diff --git a/_doc/misctests/windwmblurbehindtest.cpp b/_doc/misctests/windwmblurbehindtest.cpp
new file mode 100644
index 00000000..1e469ed1
--- /dev/null
+++ b/_doc/misctests/windwmblurbehindtest.cpp
@@ -0,0 +1,222 @@
+// 31 august 2019
+#define UNICODE
+#define _UNICODE
+#define STRICT
+#define STRICT_TYPED_ITEMIDS
+#define WINVER			0x0600	/* from Microsoft's winnls.h */
+#define _WIN32_WINNT		0x0600
+#define _WIN32_WINDOWS	0x0600	/* from Microsoft's pdh.h */
+#define _WIN32_IE			0x0700
+#define NTDDI_VERSION		0x06000000
+#include <windows.h>
+#include <commctrl.h>
+#include <uxtheme.h>
+#include <vsstyle.h>
+#include <vssym32.h>
+#include <windowsx.h>
+#include <dwmapi.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+// cl windwmblurbehindtest.cpp -MT -link user32.lib kernel32.lib gdi32.lib comctl32.lib uxtheme.lib msimg32.lib dwmapi.lib windows.res
+
+void diele(const char *func)
+{
+	DWORD le;
+
+	le = GetLastError();
+	fprintf(stderr, "%s: %I32u\n", func, le);
+	exit(EXIT_FAILURE);
+}
+
+void diehr(const char *func, HRESULT hr)
+{
+	fprintf(stderr, "%s: 0x%08I32X\n", func, hr);
+	exit(EXIT_FAILURE);
+}
+
+// TODO if we merge this into libui proper, this will need to be deduplicated
+static inline HRESULT lastErrorToHRESULT(DWORD lastError)
+{
+	if (lastError == 0)
+		return E_FAIL;
+	return HRESULT_FROM_WIN32(lastError);
+}
+
+HINSTANCE hInstance;
+HRGN rgn;
+BOOL created = FALSE;
+HBRUSH opaquebrush;
+
+#define OURWIDTH 320
+#define OURHEIGHT 240
+
+void onWM_CREATE(HWND hwnd)
+{
+	DWM_BLURBEHIND dbb;
+	HRESULT hr = S_OK;
+
+	rgn = CreateRectRgn(0, 0, OURWIDTH / 2, OURHEIGHT);
+	if (rgn == NULL)
+		diele("CreateRectRgn()");
+	ZeroMemory(&dbb, sizeof (DWM_BLURBEHIND));
+	dbb.dwFlags = DWM_BB_ENABLE | DWM_BB_BLURREGION;
+	dbb.fEnable = TRUE;
+	dbb.hRgnBlur = NULL;//rgn;
+	hr = DwmEnableBlurBehindWindow(hwnd, &dbb);
+	if (hr != S_OK)
+		diehr("DwmEnableBlurBehindWindow()", hr);
+CreateWindowExW(0,
+L"BUTTON",L"Hello",
+WS_CHILD|WS_VISIBLE|BS_PUSHBUTTON,
+3*OURWIDTH/4,150,
+OURWIDTH/6,25,
+hwnd,NULL,hInstance,NULL);
+SetWindowTheme(CreateWindowExW(0,
+L"BUTTON",L"Hello",
+WS_CHILD|WS_VISIBLE|BS_PUSHBUTTON,
+3*OURWIDTH/4,200,
+OURWIDTH/6,25,
+hwnd,NULL,hInstance,NULL),L"",L"");
+}
+
+void onWM_PAINT(HWND hwnd)
+{
+	HDC dc;
+	PAINTSTRUCT ps;
+	RECT r;
+
+	ZeroMemory(&ps, sizeof (PAINTSTRUCT));
+	dc = BeginPaint(hwnd, &ps);
+	if (dc == NULL)
+		diele("BeginPaint()");
+	// First, fill with BLACK_BRUSH to satisfy the DWM
+	r.left = 0;
+	r.top = 0;
+	r.right = OURWIDTH;
+	r.bottom = OURHEIGHT;
+	// TODO check error
+	FillRect(dc, &r, (HBRUSH) GetStockObject(BLACK_BRUSH));
+static DWORD c=GetSysColor(COLOR_BTNFACE);
+BYTE x[4];
+x[3]=0xFF;
+x[2]=GetRValue(c);
+x[1]=GetGValue(c);
+x[0]=GetBValue(c);
+static HBITMAP b=CreateBitmap(1,1,1,32,x);
+if(b==NULL)diele("CreateBitmap()");
+HDC dc2=CreateCompatibleDC(dc);
+if(dc==NULL)diele("CreateCompatibleDC()");
+HGDIOBJ prev=SelectObject(dc2,b);
+StretchBlt(dc,OURWIDTH/2,0,OURWIDTH/2,OURHEIGHT,
+dc2,0,0,1,1,SRCCOPY);
+SelectObject(dc2,prev);
+DeleteDC(dc2);
+DeleteObject(b);
+r.left=3*OURWIDTH/4;
+r.top=100;
+r.right=7*OURWIDTH/8;
+r.bottom=25;
+auto m=SetBkMode(dc,TRANSPARENT);
+TextOutW(dc,r.left,r.top,L"Hello",5);
+SetBkMode(dc, m);
+	EndPaint(hwnd, &ps);
+}
+
+LRESULT CALLBACK wndproc(HWND hwnd, UINT uMsg, WPARAM wParam, LPARAM lParam)
+{
+	switch (uMsg) {
+	case WM_CREATE:
+		onWM_CREATE(hwnd);
+		break;
+	case WM_PAINT:
+		onWM_PAINT(hwnd);
+		break;
+	case WM_CLOSE:
+		PostQuitMessage(0);
+		break;
+	}
+	return DefWindowProcW(hwnd, uMsg, wParam, lParam);
+}
+
+EXTERN_C IMAGE_DOS_HEADER __ImageBase;
+
+int main(int argc, char *argv[])
+{
+	STARTUPINFOW si;
+	int nCmdShow;
+	INITCOMMONCONTROLSEX icc;
+	HICON hDefaultIcon;
+	HCURSOR hDefaultCursor;
+	DWORD dwStyle, dwExStyle;
+	RECT r;
+	WNDCLASSW wc;
+	HWND mainwin;
+	MSG msg;
+	HRESULT hr;
+
+	hInstance = (HINSTANCE) (&__ImageBase);
+	nCmdShow = SW_SHOWDEFAULT;
+	GetStartupInfoW(&si);
+	if ((si.dwFlags & STARTF_USESHOWWINDOW) != 0)
+		nCmdShow = si.wShowWindow;
+
+	ZeroMemory(&icc, sizeof (INITCOMMONCONTROLSEX));
+	icc.dwSize = sizeof (INITCOMMONCONTROLSEX);
+	icc.dwICC = ICC_STANDARD_CLASSES | ICC_BAR_CLASSES | ICC_COOL_CLASSES;
+	if (InitCommonControlsEx(&icc) == 0)
+		diele("InitCommonControlsEx()");
+
+	hDefaultIcon = LoadIconW(NULL, IDI_APPLICATION);
+	if (hDefaultIcon == NULL)
+		diele("LoadIconW(IDI_APPLICATION)");
+	hDefaultCursor = LoadCursorW(NULL, IDC_ARROW);
+	if (hDefaultCursor == NULL)
+		diele("LoadCursorW(IDC_ARROW)");
+
+	ZeroMemory(&wc, sizeof (WNDCLASSW));
+	wc.lpszClassName = L"mainwin";
+	wc.lpfnWndProc = wndproc;
+	wc.hInstance = hInstance;
+	wc.hIcon = hDefaultIcon;
+	wc.hCursor = hDefaultCursor;
+	wc.hbrBackground = (HBRUSH) (COLOR_BTNFACE + 1);
+	if (RegisterClassW(&wc) == 0)
+		diele("RegisterClassW()");
+
+	dwStyle = WS_OVERLAPPEDWINDOW & ~(WS_THICKFRAME | WS_MAXIMIZEBOX);
+	dwExStyle = 0;
+	r.left = 0;
+	r.top = 0;
+	r.right = OURWIDTH;
+	r.bottom = OURHEIGHT;
+	if (AdjustWindowRectEx(&r, dwStyle, FALSE, dwExStyle) == 0)
+		diele("AdjustWindowRectEx()");
+	mainwin = CreateWindowExW(dwExStyle,
+		L"mainwin", L"Main Window",
+		dwStyle,
+		CW_USEDEFAULT, CW_USEDEFAULT,
+		r.right - r.left, r.bottom - r.top,
+		NULL, NULL, hInstance, NULL);
+	if (mainwin == NULL)
+		diele("CreateWindowExW(L\"mainwin\")");
+
+	ShowWindow(mainwin, nCmdShow);
+	if (UpdateWindow(mainwin) == 0)
+		diele("UpdateWindow()");
+
+	for (;;) {
+		int res;
+
+		res = GetMessageW(&msg, NULL, 0, 0);
+		if (res < 0)
+			diele("GetMessageW()");
+		if (res == 0)
+			break;
+		if (IsDialogMessageW(mainwin, &msg) == 0) {
+			TranslateMessage(&msg);
+			DispatchMessageW(&msg);
+		}
+	}
+	return 0;
+}