How can I extract text information from an owner-drawn window, given a HWND?

I'm writing a simple automated test application for Win32. It runs as a separate process and acce开发者_JAVA技巧sses the target application via the Windows API. I can read window hierarchies, find labels and textboxes, and click buttons by sending/posting messages etc. All fine.

Unfortunately many controls in the target application are composed of nothing more than an owner-drawn control/window. (For example, we use the BCG menus and controlbars). Finding the correct part of the control to send a 'click' to is problematic.

Is there any way, given a HWND, to extract GDI drawing commands? I'd like to know each piece of text drawn to that control, and its coordinates.

Failing that, is there any way to capture a single control/window (again by HWND) into a bitmap? Worse-case scenario, I could OCR it.

You can use TextGRAB SDK to do this. Unfortunately it is shareware and costs $30.

To capture a window as a bitmap:

RECT rc;
GetClientRect(hWnd, &rc);
int cx = rc.right-rc.left;
int cy = rc.bottom-rc.top;

HDC winDC = ::GetDC(hWnd);
HDC tempDC = ::CreateCompatibleDC(winDC);
HBITMAP newBMP = ::CreateCompatibleBitmap(winDC, cx, cy);

HBITMAP oldBmp = (HBITMAP)::SelectObject(tempDC, newBMP);
BitBlt(tempDC,0,0,cx,cy, winDC,0,0,SRCCOPY|CAPTUREBLT);
// now you have the window content in the newBMP bitmap, do with it as you please here

::SelectObject(tempDC, oldBmp);
::DeleteObject(newBMP);
::DeleteDC(tempDC);
::ReleaseDC(hWnd, winDC);