Declare Function RectInRegion Lib "gdi32.dll" (ByVal hRgn As Long, lpRect As RECT) As Long
Platforms: Win 32s, Win 95/98, Win NT
RectInRegion determines if a rectangle lies within a given region. The rectangle is considered to be inside the region if any portion of it -- not necessarily all of it -- lies within the region. The function returns 0 if the rectangle is completely outside the region, or a non-zero value if the rectangle is at least partially within the region.
Example:
' Consider a line connecting the upper-right and lower-left corners of the
' screen, and consider the region made of the upper-left side of this line. Determine
' if window Form1 at least partially lies within the region..
Dim swidth As Long, sheight As Long ' width and height of the screen
Dim hRgn As Long ' handle to the triangular region explained above
Dim winrect As RECT ' receives Form1's rectangle
Dim vertices(0 To 2) As POINT_TYPE ' vertices of region to create
Dim isinside As Long ' receives 0 if not inside, non-zero otherwise
Dim retval As Long ' generic return value
' Get the screen's width and height. Use this information to create the region.
swidth = GetSystemMetrics(SM_CXSCREEN) ' screen width
sheight = GetSystemMetrics(SM_CYSCREEN) ' screen height
' Load region's vertices into the array and create it.
vertices(0).x = 0: vertices(0).y = 0 ' vertex #1: upper-left corner of screen
vertices(1).x = swidth: vertices(1).y = 0 ' vertex #2: upper-right corner of screen
vertices(2).x = 0: vertices(2).y = sheight ' vertex #3: lower-left corner of screen
hRgn = CreatePolygonRgn(vertices(0), 3, ALTERNATE) ' create the region
' Get the rectangle of window Form1, identifying the corners of the window.
retval = GetWindowRect(Form1.hWnd, winrect)
' Determine if the rectangle lies within the region.
isinside = RectInRegion(hRgn, winrect) ' is the rectangle in the region?
If isinside = 0 Then ' not inside
Debug.Print "Form1 is completely outside the region."
Else
Debug.Print "Form1 lies at least partially inside the region."
End If
' Delete the region to free up resources.
retval = DeleteObject(hRgn)See Also: PtInRegion
Category: Regions
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