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Splitter Control for Dialog

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29 Sep 2018CPOL5 min read 58.8K   6K   45   13
A splitter control for dialog can auto change the linked window's position

Image 1


Yes, that is another-another splitter control. This control based the control of this (Another splitter control for dialog). I have taken some changes of the origin code to make it much more easy to use. The new splitter-control can auto change the linked control's pos automatically, when the user changes the split-bar. That is it!


I'm working for a GUI application which has many dialogs. But the developer before me makes all of the dialogs fixed size. Sometimes, that is ok. But the others will make the interface be hard to use. I have to move the scroll bar to see the part which be hidden by the fixed sized dialog. When I have a chance to modify it, I decide to make some change. From that time on, I look for a splitter control which can be used in the dialog.

There are many kinds of splitter-control in CodeProject. I like the one which is written by Hung Nguyen very much: Another splitter control for dialog. The commit dialog of the svn uses that one too. When I used this control in many of my application, I found that it has some small problem that I have to call ChangePos function in many places. In other words, it cannot move the relation control automatically. So I make a new one to solve this problem.

Using the Code

Step 1: Add a Picture Control on Your Dialog at the Resource Editor.

Put a picture control on your dialog, give it id IDC_SPLITTER1. Change the size of the control to make it look like a horizontal bar. Double click the control of IDC_SPLITTER1, change the property as below. And then add a vertical one the same way, give it id IDC_SPLITTER2.

Actually, all the operations above just want to make us not calc the splitter size. You can specify the size of the splitter by the CSplitterControl::Create function.

Image 2

Step 2: Add Splitters to the Dialog Class

Add SplitterControl.h and SplitterControl.cpp to your project. Insert #include "splittercontrol.h" to the .h file of the dialog class.

And then, add member variables:

    CSplitterControl    m_wndSplitter1;
    CSplitterControl    m_wndSplitter2;

In the function of OnInitDialog, create the splitters.

There are some notices here:

  • Use SPS_VERTICAL or SPS_HORIZONTAL to special the splitter style.
  • You can special a RGB color (the default id RGB(120, 120, 120)) for the splitter line.
  • You can special the splitter line width (the default is 1).
  • The width(SPS_VERTICAL) or height(SPS_HORIZONTAL) of the splitter depend on the width of rect when you call Create function.
BOOL CSplitterControlDemoDlg::OnInitDialog()

    //  Here, I ignore some code we not care about.
    //  You can reference the sample code for details.

    CRect rc;
    CWnd* pWnd;

    pWnd = GetDlgItem(IDC_SPLITTER1);
    BOOL bRet = m_wndSplitter1.Create(WS_CHILD | WS_VISIBLE, rc, 
                this, IDC_SPLITTER1, SPS_VERTICAL|SPS_DELTA_NOTIFY);//, RGB(255, 0, 0));
    if (FALSE == bRet)
        AfxMessageBox("m_wndSplitter1 create failed");

    pWnd = GetDlgItem(IDC_SPLITTER2);
    bRet = m_wndSplitter2.Create(WS_CHILD | WS_VISIBLE, rc, 
           this, IDC_SPLITTER2, SPS_HORIZONTAL, RGB(0, 0, 255));
    if (FALSE == bRet)
        AfxMessageBox("m_wndSplitter2 create failed");

Step 3: Add Linked Windows

The splitter can move the linked window pos automatically as the user changes the splitter's pos. So we should specify which window needs to change the pos.CSplitterControl::RegisterLinkedWindow function take the work. Check the example below:

//  register windows for splitter
this->m_wndSplitter1.RegisterLinkedWindow(SPLS_LINKED_LEFT,     GetDlgItem(IDC_TREE));
this->m_wndSplitter1.RegisterLinkedWindow(SPLS_LINKED_RIGHT,    GetDlgItem(IDC_LIST));
this->m_wndSplitter1.RegisterLinkedWindow(SPLS_LINKED_RIGHT,    GetDlgItem(IDC_EDIT));
this->m_wndSplitter1.RegisterLinkedWindow(SPLS_LINKED_RIGHT,    &m_wndSplitter2);

this->m_wndSplitter2.RegisterLinkedWindow(SPLS_LINKED_UP,       GetDlgItem(IDC_LIST));
this->m_wndSplitter2.RegisterLinkedWindow(SPLS_LINKED_DOWN,     GetDlgItem(IDC_EDIT));

//  relayout the splitter to make them good look

Remember that SPLS_LINKED_LEFT means the control is on the left side of the splitter. SPLS_LINKED_RIGHT means the right. The two used for the splitter of vertical. If the control linked to a splitter of vertical with SPLS_LINKED_LEFT, that means the right pos of the control will be changed by the splitter. SPLS_LINKED_RIGHT is similar to SPLS_LINKED_LEFT.

SPLS_LINKED_UP and SPLS_LINKED_DOWN as the name means the control will be at the up side of a horizontal splitter.

We have almost finished, after we have linked the controls to the splitter. In order to make the interface look better, we should call CSplitterControl::Relayout function to make the initializing layout. You can call CSplitterControl::Relayout function at any time you need.

Step 4: Splitter's Limit Pos

Usually, we need to set the splitter's moving range. That is not very important in the Document-View based application. But in the dialog based application, we have to process the window's edge ourselves. So, the limit pos of the splitter is very important for dialog based application.

In the sizabled dialog, the limit pos of the splitter is not fixed. Once we change the dialog size, we have to change the new limit pos of the splitter. That is not very good. In my splitter control, they send a notify message to the parent window before you are ready to change the splitter pos every time. So if you want to use this, set the limit pos, just handle the notify message. The notify message is named SPN_MAXMINPOS. There is some sample code here.

Add message handle function in the .h file of the dialog class for the notify message (SPN_MAXMINPOS):

afx_msg void OnMaxMinInfo(NMHDR* pNMHDR, LRESULT* pResult);

Map the message:

BEGIN_MESSAGE_MAP(CSplitterControlDemoDlg, CDialog)
    //  ...
    //  ...

Implement the message handle function:

void CSplitterControlDemoDlg::OnMaxMinInfo(NMHDR* pNMHDR, LRESULT* pResult)
    //  Get current pos of the child controls
    CRect rcTree;
    CRect rcList;
    CRect rcEdit;
    CRect rcCancel;
    //  return the pos limit
    if (IDC_SPLITTER1 == pNMHDR->idFrom)
        pNewMaxMinPos->lMin = rcTree.left + 50;
        pNewMaxMinPos->lMax = rcCancel.left - STD_GAP;
        pNewMaxMinPos->lMin = + 50;
        pNewMaxMinPos->lMax = rcEdit.bottom - 50;

Step 5: Some Special Used Method

Not everything will automatically be ok. The splitter needs us to register all of the linked controls to it when the dialog is initializing. So if a control is not created at that time, we cannot register it to the splitter. So the splitter provided another way to change the pos of these controls. The kernel function is CSplitterControl::ChangePos. This function accepts a parameter dwLinkedSide to specify the control is which side of the splitter. And the lDelta usually is from the notify message SPN_DELTA.

The SPN_DELTA notify message is sent when the user releases the mouse. It is defined in the SplitterControl.h.

//  Notify event : tell the parent to do some special things
//      some times, the parent window can not register the child control for reason 
//      it does not created yet.
//      so, SPN_DELTA event give the parent window a chance to change the child control's pos.
#define SPN_DELTA           (WM_USER + 2)
    NMHDR   hdr;
    LONG    lDelta;

There is some sample code to show how to use this notify message:

Firstly, we need to use the SPS_DELTA_NOTIFY style as we create the splitter.

BOOL bRet = m_wndSplitter1.Create(WS_CHILD | WS_VISIBLE, rc, 

And then, add message maps:

BEGIN_MESSAGE_MAP(CSplitterControlDemoDlg, CDialog)
    //  ...
    ON_NOTIFY(SPN_DELTA,     IDC_SPLITTER1, OnSplitter1Delta)
    //  ...

At last, implement it:

void CSplitterControlDemoDlg::OnSplitter1Delta(NMHDR* pNMHDR, LRESULT* pResult)
    //  this function just want to show you how to use the delta event
    *pResult = 0;

    if (NULL == pDelta)

    m_wndSplitter1.ChangePos(&m_edHelp, SPLS_LINKED_LEFT, pDelta->lDelta);


Thanks to Hung Nguyen and his(or her) article, Another splitter control for dialog and the demo project. That helped me a lot, and my sample code is based on that too. Oh, I'm so lazy.

Points of Interest

The sample way always exists.


  • 2013-05-19: First version


This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

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Comments and Discussions

QuestionIt's already posted before Pin
stevehoang22-Oct-14 11:29
stevehoang22-Oct-14 11:29 
QuestionI have a question Pin
Member 1074734920-Aug-14 18:05
Member 1074734920-Aug-14 18:05 
GeneralNot Work Pin
Member 1020599321-Aug-13 6:24
Member 1020599321-Aug-13 6:24 
QuestionMy Vote of 5,Just what I need in MFC! Pin
Jason.LYJ15-Aug-13 1:42
professionalJason.LYJ15-Aug-13 1:42 
GeneralJust what i needed Pin
Member 1017340525-Jul-13 12:58
Member 1017340525-Jul-13 12:58 
GeneralMy vote of 5 Pin
Ștefan-Mihai MOGA13-Jun-13 20:44
professionalȘtefan-Mihai MOGA13-Jun-13 20:44 
QuestionLooks very simple to use Pin
.dan.g.22-May-13 16:12
professional.dan.g.22-May-13 16:12 
AnswerRe: Looks very simple to use Pin
libbyliugang23-May-13 0:51
libbyliugang23-May-13 0:51 
QuestionGreat work ! Pin
Matth Moestl21-May-13 23:55
professionalMatth Moestl21-May-13 23:55 
QuestionNot able to download demo Pin
P Uday kishore20-May-13 21:05
professionalP Uday kishore20-May-13 21:05 
AnswerRe: Not able to download demo Pin
Marco Bertschi20-May-13 21:30
protectorMarco Bertschi20-May-13 21:30 
GeneralRe: Not able to download demo Pin
P Uday kishore20-May-13 21:36
professionalP Uday kishore20-May-13 21:36 
AnswerRe: Not able to download demo Pin
libbyliugang23-May-13 0:54
libbyliugang23-May-13 0:54 

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