Managing Window Z-Order Like Photoshop CS

Question

So I've got an application whose window behavior I would like to behave more like Photoshop CS. In Photoshop CS, the document windows always stay behind the tool windows, but are still top level windows. For MDI child windows, since the document window is actually a child, you can't move it outside of the main window. In CS, though, you can move your image to a different monitor fine, which is a big advantage over docked applications like Visual Studio, and over regular MDI applications.

Anyway, here's my research so far. I've tried to intercept the WM_MOUSEACTIVATE message, and use the DeferWindowPos commands to do my own ordering of the window, and then return MA_NOACTIVATEANDEAT, but that causes the window to not be activated properly, and I believe there are other commands that "activate" a window without calling WM_MOUSEACTIVATE (like SetFocus() I think), so that method probably won't work anyway.

I believe Windows' procedure for "activating" a window is 1. notify the unactivated window with the WM_NCACTIVATE and WM_ACTIVATE messages 2. move the window to the top of the z-order (sending WM_POSCHANGING, WM_POSCHANGED and repaint messages) 3. notify the newly activated window with WM_NCACTIVATE and WM_ACTIVATE messages.

It seems the cleanest way to do it would be to intercept the first WM_ACTIVATE message, and somehow notify Windows that you're going to override their way of doing the z-ordering, and then use the DeferWindowPos commands, but I can't figure out how to do it that way. It seems once Windows sends the WM_ACTIVATE message, it's already going to do the reordering its own way, so any DeferWindowPos commands I use are overridden.

Right now I've got a basic implementation quasy-working that makes the tool windows topmost when the app is activated, but then makes them non-topmost when it's not, but it's very quirky (it sometimes gets on top of other windows like the task manager, whereas Photoshop CS doesn't do that, so I think Photoshop somehow does it differently) and it just seems like there would be a more intuitive way of doing it.

Anyway, does anyone know how Photoshop CS does it, or a better way than using topmost?

Answer 1

I would imagine they've, since they're not using .NET, rolled their own windowing code over the many years of its existence and it is now, like Amazon's original OBIDOS, so custom to their product that off-the-shelf (aka .NET's MDI support) just aren't going to come close.

I don't like answering without a real answer, but likely you'd have to spend a lot of time and effort to get something similar if Photoshop-like is truly your goal. Is it worth your time? Just remember many programmers over many years and versions have come together to get Photoshop's simple-seeming windowing behavior to work just right and to feel natural to you.

It looks like you're already having to delve pretty deep into Win32 API functions and values to even glimpse at a "solution" and that should be your first red flag. Is it eventually possible? Probably. But depending on your needs and your time and a lot of other factors only you could decide, it may not be practical.

Answer 2

Not being familiar to Photoshop CS it is bit hard to know exactly what look and feel you are trying to achieve.

But I would have thought if you created a modeless dialog window as you tool window and you made sure it had the WS_POPUP style then the resulting tool window would not be clipped to the main parent window and Windows would automatically manage the z-Order making sure that the tool window stayed on top of the parent window.

And as the tool window dialog is modeless it would not interfere with the main window.

Answer 3

http://stackoverflow.com/questions/153685/managing-window-z-order-like-photoshop-cs#160862

You should create the toolwindow with the image as the parent so that windows manage the zorder. There is no need to set WS_POPUP or WS_EX_TOOLWINDOW. Those flags only control the rendering of the window.

Call CreateWindowEx with the hwnd of the image window as the parent.

Answer 4

I havn't seen anything remarkable about Photoshop CS that requries anything close to this level of hacking that can't instead be done simply by specifying the correct owner window relationships when creating windows. i.e. any window that must be shown above some other window specifies that window as its owner when being created - if you have multiple document windows, each one gets its own set of owned child windows that you can dynamically show and hide as the document window gains and looses activation.

Answer 5

In reply to Chris and Emmanuel, the problem with using the owner window feature is that a window can only be owned by one other window, and you can't change who owns a window. So if tool windows A and B always need to be on top of document windows C and D, then when doc window C is active, I want it to own windows A and B so that A and B will always be on top of it. But when I activate doc window D, I would have to change ownership of tool windows A and B to D, or else they will go behind window D (since they're owned by window C). However, Windows doesn't allow you to change ownership of a window, so that option isn't available.

For now I've got it working with the topmost feature, but it is a hack at best. I do get some consolation in the fact that GIMP has tried themselves to emulate Photoshop with their version 2.6, but even their implementation occasionally acts quirky, which leads me to believe that their implementation was a hack as well.

Answer 6

Have you tried to make the tool windows topmost when the main window receives focus, and non-topmost when it loses focus? It sounds like you've already started to look at this sort of solution... but much more elaborate.

As a note, it seems to be quite well documented that tool windows exhibit unexpected behavior when it comes to z-ordering. I haven't found anything on MSDN to confirm it, but it could be that Windows manages them specially.