Cleaning Up Glass

All those bitmaps and device contexts in Create have to be cleaned up. The Destroy method (which is called by the Class_Terminate event procedure) provides a place where you can be sure that cleanup happens. Here’s the code:

Sub Destroy()
    BugAssert fExist
    ‘ Select old mask back to DC
    Call SelectObject(hdcMask, hbmpMaskOld)
    ‘ Now it’s safe to delete DC and bitmask
    Call DeleteDC(hdcMask)
    Call DeleteObject(hbmpMask)
    ‘ Clean up inverted image DC
    Call SelectObject(hdcImage, hbmpImageOld)
    Call DeleteDC(hdcImage)
    Call DeleteObject(hbmpImage)
    ‘ Clean up cache DC
    Call SelectObject(hdcCache, hbmpCacheOld)
    Call DeleteDC(hdcCache)
    Call DeleteObject(hbmpCache)
    ‘ Clean up old background DC
    Call SelectObject(hdcBack, hbmpBackOld)
    Call DeleteDC(hdcBack)
    Call DeleteObject(hbmpBack)
    xOld = -1: yOld = -1
    fExist = False
End Sub