diff --git a/redo/area_windows.c b/redo/area_windows.c
index e6347bd..e9ded14 100644
--- a/redo/area_windows.c
+++ b/redo/area_windows.c
@@ -314,19 +314,11 @@ static LRESULT CALLBACK areaWndProc(HWND hwnd, UINT uMsg, WPARAM wParam, LPARAM
 	void *data;
 	DWORD which;
 	uintptr_t heldButtons = (uintptr_t) wParam;
+	LRESULT lResult;
 
-	data = (void *) GetWindowLongPtrW(hwnd, GWLP_USERDATA);
-	if (data == NULL) {
-		// the lpParam is available during WM_NCCREATE and WM_CREATE
-		if (uMsg == WM_NCCREATE) {
-			storelpParam(hwnd, lParam);
-			data = (void *) GetWindowLongPtrW(hwnd, GWLP_USERDATA);
-			storeAreaHWND(data, hwnd);
-		}
-		// act as if we're not ready yet, even during WM_NCCREATE (nothing important to the switch statement below happens here anyway)
-		return DefWindowProcW(hwnd, uMsg, wParam, lParam);
-	}
-
+	data = getWindowData(hwnd, uMsg, wParam, lParam, &lResult, storeAreaHWND);
+	if (data == NULL)
+		return lResult;
 	switch (uMsg) {
 	case WM_PAINT:
 		paintArea(hwnd, data);
diff --git a/redo/common_windows.c b/redo/common_windows.c
index 01da0ef..53f2b3e 100644
--- a/redo/common_windows.c
+++ b/redo/common_windows.c
@@ -29,11 +29,23 @@ void updateWindow(HWND hwnd)
 		xpanic("error calling UpdateWindow()", GetLastError());
 }
 
-void storelpParam(HWND hwnd, LPARAM lParam)
+void *getWindowData(HWND hwnd, UINT uMsg, WPARAM wParam, LPARAM lParam, LRESULT *lResult, void (*storeHWND)(void *, HWND))
 {
 	CREATESTRUCTW *cs = (CREATESTRUCTW *) lParam;
+	void *data;
 
-	SetWindowLongPtrW(hwnd, GWLP_USERDATA, (LONG_PTR) (cs->lpCreateParams));
+	data = (void *) GetWindowLongPtrW(hwnd, GWLP_USERDATA);
+	if (data == NULL) {
+		// the lpParam is available during WM_NCCREATE and WM_CREATE
+		if (uMsg == WM_NCCREATE) {
+			SetWindowLongPtrW(hwnd, GWLP_USERDATA, (LONG_PTR) (cs->lpCreateParams));
+			data = (void *) GetWindowLongPtrW(hwnd, GWLP_USERDATA);
+			(*storeHWND)(data, hwnd);
+		}
+		// act as if we're not ready yet, even during WM_NCCREATE (nothing important to the switch statement below happens here anyway)
+		*lResult = DefWindowProcW(hwnd, uMsg, wParam, lParam);
+	}
+	return data;
 }
 
 /*
diff --git a/redo/container_windows.c b/redo/container_windows.c
index 4d5215a..a95818d 100644
--- a/redo/container_windows.c
+++ b/redo/container_windows.c
@@ -15,21 +15,13 @@ static LRESULT CALLBACK containerWndProc(HWND hwnd, UINT uMsg, WPARAM wParam, LP
 {
 	void *data;
 	RECT r;
-	LRESULT shared;
+	LRESULT lResult;
 
-	data = (void *) GetWindowLongPtrW(hwnd, GWLP_USERDATA);
-	if (data == NULL) {
-		// the lpParam is available during WM_NCCREATE and WM_CREATE
-		if (uMsg == WM_NCCREATE) {
-			storelpParam(hwnd, lParam);
-			data = (void *) GetWindowLongPtrW(hwnd, GWLP_USERDATA);
-			storeContainerHWND(data, hwnd);
-		}
-		// act as if we're not ready yet, even during WM_NCCREATE (nothing important to the switch statement below happens here anyway)
-		return DefWindowProcW(hwnd, uMsg, wParam, lParam);
-	}
-	if (sharedWndProc(hwnd, uMsg, wParam, lParam, &shared))
-		return shared;
+	data = getWindowData(hwnd, uMsg, wParam, lParam, &lResult, storeContainerHWND);
+	if (data == NULL)
+		return lResult;
+	if (sharedWndProc(hwnd, uMsg, wParam, lParam, &lResult))
+		return lResult;
 	switch (uMsg) {
 	case WM_SIZE:
 		if (GetClientRect(hwnd, &r) == 0)
diff --git a/redo/winapi_windows.h b/redo/winapi_windows.h
index 328e0a3..028f3c3 100644
--- a/redo/winapi_windows.h
+++ b/redo/winapi_windows.h
@@ -81,7 +81,7 @@ extern LRESULT getWindowTextLen(HWND);
 extern void getWindowText(HWND, WPARAM, LPWSTR);
 extern void setWindowText(HWND, LPWSTR);
 extern void updateWindow(HWND);
-extern void storelpParam(HWND, LPARAM);
+extern void *getWindowData(HWND, UINT, WPARAM, LPARAM, LRESULT *, void (*)(void *, HWND));
 extern BOOL sharedWndProc(HWND, UINT, WPARAM, LPARAM, LRESULT *);
 
 // tab_windows.go
diff --git a/redo/window_windows.c b/redo/window_windows.c
index 5ea83f1..e4ea875 100644
--- a/redo/window_windows.c
+++ b/redo/window_windows.c
@@ -9,21 +9,13 @@ static LRESULT CALLBACK windowWndProc(HWND hwnd, UINT uMsg, WPARAM wParam, LPARA
 {
 	void *data;
 	RECT r;
-	LRESULT shared;
+	LRESULT lResult;
 
-	data = (void *) GetWindowLongPtrW(hwnd, GWLP_USERDATA);
-	if (data == NULL) {
-		// the lpParam is available during WM_NCCREATE and WM_CREATE
-		if (uMsg == WM_NCCREATE) {
-			storelpParam(hwnd, lParam);
-			data = (void *) GetWindowLongPtrW(hwnd, GWLP_USERDATA);
-			storeWindowHWND(data, hwnd);
-		}
-		// act as if we're not ready yet, even during WM_NCCREATE (nothing important to the switch statement below happens here anyway)
-		return DefWindowProcW(hwnd, uMsg, wParam, lParam);
-	}
-	if (sharedWndProc(hwnd, uMsg, wParam, lParam, &shared))
-		return shared;
+	data = getWindowData(hwnd, uMsg, wParam, lParam, &lResult, storeWindowHWND);
+	if (data == NULL)
+		return lResult;
+	if (sharedWndProc(hwnd, uMsg, wParam, lParam, &lResult))
+		return lResult;
 	switch (uMsg) {
 	case WM_SIZE:
 		if (GetClientRect(hwnd, &r) == 0)