diff --git a/redo/ui_windows.h b/redo/ui_windows.h
index 9a969e6a..88543d6b 100644
--- a/redo/ui_windows.h
+++ b/redo/ui_windows.h
@@ -22,12 +22,6 @@ struct uiWindowsMakeControlParams {
 	// Set this to non-FALSE to use the standard control font used by other ui controls.
 	BOOL useStandardControlFont;
 
-	// These are called when the control sends a WM_COMMAND, WM_NOTIFY, or WM_HSCROLL (respectively) to its parent.
-	// ui redirects the message back and calls these functions.
-	// Store the result in *lResult and return any non-FALSE value (such as TRUE) to return the given result; return FALSE to pass the notification up to your window procedure.
-	// Note that these are only issued if they come from the uiControl itself; notifications from children of the uiControl (such as a header control) will be received normally.
-	BOOL (*onWM_HSCROLL)(uiControl *c, WORD code, LRESULT *lResult);
-
 	// This is called when the widget is ready to be destroyed.
 	void (*onDestroy)(void *data);
 	void *onDestroyData;
diff --git a/redo/windows/separator.c b/redo/windows/separator.c
index e41c3221..d6f89136 100644
--- a/redo/windows/separator.c
+++ b/redo/windows/separator.c
@@ -10,11 +10,6 @@ struct separator {
 	HWND hwnd;
 };
 
-static BOOL onWM_HSCROLL(uiControl *c, WORD code, LRESULT *lResult)
-{
-	return FALSE;
-}
-
 static void onDestroy(void *data)
 {
 	struct separator *s = (struct separator *) data;
@@ -47,7 +42,6 @@ uiSeparator *uiNewHorizontalSeparator(void)
 	p.hInstance = hInstance;
 	p.lpParam = NULL;
 	p.useStandardControlFont = TRUE;
-	p.onWM_HSCROLL = onWM_HSCROLL;
 	p.onDestroy = onDestroy;
 	p.onDestroyData = s;
 	uiWindowsMakeControl(uiControl(s), &p);
diff --git a/redo/windows/slider.c b/redo/windows/slider.c
index 2bc040d3..151cb5b6 100644
--- a/redo/windows/slider.c
+++ b/redo/windows/slider.c
@@ -26,6 +26,7 @@ static void onDestroy(void *data)
 {
 	struct slider *s = (struct slider *) data;
 
+	uiWindowsUnregisterWM_HSCROLLHandler(s->hwnd);
 	uiFree(s);
 }
 
@@ -84,12 +85,12 @@ uiSlider *uiNewSlider(intmax_t min, intmax_t max)
 	p.hInstance = hInstance;
 	p.lpParam = NULL;
 	p.useStandardControlFont = TRUE;
-	p.onWM_HSCROLL = onWM_HSCROLL;
 	p.onDestroy = onDestroy;
 	p.onDestroyData = s;
 	uiWindowsMakeControl(uiControl(s), &p);
 
 	s->hwnd = (HWND) uiControlHandle(uiControl(s));
+	uiWindowsRegisterWM_HSCROLLHandler(s->hwnd, onWM_HSCROLL, uiControl(s));
 
 	SendMessageW(s->hwnd, TBM_SETRANGEMIN, (WPARAM) TRUE, (LPARAM) min);
 	SendMessageW(s->hwnd, TBM_SETRANGEMAX, (WPARAM) TRUE, (LPARAM) max);
diff --git a/redo/windows/spinbox.c b/redo/windows/spinbox.c
index 814192fe..4fc7b310 100644
--- a/redo/windows/spinbox.c
+++ b/redo/windows/spinbox.c
@@ -47,11 +47,6 @@ static BOOL onWM_COMMAND(uiControl *c, WORD code, LRESULT *lResult)
 	return TRUE;
 }
 
-static BOOL onWM_HSCROLL(uiControl *c, WORD code, LRESULT *lResult)
-{
-	return FALSE;
-}
-
 static void onDestroy(void *data)
 {
 	struct spinbox *s = (struct spinbox *) data;
@@ -165,7 +160,6 @@ uiSpinbox *uiNewSpinbox(intmax_t min, intmax_t max)
 	p.hInstance = hInstance;
 	p.lpParam = NULL;
 	p.useStandardControlFont = TRUE;
-	p.onWM_HSCROLL = onWM_HSCROLL;
 	p.onDestroy = onDestroy;
 	p.onDestroyData = s;
 	uiWindowsMakeControl(uiControl(s), &p);
diff --git a/redo/windows/tab.c b/redo/windows/tab.c
index 9e71aafd..3eefa75f 100644
--- a/redo/windows/tab.c
+++ b/redo/windows/tab.c
@@ -54,11 +54,6 @@ static BOOL onWM_NOTIFY(uiControl *c, NMHDR *nm, LRESULT *lResult)
 	return TRUE;
 }
 
-static BOOL onWM_HSCROLL(uiControl *c, WORD code, LRESULT *lResult)
-{
-	return FALSE;
-}
-
 static void onDestroy(void *data)
 {
 	// TODO
@@ -214,7 +209,6 @@ uiTab *uiNewTab(void)
 	p.hInstance = hInstance;
 	p.lpParam = NULL;
 	p.useStandardControlFont = TRUE;
-	p.onWM_HSCROLL = onWM_HSCROLL;
 	p.onDestroy = onDestroy;
 	p.onDestroyData = t;
 	uiWindowsMakeControl(uiControl(t), &p);