ScrollBar issue

[qhimq]

Hi windows API programmers,

I'm so close to making my vertical scrollbar to work properly, except for:

After pushing or dragging the scrollbar the window scrolls properly until I let go of the mouse. When I let go the window scrolls another unit to which I don't want to happen. I want to have the scrollbar place the window where it was set rather than 1 unit up or down.

Another odd thing is the WM_VSCROLL message is called once when the mouse is down and once when the mouse is up. I think if I can make it only call it for mousedown then it would fix this problem.


Suggestions? Thanks.

case WM_VSCROLL:
{
    int nScrollCode = (int)LOWORD(wParam);
    int nPos = (short int)HIWORD(wParam);
    controlVbar(nScrollCode, nPos);
 
    if(curScrollPos!=oldScrollPos && curScrollPos > 0 && curScrollPos < 100)
    {
        ScrollWindowEx(hwndMain, 0, oldScrollPos-curScrollPos, NULL, NULL, NULL, NULL, SW_SCROLLCHILDREN);
        RedrawWindow(hwndMain, NULL, NULL, RDW_ERASE | RDW_INVALIDATE );
 
    }
}    
break;
 

The following is the controlVbar function called from the above line 5.

void mainWindow::controlVbar(int nScrollCode, int nPos)
{
 
    switch (nScrollCode)
    {
        // Include code that checks for other values of nScrollCode.
        // ...
        case SB_THUMBTRACK:
        {
            oldScrollPos=curScrollPos;
            curScrollPos=nPos;
            SetScrollPos(hwndMain, SB_VERT, nPos, TRUE);
        }
        break;
 
        case SB_LINEUP:
        {
            if(curScrollPos > 0)
            {
                oldScrollPos=curScrollPos;
                curScrollPos=oldScrollPos-1;
            }
            SetScrollPos(hwndMain, SB_VERT, curScrollPos, TRUE);
        }
        break;
 
        case SB_LINEDOWN:
        {
            oldScrollPos=curScrollPos;
            if(curScrollPos < 100)
            {
                oldScrollPos=curScrollPos;
                curScrollPos=oldScrollPos+1;
            }
            SetScrollPos(hwndMain, SB_VERT, curScrollPos, TRUE);
        }
        break;
 
    }
 
 
}
 

[qhimq]

to complete this with an answer I figured out:

first make 3 global int

int oldScrollPos=0;
int curScrollPos=1;
int lastScroll;
 

Then add these functions:

void msWheel(HWND hwnd, int zDelta)
{
    if(zDelta > 0)
        zDelta=120;
    else
        zDelta=-120;
 
    oldScrollPos=curScrollPos;
    if(curScrollPos <= 680 && zDelta < 0)
        curScrollPos+=120;
    else if(curScrollPos > 680 && zDelta < 0)
        curScrollPos=799;
 
    if(curScrollPos > 120 && zDelta > 0)
        curScrollPos+=-120;
    else if(curScrollPos < 120 && zDelta > 0)
        curScrollPos=1;
 
    SetScrollPos(hwnd, SB_VERT, curScrollPos, TRUE);
 
    if(curScrollPos!=lastScroll && curScrollPos > 0 && curScrollPos < 800)
    {
        ScrollWindowEx(hwnd, 0, oldScrollPos-curScrollPos,
                        NULL, NULL, NULL, NULL, SW_SCROLLCHILDREN);
        RedrawWindow(hwnd, NULL, NULL, RDW_ERASE | RDW_INVALIDATE );//| RDW_ALLCHILDREN
 
        lastScroll=curScrollPos;
 
    }
 
}
 
void controlVbar(int nScrollCode, int nPos, HWND hwnd)
{
 
    switch (nScrollCode)
    {
        // Include code that checks for other values of nScrollCode.
        // ...
        case SB_THUMBTRACK:
        {
            oldScrollPos=curScrollPos;
            curScrollPos=nPos;
            SetScrollPos(hwnd, SB_VERT, nPos, TRUE);
        }
        break;
 
        case SB_LINEUP:
        {
            if(curScrollPos > 0)
            {
                oldScrollPos=curScrollPos;
                if(curScrollPos > 10)
                    curScrollPos=oldScrollPos-10;
                else
                    curScrollPos=1;
            }
            SetScrollPos(hwnd, SB_VERT, curScrollPos, TRUE);
        }
        break;
 
        case SB_LINEDOWN:
        {
            oldScrollPos=curScrollPos;
            if(curScrollPos < 800)
            {
                oldScrollPos=curScrollPos;
                curScrollPos=oldScrollPos+10;
            }
            SetScrollPos(hwnd, SB_VERT, curScrollPos, TRUE);
        }
        break;
 
    }
 
            if(curScrollPos!=lastScroll && curScrollPos > 0 && curScrollPos < 800)
            {
                ScrollWindowEx(hwnd, 0, oldScrollPos-curScrollPos,
                                NULL, NULL, NULL, NULL, SW_SCROLLCHILDREN);
                RedrawWindow(hwnd, NULL, NULL, RDW_ERASE | RDW_INVALIDATE );//| RDW_ALLCHILDREN
 
                lastScroll=curScrollPos;
            }
 
 
}
 

Then to call those functions add these cases in your CALLBACK switch:

case WM_VSCROLL:
    {
        int nScrollCode = (int)LOWORD(wParam);
        int nPos = (short int)HIWORD(wParam);//short int?
        controlVbar(nScrollCode, nPos, hwnd);
    }
        break;
    case WM_MOUSEWHEEL:
        msWheel(hwnd, GET_WHEEL_DELTA_WPARAM(wParam));
 
 
    break;
 

[qhimq]

To create the scrollbar I added the vertical scrollbar style on the parent dialog.

then did this code in the main:

SCROLLINFO si = {sizeof(SCROLLINFO), 
            SIF_PAGE|SIF_POS|SIF_RANGE|SIF_TRACKPOS, 1, 799, 0, 0, 
            0};
    SetScrollInfo (hwnd, SB_VERT, &si, TRUE);