Big problems with MFC/WinAPI

Question

I need to create a SDI form with a formview that has two tabs, which encapsulate multiple dialogs as the tab content. But the form has to have a colored background.

And things like these makes me hate programming.

First, I tried CTabControl, via resource editor, tried different things, but the undocumented behavior and the quirks with no answers led me into a roadblock.

After many hours of searching, I found that there is a control called property sheet, which is actually what I need.

Some more searching later, I found that property sheet can even be actually embedded onto CFormView like so: http://www.codeguru.com/Cpp/controls/propertysheet/article.php/c591

And that the dialog classes derived from CPropertyPage can be directly added as pages via AddPage method of CPropertySheet.

Great! Not quite so... Some of the controls didn't worked, and were not created, ran into weird asserts. Turns out the DS_CONTROL style was missing from the dialogs. Found it completely accidentaly on Link, no word about that on MSDN!!!! Property page must have: DS_3DLOOK | DS_CONTROL | WS_CHILD | WS_TABSTOP, and can have: DS_SHELLFONT | DS_LOCALEDIT | WS_CLIPCHILDREN styles! Not any other, which are created by default with resource editor. Sweet, super hidden information for software developers!

The quote in comments on that page: "OMG. That's where that behavior came from...

It turns out that the PlaySound API relied on that behavior when playing sounds on 64bit machines." by Larry Osterman, who as I understand works for Microsoft for 20 years, got me laughing out loud.

Anyway, fixed that, the dialog-controls(CPropertyPages) are created as expected now, and that part looks something remotely promising, but the next part with color is dead end again!

Normally you override WM_CTLCOLOR, check for control ID or hwnd and supply the necessary brush to set the color you need. Not quite so with CPropertySheet, the whole top row stays gray! For CTabCtrl it somehow works, for CPropertySheet it doesn't.

Why? Seems that the CPropertySheet is kinda embedded inside CTabControl or something, because if I override WM_ERASEBKGND, only the internal part changes the color.

Now it seems that there is a GetTabControl() method in the CPropertySheet, that returns the actual CTabCtrl* of the CPropertySheet. But since it's constructed internally, I can't find how to override it's WM_CTLCOLOR message processing.

There seems to be a way to subclass the windowproc, but after multiple tries I can't find any good source on how to do it. SubclassWindow doc on MSDN says: "The window must not already be attached to an MFC object when this function is called."?! What's that?

I tried creating a custom CCustomTabCtrl class based on CTabCtrl via MFC wizard, created an instance of it, called SubclassWindow from one of the CCustomPropertySheet handlers to override the internal CTabCtrl, but nothing works, mystical crashes deep inside MFC.

Tried setting WindowLong with GCL_HBRBACKGROUND for the internal CTabCtrl, nothing changed.

And worst of all, I can't find any sort of useful documentation or tutorials on the topic.

Most I can find is how to ownerdraw the tab control, but this is seriously wrong on so many ways, I want a standard control behavior minus background color, I don't want to support different color schemes, windows versions, IAccesible interfaces and all this stuff, and none of the ownerdraw samples I've seen can get even 10% of all the standard control behavior right. I have no illusion that I will create something better, I wont with the resources at hand.

I stumbled upon this thread, and I can't agree with the author more: http://arstechnica.com/civis/viewtopic.php?f=20&t=169886&sid=aad002424e80121e514548d428cf09c6 owner draw controls are undocumented PITA, that are impossible to do right, and there is NULL information on MSDN to help.

So is there anything I have missed or haven't tried yet? How to change the top strip background color of the CPropertySheet? Anyone?

Answer 1

Your only option is to ownerdraw the tab control. It's not that hard. Well, it is frustrating because MFC doesn't tell you how to make the necessary Win32 calls.

In your CPropertySheet-derived class, overwrite OnInitDialog() and add:

GetTabControl()->ModifyStyle(0,TCS_OWNERDRAWFIXED);

This puts your CPropertySheet-derived class in charge of drawing the tab control. Add a handler for WM_DRAWITEM (OnDrawItem) and change backgroundColor and textColor to match whatever colors you wanted. Code for OnDrawItem follows:

void CPropSht::OnDrawItem(int nIDCtl, LPDRAWITEMSTRUCT lpDrawItemStruct)
{
    if (ODT_TAB != lpDrawItemStruct->CtlType)
    {
        CPropertySheet::OnDrawItem(nIDCtl, lpDrawItemStruct);
        return;
    }

    // prepare to draw the tab control
    COLORREF backgroundColor = RGB(0,255,0);
    COLORREF textColor = RGB(0,0,255);
    CTabCtrl *c_Tab = GetTabControl();

    //  Get the current tab item text.
    TCHAR buffer[256] = {0};
    TC_ITEM tcItem;
    tcItem.pszText = buffer;
    tcItem.cchTextMax = 256;
    tcItem.mask = TCIF_TEXT;

    if (!c_Tab->GetItem(c_Tab->GetCurSel(), &tcItem )) return;

    // draw it
    CDC aDC;
    aDC.Attach(lpDrawItemStruct->hDC);
    int nSavedDC = aDC.SaveDC();

    CBrush newBrush;
    newBrush.CreateSolidBrush(backgroundColor);
    aDC.SelectObject(&newBrush);
    aDC.FillRect(&lpDrawItemStruct->rcItem, &newBrush);
    aDC.SetBkMode(TRANSPARENT); 
    aDC.SetTextColor(textColor);
    aDC.DrawText(tcItem.pszText, &lpDrawItemStruct->rcItem, DT_CENTER|DT_VCENTER|DT_SINGLELINE);

    aDC.RestoreDC(nSavedDC);

    aDC.Detach();
}

Answer 2

Thank you for this solution but...

The above solution works well with one tab, but when you have multiple tabs it seems rename the wrong tabs. I needed to change the if statement for GetItem to:

if (!c_Tab->GetItem(lpDrawItemStruct->itemID, &tcItem )) return;

Needed lpDrawItemStruct->itemID to get the tabs named correctly