Mostly added Checkbox to the Windows backend; it doesn't show up right away and it crashes in WM_NCDESTROY...

redo/controls_windows.c

@@ -75,3 +75,53 @@ void setButtonSubclass(HWND hwnd, void *data)
 	if ((*fv_SetWindowSubclass)(hwnd, buttonSubProc, 0, (DWORD_PTR) data) == FALSE)
 		xpanic("error subclassing Button to give it its own event handler", GetLastError());
 }
+
+static LRESULT CALLBACK checkboxSubProc(HWND hwnd, UINT uMsg, WPARAM wParam, LPARAM lParam, UINT_PTR id, DWORD_PTR data)
+{
+	switch (uMsg) {
+	case msgCOMMAND:
+		if (HIWORD(wParam) == BN_CLICKED) {
+			WPARAM check;
+
+			/* we didn't use BS_AUTOCHECKBOX (see controls_windows.go) so we have to manage the check state ourselves */
+			check = BST_CHECKED;
+			if (SendMessage(hwnd, BM_GETCHECK, 0, 0) == BST_CHECKED)
+				check = BST_UNCHECKED;
+			SendMessage(hwnd, BM_SETCHECK, check, 0);
+			checkboxToggled((void *) data);
+			return 0;
+		}
+		return (*fv_DefSubclassProc)(hwnd, uMsg, wParam, lParam);
+	case WM_NCDESTROY:
+		if ((*fv_RemoveWindowSubclass)(hwnd, buttonSubProc, id) == FALSE)
+			xpanic("error removing Checkbox subclass (which was for its own event handler)", GetLastError());
+		return (*fv_DefSubclassProc)(hwnd, uMsg, wParam, lParam);
+	default:
+		return (*fv_DefSubclassProc)(hwnd, uMsg, wParam, lParam);
+	}
+	xmissedmsg("Checkbox", "checkboxSubProc()", uMsg);
+	return 0;		/* unreached */
+}
+
+void setCheckboxSubclass(HWND hwnd, void *data)
+{
+	if ((*fv_SetWindowSubclass)(hwnd, checkboxSubProc, 0, (DWORD_PTR) data) == FALSE)
+		xpanic("error subclassing Checkbox to give it its own event handler", GetLastError());
+}
+
+BOOL checkboxChecked(HWND hwnd)
+{
+	if (SendMessage(hwnd, BM_GETCHECK, 0, 0) == BST_UNCHECKED)
+		return FALSE;
+	return TRUE;
+}
+
+void checkboxSetChecked(HWND hwnd, BOOL c)
+{
+	WPARAM check;
+
+	check = BST_CHECKED;
+	if (c == FALSE)
+		check = BST_UNCHECKED;
+	SendMessage(hwnd, BM_SETCHECK, check, 0);
+}

redo/controls_windows.go

@@ -46,9 +46,9 @@ type button struct {
 
 var buttonclass = toUTF16("BUTTON")
 
-func newButton(text string) *button {
+func startNewButton(text string, style C.DWORD) *button {
 	w := newWidget(buttonclass,
-		C.BS_PUSHBUTTON | C.WS_TABSTOP,
+		style | C.WS_TABSTOP,
 		0)
 	C.setWindowText(w.hwnd, toUTF16(text))
 	C.controlSetControlFont(w.hwnd)
@@ -56,7 +56,12 @@ func newButton(text string) *button {
 		widgetbase:	w,
 		clicked:		newEvent(),
 	}
-	C.setButtonSubclass(w.hwnd, unsafe.Pointer(b))
+	return b
+}
+
+func newButton(text string) *button {
+	b := startNewButton(text, C.BS_PUSHBUTTON)
+	C.setButtonSubclass(b.hwnd, unsafe.Pointer(b))
 	return b
 }
 
@@ -78,3 +83,39 @@ func buttonClicked(data unsafe.Pointer) {
 	b.clicked.fire()
 	println("button clicked")
 }
+
+type checkbox struct {
+	*button
+}
+
+func newCheckbox(text string) *checkbox {
+	c := &checkbox{
+		// don't use BS_AUTOCHECKBOX here because it creates problems when refocusing (see http://blogs.msdn.com/b/oldnewthing/archive/2014/05/22/10527522.aspx)
+		// we'll handle actually toggling the check state ourselves (see controls_windows.c)
+		button:	startNewButton(text, C.BS_CHECKBOX),
+	}
+	C.setCheckboxSubclass(c.hwnd, unsafe.Pointer(c))
+	return c
+}
+
+func (c *checkbox) Checked() bool {
+	if C.checkboxChecked(c.hwnd) == C.FALSE {
+		return false
+	}
+	return true
+}
+
+func (c *checkbox) SetChecked(checked bool) {
+	if checked {
+		C.checkboxSetChecked(c.hwnd, C.TRUE)
+		return
+	}
+	C.checkboxSetChecked(c.hwnd, C.FALSE)
+}
+
+//export checkboxToggled
+func checkboxToggled(data unsafe.Pointer) {
+	c := (*checkbox)(data)
+	c.clicked.fire()
+	println("checkbox toggled")
+}

redo/winapi_windows.h

@@ -43,6 +43,9 @@ extern void controlSetParent(HWND, HWND);
 extern void controlSetControlFont(HWND);
 extern LRESULT forwardCommand(HWND, UINT, WPARAM, LPARAM);
 extern void setButtonSubclass(HWND, void *);
+extern void setCheckboxSubclass(HWND, void *);
+extern BOOL checkboxChecked(HWND);
+extern void checkboxSetChecked(HWND, BOOL);
 
 /* init_windows.c */
 extern HINSTANCE hInstance;