MFC window scroll bar usage

    Hello friends , I haven't updated my official account for several days , Because Wenzi went home to eat zongzi .

     Today I want to share with you the usage of a window scroll bar . You'll wonder what a scroll bar is ？ A scroll bar is a scrollable bar , As shown in the figure ：

    

     This is the scroll bar , So what's its function ？ You can think about a fixed size interface , You have a lot of space , When there is no gap in the interface , At this time, you need a scroll bar to help expand the interface , Don't say anything , Look at the renderings first ：

     This is the effect of not using the interface scroll bar , We can see that there are 24 Button , this 24 Buttons are fixed , Then the width and height of the interface are fixed , Next, let's take a look at the renderings with scrollbars ：

     You can see the horizontal scroll bar and vertical scroll bar appear on the interface , You can pull the scroll bar up and down to expand the interface vertically , You can also pull the scroll bar left and right to expand the interface horizontally . however , One problem is ： When you pull the scroll bar , The interface is unresponsive , It is because our code does not add the event function of the scroll bar , You need to add the response function of the scroll bar in the code of this interface .

The way to add a scroll bar to the interface is ：

1. Select interface ;

2. Click interface properties , Put... In the attribute “ Vertical scroll bar ” and “ Horizontal scroll bar ” All set to True;

Then select the class of this interface in the class view , Then right-click properties , Then select the message in the attribute , Look in the message WM_HSCROLL and WM_VSCROLL, Add these two event functions ：

Then add the following code to these two time functions ：

• 
   

void CceshiDlg::OnHScroll(UINT nSBCode, UINT nPos, CScrollBar* pScrollBar)
{
  // TODO:  Add message handler code and / Or call the default value 
​
  CDialog::OnHScroll(nSBCode, nPos, pScrollBar);
  SCROLLINFO scrollinfo;
  GetScrollInfo(SB_HORZ, &scrollinfo, SIF_ALL);
  //
  switch (nSBCode)
  {
  case SB_LEFT:
    ScrollWindow((scrollinfo.nPos - scrollinfo.nMin) * 10, 0);
    scrollinfo.nPos = scrollinfo.nMin;
    SetScrollInfo(SB_HORZ, &scrollinfo, SIF_ALL);
    break;
  case SB_RIGHT:
    ScrollWindow((scrollinfo.nPos - scrollinfo.nMax) * 10, 0);
    scrollinfo.nPos = scrollinfo.nMax;
    SetScrollInfo(SB_HORZ, &scrollinfo, SIF_ALL);
    break;
  case SB_LINELEFT:
    scrollinfo.nPos -= 1;
    if (scrollinfo.nPos < scrollinfo.nMin)
    {
      scrollinfo.nPos = scrollinfo.nMin;
      break;
    }
    SetScrollInfo(SB_HORZ, &scrollinfo, SIF_ALL);
    ScrollWindow(10, 0);
    break;
  case SB_LINERIGHT:
    scrollinfo.nPos += 1;
    if (scrollinfo.nPos > scrollinfo.nMax)
    {
      scrollinfo.nPos = scrollinfo.nMax;
      break;
    }
    SetScrollInfo(SB_HORZ, &scrollinfo, SIF_ALL);
    ScrollWindow(-10, 0);
    break;
  case SB_PAGELEFT:
    scrollinfo.nPos -= 5;
    if (scrollinfo.nPos < scrollinfo.nMin)
    {
      scrollinfo.nPos = scrollinfo.nMin;
      break;
    }
    SetScrollInfo(SB_HORZ, &scrollinfo, SIF_ALL);
    ScrollWindow(10 * 5, 0);
    break;
  case SB_PAGERIGHT:
    scrollinfo.nPos += 5;
    if (scrollinfo.nPos > scrollinfo.nMax)
    {
      scrollinfo.nPos = scrollinfo.nMax;
      break;
    }
    SetScrollInfo(SB_HORZ, &scrollinfo, SIF_ALL);
    ScrollWindow(-10 * 5, 0);
    break;
  case SB_THUMBPOSITION:
    break;
  case SB_THUMBTRACK:
    ScrollWindow((scrollinfo.nPos - nPos) * 10, 0);
    scrollinfo.nPos = nPos;
    SetScrollInfo(SB_HORZ, &scrollinfo, SIF_ALL);
    break;
  case SB_ENDSCROLL:
    break;
  }
}
​
​
void CceshiDlg::OnVScroll(UINT nSBCode, UINT nPos, CScrollBar* pScrollBar)
{
  // TODO:  Add message handler code and / Or call the default value 
​
  CDialog::OnVScroll(nSBCode, nPos, pScrollBar);
  SCROLLINFO scrollinfo;
  GetScrollInfo(SB_VERT, &scrollinfo, SIF_ALL);
  switch (nSBCode)
  {
  case SB_LINEUP:          //Scroll one line up
    scrollinfo.nPos -= 1;
    if (scrollinfo.nPos < scrollinfo.nMin)
    {
      scrollinfo.nPos = scrollinfo.nMin;
      break;
    }
    SetScrollInfo(SB_VERT, &scrollinfo, SIF_ALL);
    ScrollWindow(0, 10);
    break;
  case SB_LINEDOWN:           //Scroll one line down
    scrollinfo.nPos += 1;
    if (scrollinfo.nPos + scrollinfo.nPage > scrollinfo.nMax)  // Be sure to add the length of the slider here , Judge again 
    {
      scrollinfo.nPos = scrollinfo.nMax;
      break;
    }
    SetScrollInfo(SB_VERT, &scrollinfo, SIF_ALL);
    ScrollWindow(0, -10);
    break;
  case SB_PAGEUP:            //Scroll one page up.
    scrollinfo.nPos -= 5;
    if (scrollinfo.nPos <= scrollinfo.nMin)
    {
      scrollinfo.nPos = scrollinfo.nMin;
      break;
    }
    SetScrollInfo(SB_VERT, &scrollinfo, SIF_ALL);
    ScrollWindow(0, 10 * 5);
    break;
  case SB_PAGEDOWN:        //Scroll one page down        
    scrollinfo.nPos += 5;
    if (scrollinfo.nPos + scrollinfo.nPage >= scrollinfo.nMax)  // Be sure to add the length of the slider here , Judge again 
    {
      scrollinfo.nPos = scrollinfo.nMax;
      break;
    }
    SetScrollInfo(SB_VERT, &scrollinfo, SIF_ALL);
    ScrollWindow(0, -10 * 5);
    break;
  case SB_ENDSCROLL:      //End scroll     
    break;
  case SB_THUMBPOSITION:  //Scroll to the absolute position. The current position is provided in nPos
    break;
  case SB_THUMBTRACK:                  //Drag scroll box to specified position. The current position is provided in nPos
    ScrollWindow(0, (scrollinfo.nPos - nPos) * 10);
    scrollinfo.nPos = nPos;
    SetScrollInfo(SB_VERT, &scrollinfo, SIF_ALL);
    break;
  }
}
​

After adding, you can see the effect of the interface as shown in the following figure ：

​

That is, the scroll bar can be pulled at will , The interface can be expanded horizontally and vertically .