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This codes demonstrates what is involved in writing a dialog-based application for Windows® using nothing but C and the Windows API. It further explores concepts pertaining to the GDI, with a focus on device contexts and bit block transfers. And, it shows how to manipulate the clipboard.

There was a workaround needed for the "Grab Color" feature. The reason being is that I used the GetPixel function for it; therefore, if you have coordinates for a non-client area in a window, it returns -1. This is not a valid color, so I used BitBlt to rectify the problem by copying the pixel to a static control and then using GetPixel on the control, thus returning a valid color. The following code demonstrates this technique.

// get a handle to the window under the cursor
hWndxy = WindowFromPoint(spoint);

// get a handle to the preview pane
hPreview = GetDlgItem(hWnd,IDC_STATIC_PREVIEW);

// get the dc for the window in question
hDC = GetDC(hWndxy);

// GetPixel() requires client coordinates
ScreenToClient(hWndxy, &cursor);
rgb = GetPixel(hDC, cursor.x, cursor.y);

/*/
/ / The following is a workaround for the GetPixel API. If the
/ / cursor is over a titlebar or other non-client areas of the
/ / window it'll return -1 for the RGB intensities. In this case
/ / we use BitBlt to copy the color to our control and extract
/ / the the intensities from that.
/*/

// check to see if intensities are valid
if(rgb == -1)
{
    HDC hDCPrev = GetDC(hPreview);

    BitBlt(hDCPrev, 0, 0, 1, 1, hDC, 
           cursor.x, cursor.y, SRCCOPY);
    rgb = GetPixel(hDCPrev, 0, 0);

    // clean up
    ReleaseDC(hPreview, hDCPrev);
}

// clean up
ReleaseDC(hWndxy, hDC);