDC( &thisDC );
   INT OldThisMapMode = thisMem.SetMapMode( MM_LOENGLISH );

   CSize sz = pos.Size();

   m_Background.DeleteObject();
   m_Background.CreateCompatibleBitmap( &thisDC, sz.cx, -sz.cy );

   pOldThisBmp = thisMem.SelectObject( &m_Background );

   thisMem.BitBlt( 0, 0, sz.cx, sz.cy, &parentDC, pos.left,
                   pos.top, SRCCOPY );

   thisMem.SetMapMode( OldThisMapMode );
   thisMem.SelectObject( pOldThisBmp );

   parentDC.SetMapMode( OldParentMapMode );

   m_Brush.DeleteObject();

   m_Brush.CreatePatternBrush( &m_Background );
   if ( m_Brush.m_hObject != NULL )
      m_Brush.UnrealizeObject();
}

and then this:

HBRUSH CInPlaceEdit::CtlColor(CDC* pDC, UINT nCtlColor)
{
   pDC->SelectObject( &m_Brush );

   pDC->SetBrushOrg( 0, 0 );

   pDC->SetBkMode(TRANSPARENT);

   return (HBRUSH)m_Brush;
}
Note: The PrepareBackgound method must be called before showing the edit control. I have created an small sample application to ilustrate that approach. See the code for details.

I hope this can help somebody.

Thanks.



Downloads

Comments

Leave a Comment
  • Your email address will not be published. All fields are required.

Top White Papers and Webcasts

  • Hybrid cloud platforms need to think in terms of sweet spots when it comes to application platform interface (API) integration. Cloud Velocity has taken a unique approach to tight integration with the API sweet spot; enough to support the agility of physical and virtual apps, including multi-tier environments and databases, while reducing capital and operating costs. Read this case study to learn how a global-level Fortune 1000 company was able to deploy an entire 6+ TB Oracle eCommerce stack in Amazon Web …

  • Live Event Date: August 20, 2014 @ 1:00 p.m. ET / 10:00 a.m. PT When you look at natural user interfaces as a developer, it isn't just fun and games. There are some very serious, real-world usage models of how things can help make the world a better place – things like Intel® RealSense™ technology. Check out this upcoming eSeminar and join the panel of experts, both from inside and outside of Intel, as they discuss how natural user interfaces will likely be getting adopted in a wide variety …

Most Popular Programming Stories

More for Developers

Latest Developer Headlines

RSS Feeds