# Go调用SDL2的C语言动态库
在网上找到go的GUI项目基本都需要安装额外软件库，尝试了一下使用go调用dll库的，有所收获，抛砖引玉，留个记录怕以后忘了。
## 1.目录结构
```
└─libtest
│ main.go
│ sdl.go
└─ lib
SDL2.dll
```
## 2. 库函数封装(sdl.go)
```
package main
import (
"syscall"
"unsafe"
)
//SDL_INIT_Flag 初始化标志
const (
SDL_INIT_TIMER = 0x00000001
SDL_INIT_AUDIO = 0x00000010
SDL_INIT_VIDEO = 0x00000020 /**< SDL_INIT_VIDEO implies SDL_INIT_EVENTS */
SDL_INIT_JOYSTICK = 0x00000200 /**< SDL_INIT_JOYSTICK implies SDL_INIT_EVENTS */
SDL_INIT_HAPTIC = 0x00001000
SDL_INIT_GAMECONTROLLER = 0x00002000 /**< SDL_INIT_GAMECONTROLLER implies SDL_INIT_JOYSTICK */
SDL_INIT_EVENTS = 0x00004000
SDL_INIT_NOPARACHUTE = 0x00100000 /**< compatibility; this flag is ignored. */
SDL_INIT_EVERYTHING = SDL_INIT_TIMER | SDL_INIT_AUDIO | SDL_INIT_VIDEO | SDL_INIT_EVENTS |
SDL_INIT_JOYSTICK | SDL_INIT_HAPTIC | SDL_INIT_GAMECONTROLLER
)
// SDL_WindowFlags 窗体标志
const (
/* !!! FIXME: change this to name = (1<<x). */
SDL_WINDOW_FULLSCREEN = 0x00000001 /**< fullscreen window */
SDL_WINDOW_OPENGL = 0x00000002 /**< window usable with OpenGL context */
SDL_WINDOW_SHOWN = 0x00000004 /**< window is visible */
SDL_WINDOW_HIDDEN = 0x00000008 /**< window is not visible */
SDL_WINDOW_BORDERLESS = 0x00000010 /**< no window decoration */
SDL_WINDOW_RESIZABLE = 0x00000020 /**< window can be resized */
SDL_WINDOW_MINIMIZED = 0x00000040 /**< window is minimized */
SDL_WINDOW_MAXIMIZED = 0x00000080 /**< window is maximized */
SDL_WINDOW_INPUT_GRABBED = 0x00000100 /**< window has grabbed input focus */
SDL_WINDOW_INPUT_FOCUS = 0x00000200 /**< window has input focus */
SDL_WINDOW_MOUSE_FOCUS = 0x00000400 /**< window has mouse focus */
SDL_WINDOW_FULLSCREEN_DESKTOP = (SDL_WINDOW_FULLSCREEN | 0x00001000)
SDL_WINDOW_FOREIGN = 0x00000800 /**< window not created by SDL */
SDL_WINDOW_ALLOW_HIGHDPI = 0x00002000 /**< window should be created in high-DPI mode if supported.
On macOS NSHighResolutionCapable must be set true in the
application's Info.plist for this to have any effect. */
SDL_WINDOW_MOUSE_CAPTURE = 0x00004000 /**< window has mouse captured (unrelated to INPUT_GRABBED) */
SDL_WINDOW_ALWAYS_ON_TOP = 0x00008000 /**< window should always be above others */
SDL_WINDOW_SKIP_TASKBAR = 0x00010000 /**< window should not be added to the taskbar */
SDL_WINDOW_UTILITY = 0x00020000 /**< window should be treated as a utility window */
SDL_WINDOW_TOOLTIP = 0x00040000 /**< window should be treated as a tooltip */
SDL_WINDOW_POPUP_MENU = 0x00080000 /**< window should be treated as a popup menu */
SDL_WINDOW_VULKAN = 0x10000000 /**< window usable for Vulkan surface */
)
// SDL_Window SDL窗体
type SDL_Window struct{}
// SDL_Event SDL 事件
type SDL_Event struct{}
// SDL_Init SDL 初始化
func SDL_Init(flags uint32) bool {
ret := SysCallDll("SDL_Init", 1, uintptr(flags))
if int(ret) == 0 {
return true
}
return false
}
// SDL_CreateWindow 创建window窗体,失败返回nil
func SDL_CreateWindow(title string, posX, posY, width, height, sdlWindowFlag int32) *SDL_Window {
var tp, _ = syscall.BytePtrFromString(title) // 将string转为*byte
var tptr = unsafe.Pointer(tp) // 获取*byte指针
ret := SysCallDll("SDL_CreateWindow", 6, uintptr(tptr), uintptr(posX), uintptr(posY),
uintptr(width), uintptr(height), uintptr(sdlWindowFlag))
if int(ret) == 0 {
return nil
}
return (*SDL_Window)(unsafe.Pointer(ret))
}
// SDL_Delay 延迟xxx ms后返回
func SDL_Delay(ms uint32) {
SysCallDll("SDL_Delay", 1, uintptr(ms))
}
// SDL_DestroyWindow 销毁窗体
func SDL_DestroyWindow(window *SDL_Window) {
SysCallDll("SDL_DestroyWindow", 1, uintptr(unsafe.Pointer(window)))
}
//SDL_Quit(void) 退出SDL系统
func SDL_Quit() {
SysCallDll("SDL_Quit", 0)
}
// SDL_PollEvent 轮询当前挂起的事件
func SDL_PollEvent(event *SDL_Event) bool {
ret := SysCallDll("SDL_PollEvent", 1, uintptr(unsafe.Pointer(event)))
if int(ret) == 1 {
return true
}
return false
}
```
## 3. 加载动态库(main.go)
```
package main
import (
"fmt"
"syscall"
"unsafe"
)
// ThrowErr 抛出异常
func ThrowErr(str string, err error) {
if err != nil {
fmt.Printf("[Err]:%s,%v\n", str, err)
}
}
// 动态库的指针
var hsdl syscall.Handle
// LoadDLL 加载动态库
func LoadDll() {
var err error
hsdl, err = syscall.LoadLibrary("lib/SDL2.dll")
ThrowErr("LoadLibrary-SDL", err)
}
// FreeDll 释放动态库
func FreeDll() {
if hsdl != 0 {
syscall.FreeLibrary(hsdl)
}
}
// SysCallDll 包装syscall.Syscall/6/9/12 调用动态库内函数
// funcName 函数名; argsNum 参数个数; args 可变参数
func SysCallDll(funcName string, argsNum int32, args ...uintptr) (r uintptr) {
proc, err := syscall.GetProcAddress(hsdl, funcName)
ThrowErr(funcName, err)
var errs error
var debug bool = false
var fargs = [12]uintptr{} //获取参数
for i, arg := range args {
fargs[i] = arg
}
if (argsNum > -1) && (argsNum < 4) { //小于等于3个参数
r, _, errs = syscall.Syscall(uintptr(proc), uintptr(argsNum),
fargs[0], fargs[1], fargs[2])
//ThrowErr(funcName, errs)
} else if (argsNum > 3) && (argsNum < 7) { //小于等于6个参数
r, _, errs = syscall.Syscall6(uintptr(proc), uintptr(argsNum),
fargs[0], fargs[1], fargs[2], fargs[3], fargs[4], fargs[5])
//ThrowErr(funcName, errs)
} else if (argsNum > 6) && (argsNum < 10) { //小于等于9个参数
r, _, errs = syscall.Syscall9(uintptr(proc), uintptr(argsNum), fargs[0], fargs[1],
fargs[2], fargs[3], fargs[4], fargs[5], fargs[6], fargs[7], fargs[8])
//ThrowErr(funcName, errs)
} else if (argsNum > 9) && (argsNum < 13) { //小于等于12个参数
r, _, errs = syscall.Syscall12(uintptr(proc), uintptr(argsNum), fargs[0], fargs[1],
fargs[2], fargs[3], fargs[4], fargs[5], fargs[6], fargs[7], fargs[8],
fargs[9], fargs[10], fargs[11])
//ThrowErr(funcName, errs)
} else {
fmt.Println("The args number was bigger than 12.")
}
if debug {
fmt.Println(errs)
}
return r
}
// CharPtr2String 从char指针读取string
func CharPtr2String(vcode uintptr) string {
var vbyte []byte
for i := 0; i < 20; i++ {
sbyte := *((*byte)(unsafe.Pointer(vcode)))
if sbyte == 0 {
break
}
vbyte = append(vbyte, sbyte)
vcode += 1
}
return string(vbyte)
}
// testSdlWindow 创建窗体，然后暂停程序所以窗体没响应
func testSdlWindow() {
LoadDll() // 加载动态库
if SDL_Init(SDL_INIT_VIDEO) { // 初始化视频子系统
// 创建窗体
win := SDL_CreateWindow("SDL窗体标题", 50, 50, 600, 480, SDL_WINDOW_SHOWN)
if win == nil {
fmt.Println("SDL_CreateWindow 失败")
}
SDL_Delay(6000) // 暂停程序6000ms
SDL_DestroyWindow(win) // 销毁释放窗体
}
SDL_Quit() // 退出清理SDL
defer FreeDll() // 释放动态库SDL2.dll
}
// testSdlWindow2 创建窗体，使用事件循环显示可响应窗体
func testSdlWindow2() {
LoadDll() // 加载动态库
if SDL_Init(SDL_INIT_VIDEO) { // 初始化视频子系统
// 创建窗体
win := SDL_CreateWindow("SDL窗体标题", 50, 50, 600, 480, SDL_WINDOW_SHOWN)
if win == nil {
fmt.Println("SDL_CreateWindow 失败")
}
for { // 事件循环
if SDL_PollEvent(evt) { // 轮询事件队列
// 此处SDL_Event在C语言中为联合，需要其他处理
// if GetEventType(evt) == SDL_QUIT { // 退出事件
// break
// }
}
}
SDL_DestroyWindow(win) // 销毁释放窗体
SDL_Quit() // 退出清理SDL
defer FreeDll() // 释放动态库SDL2.dll
}
}
var evt = new(SDL_Event) // SDL事件
func main() {
testSdlWindow2()
}
```
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