Changed Checkbox on Windows to use BS_CHECKBOX instead of BS_AUTOCHECKBOX; this will be necessary to fix the focus issue in todo.md (see http://blogs.msdn.com/b/oldnewthing/archive/2014/05/22/10527522.aspx).

stdwndclass_windows.go

@@ -84,6 +84,25 @@ func stdWndProc(hwnd _HWND, uMsg uint32, wParam _WPARAM, lParam _LPARAM) _LRESUL
 			if wParam.HIWORD() == _BN_CLICKED {
 				ss.signal()
 			}
+		case c_checkbox:
+			// we opt into doing this ourselves because http://blogs.msdn.com/b/oldnewthing/archive/2014/05/22/10527522.aspx
+			if wParam.HIWORD() == _BN_CLICKED {
+				state, _, _ := _sendMessage.Call(
+					uintptr(ss.hwnd),
+					uintptr(_BM_GETCHECK),
+					uintptr(0),
+					uintptr(0))
+				if state == _BST_CHECKED {
+					state = _BST_UNCHECKED
+				} else if state == _BST_UNCHECKED {
+					state = _BST_CHECKED
+				}
+				_sendMessage.Call(
+					uintptr(ss.hwnd),
+					uintptr(_BM_SETCHECK),
+					state,		// already uintptr
+					uintptr(0))
+			}
 		}
 		return 0
 	case _WM_GETMINMAXINFO:

sysdata_windows.go

@@ -57,7 +57,8 @@ var classTypes = [nctypes]*classData{
 	},
 	c_checkbox:		&classData{
 		name:			toUTF16("BUTTON"),
-		style:			_BS_AUTOCHECKBOX | controlstyle,
+		// don't use BS_AUTOCHECKBOX because http://blogs.msdn.com/b/oldnewthing/archive/2014/05/22/10527522.aspx
+		style:			_BS_CHECKBOX | controlstyle,
 		xstyle:			0 | controlxstyle,
 	},
 	c_combobox:		&classData{

zconstants_windows_386.go

@@ -6,9 +6,11 @@ const _AC_SRC_OVER = 0
 const _BCM_GETIDEALSIZE = 5633
 const _BI_RGB = 0
 const _BM_GETCHECK = 240
+const _BM_SETCHECK = 241
 const _BN_CLICKED = 0
 const _BST_CHECKED = 1
-const _BS_AUTOCHECKBOX = 3
+const _BST_UNCHECKED = 0
+const _BS_CHECKBOX = 2
 const _BS_PUSHBUTTON = 0
 const _CBS_AUTOHSCROLL = 64
 const _CBS_DROPDOWN = 2

zconstants_windows_amd64.go

@@ -6,9 +6,11 @@ const _AC_SRC_OVER = 0
 const _BCM_GETIDEALSIZE = 5633
 const _BI_RGB = 0
 const _BM_GETCHECK = 240
+const _BM_SETCHECK = 241
 const _BN_CLICKED = 0
 const _BST_CHECKED = 1
-const _BS_AUTOCHECKBOX = 3
+const _BST_UNCHECKED = 0
+const _BS_CHECKBOX = 2
 const _BS_PUSHBUTTON = 0
 const _CBS_AUTOHSCROLL = 64
 const _CBS_DROPDOWN = 2