Added a button to the test main window, including click handling.

common.go

@@ -13,6 +13,7 @@ var (
 type HANDLE uintptr
 type HWND HANDLE
 type HBRUSH HANDLE
+type HMENU HANDLE
 
 const (
 	NULL = 0
@@ -25,6 +26,16 @@ type WPARAM uintptr
 type LPARAM uintptr
 type LRESULT uintptr
 
+func (w WPARAM) LOWORD() uint16 {
+	// according to windef.h
+	return uint16(w & 0xFFFF)
+}
+
+func (w WPARAM) HIWORD() uint16 {
+	// according to windef.h
+	return uint16((w >> 16) & 0xFFFF)
+}
+
 // microsoft's header files do this
 func MAKEINTRESOURCE(what uint16) uintptr {
 	return uintptr(what)

main.go

@@ -19,8 +19,21 @@ func fatalf(format string, args ...interface{}) {
 	panic(fmt.Sprintf("error trying to warn user of internal error: %v\ninternal error:\n%s", err, s))
 }
 
-func wndProc(hwnd HWND, msg uint32, wparam WPARAM, lparam LPARAM) LRESULT {
+const (
+	IDC_BUTTON = 100
+)
+
+func wndProc(hwnd HWND, msg uint32, wParam WPARAM, lParam LPARAM) LRESULT {
 	switch msg {
+	case WM_COMMAND:
+		if wParam.LOWORD() == IDC_BUTTON {
+			if wParam.HIWORD() == BN_CLICKED {
+				MessageBox(hwnd, "clicked", "", MB_OK)
+			} else if wParam.HIWORD() == BN_DOUBLECLICKED {
+				MessageBox(hwnd, "double clicked", "", MB_OK)
+			}
+		}
+		return 0
 	case WM_CLOSE:
 		err := DestroyWindow(hwnd)
 		if err != nil {
@@ -34,7 +47,7 @@ func wndProc(hwnd HWND, msg uint32, wparam WPARAM, lparam LPARAM) LRESULT {
 		}
 		return 0
 	default:
-		return DefWindowProc(hwnd, msg, wparam, lparam)
+		return DefWindowProc(hwnd, msg, wParam, lParam)
 	}
 	fatalf("major bug: forgot a return on wndProc for message %d", msg)
 	panic("unreachable")
@@ -86,6 +99,16 @@ func main() {
 		fatalf("error creating window: %v", err)
 	}
 
+	_, err = CreateWindowEx(
+		0,
+		"BUTTON", "Click Me",
+		BS_PUSHBUTTON | WS_CHILD | WS_VISIBLE | WS_TABSTOP,
+		20, 20, 100, 100,
+		hwnd, HMENU(IDC_BUTTON), hInstance, NULL)
+	if err != nil {
+		fatalf("error creating button: %v", err)
+	}
+
 	_, err = ShowWindow(hwnd, nCmdShow)
 	if err != nil {
 		fatalf("error showing window: %v", err)

menus.go

@@ -0,0 +1,12 @@
+// 10 february 2014
+package main
+
+import (
+//	"syscall"
+//	"unsafe"
+)
+
+// Menu notifications.
+const (
+	WM_COMMAND = 0x0111
+)

windows.go

@@ -138,7 +138,7 @@ var (
 )
 
 // TODO use lpParam
-func CreateWindowEx(dwExStyle uint32, lpClassName string, lpWindowName string, dwStyle uint32, x int, y int, nWidth int, nHeight int, hwndParent HWND, hMenu HANDLE, hInstance HANDLE, lpParam interface{}) (hwnd HWND, err error) {
+func CreateWindowEx(dwExStyle uint32, lpClassName string, lpWindowName string, dwStyle uint32, x int, y int, nWidth int, nHeight int, hwndParent HWND, hMenu HMENU, hInstance HANDLE, lpParam interface{}) (hwnd HWND, err error) {
 	r1, _, err := createWindowEx.Call(
 		uintptr(dwExStyle),
 		uintptr(unsafe.Pointer(syscall.StringToUTF16Ptr(lpClassName))),