ebiten/cmd/ebitenmobile/gobind.go

// Copyright 2019 The Ebiten Authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

//go:build ebitenmobilegobind
// +build ebitenmobilegobind

// gobind is a wrapper of the original gobind. This command adds extra files like a view controller.
package main

import (
	"flag"
	"fmt"
	"io/ioutil"
	"log"
	"os"
	"os/exec"
	"path/filepath"
	"strings"

	"golang.org/x/tools/go/packages"
)

var (
	lang          = flag.String("lang", "", "")
	outdir        = flag.String("outdir", "", "")
	javaPkg       = flag.String("javapkg", "", "")
	prefix        = flag.String("prefix", "", "")
	bootclasspath = flag.String("bootclasspath", "", "")
	classpath     = flag.String("classpath", "", "")
	tags          = flag.String("tags", "", "")
)

var usage = `The Gobind tool generates Java language bindings for Go.

For usage details, see doc.go.`

func main() {
	flag.Parse()
	if err := run(); err != nil {
		log.Fatal(err)
	}
}

func invokeOriginalGobind(lang string) (pkgName string, err error) {
	cmd := exec.Command("gobind-original", os.Args[1:]...)
	cmd.Stdout = os.Stdout
	cmd.Stderr = os.Stderr
	if err := cmd.Run(); err != nil {
		return "", err
	}

	cfgtags := strings.Join(strings.Split(*tags, ","), " ")
	cfg := &packages.Config{}
	switch lang {
	case "java":
		cfg.Env = append(os.Environ(), "GOOS=android")
	case "objc":
		cfg.Env = append(os.Environ(), "GOOS=darwin")
		if cfgtags != "" {
			cfgtags += " "
		}
		cfgtags += "ios"
	}
	cfg.BuildFlags = []string{"-tags", cfgtags}
	pkgs, err := packages.Load(cfg, flag.Args()[0])
	if err != nil {
		return "", err
	}
	return pkgs[0].Name, nil
}

func run() error {
	writeFile := func(filename string, content string) error {
		if err := ioutil.WriteFile(filepath.Join(*outdir, filename), []byte(content), 0644); err != nil {
			return err
		}
		return nil
	}

	// Add additional files.
	langs := strings.Split(*lang, ",")
	for _, lang := range langs {
		pkgName, err := invokeOriginalGobind(lang)
		if err != nil {
			return err
		}
		prefixLower := *prefix + pkgName
		prefixUpper := strings.Title(*prefix) + strings.Title(pkgName)
		replacePrefixes := func(content string) string {
			content = strings.ReplaceAll(content, "{{.PrefixUpper}}", prefixUpper)
			content = strings.ReplaceAll(content, "{{.PrefixLower}}", prefixLower)
			content = strings.ReplaceAll(content, "{{.JavaPkg}}", *javaPkg)
			return content
		}

		switch lang {
		case "objc":
			// iOS
			if err := writeFile(filepath.Join("src", "gobind", prefixLower+"ebitenviewcontroller_ios.m"), replacePrefixes(objcM)); err != nil {
				return err
			}
			if err := writeFile(filepath.Join("src", "gobind", prefixLower+"ebitenviewcontroller_ios.go"), `package main

// #cgo CFLAGS: -DGLES_SILENCE_DEPRECATION
import "C"`); err != nil {
				return err
			}
		case "java":
			// Android
			dir := filepath.Join(strings.Split(*javaPkg, ".")...)
			dir = filepath.Join(dir, prefixLower)
			if err := writeFile(filepath.Join("java", dir, "EbitenView.java"), replacePrefixes(viewJava)); err != nil {
				return err
			}
			if err := writeFile(filepath.Join("java", dir, "EbitenSurfaceView.java"), replacePrefixes(surfaceViewJava)); err != nil {
				return err
			}
		case "go":
			// Do nothing.
		default:
			panic(fmt.Sprintf("unsupported language: %s", lang))
		}
	}

	return nil
}

const objcM = `// Code generated by ebitenmobile. DO NOT EDIT.

//go:build ios
// +build ios

#import <TargetConditionals.h>

#import <stdint.h>
#import <UIKit/UIKit.h>
#import <GLKit/GLKit.h>

#import "Ebitenmobileview.objc.h"

@interface {{.PrefixUpper}}EbitenViewController : UIViewController<EbitenmobileviewRenderRequester>
@end

@implementation {{.PrefixUpper}}EbitenViewController {
  UIView*        metalView_;
  GLKView*       glkView_;
  bool           started_;
  bool           active_;
  bool           error_;
  CADisplayLink* displayLink_;
  bool           explicitRendering_;
}

- (UIView*)metalView {
  if (!metalView_) {
    metalView_ = [[UIView alloc] init];
    metalView_.multipleTouchEnabled = YES;
  }
  return metalView_;
}

- (GLKView*)glkView {
  if (!glkView_) {
    glkView_ = [[GLKView alloc] init];
    glkView_.multipleTouchEnabled = YES;
  }
  return glkView_;
}

- (void)viewDidLoad {
  [super viewDidLoad];

  if (!started_) {
    @synchronized(self) {
      active_ = true;
    }
    started_ = true;
  }

  if (EbitenmobileviewIsGL()) {
    self.glkView.delegate = (id<GLKViewDelegate>)(self);
    [self.view addSubview: self.glkView];

    EAGLContext *context = [[EAGLContext alloc] initWithAPI:kEAGLRenderingAPIOpenGLES2];
    [self glkView].context = context;
	
    [EAGLContext setCurrentContext:context];
  } else {
    [self.view addSubview: self.metalView];
    EbitenmobileviewSetUIView((uintptr_t)(self.metalView));
  }

  displayLink_ = [CADisplayLink displayLinkWithTarget:self selector:@selector(drawFrame)];
  [displayLink_ addToRunLoop:[NSRunLoop currentRunLoop] forMode:NSDefaultRunLoopMode];
  EbitenmobileviewSetRenderRequester(self);
}

- (void)viewWillLayoutSubviews {
  CGRect viewRect = [[self view] frame];
  if (EbitenmobileviewIsGL()) {
    [[self glkView] setFrame:viewRect];
  } else {
    [[self metalView] setFrame:viewRect];
  }
}

- (void)viewDidLayoutSubviews {
  [super viewDidLayoutSubviews];
  CGRect viewRect = [[self view] frame];

  EbitenmobileviewLayout(viewRect.size.width, viewRect.size.height);
}

- (void)didReceiveMemoryWarning {
  [super didReceiveMemoryWarning];
  // Dispose of any resources that can be recreated.
  // TODO: Notify this to Go world?
}

- (void)drawFrame{
  @synchronized(self) {
    if (!active_) {
      return;
    }

    if (EbitenmobileviewIsGL()) {
      [[self glkView] setNeedsDisplay];
    } else {
      [self updateEbiten];
    }

    if (explicitRendering_) {
      [displayLink_ setPaused:YES];
    }
  }
}

- (void)glkView:(GLKView*)view drawInRect:(CGRect)rect {
  @synchronized(self) {
    [self updateEbiten];
  }
}

- (void)updateEbiten {
  if (error_) {
    return;
  }
  NSError* err = nil;
  EbitenmobileviewUpdate(&err);
  if (err != nil) {
    [self performSelectorOnMainThread:@selector(onErrorOnGameUpdate:)
                           withObject:err
                        waitUntilDone:NO];
    error_ = true;
  }
}

- (void)onErrorOnGameUpdate:(NSError*)err {
  NSLog(@"Error: %@", err);
}

- (void)updateTouches:(NSSet*)touches {
  for (UITouch* touch in touches) {
    if (EbitenmobileviewIsGL()) {
      if (touch.view != [self glkView]) {
        continue;
      }
    } else {
      if (touch.view != [self metalView]) {
        continue;
      }
    }
    CGPoint location = [touch locationInView:touch.view];
    EbitenmobileviewUpdateTouchesOnIOS(touch.phase, (uintptr_t)touch, location.x, location.y);
  }
}

- (void)touchesBegan:(NSSet*)touches withEvent:(UIEvent*)event {
  [self updateTouches:touches];
}

- (void)touchesMoved:(NSSet*)touches withEvent:(UIEvent*)event {
  [self updateTouches:touches];
}

- (void)touchesEnded:(NSSet*)touches withEvent:(UIEvent*)event {
  [self updateTouches:touches];
}

- (void)touchesCancelled:(NSSet*)touches withEvent:(UIEvent*)event {
  [self updateTouches:touches];
}

- (void)suspendGame {
  NSAssert(started_, @"suspendGame must not be called before viewDidLoad is called");

  @synchronized(self) {
    active_ = false;
    NSError* err = nil;
    EbitenmobileviewSuspend(&err);
    if (err != nil) {
      [self onErrorOnGameUpdate:err];
    }
  }
}

- (void)resumeGame {
  NSAssert(started_, @"resumeGame must not be called before viewDidLoad is called");

  @synchronized(self) {
    active_ = true;
    NSError* err = nil;
    EbitenmobileviewResume(&err);
    if (err != nil) {
      [self onErrorOnGameUpdate:err];
    }
  }
}

- (void)setExplicitRenderingMode:(BOOL)explicitRendering {
  @synchronized(self) {
    explicitRendering_ = explicitRendering;
    if (explicitRendering_) {
      [displayLink_ setPaused:YES];
    }
  }
}

- (void)requestRenderIfNeeded {
  @synchronized(self) {
    if (explicitRendering_) {
      // Resume the callback temporarily.
      // This is paused again soon in drawFrame.
      [displayLink_ setPaused:NO];
    }
  }
}

@end
`

const viewJava = `// Code generated by ebitenmobile. DO NOT EDIT.

package {{.JavaPkg}}.{{.PrefixLower}};

import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.List;

import android.content.Context;
import android.hardware.input.InputManager;
import android.os.Handler;
import android.os.Looper;
import android.util.AttributeSet;
import android.util.DisplayMetrics;
import android.util.Log;
import android.view.Display;
import android.view.KeyEvent;
import android.view.InputDevice;
import android.view.MotionEvent;
import android.view.ViewGroup;
import android.view.WindowManager;

import {{.JavaPkg}}.ebitenmobileview.Ebitenmobileview;

public class EbitenView extends ViewGroup implements InputManager.InputDeviceListener {
    static class Gamepad {
        public int deviceId;
        public ArrayList<InputDevice.MotionRange> axes;
        public ArrayList<InputDevice.MotionRange> hats;
    }

    // See https://github.com/libsdl-org/SDL/blob/2df2da11f627299c6e05b7e0aff407c915043372/android-project/app/src/main/java/org/libsdl/app/SDLControllerManager.java#L154-L173
    static class RangeComparator implements Comparator<InputDevice.MotionRange> {
        @Override
        public int compare(InputDevice.MotionRange arg0, InputDevice.MotionRange arg1) {
            int arg0Axis = arg0.getAxis();
            int arg1Axis = arg1.getAxis();
            if (arg0Axis == MotionEvent.AXIS_GAS) {
                arg0Axis = MotionEvent.AXIS_BRAKE;
            } else if (arg0Axis == MotionEvent.AXIS_BRAKE) {
                arg0Axis = MotionEvent.AXIS_GAS;
            }
            if (arg1Axis == MotionEvent.AXIS_GAS) {
                arg1Axis = MotionEvent.AXIS_BRAKE;
            } else if (arg1Axis == MotionEvent.AXIS_BRAKE) {
                arg1Axis = MotionEvent.AXIS_GAS;
            }
            return arg0Axis - arg1Axis;
        }
    }

    private static double pxToDp(double x) {
        return x / Ebitenmobileview.deviceScale();
    }

    public EbitenView(Context context) {
        super(context);
        initialize(context);
    }

    public EbitenView(Context context, AttributeSet attrs) {
        super(context, attrs);
        initialize(context);
    }

    private void initialize(Context context) {
        this.gamepads = new ArrayList<Gamepad>();

        this.ebitenSurfaceView = new EbitenSurfaceView(getContext());
        LayoutParams params = new LayoutParams(LayoutParams.MATCH_PARENT, LayoutParams.MATCH_PARENT);
        addView(this.ebitenSurfaceView, params);

        this.inputManager = (InputManager)context.getSystemService(Context.INPUT_SERVICE);
        this.inputManager.registerInputDeviceListener(this, null);
        for (int id : this.inputManager.getInputDeviceIds()) {
            this.onInputDeviceAdded(id);
        }
    }

    @Override
    protected void onLayout(boolean changed, int left, int top, int right, int bottom) {
        this.ebitenSurfaceView.layout(0, 0, right - left, bottom - top);
        double widthInDp = pxToDp(right - left);
        double heightInDp = pxToDp(bottom - top);
        Ebitenmobileview.layout(widthInDp, heightInDp);
    }

    @Override
    public boolean onKeyDown(int keyCode, KeyEvent event) {
        Ebitenmobileview.onKeyDownOnAndroid(keyCode, event.getUnicodeChar(), event.getSource(), event.getDeviceId());
        return true;
    }

    @Override
    public boolean onKeyUp(int keyCode, KeyEvent event) {
        Ebitenmobileview.onKeyUpOnAndroid(keyCode, event.getSource(), event.getDeviceId());
        return true;
    }

    @Override
    public boolean onTouchEvent(MotionEvent e) {
        // getActionIndex returns a valid value only for the action whose index is the returned value of getActionIndex (#2220).
        // See https://developer.android.com/reference/android/view/MotionEvent#getActionMasked().
        // For other pointers, treat their actions as MotionEvent.ACTION_MOVE.
        int touchIndex = e.getActionIndex();
        for (int i = 0; i < e.getPointerCount(); i++) {
            int id = e.getPointerId(i);
            int x = (int)e.getX(i);
            int y = (int)e.getY(i);
            int action = (i == touchIndex) ? e.getActionMasked() : MotionEvent.ACTION_MOVE;
            Ebitenmobileview.updateTouchesOnAndroid(action, id, (int)pxToDp(x), (int)pxToDp(y));
        }
        return true;
    }

    private Gamepad getGamepad(int deviceId) {
        for (Gamepad gamepad : this.gamepads) {
            if (gamepad.deviceId == deviceId) {
                return gamepad;
            }
        }
        return null;
    }

    @Override
    public boolean onGenericMotionEvent(MotionEvent event) {
        if ((event.getSource() & InputDevice.SOURCE_JOYSTICK) != InputDevice.SOURCE_JOYSTICK) {
            return super.onGenericMotionEvent(event);
        }
        if (event.getAction() != MotionEvent.ACTION_MOVE) {
            return super.onGenericMotionEvent(event);
        }

        // See https://github.com/libsdl-org/SDL/blob/2df2da11f627299c6e05b7e0aff407c915043372/android-project/app/src/main/java/org/libsdl/app/SDLControllerManager.java#L256-L277
        Gamepad gamepad = this.getGamepad(event.getDeviceId());
        if (gamepad == null) {
            return true;
        }

        int actionPointerIndex = event.getActionIndex();
        for (int i = 0; i < gamepad.axes.size(); i++) {
            InputDevice.MotionRange range = gamepad.axes.get(i);
            float axisValue = event.getAxisValue(range.getAxis(), actionPointerIndex);
            float value = (axisValue - range.getMin()) / range.getRange() * 2.0f - 1.0f;
            Ebitenmobileview.onGamepadAxisChanged(gamepad.deviceId, i, value);
        }
        for (int i = 0; i < gamepad.hats.size() / 2; i++) {
            int hatX = Math.round(event.getAxisValue(gamepad.hats.get(2*i).getAxis(), actionPointerIndex));
            int hatY = Math.round(event.getAxisValue(gamepad.hats.get(2*i+1).getAxis(), actionPointerIndex));
            Ebitenmobileview.onGamepadHatChanged(gamepad.deviceId, i, hatX, hatY);
        }
        return true;
    }

    @Override
    public void onInputDeviceAdded(int deviceId) {
        InputDevice inputDevice = this.inputManager.getInputDevice(deviceId);
        // The InputDevice can be null on some deivces (#1342).
        if (inputDevice == null) {
            return;
        }

        // A fingerprint reader is unexpectedly recognized as a joystick. Skip this (#1542).
        if (inputDevice.getName().equals("uinput-fpc")) {
            return;
        }

        int sources = inputDevice.getSources();
        if ((sources & InputDevice.SOURCE_GAMEPAD) != InputDevice.SOURCE_GAMEPAD &&
            (sources & InputDevice.SOURCE_JOYSTICK) != InputDevice.SOURCE_JOYSTICK) {
            return;
        }

        // See https://github.com/libsdl-org/SDL/blob/2df2da11f627299c6e05b7e0aff407c915043372/android-project/app/src/main/java/org/libsdl/app/SDLControllerManager.java#L182-L216
        List<InputDevice.MotionRange> ranges = inputDevice.getMotionRanges();
        Collections.sort(ranges, new RangeComparator());

        Gamepad gamepad = new Gamepad();
        gamepad.deviceId = deviceId;
        gamepad.axes = new ArrayList<InputDevice.MotionRange>();
        gamepad.hats = new ArrayList<InputDevice.MotionRange>();
        for (InputDevice.MotionRange range : ranges) {
            if (range.getAxis() == MotionEvent.AXIS_HAT_X || range.getAxis() == MotionEvent.AXIS_HAT_Y) {
                gamepad.hats.add(range);
            } else {
                gamepad.axes.add(range);
            }
        }
        this.gamepads.add(gamepad);

        String descriptor = inputDevice.getDescriptor();
        int vendorId = inputDevice.getVendorId();
        int productId = inputDevice.getProductId();

        // These values are required to calculate SDL's GUID.
        int buttonMask = getButtonMask(inputDevice, gamepad.hats.size()/2);
        int axisMask = getAxisMask(inputDevice);

        Ebitenmobileview.onGamepadAdded(deviceId, inputDevice.getName(), gamepad.axes.size(), gamepad.hats.size()/2, descriptor, vendorId, productId, buttonMask, axisMask);

        // Initialize the trigger axes values explicitly, or the initial button values would be 0.5 instead of 0.
        if (gamepad.axes.size() >= 6) {
            Ebitenmobileview.onGamepadAxisChanged(deviceId, 4, -1);
            Ebitenmobileview.onGamepadAxisChanged(deviceId, 5, -1);
        }
    }

    // The implementation is copied from SDL:
    // https://github.com/libsdl-org/SDL/blob/0e9560aea22818884921e5e5064953257bfe7fa7/android-project/app/src/main/java/org/libsdl/app/SDLControllerManager.java#L308
    private static int getButtonMask(InputDevice joystickDevice, int nhats) {
        int buttonMask = 0;
        int[] keys = new int[] {
            KeyEvent.KEYCODE_BUTTON_A,
            KeyEvent.KEYCODE_BUTTON_B,
            KeyEvent.KEYCODE_BUTTON_X,
            KeyEvent.KEYCODE_BUTTON_Y,
            KeyEvent.KEYCODE_BACK,
            KeyEvent.KEYCODE_BUTTON_MODE,
            KeyEvent.KEYCODE_BUTTON_START,
            KeyEvent.KEYCODE_BUTTON_THUMBL,
            KeyEvent.KEYCODE_BUTTON_THUMBR,
            KeyEvent.KEYCODE_BUTTON_L1,
            KeyEvent.KEYCODE_BUTTON_R1,
            KeyEvent.KEYCODE_DPAD_UP,
            KeyEvent.KEYCODE_DPAD_DOWN,
            KeyEvent.KEYCODE_DPAD_LEFT,
            KeyEvent.KEYCODE_DPAD_RIGHT,
            KeyEvent.KEYCODE_BUTTON_SELECT,
            KeyEvent.KEYCODE_DPAD_CENTER,

            // These don't map into any SDL controller buttons directly
            KeyEvent.KEYCODE_BUTTON_L2,
            KeyEvent.KEYCODE_BUTTON_R2,
            KeyEvent.KEYCODE_BUTTON_C,
            KeyEvent.KEYCODE_BUTTON_Z,
            KeyEvent.KEYCODE_BUTTON_1,
            KeyEvent.KEYCODE_BUTTON_2,
            KeyEvent.KEYCODE_BUTTON_3,
            KeyEvent.KEYCODE_BUTTON_4,
            KeyEvent.KEYCODE_BUTTON_5,
            KeyEvent.KEYCODE_BUTTON_6,
            KeyEvent.KEYCODE_BUTTON_7,
            KeyEvent.KEYCODE_BUTTON_8,
            KeyEvent.KEYCODE_BUTTON_9,
            KeyEvent.KEYCODE_BUTTON_10,
            KeyEvent.KEYCODE_BUTTON_11,
            KeyEvent.KEYCODE_BUTTON_12,
            KeyEvent.KEYCODE_BUTTON_13,
            KeyEvent.KEYCODE_BUTTON_14,
            KeyEvent.KEYCODE_BUTTON_15,
            KeyEvent.KEYCODE_BUTTON_16,
        };
        int[] masks = new int[] {
            (1 << 0),   // A -> A
            (1 << 1),   // B -> B
            (1 << 2),   // X -> X
            (1 << 3),   // Y -> Y
            (1 << 4),   // BACK -> BACK
            (1 << 5),   // MODE -> GUIDE
            (1 << 6),   // START -> START
            (1 << 7),   // THUMBL -> LEFTSTICK
            (1 << 8),   // THUMBR -> RIGHTSTICK
            (1 << 9),   // L1 -> LEFTSHOULDER
            (1 << 10),  // R1 -> RIGHTSHOULDER
            (1 << 11),  // DPAD_UP -> DPAD_UP
            (1 << 12),  // DPAD_DOWN -> DPAD_DOWN
            (1 << 13),  // DPAD_LEFT -> DPAD_LEFT
            (1 << 14),  // DPAD_RIGHT -> DPAD_RIGHT
            (1 << 4),   // SELECT -> BACK
            (1 << 0),   // DPAD_CENTER -> A
            (1 << 15),  // L2 -> ??
            (1 << 16),  // R2 -> ??
            (1 << 17),  // C -> ??
            (1 << 18),  // Z -> ??
            (1 << 20),  // 1 -> ??
            (1 << 21),  // 2 -> ??
            (1 << 22),  // 3 -> ??
            (1 << 23),  // 4 -> ??
            (1 << 24),  // 5 -> ??
            (1 << 25),  // 6 -> ??
            (1 << 26),  // 7 -> ??
            (1 << 27),  // 8 -> ??
            (1 << 28),  // 9 -> ??
            (1 << 29),  // 10 -> ??
            (1 << 30),  // 11 -> ??
            (1 << 31),  // 12 -> ??
            // We're out of room...
            0xFFFFFFFF,  // 13 -> ??
            0xFFFFFFFF,  // 14 -> ??
            0xFFFFFFFF,  // 15 -> ??
            0xFFFFFFFF,  // 16 -> ??
        };
        boolean[] hasKeys = joystickDevice.hasKeys(keys);
        for (int i = 0; i < keys.length; ++i) {
            if (hasKeys[i]) {
                buttonMask |= masks[i];
            }
        }
        // https://github.com/libsdl-org/SDL/blob/47f2373dc13b66c48bf4024fcdab53cd0bdd59bb/src/joystick/android/SDL_sysjoystick.c#L360-L367
        if (nhats > 0) {
            // Add Dpad buttons.
            buttonMask |= 1 << 11;
            buttonMask |= 1 << 12;
            buttonMask |= 1 << 13;
            buttonMask |= 1 << 14;
        }
        return buttonMask;
    }

    private static int getAxisMask(InputDevice joystickDevice) {
        final int SDL_CONTROLLER_AXIS_LEFTX = 0;
        final int SDL_CONTROLLER_AXIS_LEFTY = 1;
        final int SDL_CONTROLLER_AXIS_RIGHTX = 2;
        final int SDL_CONTROLLER_AXIS_RIGHTY = 3;
        final int SDL_CONTROLLER_AXIS_TRIGGERLEFT = 4;
        final int SDL_CONTROLLER_AXIS_TRIGGERRIGHT = 5;

        int naxes = 0;
        for (InputDevice.MotionRange range : joystickDevice.getMotionRanges()) {
            if ((range.getSource() & InputDevice.SOURCE_CLASS_JOYSTICK) != 0) {
                if (range.getAxis() != MotionEvent.AXIS_HAT_X && range.getAxis() != MotionEvent.AXIS_HAT_Y) {
                    naxes++;
                }
            }
        }
        // The variable is_accelerometer seems always false, then skip the checking:
        // https://github.com/libsdl-org/SDL/blob/0e9560aea22818884921e5e5064953257bfe7fa7/android-project/app/src/main/java/org/libsdl/app/SDLControllerManager.java#L207
        int axisMask = 0;
        if (naxes >= 2) {
            axisMask |= ((1 << SDL_CONTROLLER_AXIS_LEFTX) | (1 << SDL_CONTROLLER_AXIS_LEFTY));
        }
        if (naxes >= 4) {
            axisMask |= ((1 << SDL_CONTROLLER_AXIS_RIGHTX) | (1 << SDL_CONTROLLER_AXIS_RIGHTY));
        }
        if (naxes >= 6) {
            axisMask |= ((1 << SDL_CONTROLLER_AXIS_TRIGGERLEFT) | (1 << SDL_CONTROLLER_AXIS_TRIGGERRIGHT));
        }
        return axisMask;
    }

    @Override
    public void onInputDeviceChanged(int deviceId) {
        // Do nothing.
    }

    @Override
    public void onInputDeviceRemoved(int deviceId) {
        // Do not call inputManager.getInputDevice(), which returns null (#1185).
        Ebitenmobileview.onInputDeviceRemoved(deviceId);
        this.gamepads.remove(this.getGamepad(deviceId));
    }

    // suspendGame suspends the game.
    // It is recommended to call this when the application is being suspended e.g.,
    // Activity's onPause is called.
    public void suspendGame() {
        this.inputManager.unregisterInputDeviceListener(this);
        this.ebitenSurfaceView.onPause();
        try {
            Ebitenmobileview.suspend();
        } catch (final Exception e) {
            onErrorOnGameUpdate(e);
        }
    }

    // resumeGame resumes the game.
    // It is recommended to call this when the application is being resumed e.g.,
    // Activity's onResume is called.
    public void resumeGame() {
        this.inputManager.registerInputDeviceListener(this, null);
        this.ebitenSurfaceView.onResume();
        try {
            Ebitenmobileview.resume();
        } catch (final Exception e) {
            onErrorOnGameUpdate(e);
        }
    }

    // onErrorOnGameUpdate is called on the main thread when an error happens when updating a game.
    // You can define your own error handler, e.g., using Crashlytics, by overriding this method.
    protected void onErrorOnGameUpdate(Exception e) {
        Log.e("Go", e.toString());
    }

    private EbitenSurfaceView ebitenSurfaceView;
    private InputManager inputManager;
    private ArrayList<Gamepad> gamepads;
}
`

const surfaceViewJava = `// Code generated by ebitenmobile. DO NOT EDIT.

package {{.JavaPkg}}.{{.PrefixLower}};

import android.content.Context;
import android.opengl.GLSurfaceView;
import android.os.Handler;
import android.os.Looper;
import android.util.AttributeSet;
import android.util.Log;

import javax.microedition.khronos.egl.EGLConfig;
import javax.microedition.khronos.opengles.GL10;

import {{.JavaPkg}}.ebitenmobileview.Ebitenmobileview;
import {{.JavaPkg}}.ebitenmobileview.RenderRequester;
import {{.JavaPkg}}.{{.PrefixLower}}.EbitenView;

class EbitenSurfaceView extends GLSurfaceView implements RenderRequester {

    private class EbitenRenderer implements GLSurfaceView.Renderer {

        private boolean errored_ = false;

        @Override
        public void onDrawFrame(GL10 gl) {
            if (errored_) {
                return;
            }
            try {
                Ebitenmobileview.update();
            } catch (final Exception e) {
                new Handler(Looper.getMainLooper()).post(new Runnable() {
                    @Override
                    public void run() {
                        onErrorOnGameUpdate(e);
                    }
                });
                errored_ = true;
            }
        }

        @Override
        public void onSurfaceCreated(GL10 gl, EGLConfig config) {
            Ebitenmobileview.onContextLost();
        }

        @Override
        public void onSurfaceChanged(GL10 gl, int width, int height) {
        }
    }

    public EbitenSurfaceView(Context context) {
        super(context);
        initialize();
    }

    public EbitenSurfaceView(Context context, AttributeSet attrs) {
        super(context, attrs);
        initialize();
    }

    private void initialize() {
        setEGLContextClientVersion(2);
        setEGLConfigChooser(8, 8, 8, 8, 0, 0);
        setRenderer(new EbitenRenderer());
        Ebitenmobileview.setRenderRequester(this);
    }

    private void onErrorOnGameUpdate(Exception e) {
        ((EbitenView)getParent()).onErrorOnGameUpdate(e);
    }

    @Override
    public synchronized void setExplicitRenderingMode(boolean explicitRendering) {
        if (explicitRendering) {
            setRenderMode(RENDERMODE_WHEN_DIRTY);
        } else {
            setRenderMode(RENDERMODE_CONTINUOUSLY);
        }
    }

    @Override
    public synchronized void requestRenderIfNeeded() {
        if (getRenderMode() == RENDERMODE_WHEN_DIRTY) {
            requestRender();
        }
    }
}
`