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// 7 february 2014
package main
import (
"fmt"
"os"
"runtime"
)
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 (
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 {
fatalf("error destroying window: %v", err)
}
return 0
case WM_DESTROY:
err := PostQuitMessage(0)
if err != nil {
fatalf("error posting quit message: %v", err)
}
return 0
default:
return DefWindowProc(hwnd, msg, wParam, lParam)
}
fatalf("major bug: forgot a return on wndProc for message %d", msg)
panic("unreachable")
}
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: wndProc,
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 = 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)
}
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)
}
}
}
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