Updating the Z-Order of Many Windows Using Win32 API

Question

The scenario is that I have a list of window handles to top level windows and I want to shift them around so they are arranged in the z-order of my choosing. I started off by iterating the list (with the window I want to end up on top last), calling SetForegroundWindow on each one. This seemed to work some of the time but not always, improving a little when I paused slightly in between each call.

Is there a better way to do this?

Edit:

It looks like the BeginDeferWindowPos/DeferWindowPos/EndDeferWindowPos route is the way to go. However, I can't seem to get it to work with more than one window at a time. When I limit the window list to a single window, it works correctly. When the list has multiple windows, it only seems to get one of them. Here is pseudo code of what I'm doing:

HWND[] windows;
HWND lastWindowHandle = 0;
HDWP positionStructure = BeginDeferWindowPos(windows.length);

for (int i = 0; i < windows.length; i++)
{
    positionStructure = DeferWindowPos(positionStructure, windows[i], 
        lastWindowHandle, 0, 0, 0, 0, SWP_NOMOVE | SWP_NOSIZE);
}

EndDeferWindowPos(positionStructure);

I'm sure it's something small/obvious I'm missing here but I'm just not seeing it.

Anders · Accepted Answer · 2010-07-19 21:05:18Z

13

There is a special set of api's for setting window positions for multiple windows: BeginDeferWindowPos + DeferWindowPos + EndDeferWindowPos (SetWindowPos in a loop will also work of course, but it might have more flicker)

edited Jul 19, 2010 at 21:05

answered Jul 19, 2010 at 18:33

Anders

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3 Comments

Jerry Coffin Over a year ago

+1: this is definitely the better route, especially if you're dealing with a large number of windows.

Greg Shackles Over a year ago

Thanks for the tip, this does seem like the right approach to take. See my edit of the question for the problem I'm running into with it.

Anders Over a year ago

@Greg Shackles: You probably want SWP_NOACTIVATE, and maybe SWP_ASYNCWINDOWPOS

In silico · Accepted Answer · 2010-07-19 15:41:51Z

5

You can use SetWindowPos to order your top-level windows.

// Hypothetical function to get an array of handles to top-level windows
// sorted with the window that's supposed to be topmost at the end of array.
HWND* windows = GetTopLevelWindowsInOrder();
int numWindows = GetTopLevelWindowCount();

for(int i = 0; i < numWindows; ++i)
{
    ::SetWindowPos(windows[i], HWND_TOP, 0, 0, 0, 0, SWP_NOMOVE | SWP_NOSIZE);
}

edited Jul 19, 2010 at 15:41

answered Jul 19, 2010 at 15:23

In silico

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4 Comments

Greg Shackles Over a year ago

Good call, I hadn't noticed that SetWindowPos also had a parameter for z-order. Do you know if this will suffer from the same timing problems I mentioned with SetForegroundWindow?

In silico Over a year ago

Try it and see if it performs better than SetForegroundWindow() :-)

Greg Shackles Over a year ago

I plan on it, I just can't do that until later. Will report back later with the results :)

Adrian McCarthy Over a year ago

SetForegoundWindow does more than change the Z-order. It "activates" the window, which has an effect on things like focus, which requires messages to go flying through the system, which is probably why the timing seemed critical. Use SetWindowPos as In Silico recommends, at least for the first n-1 windows. Depending on what you're trying to achieve, you may want to do SetWindowPos on the final window.

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