Create a window and display pictures under windows with Golang

This is a creation in Article, where the information may have evolved or changed.

This is a package (library) I have written:

Github.com/jthmath/winapi

This package implements the Golang encapsulation of some Windows API functions.

As for why it is not available (e.g. walk), I will explain it in other words. Let's take a look at the code first.

1th Step, Register window class

Func myregisterclass (Hinstance winapi. HINSTANCE)   (atom uint16, err error)  {    var wc winapi. WNDCLASS    WC. STYLE = WINAPI.CS_HREDRAW | WINAPI.CS_VREDRAW    WC. PFNWNDPROC = WNDPROC    WC. CBCLSEXTRA = 0    WC. CBWNDEXTRA = 0    WC. HINSTANCE = HINSTANCE    WC. HICON = 0    WC. Hcursor, err = winapi. Loadcursorbyid (0, winapi. Idc_arrow)     if err != nil {         RETURN    }    WC. Hbrbackground = winapi. COLOR_WINDOW + 1    WC. pszmenuname =  ""     WC. pszclassname =  "main window class"     WC. Hiconsmall&nbSp;= 0    return winapi. RegisterClass (&WC)}

2nd step, create a window

WND, err: = WINAPI. CreateWindow ("Main window Class", "Golang Windows Programming", WINAPI. Ws_overlappedwindow, 0, WINAPI. Cw_usedefault, WINAPI. Cw_usedefault, WINAPI. Cw_usedefault, WINAPI. Cw_usedefault, 0, 0, Inst, 0) if err! = Nil {fmt. Println ("Create Window Failed") return 0}FMT. Println ("Create Window succeeded", WND) winapi. ShowWindow (WND, Winapi.sw_show) winapi. UpdateWindow (WND)

3rd step, main message loop

var msg winapi. Msgmsg.message = WINAPI. Wm_quit + 1//Let it not be equal to WINAPI. Wm_quitfor WINAPI. GetMessage (&msg, 0, 0, 0) > 0 {winapi. TranslateMessage (&msg) winapi. DispatchMessage (&MSG)}

These steps are no different than writing Windows programs in C or C + +, except that the current function is Golang style.

Of course, you should also map the corresponding WM_PAINT message.

Func wndproc (Hwnd winapi. HWND, MESSAGE UINT32, WPARAM UINTPTR, LPARAM UINTPTR)  uintptr {     var htemp winapi. Handle    switch message {    case winapi. Wm_create:        htemp, _ = winapi. Loadimagebyname (0,  "D:\\0004.bmp",             winapi. Image_bitmap, 0, 0, winapi. Lr_loadfromfile)         hbitmap = winapi. Hbitmap (htemp)     case winapi. Wm_paint:        onpaint (hWnd)     case winapi . Wm_destroy:        winapi. PostQuitMessage (0)     case winapi. Wm_command:        oncommand (hwnd, wParam, lparam)     default:        return  winapi. DefWindowProc (Hwnd, message, wparam, lparam)     }     Return 0}func onpaint (Hwnd winapi. HWND)  {    var err error    var ps winapi. Paintstruct    hdc, err := winapi. BeginPaint (HWND, &PS)     if err != nil {         return    }    defer winapi. EndPaint (HWND, &PS)  // defer  finally comes in handy     // HDC MDC  = CREATECOMPATIBLEDC (hdc);     mdc, err := winapi. CreateCompatibleDC (HDC)     if err != nil {         return&nbSp;   }    defer winapi. DeleteDC (MDC)     winapi. SelectObject (Mdc, winapi. Hgdiobj (HBITMAP))     winapi. BitBlt (Hdc, 0, 0, 480, 640, mdc, 0, 0, winapi. Srccopy)}

The effect is as follows:

Full code

package mainimport  (     "FMT"      "Runtime"       "GITHUB.COM/JTHMATH/WINAPI")//  global variable VAR HBITMAP WINAPI. Hbitmapfunc init ()  {    runtime. Gomaxprocs (runtime. NUMCPU ())}func main ()  {    inst, err := winapi. GetModuleHandle ("")     if err != nil {         fmt. Println ("Get instance failed")         return    }     r := winmain (inst,  "",  0)     fmt. PRINTLN ("WinMain function returns",  r)}func winmain (Inst winapi. Hinstance, cmd string, ncmdshow int32)  int32 {    var  err error    // 1.  Register window class     atom, err :=  myregisterclass (Inst)     if err != nil {        fmt. PRINTLN ("Register window class failed")         return 0    }     fmt. PRINTLN ("Register window class succeeded",  atom)     // 2.  Create window     wnd, err  := winapi. CreateWindow ("Main window class",  "golang windows  Programming",         WINAPI . Ws_overlappedwindow, 0,        winapi. Cw_usedefault, winapi. Cw_usedefault, winapi. Cw_usedefault, winapi. cw_usedefault,        0, 0, inst, 0)      if err != nil {        fmt. Println ("Create Window failed")         return 0    }     fmt. Println ("Create Window succeeded",  wnd) &NBSp;   winapi. ShowWindow (wnd, winapi.sw_show)     winapi. UpdateWindow (WND)     // 3.  main message loop     var msg winapi . Msg    msg. Message = winapi. wm_quit + 1 //  make it not equal to  WINAPI. Wm_quit    for winapi. GetMessage (&msg, 0, 0, 0)  > 0 {         winapi. TranslateMessage (&msg)         winapi. DispatchMessage (&msg)     }    return int32 (Msg. WParam)}func wndproc (Hwnd winapi. HWND, MESSAGE UINT32, WPARAM UINTPTR, LPARAM UINTPTR)  uintptr {     var htemp winapi. Handle    switch message {    case winapi. Wm_create:     &nBsp;  htemp, _ = winapi. Loadimagebyname (0,  "D:\\0004.bmp",             winapi. Image_bitmap, 0, 0, winapi. Lr_loadfromfile)         hbitmap = winapi. Hbitmap (htemp)     case winapi. Wm_paint:        onpaint (hWnd)     case winapi . Wm_destroy:        winapi. PostQuitMessage (0)     case winapi. Wm_command:        oncommand (Hwnd, wparam, lparam)      default:        return winapi. DefWindowProc (Hwnd, message, wparam, lparam)     }     Return 0}func onpaint (Hwnd winapi. HWND)  {    var err  Error    var ps winapi. Paintstruct    hdc, err := winapi. BeginPaint (HWND, &PS)     if err != nil {         return    }    defer winapi. EndPaint (HWND, &PS)  // defer  finally comes in handy     // HDC MDC  = CREATECOMPATIBLEDC (hdc);     mdc, err := winapi. CreateCompatibleDC (HDC)     if err != nil {         return    }    defer winapi. DeleteDC (MDC)     winapi. SelectObject (Mdc, winapi. Hgdiobj (HBITMAP)     //  the 4th and 5 parameters of this function are the width and height of the picture     //  for simplicity, I wrote it right here.     //  the actual project, of course, to use the program to get a     wInapi. BitBlt (Hdc, 0, 0, 480, 640, mdc, 0, 0, winapi. srccopy)}func oncommand (Hwnd winapi. HWND, WPARAM UINTPTR, LPARAM UINTPTR)  {    //  No special treatment required for the time being  wm_command    winapi. DefWindowProc (Hwnd, winapi. Wm_command, wparam, lparam)}func myregisterclass (Hinstance winapi. HINSTANCE)   (atom uint16, err error)  {    var wc winapi. WNDCLASS    WC. STYLE = WINAPI.CS_HREDRAW | WINAPI.CS_VREDRAW    WC. PFNWNDPROC = WNDPROC    WC. CBCLSEXTRA = 0    WC. CBWNDEXTRA = 0    WC. HINSTANCE = HINSTANCE    WC. HICON = 0    WC. Hcursor, err = winapi. Loadcursorbyid (0, winapi. Idc_arrow)   &NBsp; if err != nil {        return     }    WC. Hbrbackground = winapi. COLOR_WINDOW + 1    WC. pszmenuname =  ""     WC. pszclassname =  "main window class"     WC. Hiconsmall = 0    return winapi. RegisterClass (&WC)}