io,app: add deeplinking support

Now, it's possible to launch one Gio app using a custom URI scheme, such as `gio://some/data`.

This feature is supported on Android, iOS, macOS and Windows, issuing a new deeplink.Event,
containing the URL launched. If the program is already opened, one deeplink.Event will be
sent to the current opened app.

Limitations:
On Windows, if the program uses deeplink (compiled with `-deeplink`), then just a single
instance of the app can be open. In other words, just a single `myprogram.exe` can
be active.

Security:
Deeplinking have the same level of security of clipboard. Any other software can send such
information and read the content, without any restriction. That should not be used to transfer
sensible data, and can't be fully trusted.

Setup/Compiling:
In order to set the custom scheme, you need to use the new `-deeplink` flag in `gogio`, using
as `-deeplink gio` will listen to `gio://`.

If you are not using gogio you need to defined some values, which varies for each OS:

macOS/iOS - You need to define the following Properly List:
```
<key>CFBundleURLTypes</key>
<array>
  <dict>
	<key>CFBundleURLSchemes</key>
	<array>
	  <string>yourCustomScheme</string>
	</array>
  </dict>
</array>
```

Windows - You need to compiling using -X argument:
```
-ldflags="-X "gioui.org/app.schemesDeeplink=yourCustomScheme" -H=windowsgui"
```

Android - You need to add IntentFilter in GioActivity:
```
<intent-filter>
	<action android:name="android.intent.action.VIEW"></action>
	<category android:name="android.intent.category.DEFAULT"></category>
	<category android:name="android.intent.category.BROWSABLE"></category>
	<data android:scheme="yourCustomScheme"></data>
</intent-filter>
```

That assumes that you still using GioActivity and GioAppDelegate, otherwise more
changes are required.

Signed-off-by: inkeliz <inkeliz@inkeliz.com>

Author: inkeliz

app/GioActivity.java

@@ -4,6 +4,7 @@
 
 import android.app.Activity;
 import android.os.Bundle;
+import android.content.Intent;
 import android.content.res.Configuration;
 import android.view.ViewGroup;
 import android.view.View;
@@ -29,6 +30,7 @@ public final class GioActivity extends Activity {
 
             layer.addView(view);
             setContentView(layer);
+            onNewIntent(this.getIntent());
 	}
 
 	@Override public void onDestroy() {
@@ -60,4 +62,9 @@ public final class GioActivity extends Activity {
 		if (!view.backPressed())
 			super.onBackPressed();
 	}
+
+	@Override protected void onNewIntent(Intent intent) {
+		super.onNewIntent(intent);
+        view.onIntentEvent(intent);
+	}
 }

app/GioView.java

@@ -12,6 +12,7 @@
 import android.app.FragmentManager;
 import android.app.FragmentTransaction;
 import android.content.Context;
+import android.content.Intent;
 import android.graphics.Canvas;
 import android.graphics.Color;
 import android.graphics.Matrix;
@@ -311,6 +312,15 @@ private void setHighRefreshRate() {
 		window.setAttributes(layoutParams);
 	}
 
+	protected void onIntentEvent(Intent intent) {
+        if (intent == null) {
+            return;
+        }
+        if (intent.getData() != null) {
+            this.onDeeplink(nhandle, intent.getData().toString());
+        }
+    }
+
 	@Override protected boolean dispatchHoverEvent(MotionEvent event) {
 		if (!accessManager.isTouchExplorationEnabled()) {
 			return super.dispatchHoverEvent(event);
@@ -549,6 +559,7 @@ void updateCaret(float m00, float m01, float m02, float m10, float m11, float m1
 	static private native void onExitTouchExploration(long handle);
 	static private native void onA11yFocus(long handle, int viewId);
 	static private native void onClearA11yFocus(long handle, int viewId);
+	static private native void onDeeplink(long handle, String uri);
 	static private native void imeSetSnippet(long handle, int start, int end);
 	static private native String imeSnippet(long handle);
 	static private native int imeSnippetStart(long handle);

app/framework_ios.h

@@ -3,4 +3,5 @@
 #include <UIKit/UIKit.h>
 
 @interface GioViewController : UIViewController
+- (BOOL)onDeeplink:(NSString *)url;
 @end

app/internal/windows/windows.go

@@ -99,6 +99,8 @@ const (
 
 	CW_USEDEFAULT = -2147483648
 
+	ERROR_ALREADY_EXISTS = 183
+
 	GWL_STYLE = ^(uintptr(16) - 1) // -16
 
 	GCS_COMPSTR       = 0x0008
@@ -111,7 +113,8 @@ const (
 	CFS_POINT        = 0x0002
 	CFS_CANDIDATEPOS = 0x0040
 
-	HWND_TOPMOST = ^(uint32(1) - 1) // -1
+	HWND_TOPMOST   = ^(uint32(1) - 1) // -1
+	HWND_BROADCAST = 0xFFFF
 
 	HTCAPTION     = 2
 	HTCLIENT      = 1
@@ -303,15 +306,25 @@ const (
 	LR_MONOCHROME       = 0x00000001
 	LR_SHARED           = 0x00008000
 	LR_VGACOLOR         = 0x00000080
+
+	FILE_MAP_READ = 0x0004
+)
+
+var (
+	GIO_DEEPLINKING uint32 // Custom message for deep linking, lazy init
 )
 
 var (
 	kernel32          = syscall.NewLazySystemDLL("kernel32.dll")
+	_CreateMutex      = kernel32.NewProc("CreateMutexW")
+	_GetMutexInfo     = kernel32.NewProc("GetMutexInfo")
 	_GetModuleHandleW = kernel32.NewProc("GetModuleHandleW")
 	_GlobalAlloc      = kernel32.NewProc("GlobalAlloc")
 	_GlobalFree       = kernel32.NewProc("GlobalFree")
 	_GlobalLock       = kernel32.NewProc("GlobalLock")
 	_GlobalUnlock     = kernel32.NewProc("GlobalUnlock")
+	_OpenFileMapping  = kernel32.NewProc("OpenFileMappingA")
+	_ReleaseMutex     = kernel32.NewProc("ReleaseMutex")
 
 	user32                       = syscall.NewLazySystemDLL("user32.dll")
 	_AdjustWindowRectEx          = user32.NewProc("AdjustWindowRectEx")
@@ -347,9 +360,11 @@ var (
 	_PostQuitMessage             = user32.NewProc("PostQuitMessage")
 	_ReleaseCapture              = user32.NewProc("ReleaseCapture")
 	_RegisterClassExW            = user32.NewProc("RegisterClassExW")
+	_RegisterWindowMessage       = user32.NewProc("RegisterWindowMessageW")
 	_ReleaseDC                   = user32.NewProc("ReleaseDC")
 	_ScreenToClient              = user32.NewProc("ScreenToClient")
 	_ShowWindow                  = user32.NewProc("ShowWindow")
+	_SendMessage                 = user32.NewProc("SendMessageW")
 	_SetCapture                  = user32.NewProc("SetCapture")
 	_SetCursor                   = user32.NewProc("SetCursor")
 	_SetClipboardData            = user32.NewProc("SetClipboardData")
@@ -651,6 +666,42 @@ func GlobalUnlock(h syscall.Handle) {
 	_GlobalUnlock.Call(uintptr(h))
 }
 
+func CreateMutex(name string) (ptr syscall.Handle, alreadyExists bool, err error) {
+	r, _, err := _CreateMutex.Call(0, 0, uintptr(unsafe.Pointer(syscall.StringToUTF16Ptr(name))))
+	switch err.(syscall.Errno) {
+	case 0:
+		return syscall.Handle(r), false, nil
+	case ERROR_ALREADY_EXISTS:
+		return syscall.Handle(r), true, nil
+	default:
+		return 0, false, fmt.Errorf("CreateMutex: %v", err)
+	}
+}
+
+func GetMutexInfo(h syscall.Handle) (pid, count uint32, err error) {
+	r, _, err := _GetMutexInfo.Call(uintptr(h), uintptr(unsafe.Pointer(&pid)), uintptr(unsafe.Pointer(&count)))
+	if r == 0 {
+		return 0, 0, fmt.Errorf("GetMutexInfo: %v", err)
+	}
+	return pid, count, nil
+}
+
+func OpenFileMapping(name string) (ptr syscall.Handle, err error) {
+	r, _, err := _OpenFileMapping.Call(FILE_MAP_READ, 0, uintptr(unsafe.Pointer(syscall.StringToUTF16Ptr(name))))
+	if r == 0 {
+		return 0, fmt.Errorf("OpenFileMapping: %v", err)
+	}
+	return syscall.Handle(r), nil
+}
+
+func ReleaseMutex(h uintptr) error {
+	r, _, err := _ReleaseMutex.Call(h)
+	if r == 0 {
+		return fmt.Errorf("ReleaseMutex: %v", err)
+	}
+	return nil
+}
+
 func KillTimer(hwnd syscall.Handle, nIDEvent uintptr) error {
 	r, _, err := _SetTimer.Call(uintptr(hwnd), uintptr(nIDEvent), 0, 0)
 	if r == 0 {
@@ -735,10 +786,26 @@ func RegisterClassEx(cls *WndClassEx) (uint16, error) {
 	return uint16(a), nil
 }
 
+func RegisterWindowMessage(name string) (uint32, error) {
+	r, _, err := _RegisterWindowMessage.Call(uintptr(unsafe.Pointer(syscall.StringToUTF16Ptr(name))))
+	if r == 0 {
+		return 0, fmt.Errorf("RegisterWindowMessage: %v", err)
+	}
+	return uint32(r), nil
+}
+
 func ReleaseDC(hdc syscall.Handle) {
 	_ReleaseDC.Call(uintptr(hdc))
 }
 
+func SendMessage(hwnd syscall.Handle, msg uint32, wParam, lParam uintptr) error {
+	r, _, err := _SendMessage.Call(uintptr(hwnd), uintptr(msg), wParam, lParam)
+	if r == 0 {
+		return fmt.Errorf("SendMessage failed: %v", err)
+	}
+	return nil
+}
+
 func SetForegroundWindow(hwnd syscall.Handle) {
 	_SetForegroundWindow.Call(uintptr(hwnd))
 }

app/os_android.go

@@ -121,9 +121,11 @@ import "C"
 import (
 	"errors"
 	"fmt"
+	"gioui.org/io/deeplink"
 	"image"
 	"image/color"
 	"math"
+	"net/url"
 	"os"
 	"path/filepath"
 	"runtime"
@@ -659,6 +661,16 @@ func Java_org_gioui_GioView_onClearA11yFocus(env *C.JNIEnv, class C.jclass, view
 	}
 }
 
+//export Java_org_gioui_GioView_onDeeplink
+func Java_org_gioui_GioView_onDeeplink(env *C.JNIEnv, class C.jclass, view C.jlong, uri C.jstring) {
+	w := cgo.Handle(view).Value().(*window)
+	u, err := url.Parse(goString(env, uri))
+	if err != nil {
+		return
+	}
+	w.callbacks.Event(deeplink.Event{URL: u})
+}
+
 func (w *window) initAccessibilityNodeInfo(env *C.JNIEnv, sem router.SemanticNode, off image.Point, info C.jobject) error {
 	for _, ch := range sem.Children {
 		err := callVoidMethod(env, info, android.accessibilityNodeInfo.addChild, jvalue(w.view), jvalue(w.virtualIDFor(ch.ID)))

app/os_ios.go

@@ -71,7 +71,9 @@ static struct drawParams viewDrawParams(CFTypeRef viewRef) {
 import "C"
 
 import (
+	"gioui.org/io/deeplink"
 	"image"
+	"net/url"
 	"runtime"
 	"runtime/debug"
 	"time"
@@ -131,6 +133,9 @@ func onCreate(view, controller C.CFTypeRef) {
 	w.Configure(wopts.options)
 	w.w.Event(system.StageEvent{Stage: system.StagePaused})
 	w.w.Event(ViewEvent{ViewController: uintptr(controller)})
+	if startupDeeplink != nil {
+		w.w.Event(deeplink.Event{URL: startupDeeplink})
+	}
 }
 
 //export gio_onDraw
@@ -351,6 +356,23 @@ func newWindow(win *callbacks, options []Option) error {
 func osMain() {
 }
 
+var startupDeeplink *url.URL
+
+//export gio_onDeeplink
+func gio_onDeeplink(uri C.CFTypeRef) {
+	u, err := url.Parse(nsstringToString(uri))
+	if err != nil {
+		return
+	}
+	if len(views) == 0 {
+		startupDeeplink = u
+		return
+	}
+	for _, w := range views {
+		w.w.Event(deeplink.Event{URL: u})
+	}
+}
+
 //export gio_runMain
 func gio_runMain() {
 	runMain()

app/os_ios.m

@@ -99,6 +99,11 @@ - (void)keyboardWillHide:(NSNotification *)note {
 	_keyboardHeight = 0.0;
 	[self.view setNeedsLayout];
 }
+
+- (BOOL)onDeeplink:(NSString *)url {
+    gio_onDeeplink((__bridge CFTypeRef)url);
+    return YES;
+}
 @end
 
 static void handleTouches(int last, UIView *view, NSSet<UITouch *> *touches, UIEvent *event) {

app/os_macos.go

@@ -7,7 +7,9 @@ package app
 
 import (
 	"errors"
+	"gioui.org/io/deeplink"
 	"image"
+	"net/url"
 	"runtime"
 	"time"
 	"unicode"
@@ -842,6 +844,23 @@ func gio_onFinishLaunching() {
 	close(launched)
 }
 
+var startupDeeplink *url.URL
+
+//export gio_onDeeplink
+func gio_onDeeplink(uri C.CFTypeRef) {
+	u, err := url.Parse(nsstringToString(uri))
+	if err != nil {
+		return
+	}
+	if len(viewMap) == 0 {
+		startupDeeplink = u
+		return
+	}
+	for _, w := range viewMap {
+		w.w.Event(deeplink.Event{URL: u})
+	}
+}
+
 func newWindow(win *callbacks, options []Option) error {
 	<-launched
 	errch := make(chan error)
@@ -867,6 +886,9 @@ func newWindow(win *callbacks, options []Option) error {
 		C.makeKeyAndOrderFront(window)
 		layer := C.layerForView(w.view)
 		w.w.Event(ViewEvent{View: uintptr(w.view), Layer: uintptr(layer)})
+		if startupDeeplink != nil {
+			w.w.Event(deeplink.Event{URL: startupDeeplink})
+		}
 	})
 	return <-errch
 }

app/os_macos.m

@@ -376,6 +376,7 @@ @implementation GioAppDelegate
 - (void)applicationDidFinishLaunching:(NSNotification *)aNotification {
 	[NSApp setActivationPolicy:NSApplicationActivationPolicyRegular];
 	[NSApp activateIgnoringOtherApps:YES];
+
 	gio_onFinishLaunching();
 }
 - (void)applicationDidHide:(NSNotification *)aNotification {
@@ -384,6 +385,11 @@ - (void)applicationDidHide:(NSNotification *)aNotification {
 - (void)applicationWillUnhide:(NSNotification *)notification {
 	gio_onAppShow();
 }
+- (void)application:(NSApplication *)application openURLs:(NSArray<NSURL *> *)urls {
+	for (NSURL *url in urls) {
+		gio_onDeeplink((__bridge CFTypeRef)url.absoluteString);
+	}
+}
 @end
 
 void gio_main() {