"minimize to tray" function - clean programming

I'm currently trying to add a "minimize to tray" function to one of my programs. But I'm usure how the code should work correctly, since currently I'm using a some invalid code (but for some reason it works).

The program uses a DialogBox as main window and works like the pseudo code below (number of function parameters here is NOT correct - it's just pseudo code):

if (cmd = WM_SYSCOMMAND)
{
  if (wParam = SC_MINIMIZE)
  {
// Variant 1
    ShowWindow(SW_HIDE)
    return FALSE

// Variant 2
    ShowWindow(SW_HIDE)
    return TRUE

// Variant 3
    SendMessage(SC_MINIMIZE)
    ShowWindow(SW_HIDE)
    return FALSE

// Variant 4
    DefWindowProc()
    ShowWindow(SW_HIDE)
    return FALSE
  }
}

Variant 1:
The DialogBox vanishes without the default minimizing animation and will not disappear from the taskbar.

Variant 2:
The DialogBox vanishes and is removed from the taskbar, but the minimizing animation is not shown. When restoring the DialogBox from the tray icon by calling ShowWindow(SW_SHOW) and SendMessage(SC_RESTORE), it is visible at once and not restored with the default restore animation. It's no "minimize to tray", but just a "hide to tray" function.

Variant 3:
As you might have guessed, it's an infinite loop.

Variant 4:
The DialogBox is minimized to the taskbar and will be hidden after that. It's exactly what I want. Unhiding and restoring works also like I want it.

The problem is that I'm using "DefWindowProc". It is only a valid call in window procedures, not in dialog box procedures. "DefDlgProc" is also invalid, since it will produce an infinite loop.

How do I code the "minimize to tray" function correctly, so that I'm using "clean" code and not some hack which works for some reason?

One other thing I would like to know it the following:

When disassembling some programs which have the "minimize to tray" function, I saw that many of then compare not "wParam", but "wParam & 0x0000FFF0" to SC_MINIMIZE. According to MSDN, wParam can be only one of the SC_* parameters and not some bitmask. Why would somebody use this code if it's not neccessary?

p.s. 1: I know why Variant 1-3 fails the way I coded it above, so please don't explain me that. But in my oppinion Variant 4 should fail too.

p.s. 2: The programs I disassembled for "minimize to tray" all use Variant 2 ("hide to tray"). For some reason I wasn't able to find the "minimize to tray" code in the programs which really minimize before hiding.