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webview.go
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webview.go
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package webview
/*
#cgo linux openbsd freebsd CXXFLAGS: -DWEBVIEW_GTK -std=c++11
#cgo linux openbsd freebsd pkg-config: gtk+-3.0 webkit2gtk-4.0
#cgo darwin CXXFLAGS: -DWEBVIEW_COCOA -std=c++11
#cgo darwin LDFLAGS: -framework WebKit
#cgo windows CXXFLAGS: -std=c++11
#cgo windows,amd64 LDFLAGS: -L./dll/x64 -lwebview -lWebView2Loader
#cgo windows,386 LDFLAGS: -L./dll/x86 -lwebview -lWebView2Loader
#define WEBVIEW_HEADER
#include "webview.h"
#include <stdlib.h>
#include <stdint.h>
extern void _webviewDispatchGoCallback(void *);
static inline void _webview_dispatch_cb(webview_t w, void *arg) {
_webviewDispatchGoCallback(arg);
}
static inline void CgoWebViewDispatch(webview_t w, uintptr_t arg) {
webview_dispatch(w, _webview_dispatch_cb, (void *)arg);
}
struct binding_context {
webview_t w;
uintptr_t index;
};
extern void _webviewBindingGoCallback(webview_t, char *, char *, uintptr_t);
static inline void _webview_binding_cb(const char *id, const char *req, void *arg) {
struct binding_context *ctx = (struct binding_context *) arg;
_webviewBindingGoCallback(ctx->w, (char *)id, (char *)req, ctx->index);
}
static inline void CgoWebViewBind(webview_t w, const char *name, uintptr_t index) {
struct binding_context *ctx = calloc(1, sizeof(struct binding_context));
ctx->w = w;
ctx->index = index;
webview_bind(w, name, _webview_binding_cb, (void *)ctx);
}
*/
import "C"
import (
"encoding/json"
"errors"
"reflect"
"runtime"
"strings"
"sync"
"unsafe"
// App
"net"
"net/http"
"io/fs"
"strconv"
"embed"
"fmt"
)
func init() {
// Ensure that main.main is called from the main thread
runtime.LockOSThread()
}
// Hints are used to configure window sizing and resizing
type Hint int
const (
// Width and height are default size
HintNone = C.WEBVIEW_HINT_NONE
// Window size can not be changed by a user
HintFixed = C.WEBVIEW_HINT_FIXED
// Width and height are minimum bounds
HintMin = C.WEBVIEW_HINT_MIN
// Width and height are maximum bounds
HintMax = C.WEBVIEW_HINT_MAX
)
type WebView interface {
// Run runs the main loop until it's terminated. After this function exits -
// you must destroy the webview.
Run()
// Terminate stops the main loop. It is safe to call this function from
// a background thread.
Terminate()
// Dispatch posts a function to be executed on the main thread. You normally
// do not need to call this function, unless you want to tweak the native
// window.
Dispatch(f func())
// Destroy destroys a webview and closes the native window.
Destroy()
// Window returns a native window handle pointer. When using GTK backend the
// pointer is GtkWindow pointer, when using Cocoa backend the pointer is
// NSWindow pointer, when using Win32 backend the pointer is HWND pointer.
Window() unsafe.Pointer
// SetTitle updates the title of the native window. Must be called from the UI
// thread.
SetTitle(title string)
// SetSize updates native window size. See Hint constants.
SetSize(w int, h int, hint Hint)
// Navigate navigates webview to the given URL. URL may be a data URI, i.e.
// "data:text/text,<html>...</html>". It is often ok not to url-encode it
// properly, webview will re-encode it for you.
Navigate(url string)
// Init injects JavaScript code at the initialization of the new page. Every
// time the webview will open a the new page - this initialization code will
// be executed. It is guaranteed that code is executed before window.onload.
Init(js string)
// Eval evaluates arbitrary JavaScript code. Evaluation happens asynchronously,
// also the result of the expression is ignored. Use RPC bindings if you want
// to receive notifications about the results of the evaluation.
Eval(js string)
// Bind binds a callback function so that it will appear under the given name
// as a global JavaScript function. Internally it uses webview_init().
// Callback receives a request string and a user-provided argument pointer.
// Request string is a JSON array of all the arguments passed to the
// JavaScript function.
//
// f must be a function
// f must return either value and error or just error
Bind(name string, f interface{}) error
// Topmost forces a window to float above all other windows
Topmost(makeTopmost ...bool)
// SetPosition updates the position of the native window
SetPosition(x int, y int)
// Center centers the window relative to the primary monitor
Center()
// NoCtx, removes the default right click context menu in the webview
NoCtx()
}
type webview struct {
w C.webview_t
}
var (
m sync.Mutex
index uintptr
dispatch = map[uintptr]func(){}
bindings = map[uintptr]func(id, req string) (interface{}, error){}
)
func boolToInt(b bool) C.int {
if b {
return 1
}
return 0
}
// New calls NewWindow to create a new window and a new webview instance. If debug
// is non-zero - developer tools will be enabled (if the platform supports them).
func New(debug ...bool) WebView {
d := false
if len(debug) > 0 {
d = debug[0]
}
return NewWindow(d, nil)
}
// NewWindow creates a new webview instance. If debug is non-zero - developer
// tools will be enabled (if the platform supports them). Window parameter can be
// a pointer to the native window handle. If it's non-null - then child WebView is
// embedded into the given parent window. Otherwise a new window is created.
// Depending on the platform, a GtkWindow, NSWindow or HWND pointer can be passed
// here.
func NewWindow(debug bool, window unsafe.Pointer) WebView {
w := &webview{}
w.w = C.webview_create(boolToInt(debug), window)
return w
}
// EscapeJs is a helper function that escapes characters in html/js code that would otherwise be removed by url_decode, causing errors
// if your url is as data:text/html, with a script tag containing the characters + or %, use this function and pass its output to Navigate
func EscapeJs(js string) string {
length := len(js)
var output strings.Builder
for i := 0; i < length; i++ {
if js[i] == '+' {
output.WriteString("%2b")
} else if js[i] == '%' {
output.WriteString("%25")
} else {
output.WriteByte(js[i])
}
}
return output.String()
}
func (w *webview) Destroy() {
C.webview_destroy(w.w)
}
func (w *webview) Run() {
C.webview_run(w.w)
}
func (w *webview) Terminate() {
C.webview_terminate(w.w)
}
func (w *webview) Window() unsafe.Pointer {
return C.webview_get_window(w.w)
}
func (w *webview) Navigate(url string) {
s := C.CString(url)
defer C.free(unsafe.Pointer(s))
C.webview_navigate(w.w, s)
}
func (w *webview) SetTitle(title string) {
s := C.CString(title)
defer C.free(unsafe.Pointer(s))
C.webview_set_title(w.w, s)
}
func (w *webview) SetSize(width int, height int, hint Hint) {
C.webview_set_size(w.w, C.int(width), C.int(height), C.int(hint))
}
func (w *webview) Init(js string) {
s := C.CString(js)
defer C.free(unsafe.Pointer(s))
C.webview_init(w.w, s)
}
func (w *webview) Eval(js string) {
s := C.CString(js)
defer C.free(unsafe.Pointer(s))
C.webview_eval(w.w, s)
}
func (w *webview) Dispatch(f func()) {
m.Lock()
for ; dispatch[index] != nil; index++ {
}
dispatch[index] = f
m.Unlock()
C.CgoWebViewDispatch(w.w, C.uintptr_t(index))
}
//export _webviewDispatchGoCallback
func _webviewDispatchGoCallback(index unsafe.Pointer) {
m.Lock()
f := dispatch[uintptr(index)]
delete(dispatch, uintptr(index))
m.Unlock()
f()
}
//export _webviewBindingGoCallback
func _webviewBindingGoCallback(w C.webview_t, id *C.char, req *C.char, index uintptr) {
m.Lock()
f := bindings[uintptr(index)]
m.Unlock()
jsString := func(v interface{}) string { b, _ := json.Marshal(v); return string(b) }
status, result := 0, ""
if res, err := f(C.GoString(id), C.GoString(req)); err != nil {
status = -1
result = jsString(err.Error())
} else if b, err := json.Marshal(res); err != nil {
status = -1
result = jsString(err.Error())
} else {
status = 0
result = string(b)
}
s := C.CString(result)
defer C.free(unsafe.Pointer(s))
C.webview_return(w, id, C.int(status), s)
}
func (w *webview) Bind(name string, f interface{}) error {
v := reflect.ValueOf(f)
// f must be a function
if v.Kind() != reflect.Func {
return errors.New("only functions can be bound")
}
// f must return either value and error or just error
if n := v.Type().NumOut(); n > 2 {
return errors.New("function may only return a value or a value+error")
}
binding := func(id, req string) (interface{}, error) {
raw := []json.RawMessage{}
if err := json.Unmarshal([]byte(req), &raw); err != nil {
return nil, err
}
isVariadic := v.Type().IsVariadic()
numIn := v.Type().NumIn()
if (isVariadic && len(raw) < numIn-1) || (!isVariadic && len(raw) != numIn) {
return nil, errors.New("function arguments mismatch")
}
args := []reflect.Value{}
for i := range raw {
var arg reflect.Value
if isVariadic && i >= numIn-1 {
arg = reflect.New(v.Type().In(numIn - 1).Elem())
} else {
arg = reflect.New(v.Type().In(i))
}
if err := json.Unmarshal(raw[i], arg.Interface()); err != nil {
return nil, err
}
args = append(args, arg.Elem())
}
errorType := reflect.TypeOf((*error)(nil)).Elem()
res := v.Call(args)
switch len(res) {
case 0:
// No results from the function, just return nil
return nil, nil
case 1:
// One result may be a value, or an error
if res[0].Type().Implements(errorType) {
if res[0].Interface() != nil {
return nil, res[0].Interface().(error)
}
return nil, nil
}
return res[0].Interface(), nil
case 2:
// Two results: first one is value, second is error
if !res[1].Type().Implements(errorType) {
return nil, errors.New("second return value must be an error")
}
if res[1].Interface() == nil {
return res[0].Interface(), nil
}
return res[0].Interface(), res[1].Interface().(error)
default:
return nil, errors.New("unexpected number of return values")
}
}
m.Lock()
for ; bindings[index] != nil; index++ {
}
bindings[index] = binding
m.Unlock()
cname := C.CString(name)
defer C.free(unsafe.Pointer(cname))
C.CgoWebViewBind(w.w, cname, C.uintptr_t(index))
return nil
}
func (w *webview) Topmost(makeTopmost ...bool) {
var setting C.int
if len(makeTopmost) > 0 {
if t := makeTopmost[0]; t {
setting = 1
} else {
setting = 0
}
}
C.webview_topmost(w.w, setting)
}
func (w *webview) SetPosition(x int, y int) {
C.webview_set_position(w.w, C.int(x), C.int(y))
}
func (w *webview) Center() {
C.webview_center(w.w)
}
func (w *webview) NoCtx() {
C.webview_no_ctx(w.w)
}
type RouteFunc = func(http.ResponseWriter, *http.Request)
type App struct {
Width int
Height int
Title string
Content embed.FS
ContentRoot string
Init func(WebView)
ServerInit func()
Routes map[string] RouteFunc
Topmost bool
Debug bool
server *http.ServeMux
}
func (app App) Run() {
portChannel := make(chan string)
go serve(&app, portChannel)
runtime.LockOSThread()
w := New(app.Debug)
defer w.Destroy()
if app.Width == 0 {
app.Width = 500
}
if app.Height == 0 {
app.Height = 500
}
w.SetSize(app.Width, app.Height, HintFixed)
w.Center()
if !app.Debug {
w.NoCtx()
}
w.SetTitle(app.Title)
if app.Topmost {
w.Topmost(true)
}
if (app.Init != nil) {
app.Init(w)
}
port := <- portChannel
w.Navigate("http://localhost:"+port)
w.Bind("_webview_log", func(args []string){
joined := strings.Join(args, " ")
println(joined)
})
w.Init(fmt.Sprintf(`
const _webview_width=%d;
const _webview_height=%d;
const _webview={
width:_webview_width,
height:_webview_height,
title:'%s',
address:'http://localhost:%s/',
log(){
const args = Array.from(arguments).map(a=>typeof a == 'object' ? JSON.stringify(a) : a.toString());
_webview_log(args);
}
};
Object.freeze(_webview);
window.addEventListener("load", ()=>{
document.body.style.cssText += 'margin:0px;overflow:hidden;'
})
`, app.Width, app.Height, app.Title, port))
w.Run()
}
func serve(app *App, portChannel chan<- string) {
if app.server == nil {
app.server = http.NewServeMux()
}
content, _ := fs.Sub(app.Content, app.ContentRoot)
app.server.Handle("/", http.FileServer(http.FS(content)))
if app.ServerInit != nil {
app.ServerInit()
}
// handle routes
if app.Routes != nil {
for route, handler := range app.Routes {
wrapper := func(w http.ResponseWriter, r *http.Request) {
// set headers to allow fetch locally
w.Header().Set("Access-Control-Allow-Origin", "*")
w.Header().Set("Access-Control-Allow-Methods", "POST, GET, OPTIONS, PUT, DELETE")
w.Header().Set("Access-Control-Allow-Headers", "Accept, Content-Type, Content-Length, Accept-Encoding, X-CSRFToken, Authorization")
// call the actual handler function
handler(w,r)
}
app.server.HandleFunc(route, wrapper)
}
}
listener, err := net.Listen("tcp", ":0")
if err != nil {
panic(err)
}
port := strconv.Itoa(listener.Addr().(*net.TCPAddr).Port)
portChannel <- port
close(portChannel)
http.Serve(listener, app.server)
}