Added the rest of the skeleton necessary for opening a simple window as well as the code to actually open one. Now for custom window procedures!

main.go

@@ -1,12 +1,95 @@
 // 7 february 2014
 package main
 
-import "fmt"
+import (
+	"fmt"
+	"os"
+	"runtime"
+)
 
-func main() {
-	fmt.Println(MessageBox(NULL,
-		"hello, world",
-		"hello",
-		0))
+func fatalf(format string, args ...interface{}) {
+	s := fmt.Sprintf(format, args...)
+	_, err := MessageBox(NULL,
+		"An internal error has occured:\n" + s,
+		os.Args[0],
+		MB_OK | MB_ICONERROR)
+	if err == nil {
+		os.Exit(1)
+	}
+	panic(fmt.Sprintf("error trying to warn user of internal error: %v\ninternal error:\n%s", err, s))
+}
+
+const className = "mainwin"
+
+func main() {
+	runtime.LockOSThread()
+
+	hInstance, err := getWinMainhInstance()
+	if err != nil {
+		fatalf("error getting WinMain hInstance: %v", err)
+	}
+	nCmdShow, err := getWinMainnCmdShow()
+	if err != nil {
+		fatalf("error getting WinMain nCmdShow: %v", err)
+	}
+
+	icon, err := LoadIcon_ResourceID(NULL, IDI_APPLICATION)
+	if err != nil {
+		fatalf("error getting window icon: %v", err)
+	}
+	cursor, err := LoadCursor_ResourceID(NULL, IDC_ARROW)
+	if err != nil {
+		fatalf("error getting window cursor: %v", err)
+	}
+
+	wc := &WNDCLASS{
+		LpszClassName:	className,
+		LpfnWndProc:		DefWindowProc,
+		HInstance:		hInstance,
+		HIcon:			icon,
+		HCursor:			cursor,
+		HbrBackground:	HBRUSH(COLOR_WINDOW + 1),
+	}
+	_, err = RegisterClass(wc)
+	if err != nil {
+		fatalf("error registering window class: %v", err)
+	}
+
+	hwnd, err := CreateWindowEx(
+		WS_EX_OVERLAPPEDWINDOW,
+		className, "Main Window",
+		WS_OVERLAPPEDWINDOW,
+		CW_USEDEFAULT, CW_USEDEFAULT, 320, 240,
+		NULL, NULL, hInstance, NULL)
+	if err != nil {
+		fatalf("error creating window: %v", err)
+	}
+
+	_, err = ShowWindow(hwnd, nCmdShow)
+	if err != nil {
+		fatalf("error showing window: %v", err)
+	}
+	err = UpdateWindow(hwnd)
+	if err != nil {
+		fatalf("error updating window: %v", err)
+	}
+
+	for {
+		msg, done, err := GetMessage(NULL, 0, 0)
+		if err != nil {
+			fatalf("error getting message: %v", err)
+		}
+		if done {
+			break
+		}
+		_, err = TranslateMessage(msg)
+		if err != nil {
+			fatalf("error translating message: %v", err)
+		}
+		_, err = DispatchMessage(msg)
+		if err != nil {
+			fatalf("error dispatching message: %v", err)
+		}
+	}
 }
 

messages.go

@@ -0,0 +1,49 @@
+// 9 february 2014
+package main
+
+import (
+//	"syscall"
+	"unsafe"
+)
+
+type MSG struct {
+	Hwnd	HWND
+	Message	uint32
+	WParam	WPARAM
+	LParam	LPARAM
+	Time		uint32
+	Pt		POINT
+}
+
+var (
+	dispatchMessage = user32.NewProc("DispatchMessageW")
+	getMessage = user32.NewProc("GetMessageW")
+	translateMessage = user32.NewProc("TranslateMessage")
+)
+
+// TODO handle errors
+func DispatchMessage(lpmsg *MSG) (result LRESULT, err error) {
+	r1, _, _ := dispatchMessage.Call(uintptr(unsafe.Pointer(lpmsg)))
+	return LRESULT(r1), nil
+}
+
+var getMessageFail = -1		// because Go doesn't let me
+
+func GetMessage(hWnd HWND, wMsgFilterMin uint32, wMsgFilterMax uint32) (lpMsg *MSG, quit bool, err error) {
+	lpMsg = new(MSG)
+	r1, _, err := getMessage.Call(
+		uintptr(unsafe.Pointer(lpMsg)),
+		uintptr(hWnd),
+		uintptr(wMsgFilterMin),
+		uintptr(wMsgFilterMax))
+	if r1 == uintptr(getMessageFail) {		// failure
+		return nil, false, err
+	}
+	return lpMsg, r1 == 0, nil
+}
+
+// TODO handle errors
+func TranslateMessage(lpMsg *MSG) (translated bool, err error) {
+	r1, _, _ := translateMessage.Call(uintptr(unsafe.Pointer(lpMsg)))
+	return r1 != 0, nil
+}

painting.go

@@ -0,0 +1,20 @@
+// 9 february 2014
+package main
+
+import (
+//	"syscall"
+//	"unsafe"
+)
+
+var (
+	updateWindow = user32.NewProc("UpdateWindow")
+)
+
+// TODO is error handling valid here? MSDN just says zero on failure; syscall.LazyProc.Call() always returns non-nil
+func UpdateWindow(hWnd HWND) (err error) {
+	r1, _, err := updateWindow.Call(uintptr(hWnd))
+	if r1 == 0 {		// failure
+		return err
+	}
+	return nil
+}

rectangles.go

@@ -0,0 +1,14 @@
+// 9 february 2014
+package main
+
+import (
+//	"syscall"
+//	"unsafe"
+)
+
+// TODO merge with common.go?
+
+type POINT struct {
+	X	int32
+	Y	int32
+}

windows.go

@@ -6,6 +6,37 @@ import (
 	"unsafe"
 )
 
+// Window styles.
+const (
+	WS_BORDER = 0x00800000
+	WS_CAPTION = 0x00C00000
+	WS_CHILD = 0x40000000
+	WS_CHILDWINDOW = 0x40000000
+	WS_CLIPCHILDREN = 0x02000000
+	WS_CLIPSIBLINGS = 0x04000000
+	WS_DISABLED = 0x08000000
+	WS_DLGFRAME = 0x00400000
+	WS_GROUP = 0x00020000
+	WS_HSCROLL = 0x00100000
+	WS_ICONIC = 0x20000000
+	WS_MAXIMIZE = 0x01000000
+	WS_MAXIMIZEBOX = 0x00010000
+	WS_MINIMIZE = 0x20000000
+	WS_MINIMIZEBOX = 0x00020000
+	WS_OVERLAPPED = 0x00000000
+	WS_OVERLAPPEDWINDOW = (WS_OVERLAPPED | WS_CAPTION | WS_SYSMENU | WS_THICKFRAME | WS_MINIMIZEBOX | WS_MAXIMIZEBOX)
+	WS_POPUP = 0x80000000
+	WS_POPUPWINDOW = (WS_POPUP | WS_BORDER | WS_SYSMENU)
+	WS_SIZEBOX = 0x00040000
+	WS_SYSMENU = 0x00080000
+	WS_TABSTOP = 0x00010000
+	WS_THICKFRAME = 0x00040000
+	WS_TILED = 0x00000000
+	WS_TILEDWINDOW = (WS_OVERLAPPED | WS_CAPTION | WS_SYSMENU | WS_THICKFRAME | WS_MINIMIZEBOX | WS_MAXIMIZEBOX)
+	WS_VISIBLE = 0x10000000
+	WS_VSCROLL = 0x00200000
+)
+
 // Extended window styles.
 const (
 	WS_EX_ACCEPTFILES = 0x00000010
@@ -36,7 +67,12 @@ const (
 	WS_EX_WINDOWEDGE = 0x00000100
 )
 
-// TODO CW_USEDEFAULT
+// bizarrely, this value is given on the page for CreateMDIWindow, but not CreateWindow or CreateWindowEx
+// I do it this way because Go won't let me shove the exact value into an int
+var (
+	_uCW_USEDEFAULT uint = 0x80000000
+	CW_USEDEFAULT = int(_uCW_USEDEFAULT)
+)
 
 // GetSysColor values. These can be cast to HBRUSH (after adding 1) for WNDCLASS as well.
 const (
@@ -78,8 +114,26 @@ const (
 	COLOR_WINDOWTEXT = 8
 )
 
+// ShowWindow settings.
+const (
+	SW_FORCEMINIMIZE = 11
+	SW_HIDE = 0
+	SW_MAXIMIZE = 3
+	SW_MINIMIZE = 6
+	SW_RESTORE = 9
+	SW_SHOW = 5
+	SW_SHOWDEFAULT = 10
+	SW_SHOWMAXIMIZED = 3
+	SW_SHOWMINIMIZED = 2
+	SW_SHOWMINNOACTIVE = 7
+	SW_SHOWNA = 8
+	SW_SHOWNOACTIVATE = 4
+	SW_SHOWNORMAL = 1
+)
+
 var (
 	createWindowEx = user32.NewProc("CreateWindowExW")
+	showWindow = user32.NewProc("ShowWindow")
 )
 
 // TODO use lpParam
@@ -102,3 +156,11 @@ func CreateWindowEx(dwExStyle uint32, lpClassName string, lpWindowName string, d
 	}
 	return HWND(r1), nil
 }
+
+// TODO figure out how to handle errors
+func ShowWindow(hWnd HWND, nCmdShow int) (previouslyVisible bool, err error) {
+	r1, _, _ := showWindow.Call(
+		uintptr(hWnd),
+		uintptr(nCmdShow))
+	return r1 != 0, nil
+}

wndclass.go

@@ -21,7 +21,7 @@ type WNDCLASS struct {
 
 type _WNDCLASSW struct {
 	style				uint32
-	lpfnWndProc		WNDPROC
+	lpfnWndProc		uintptr
 	cbClsExtra		int
 	cbWndExtra		int
 	hInstance			HANDLE
@@ -39,7 +39,7 @@ func (w *WNDCLASS) toNative() *_WNDCLASSW {
 	}
 	return &_WNDCLASSW{
 		style:			w.Style,
-		lpfnWndProc:		w.LpfnWndProc,
+		lpfnWndProc:		syscall.NewCallback(w.LpfnWndProc),
 		cbClsExtra:		w.CbClsExtra,
 		cbWndExtra:		w.CbWndExtra,
 		hInstance:		w.HInstance,