Win32, Tracking data with MDI's

Hey, I posted this in coding forums as well, but with no luck. I'm currently trying to make a program that uses an MDI, but I've hit a deadend :( I can't figure out how to keep track of each set of data, that goes along with the correct MDI child window.

I have a struct that stores information about a document, and an array of these structs, one for each open child window. When a window needs repainting, I want to be able to pull the correct data for the window. I tried giving each struct for the document a handle variable, and testing for it, but to no avail. Somebody suggested about giving the MDI's a new member variable for storing the struct, but I don't have a clue about how to go about that :confused:

If anybody has any advice, or help they can give me, I'd really appreciate it. :D I hope I've explained it enough.

>> I tried giving each struct ... a handle variable ... but to no avail.
That's sounds perfectly reasonable to me. If each struct contains the window handle of the corresponding MDI child, then you'll be able to lookup the correct struct during WM_PAINT messages of the MDI child.

If you can't get that to work, post your code.

If you haven't been through the MDI reference material, read through the "Overviews" links here: http://msdn.microsoft.com/library/de...tinterface.asp

gg

I must be doing something wrong :( I can't get it to work.

Here is the code from the WM_PAINT message:

Code:

---

        // Do tha junk
        PAINTSTRUCT ps;
        HDC                        hdc;

        // simply validate the window
        hdc = BeginPaint(hwnd,&ps);       

        // paint board
        hdc = PaintBoard(hwnd, hdc);

        // end painting
        EndPaint(hwnd,&ps);

---

The PaintBoard function:

Code:

---

HDC PaintBoard(HWND hChild, HDC hdc)
{
        // Get DC
        if(!hdc)
        {
                HDC hdc = GetDC(hChild);
        }

          // Get the right circuit data
        Circuit CircuitData = GetCircuitData(hChild);

        // setup tools
        HBRUSH brush;
        HPEN pen;
                       
        // Paint background
        brush = CreateSolidBrush(CircuitData.bgcolor);
        SelectObject(hdc, brush);
        Rectangle(hdc, 0, 0 , CircuitData.size.width + (DOC_BORDER*2), CircuitData.size.height + (DOC_BORDER*2));

        // Paint Board
        brush = CreateSolidBrush(RGB(0,0,0));
        SelectObject(hdc, brush);
        Rectangle(hdc, DOC_BORDER+5, DOC_BORDER+5, CircuitData.size.width+5, CircuitData.size.height+5);
        brush = CreateSolidBrush(CircuitData.color);
        SelectObject(hdc, brush);
        pen = CreatePen(PS_SOLID, 1, RGB(0,0,0));
        SelectObject(hdc, pen);
        Rectangle(hdc, DOC_BORDER, DOC_BORDER, CircuitData.size.width, CircuitData.size.height);

        // End it
        return hdc;
}

---

The function used within that, to try for the data using the handle:

Code:

---

Circuit GetCircuitData(HWND hTest)
{
        for(int i = 0; i < NumCircuits; i++)
        {
                if(circuits[i].handle == hTest)
                {
                        break;
                }
        }
        // Get the right circuit data
        return circuits[i];
}

---

I have set circuits as a global array of the Circuit structs, and NumCircuits as the number of current windows. Here is the struct:

Code:

---

// A circuit
struct Circuit
{
        HWND handle;
        const char* title;
        const char* began;
        const char* notes;
        const char* todo;
        COLORREF color;
        COLORREF bgcolor;
        Version version;
        Size size;
        Component comps[500];
        Textbox texts[100];
        Wire wires[3000];
};

---

It doesn't seem to supply the right data. The board isn't drawn correctly, and to test it I replaced the break in the handle check loop with a messagebox, and it returned for every window. Cheers

The first thing I notice is that GetCircuitData() is returning the Circuit struct by value. This means that any modifications made to that structure will not be reflected within the global circuits[] array.
Second, your GetCircuitData() function should handle cases where it doesn't find the given HWND:

Code:

---

Circuit* GetCircuitData(HWND hTest)
{
    for (int i = 0; i < NumCircuits; ++i)
    {
        if (circuits[i].handle == hTest)
        {
            return &circuits[i];
        }
    }
   
    const char *msg = "GetCircuitData() failed";
    MessageBoxA(0, msg, msg, MB_OK);

    return 0;
}

---

Having proper error checking in your code will help to track down issues much easier and faster.

If you're still having problems, them post your code that adds to the circuits array (window creation) and removes from the circuits array (windows destruction) along with your modifed GetCircuitData() and any code that calls it.

gg

Wahey, It's working ^_^

Cheers, I used a pointer instead, and fiddled with the handle assigning a bit, and it works like a charm

Cheers, Again Mate, A real saviour :D

watch the possible dangling pointer (should not be a problem) and lost GDI objects in PaintBoard()

(unless you are using a .NET version of MSVC)

Hey, I was wondering if you could help me again. In the WM_PAINT code, when I try to show the title (though GDI or a message box), it messes up the text, and I just get a series of "Ý"'s. The title is a const char* in the struct.

Here's the code I'm using:

Code:

---

          // Get the right circuit data
        Circuit *pCircuitData = GetCircuitData(hChild);

        Circuit CircuitData  = *pCircuitData;

        // setup tools
        HBRUSH brush;
        HPEN pen;
                       
        // Paint background
        brush = CreateSolidBrush(CircuitData.bgcolor);
        SelectObject(hdc, brush);
        Rectangle(hdc, 0, 0 , CircuitData.size.width + (DOC_BORDER*2), CircuitData.size.height + (DOC_BORDER*2));

        // Paint Board
        brush = CreateSolidBrush(RGB(0,0,0));
        SelectObject(hdc, brush);
        Rectangle(hdc, DOC_BORDER+5, DOC_BORDER+5, CircuitData.size.width+5, CircuitData.size.height+5);
        brush = CreateSolidBrush(CircuitData.color);
        SelectObject(hdc, brush);
        pen = CreatePen(PS_SOLID, 1, RGB(0,0,0));
        SelectObject(hdc, pen);
        Rectangle(hdc, DOC_BORDER, DOC_BORDER, CircuitData.size.width, CircuitData.size.height);


        MessageBoxA(0, CircuitData.title, CircuitData.title, MB_OK);

---

I know I've done something wrong because I've came across it before, I just can't remember how I fixed it.

try...

don't
Circuit CircuitData = *pCircuitData;

then just
pCircuitData->title

Nope, still no luck. Still messes up the string. I think it might have been because there is no NULL terminator? but I don't know how to add one, if it is missing.

Let's see the code where you actually set the title member.

gg

Opps, sorry, forgot about that :(

It's taken from a XML file. (Using TinyXMl). This codes gets the title, and sets it:

Code:

---

                // XML
                TiXmlDocument        *xmlDoc = new TiXmlDocument(szFileName);
                if (!xmlDoc->LoadFile())
                {
                        MessageBox(hClient, "XML file load failed.", "Oh Oh...",MB_ICONEXCLAMATION | MB_OK);
                        return 0;
                }

                // Get root
                TiXmlElement* xCircuit = xmlDoc->FirstChildElement("circuit");
                if (!xCircuit)
                {
                        MessageBox(hClient, "XML root circuit element couldn't be found", "Oh Oh...",MB_ICONEXCLAMATION | MB_OK);
                        xmlDoc->Clear();
                        delete xmlDoc;
                        return 0;
                }

                //--- Get doc data --------------------------------------------------//
                TiXmlElement* xDoc = XMLGetElement(xCircuit, "doc");

                // try for the title?
                // IT FOOCKING WELL WORKS!
                TiXmlElement* xTitle = XMLGetElement(xDoc, "title");
                CircuitData.title = XMLStringVal(xTitle);

---

Using this two XML wrapper functions:

Code:

---

//------------------------------------------------------------------------------------//
// XMLGetElement()
//------------------------------------------------------------------------------------//
TiXmlElement* XMLGetElement(TiXmlElement* xParent, const char* ElementName)
{
        TiXmlElement* xElement = xParent->FirstChildElement(ElementName);
        if (!xElement)
        {
                MessageBox(hClient, strcat("XML data couldn't be found for: ", ElementName), "Oh Oh...",MB_ICONEXCLAMATION | MB_OK);
                return 0;
        }
        return xElement;
}
//------------------------------------------------------------------------------------//

//------------------------------------------------------------------------------------//
// XMLStringVal()
//------------------------------------------------------------------------------------//
const char * XMLStringVal(TiXmlElement* xElement)
{
        const char *ElementValue = (xElement->FirstChild())->Value();
        if (!ElementValue)
        {
                MessageBox(hClient, "Error extracting XML string value", "Oh Oh...",MB_ICONEXCLAMATION | MB_OK);
                return 0;
        }
        return ElementValue;
}
//------------------------------------------------------------------------------------//

---

After the title is set in CircuitData.title, the CircuitData struct gets passed to a function to create the doc:

Code:

---

hOpen = MakeNewDoc(hClient, CircuitData);

---

And heres that function:

Code:

---

HWND MakeNewDoc(HWND hClient, Circuit CircuitData)
{
        MDICREATESTRUCT        mcs;
        HWND                        hChild;
       
        // temp
        COLORREF BackgroundColor = DOC_DEF_BGCOLOR;

        mcs.szTitle = CircuitData.title;
        mcs.szClass = CHILD_CLASS_NAME;
        mcs.hOwner  = GetModuleHandle(NULL);
        mcs.x = CW_USEDEFAULT;
        mcs.cx = CircuitData.size.width + (DOC_BORDER*2);
        mcs.y = CW_USEDEFAULT;
        mcs.cy = CircuitData.size.height + (DOC_BORDER*2) + 25; // +25 for title bar etc..
        mcs.style = MDIS_ALLCHILDSTYLES;
        mcs.lParam = NumCircuits;

        hChild = (HWND)SendMessage(hClient, WM_MDICREATE, 0, (LONG)&mcs);
        if(!hChild)
        {
                MessageBox(hClient, "MDI Child creation failed.", "Oh Oh...",MB_ICONEXCLAMATION | MB_OK);
        }

        // Add to circuit count
        CircuitData.handle = hChild;
        circuits[NumCircuits] = CircuitData;
        NumCircuits++;

        return hChild;
}

---

Now setting the Window title using the CircuitData.title works there, but in the WM_PAINT, when I call the PaintBoard function above, the title is messed up.

EDIT: And heres the function I call to get the circuit data in WM_PAINT:

Code:

---

Circuit* GetCircuitData(HWND hTest)
{
    for (int i = 0; i < NumCircuits; ++i)
    {
        if (circuits[i].handle == hTest)
        {
            return &circuits[i];
        }
    }
   
    const char *msg = "GetCircuitData() failed";
    MessageBoxA(0, msg, msg, MB_OK);

    return 0;
}
//------

---

Cheers

>> const char *ElementValue = (xElement->FirstChild())->Value();
The string returned by the TiXmlNode::Value() method is only valid for the lifetime of the TiXmlNode object. And it may not even be valid for that long - I'm not familiar with tiny xml.

You need to create and manage your own buffers for your Circuit structure strings or just use std::string.

gg

Wahey, You're right, I wasn't aware about lifetimes. I've managed now, by removing the code that kills the XML object, but I'll have to look into my own buffer as you said (not really sure about that at the mo).

Cheers ^_^