Cannot Make GetWindowRect() API Call To Work Properly

Question

I require the ability to get the height of the on screen keyboard for Windows 8.1, "TabTip.exe." So far I've managed to open and close it at will, but now I also need to get it's height so I can compensate for it in my app. I have TextBox controls near the very bottom of the Window that get covered up by the keyboard.

All attempts to utilize the Win API call "GetWindowRect" have failed.

Code placed just inside the beginning of the class definition:

private const string OnScreenKeyboardName = "TabTip";

DllImport("user32.dll")]
public static extern IntPtr FindWindow(string lpClassName, string lpWindowName);

[DllImport("user32.dll")]
[return: MarshalAs(UnmanagedType.Bool)]
static extern bool GetWindowRect(HandleRef hWnd, ref RECT lpRect);

[StructLayout(LayoutKind.Sequential)]
public struct RECT
{
   public int Left;        // x position of upper-left corner
   public int Top;         // y position of upper-left corner
   public int Right;       // x position of lower-right corner
   public int Bottom;      // y position of lower-right corner
}

code placed inside one of the event handlers in the Window:

RECT rct = new RECT();

if (Process.GetProcessesByName(OnScreenKeyboardName).Length > 0)
{
   Process[] Processes = Process.GetProcessesByName(OnScreenKeyboardName);
   foreach (Process pOnScreenKeyboard in Processes)
   {
      if (!GetWindowRect(new HandleRef(this, pOnScreenKeyboard.Handle), ref rct))
      {
         MessageBox.Show("ERROR");
         return;
      }
      MessageBox.Show(rct.ToString());
   }
}

Consistent with most examples, I had originally been using a call to "FindWindow" to get the handle for the TabTip.exe Window. That seemed to work great for a while, but it stopped working all of a sudden within the last few days, and so I switched to "Process.FindByName..."

My test case involves placing the code (second part) above into the Window's "MouseMove" event handler. Then I make sure the on screen keyboard is showing, and then I move the mouse. This causes the event to fire and then it always shows the "ERROR" MessageBox, which indicates that "GetWindowRect" returns false (or has some kind of error?

I've spent a lot of time on Google searches, p/invoke, etc. This is frustrating because there seem to be very few examples of how to properly do this. And it seems there is some new thing called a HandleRef (am I using that properly? - there are basically no examples for that either!!!)

I really need to get this working. Can someone please tell me where I'm going wrong? Thanks!

score 0 · Accepted Answer · edited May 23 '17 at 11:43

0

You are passing the process handle (pOnScreenKeyboard.Handle) to GetWindowRect where GetWindowRect expects a window handle (HWND). Finding the process isn't sufficient - a process can create many windows, so you need to find the onscreen keyboard's window handle. You can try using pOnScreenKeyboard.MainWindowHandle, but from this post, you might find that it's null. You said you had a previous solution using FindWindow. I would go back to that and figure out why it stopped working.

edited May 23 '17 at 11:43

Community

1
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answered Mar 30 '15 at 04:49

pharring

1,991
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One more thing: Your first 'if' statement is unnecessary. Calling Process.GetProcessesByName can be pretty expensiveand, theoretically there's a race between your two calls where the desired process could exit. So, just "foreach" over the result. If it's empty, the foreach does nothing. – pharring Mar 30 '15 at 04:56

Cannot Make GetWindowRect() API Call To Work Properly

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