What determines the monitor my app runs on?

Question

Here's what I've found. If you want an app to open on your secondary monitor by default do the following:

1. Open the application.
2. Re-size the window so that it is not maximized or minimized.
3. Move the window to the monitor you want it to open on by default.
4. Close the application.  Do not re-size prior to closing.
5. Open the application.
   It should open on the monitor you just moved it to and closed it on.
6. Maximize the window.

The application will now open on this monitor by default. If you want to change it to another monitor, just follow steps 1-6 again.

Correctly written Windows apps that want to save their location from run to run will save the results of GetWindowPlacement() before shutting down, then use SetWindowPlacement() on startup to restore their position.

Frequently, apps will store the results of GetWindowPlacement() in the registry as a REG_BINARY for easy use.

The WINDOWPLACEMENTroute has many advantages over other methods:

• Handles the case where the screen resolution changed since the last run: SetWindowPlacement() will automatically ensure that the window is not entirely offscreen
• Saves the state (minimized/maximized) but also saves the restored (normal) size and position
• Handles desktop metrics correctly, compensating for the taskbar position, etc. (i.e. uses "workspace coordinates" instead of "screen coordinates" -- techniques that rely on saving screen coordinates may suffer from the "walking windows" problem where a window will always appear a little lower each time if the user has a toolbar at the top of the screen).

Finally, programs that handle window restoration properly will take into account the nCmdShow parameter passed in from the shell. This parameter is set in the shortcut that launches the application (Normal, Minimized, Maximize):

if(nCmdShow != SW_SHOWNORMAL)
    placement.showCmd = nCmdShow; //allow shortcut to override

For non-Win32 applications, it's important to be sure that the method you're using to save/restore window position eventually uses the same underlying call, otherwise (like Java Swing's setBounds()/getBounds() problem) you'll end up writing a lot of extra code to re-implement functionality that's already there in the WINDOWPLACEMENT functions.

Get UltraMon. Quickly.

http://realtimesoft.com/ultramon/

It doesn't let you specify what monitor an app starts on, but it lets you move an app to the another monitor, and keep its aspect ratio intact, with one mouse click. It is a very handy utility.

Most programs will start where you last left them. So if you have two monitors at work, but only one at home, it's possible to start you laptop at home and not see the apps running on the other monitor (which now isn't there). UltrMon also lets you move those orphan apps back to the main screen quickly and easily.

It's not exactly the answer to this question but I dealt with this problem with the Shift + Win + [left,right] arrow keys shortcut. You can move the currently active window to another monitor with it.

I'm fairly sure the primary monitor is the default. If the app was coded decently, when it's closed, it'll remember where it was last at and will reopen there, but -- as you've noticed -- it isn't a default behavior.

EDIT: The way I usually do it is to have the location stored in the app's settings. On load, if there is no value for them, it defaults to the center of the screen. On closing of the form, it records its position. That way, whenever it opens, it's where it was last. I don't know of a simple way to tell it to launch onto the second monitor the first time automatically, however.

-- Kevin Fairchild

Important note: If you remember the position of your application and shutdown and then start up again at that position, keep in mind that the user's monitor configuration may have changed while your application was closed.

Laptop users, for example, frequently change their display configuration. When docked there may be a 2nd monitor that disappears when undocked. If the user closes an application that was running on the 2nd monitor and the re-opens the application when the monitor is disconnected, restoring the window to the previous coordinates will leave it completely off-screen.

To figure out how big the display really is, check out GetSystemMetrics.

So I had this issue with Adobe Reader 9.0. Somehow the program forgot to open on my right monitor and was consistently opening on my left monitor. Most programs allow you to drag it over, maximize the screen, and then close it out and it will remember. Well, with Adobe, I had to drag it over and then close it before maximizing it, in order for Windows to remember which screen to open it in next time. Once you set it to the correct monitor, then you can maximize it. I think this is stupid, since almost all windows programs remember it automatically without try to rig a way for XP to remember.