Is the origin reset...

...to 0,0 when the window is resized?

I'm learning windows programming and I'm working on a practice program that uses scroll bars. The only problem is that when the window is resized, the view shifts back to the upper left corner instead of remaining where it was scrolled to. After reviewing my program several times (becoming more and more frustrated), the only thing I can come up with is that Windows resets the origin to 0,0. Is this true, or do I need to keep looking for a problem in my program? I've looked around for some sort of documentation that says Yes or No but I've come up empty.

Thanks,
fletch

Why don't you post some of the code so we can see what is going on.

- Sean

Sorry, all of you hardcore API programmers - it's MFC :)
Here are the portions I believe to be applicable: the OnSize and OnPaint message handlers.

Code:

---

void RulerMainWindow::OnSize(UINT nType, int cx, int cy)
{
        SCROLLINFO        ScrollBarData;
        CClientDC        RulerWindow(this);
        CPoint                Origin = RulerWindow.GetWindowOrg();

// Using debug, I've determined that Origin.x and
// Origin.y both equal 0 at this point

        if (cx < 1400)        // If insufficient horizontal space, create scroll bar
        {
                ScrollBarData.fMask = SIF_ALL;
                ScrollBarData.nMin = 0;
                ScrollBarData.nMax = 1399;
                ScrollBarData.nPage = cx;
                ScrollBarData.nPos = Origin.x;
                SetScrollInfo(SB_HORZ, &ScrollBarData, TRUE);
        }
        else                // If too much horizontal space, no scroll bar for you!
        {
                ScrollBarData.fMask = SIF_RANGE;
                ScrollBarData.nMin = 0;
                ScrollBarData.nMax = 0;
                SetScrollInfo(SB_HORZ, &ScrollBarData, TRUE);
        }

        if (cy < 300)        // If insufficient vertical space
        {
                ScrollBarData.fMask = SIF_ALL;
                ScrollBarData.nMin = 0;
                ScrollBarData.nMax = 299;
                ScrollBarData.nPage = cy;
                ScrollBarData.nPos = (Origin.y * -1);
                SetScrollInfo(SB_VERT, &ScrollBarData, TRUE);
        }
        else                // If too much vertical space
        {
                ScrollBarData.fMask = SIF_RANGE;
                ScrollBarData.nMin = 0;
                ScrollBarData.nMax = 0;
                SetScrollInfo(SB_VERT, &ScrollBarData, TRUE);
        }
}

---

Code:

---

void RulerMainWindow::OnPaint()
{
        int                Counter;
        CPaintDC        RulerWindow(this);                       
        CBrush                RulerBrush(RGB(255,255,0));       
        CString                RulerText;
        SCROLLINFO        ScrollBarData;
        CPoint                Origin;

        RulerWindow.SetMapMode(MM_LOENGLISH);        // Change logical mapping mode
        RulerWindow.SelectObject(&RulerBrush);        // Set yellow brush
        RulerWindow.SetBkMode(TRANSPARENT);        // Set background to transparent
        RulerWindow.SetTextAlign(TA_CENTER | TA_BOTTOM);

        GetScrollInfo(SB_VERT, &ScrollBarData, SIF_ALL);  // Get positional data from scroll bars
        Origin.y = (ScrollBarData.nPos * -1);
        GetScrollInfo(SB_HORZ, &ScrollBarData, SIF_ALL);
        Origin.x = ScrollBarData.nPos;
        RulerWindow.SetWindowOrg(Origin);            // and move origin


        RulerWindow.Rectangle(100, -100, 1300, -200);
// A whole bunch of drawing that I removed for space
}

---

I remarked in the OnSize message handler where I've used debug to determine the value of Origin. That's the chief reason why I think that Windows resets the origin when the window is resized.
If you want more code, I'll upload the whole thing. Thanks again.

fletch

Quote:

---

...the only thing I can come up with is that Windows resets the origin to 0,0. Is this true...?

---

Yes.

That's what I figured, but I couldn't find it written down, so I decided to ask the professionals before I worked around it.

Anyways, I modified my program and it now works like a champ.

Thanks,
fletch