public unsafe static RECT[] GetRegionRects(RGNDATAHEADER *regionData)
{
if (regionData is null || regionData->nCount == 0)
{
return(Array.Empty <RECT>());
}
// Region RECTs directly follow the header
return(new Span <RECT>((byte *)regionData + regionData->dwSize, (int)regionData->nCount).ToArray());
}
public static unsafe RECT[] RectsFromRegion(IntPtr hRgn)
{
RECT[] rects = new RECT[0];
// First we call GetRegionData() with a null buffer.
// The return from this call should be the size of buffer
// we need to allocate in order to receive the data.
int dataSize = WinGdiApi.GetRegionData(hRgn, 0, IntPtr.Zero);
if (dataSize != 0)
{
IntPtr bytes = IntPtr.Zero;
// Allocate as much space as the GetRegionData call
// said was needed
bytes = Marshal.AllocCoTaskMem(dataSize);
// Now, make the call again to actually get the data
int retValue = WinGdiApi.GetRegionData(hRgn, dataSize, bytes);
// From here on out, we have the data in a buffer, and we
// just need to convert it into a form that is more useful
// Since pointers are used, this whole routine is 'unsafe'
// It's a small sacrifice to make in order to get this to work.
// [RBS] Added missing second pointer identifier
RGNDATAHEADER *header = (RGNDATAHEADER *)bytes;
if (header->iType == 1)
{
rects = new RECT[header->nCount];
// The rectangle data follows the header, so we offset the specified
// header size and start reading rectangles.
int rectOffset = header->dwSize;
for (int i = 0; i < header->nCount; i++)
{
// simple assignment from the buffer to our array of rectangles
// will give us what we want.
rects[i] = *((RECT *)((byte *)bytes + rectOffset + (Marshal.SizeOf(typeof(RECT)) * i)));
}
}
}
// Return the rectangles
return(rects);
}
