GetScrollInfo returns nothing on SB_PAGELEFT

Hi everyone,

I have searched the forum but found nothing related to my problem.

I'm using a horizontal scroll bar in a dialog box. I want to process SB_PAGELEFT message.
When WM_HSCROLL arrives mesage i check LOWORD(wParam) and if it is SB_PAGELEFT i'm trying to get position of a scroll bar. But GetScrollInfo returns nothing.

Here is the source:

Code:

---

HWND slider = GetDlgItem(hwndDlg,IDC_SLIDER);
SCROLLINFO info;
ZeroMemory(&info,sizeof(info));
info.cbSize = sizeof(SCROLLINFO);
info.fMask = SIF_ALL;
GetScrollInfo(slider,SB_CTL,&info);
SetDlgItemInt(hwndDlg,IDC_EDIT1,info.nPos,false);

---

info.nPos is invalid.

On SB_THUMBPOSITION I'm using HIWORD(wParam) as a position of a scroll bar. Why i can't get the same on SB_PAGELEFT is a big mystery to me.

Because, according to the MSDN for the SB_PAGELEFT message:

Quote:

---

Parameters

wParam

The HIWORD specifies the current position of the scroll box if the LOWORD is SB_THUMBPOSITION or SB_THUMBTRACK; otherwise, this word is not used.

---

Viggy

And, according to the MSDN for GetScrollInfo, I don't see an SIF_ALL mask. Have you tried just passing the SIF_POS mask?

Viggy

Yeah, i have change my code to SIF_POS and still GetScrollInfo returns nothing. No Errors as well.

Code:

---

        case SB_PAGELEFT:
                {       
                        HWND slider = GetDlgItem(hwndDlg,IDC_SLIDER);
                        SCROLLINFO info;
                        ZeroMemory(&info,sizeof(info));
                        info.cbSize = sizeof(SCROLLINFO);
                        info.fMask = SIF_POS;
                        GetScrollInfo(slider,SB_CTL,&info);
                        SetDlgItemInt(hwndDlg,IDC_EDIT1,info.nPos,false);
                }
                break;

---

Quote:

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Originally Posted by Sh@dow

GetScrollInfo returns nothing. No Errors as well.

---

Define "nothing". What is the exact return value of GetScrollInfo? If it is zero then you should call GetLastError to get extended error information. :cool:

The structure is initialized to 0 before call. After GetScrollInfo the structure is the same as before calling GetScrollInfo. GetScrollInfo returns 1. GetLastError returns 0. So it seems everything is fine but i can't see any value in the structure.

It has no sense to call GetScrollInfo for a trackbar (slider) control, because... it has not a scrollbar. :)
Instead, send TBM_xxx messages.

Example

Code:

---

  case TB_PAGEUP:
      {
        int nMinPos = ::SendMessage(hWndSlider, TBM_GETRANGEMIN, 0, 0);
        int nMaxPos = ::SendMessage(hWndSlider, TBM_GETRANGEMAX, 0, 0);
        int nPos = ::SendMessage(hWndSlider, TBM_GETPOS, 0, 0);

        // ...
      }

---

For more info, see Trackbar.

[ later edit ]
I guess, this topic is about a slider and not about a scrollbar control, given the ID name IDC_SLIDER.

>>I guess, this topic is about a slider and not about a scrollbar control, given the ID name IDC_SLIDER.

That is my mistake. I mixed this two different things.
Thanks ovidiucucu for help.