C# Signature:
[DllImport("gdi32.dll")]
static extern int GetRegionData(IntPtr hRgn, uint dwCount, IntPtr lpRgnData);
User-Defined Types:
Notes:
This is an 'unsafe' call, and thus should be led by the [SuppressUnmanagedCodeSecurity()] attribute.
Tips & Tricks:
Please add some!
Sample Code:
using System;
using System.Runtime.InteropServices;
// this should be defined somewhere in a class
const int RDH_RECTANGLES = 1;
unsafe RECT[] RectsFromRegion(IntPtr hRgn)
{
RECT [] rects = null;
// 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 = 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 = 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 == RDH_RECTANGLES)
{
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;
}
Alternative Managed API:
Do you know one? Please contribute it!
