DimTest.cs

// Drives the running MagicVolume dimmer overlay from outside and checks the
// safety-critical properties: that it is click-through, never takes focus, and
// that raising the level hides it again (so a black screen is always escapable).
using System;
using System.Runtime.InteropServices;
using System.Threading;

class DimTest {
    const int GWL_EXSTYLE = -20;
    const int WS_EX_LAYERED = 0x00080000, WS_EX_TRANSPARENT = 0x00000020;
    const int WS_EX_TOPMOST = 0x00000008, WS_EX_NOACTIVATE = 0x08000000;
    const uint WM_APP_SETLEVEL = 0x8001;
    const uint LWA_ALPHA = 0x2;

    [StructLayout(LayoutKind.Sequential)] struct RECT { public int L, T, R, B; }

    [DllImport("user32.dll", CharSet = CharSet.Unicode)] static extern IntPtr FindWindowW(string cls, string title);
    [DllImport("user32.dll")] static extern int GetWindowLongW(IntPtr h, int i);
    [DllImport("user32.dll")] static extern bool GetWindowRect(IntPtr h, out RECT r);
    [DllImport("user32.dll")] static extern bool IsWindowVisible(IntPtr h);
    [DllImport("user32.dll")] static extern bool PostMessageW(IntPtr h, uint m, IntPtr w, IntPtr l);
    [DllImport("user32.dll")] static extern bool GetLayeredWindowAttributes(IntPtr h, out uint key, out byte alpha, out uint flags);
    [DllImport("user32.dll")] static extern int GetSystemMetrics(int i);

    static void Main() {
        IntPtr h = FindWindowW("MagicVolumeDimmer", null);
        if (h == IntPtr.Zero) { Console.WriteLine("FAIL: dimmer window not found - is MagicVolume running?"); return; }
        Console.WriteLine("dimmer window found: 0x" + h.ToInt64().ToString("X"));

        int ex = GetWindowLongW(h, GWL_EXSTYLE);
        Console.WriteLine("  click-through (WS_EX_TRANSPARENT): " + ((ex & WS_EX_TRANSPARENT) != 0));
        Console.WriteLine("  never activates (WS_EX_NOACTIVATE): " + ((ex & WS_EX_NOACTIVATE) != 0));
        Console.WriteLine("  layered (WS_EX_LAYERED):            " + ((ex & WS_EX_LAYERED) != 0));
        Console.WriteLine("  topmost (WS_EX_TOPMOST):            " + ((ex & WS_EX_TOPMOST) != 0));

        RECT r; GetWindowRect(h, out r);
        Console.WriteLine(string.Format("  covers {0}x{1} at ({2},{3}); virtual screen is {4}x{5}",
            r.R - r.L, r.B - r.T, r.L, r.T, GetSystemMetrics(78), GetSystemMetrics(79)));
        Console.WriteLine("  visible at rest: " + IsWindowVisible(h) + "  (should be False at 100%)");

        Console.WriteLine();
        Console.WriteLine("dimming to 50% for a moment...");
        PostMessageW(h, WM_APP_SETLEVEL, new IntPtr(50), IntPtr.Zero);
        Thread.Sleep(600);
        uint key, flags; byte alpha;
        bool got = GetLayeredWindowAttributes(h, out key, out alpha, out flags);
        Console.WriteLine("  visible: " + IsWindowVisible(h) + "   alpha: " + (got ? alpha.ToString() : "?") + "/255  (expect ~127)");

        Console.WriteLine("restoring to 100%...");
        PostMessageW(h, WM_APP_SETLEVEL, new IntPtr(100), IntPtr.Zero);
        Thread.Sleep(600);
        bool hidden = !IsWindowVisible(h);
        Console.WriteLine("  hidden again: " + hidden);

        Console.WriteLine();
        Console.WriteLine(hidden && (ex & WS_EX_TRANSPARENT) != 0
            ? "RESULT: dimmer works and is safely escapable."
            : "RESULT: PROBLEM - check the flags above.");
    }
}