private static byte[] ReadWindowProperty(IntPtr display, ulong windowId, ulong property)
{
const long smallPropertyLength = 1024;
LibX11.XGetWindowProperty
(
display,
windowId,
property,
0,
smallPropertyLength,
1,
0 /* AnyPropertyType */,
out ulong type,
out int format,
out ulong nItems,
out ulong bytes_after_return,
out IntPtr bufferPtr
);
if (bytes_after_return != 0)
{
if (bufferPtr != IntPtr.Zero)
{
LibX11.XFree(bufferPtr);
}
ulong actualLength = bytes_after_return + 4 * smallPropertyLength;
if (bytes_after_return > int.MaxValue || actualLength > int.MaxValue)
{
throw new InvalidOperationException
(
$"Property {property} is too long: {nameof(bytes_after_return)} = {bytes_after_return}."
);
}
LibX11.XGetWindowProperty
(
display,
windowId,
property,
0,
(long)(actualLength + 3) / 4,
1,
0 /* AnyPropertyType */,
out type,
out format,
out nItems,
out bytes_after_return,
out bufferPtr
);
}
try
{
if ((nItems != 0) && (format <= 0 || format % 8 != 0))
{
throw new InvalidOperationException($"{nameof(LibX11.XGetWindowProperty)} returned an invalid format: {format}.");
}
int chunkSize = (int)nItems * format / 8;
byte[] res = new byte [chunkSize];
if (chunkSize != 0)
{
if (bufferPtr == IntPtr.Zero)
{
throw new InvalidOperationException($"{nameof(LibX11.XGetWindowProperty)} returned an empty buffer for a non-empty value.");
}
Marshal.Copy(bufferPtr, res, 0, chunkSize);
}
return(res);
}
finally
{
if (bufferPtr != IntPtr.Zero)
{
LibX11.XFree(bufferPtr);
}
}
}