// Copyright 2015 Hajime Hoshi
//
// 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.

// +build darwin freebsd linux windows
// +build !js
// +build !android
// +build !ios

package glfw

import (
	"context"
	"image"
	"math"
	"os"
	"runtime"
	"sync"
	"time"
	"unsafe"

	"github.com/hajimehoshi/ebiten/internal/devicescale"
	"github.com/hajimehoshi/ebiten/internal/driver"
	"github.com/hajimehoshi/ebiten/internal/glfw"
	"github.com/hajimehoshi/ebiten/internal/thread"
)

type UserInterface struct {
	title           string
	window          *glfw.Window
	width           int
	windowWidth     int
	height          int
	scale           float64
	fullscreenScale float64

	running              bool
	toChangeSize         bool
	origPosX             int
	origPosY             int
	runnableInBackground bool
	vsync                bool

	lastActualScale float64

	initMonitor           *glfw.Monitor
	initFullscreenWidth   int
	initFullscreenHeight  int
	initFullscreen        bool
	initCursorVisible     bool
	initWindowDecorated   bool
	initWindowResizable   bool
	initWindowPositionX   int
	initWindowPositionY   int
	initScreenTransparent bool
	initIconImages        []image.Image

	reqWidth  int
	reqHeight int

	graphics driver.Graphics
	input    Input

	t *thread.Thread
	m sync.RWMutex
}

const (
	maxInt     = int(^uint(0) >> 1)
	minInt     = -maxInt - 1
	invalidPos = minInt
)

var (
	theUI = &UserInterface{
		origPosX:            invalidPos,
		origPosY:            invalidPos,
		initCursorVisible:   true,
		initWindowDecorated: true,
		initWindowPositionX: invalidPos,
		initWindowPositionY: invalidPos,
		vsync:               true,
	}
)

func init() {
	theUI.input.ui = theUI
}

func Get() *UserInterface {
	return theUI
}

func init() {
	hideConsoleWindowOnWindows()
	if err := initialize(); err != nil {
		panic(err)
	}
	glfw.SetMonitorCallback(func(monitor *glfw.Monitor, event glfw.PeripheralEvent) {
		cacheMonitors()
	})
	cacheMonitors()
}

func initialize() error {
	if err := glfw.Init(); err != nil {
		return err
	}
	glfw.WindowHint(glfw.Visible, glfw.False)

	// Create a window to set the initial monitor.
	w, err := glfw.CreateWindow(16, 16, "", nil, nil)
	if err != nil {
		return err
	}
	if w == nil {
		// This can happen on Windows Remote Desktop (#903).
		panic("glfw: glfw.CreateWindow must not return nil")
	}

	// TODO: Fix this hack. currentMonitorImpl now requires u.window on POSIX.
	theUI.window = w
	theUI.initMonitor = theUI.currentMonitorFromPosition()
	v := theUI.initMonitor.GetVideoMode()
	s := theUI.glfwScale()
	theUI.initFullscreenWidth = int(float64(v.Width) / s)
	theUI.initFullscreenHeight = int(float64(v.Height) / s)
	theUI.window.Destroy()
	theUI.window = nil

	return nil
}

type cachedMonitor struct {
	m  *glfw.Monitor
	vm *glfw.VidMode
	// Pos of monitor in virtual coords
	x int
	y int
}

// monitors is the monitor list cache for desktop glfw compile targets.
// populated by 'cacheMonitors' which is called on init and every
// monitor config change event.
//
// monitors must be manipulated on the main thread.
var monitors []*cachedMonitor

func cacheMonitors() {
	monitors = nil
	ms := glfw.GetMonitors()
	for _, m := range ms {
		x, y := m.GetPos()
		monitors = append(monitors, &cachedMonitor{
			m:  m,
			vm: m.GetVideoMode(),
			x:  x,
			y:  y,
		})
	}
}

// getCachedMonitor returns a monitor for the given window x/y
// returns false if monitor is not found.
//
// getCachedMonitor must be called on the main thread.
func getCachedMonitor(wx, wy int) (*cachedMonitor, bool) {
	for _, m := range monitors {
		if m.x <= wx && wx < m.x+m.vm.Width && m.y <= wy && wy < m.y+m.vm.Height {
			return m, true
		}
	}
	return nil, false
}

func (u *UserInterface) isRunning() bool {
	u.m.RLock()
	v := u.running
	u.m.RUnlock()
	return v
}

func (u *UserInterface) setRunning(running bool) {
	u.m.Lock()
	u.running = running
	u.m.Unlock()
}

func (u *UserInterface) isInitFullscreen() bool {
	u.m.RLock()
	v := u.initFullscreen
	u.m.RUnlock()
	return v
}

func (u *UserInterface) setInitFullscreen(initFullscreen bool) {
	u.m.Lock()
	u.initFullscreen = initFullscreen
	u.m.Unlock()
}

func (u *UserInterface) isInitCursorVisible() bool {
	u.m.RLock()
	v := u.initCursorVisible
	u.m.RUnlock()
	return v
}

func (u *UserInterface) setInitCursorVisible(visible bool) {
	u.m.Lock()
	u.initCursorVisible = visible
	u.m.Unlock()
}

func (u *UserInterface) isInitWindowDecorated() bool {
	u.m.RLock()
	v := u.initWindowDecorated
	u.m.RUnlock()
	return v
}

func (u *UserInterface) setInitWindowDecorated(decorated bool) {
	u.m.Lock()
	u.initWindowDecorated = decorated
	u.m.Unlock()
}

func (u *UserInterface) isRunnableInBackground() bool {
	u.m.RLock()
	v := u.runnableInBackground
	u.m.RUnlock()
	return v
}

func (u *UserInterface) setRunnableInBackground(runnableInBackground bool) {
	u.m.Lock()
	u.runnableInBackground = runnableInBackground
	u.m.Unlock()
}

func (u *UserInterface) isInitWindowResizable() bool {
	u.m.RLock()
	v := u.initWindowResizable
	u.m.RUnlock()
	return v
}

func (u *UserInterface) setInitWindowResizable(resizable bool) {
	u.m.Lock()
	u.initWindowResizable = resizable
	u.m.Unlock()
}

func (u *UserInterface) isInitScreenTransparent() bool {
	u.m.RLock()
	v := u.initScreenTransparent
	u.m.RUnlock()
	return v
}

func (u *UserInterface) setInitScreenTransparent(transparent bool) {
	u.m.RLock()
	u.initScreenTransparent = transparent
	u.m.RUnlock()
}

func (u *UserInterface) getInitIconImages() []image.Image {
	u.m.RLock()
	i := u.initIconImages
	u.m.RUnlock()
	return i
}

func (u *UserInterface) setInitIconImages(iconImages []image.Image) {
	u.m.Lock()
	u.initIconImages = iconImages
	u.m.Unlock()
}

func (u *UserInterface) getInitWindowPosition() (int, int) {
	u.m.RLock()
	defer u.m.RUnlock()
	if u.initWindowPositionX != invalidPos && u.initWindowPositionY != invalidPos {
		return u.initWindowPositionX, u.initWindowPositionY
	}
	return invalidPos, invalidPos
}

func (u *UserInterface) setInitWindowPosition(x, y int) {
	u.m.Lock()
	defer u.m.Unlock()

	u.initWindowPositionX = x
	u.initWindowPositionY = y
}

func (u *UserInterface) ScreenSizeInFullscreen() (int, int) {
	if !u.isRunning() {
		return u.initFullscreenWidth, u.initFullscreenHeight
	}

	var v *glfw.VidMode
	s := 0.0
	_ = u.t.Call(func() error {
		v = u.currentMonitor().GetVideoMode()
		s = u.glfwScale()
		return nil
	})
	return int(float64(v.Width) / s), int(float64(v.Height) / s)
}

func (u *UserInterface) SetScreenSize(width, height int) {
	if !u.isRunning() {
		panic("glfw: SetScreenSize can't be called before the main loop starts")
	}
	_ = u.t.Call(func() error {
		// TODO: What if the window is maximized? (#320)
		u.setScreenSize(width, height, u.scale, u.isFullscreen(), u.vsync)
		return nil
	})
}

func (u *UserInterface) SetScreenScale(scale float64) {
	if !u.isRunning() {
		panic("glfw: SetScreenScale can't be called before the main loop starts")
	}
	_ = u.t.Call(func() error {
		// TODO: What if the window is maximized? (#320)
		u.setScreenSize(u.width, u.height, scale, u.isFullscreen(), u.vsync)
		return nil
	})
}

func (u *UserInterface) ScreenScale() float64 {
	if !u.isRunning() {
		return 0
	}
	s := 0.0
	_ = u.t.Call(func() error {
		s = u.scale
		return nil
	})
	return s
}

// isFullscreen must be called from the main thread.
func (u *UserInterface) isFullscreen() bool {
	if !u.isRunning() {
		panic("glfw: isFullscreen can't be called before the main loop starts")
	}
	return u.window.GetMonitor() != nil
}

func (u *UserInterface) IsFullscreen() bool {
	if !u.isRunning() {
		return u.isInitFullscreen()
	}
	b := false
	_ = u.t.Call(func() error {
		b = u.isFullscreen()
		return nil
	})
	return b
}

func (u *UserInterface) SetFullscreen(fullscreen bool) {
	if !u.isRunning() {
		u.setInitFullscreen(fullscreen)
		return
	}
	_ = u.t.Call(func() error {
		u.setScreenSize(u.width, u.height, u.scale, fullscreen, u.vsync)
		return nil
	})
}

func (u *UserInterface) SetRunnableInBackground(runnableInBackground bool) {
	u.setRunnableInBackground(runnableInBackground)
}

func (u *UserInterface) IsRunnableInBackground() bool {
	return u.isRunnableInBackground()
}

func (u *UserInterface) SetVsyncEnabled(enabled bool) {
	if !u.isRunning() {
		// In general, m is used for locking init* values.
		// m is not used for updating vsync in setScreenSize so far, but
		// it should be OK since any goroutines can't reach here when
		// the game already starts and setScreenSize can be called.
		u.m.Lock()
		u.vsync = enabled
		u.m.Unlock()
		return
	}
	_ = u.t.Call(func() error {
		u.setScreenSize(u.width, u.height, u.scale, u.isFullscreen(), enabled)
		return nil
	})
}

func (u *UserInterface) IsVsyncEnabled() bool {
	u.m.RLock()
	r := u.vsync
	u.m.RUnlock()
	return r
}

func (u *UserInterface) SetWindowTitle(title string) {
	if !u.isRunning() {
		return
	}
	u.title = title
	_ = u.t.Call(func() error {
		u.window.SetTitle(title)
		return nil
	})
}

func (u *UserInterface) SetWindowIcon(iconImages []image.Image) {
	if !u.isRunning() {
		u.setInitIconImages(iconImages)
		return
	}
	_ = u.t.Call(func() error {
		u.window.SetIcon(iconImages)
		return nil
	})
}

func (u *UserInterface) ScreenPadding() (x0, y0, x1, y1 float64) {
	if !u.isRunning() {
		return 0, 0, 0, 0
	}
	if !u.IsFullscreen() {
		if u.width == u.windowWidth {
			return 0, 0, 0, 0
		}
		// The window width can be bigger than the game screen width (#444).
		ox := 0.0
		_ = u.t.Call(func() error {
			ox = (float64(u.windowWidth)*u.actualScreenScale() - float64(u.width)*u.actualScreenScale()) / 2
			return nil
		})
		return ox, 0, ox, 0
	}

	d := 0.0
	sx := 0.0
	sy := 0.0
	gs := 0.0
	vw := 0.0
	vh := 0.0
	_ = u.t.Call(func() error {
		m := u.window.GetMonitor()
		d = devicescale.GetAt(m.GetPos())
		sx = float64(u.width) * u.actualScreenScale()
		sy = float64(u.height) * u.actualScreenScale()
		gs = u.glfwScale()

		v := m.GetVideoMode()
		vw, vh = float64(v.Width), float64(v.Height)
		return nil
	})
	mx := vw * d / gs
	my := vh * d / gs

	ox := (mx - sx) / 2
	oy := (my - sy) / 2
	return ox, oy, (mx - sx) - ox, (my - sy) - oy
}

func (u *UserInterface) adjustPosition(x, y int) (int, int) {
	if !u.isRunning() {
		return x, y
	}
	ox, oy, _, _ := u.ScreenPadding()
	s := 0.0
	_ = u.t.Call(func() error {
		s = u.actualScreenScale()
		return nil
	})
	return x - int(ox/s), y - int(oy/s)
}

func (u *UserInterface) IsCursorVisible() bool {
	if !u.isRunning() {
		return u.isInitCursorVisible()
	}
	v := false
	_ = u.t.Call(func() error {
		v = u.window.GetInputMode(glfw.CursorMode) == glfw.CursorNormal
		return nil
	})
	return v
}

func (u *UserInterface) SetCursorVisible(visible bool) {
	if !u.isRunning() {
		u.setInitCursorVisible(visible)
		return
	}
	_ = u.t.Call(func() error {
		c := glfw.CursorNormal
		if !visible {
			c = glfw.CursorHidden
		}
		u.window.SetInputMode(glfw.CursorMode, c)
		return nil
	})
}

func (u *UserInterface) IsWindowDecorated() bool {
	if !u.isRunning() {
		return u.isInitWindowDecorated()
	}
	v := false
	_ = u.t.Call(func() error {
		v = u.window.GetAttrib(glfw.Decorated) == glfw.True
		return nil
	})
	return v
}

func (u *UserInterface) SetWindowDecorated(decorated bool) {
	if !u.isRunning() {
		u.setInitWindowDecorated(decorated)
		return
	}

	_ = u.t.Call(func() error {
		v := glfw.False
		if decorated {
			v = glfw.True
		}
		u.window.SetAttrib(glfw.Decorated, v)

		// The title can be lost when the decoration is gone. Recover this.
		if v == glfw.True {
			u.window.SetTitle(u.title)
		}
		return nil
	})
}

func (u *UserInterface) IsWindowResizable() bool {
	if !u.isRunning() {
		return u.isInitWindowResizable()
	}
	v := false
	_ = u.t.Call(func() error {
		v = u.window.GetAttrib(glfw.Resizable) == glfw.True
		return nil
	})
	return v
}

func (u *UserInterface) SetWindowResizable(resizable bool) {
	if !u.isRunning() {
		u.setInitWindowResizable(resizable)
		return
	}

	panic("glfw: SetWindowResizable can't be called after the main loop so far.")

	// TODO: Now SetAttrib doesn't exist on GLFW 3.2. Revisit later (#556).
}

func (u *UserInterface) DeviceScaleFactor() float64 {
	f := 0.0
	if !u.isRunning() {
		return devicescale.GetAt(u.initMonitor.GetPos())
	}

	_ = u.t.Call(func() error {
		m := u.currentMonitor()
		f = devicescale.GetAt(m.GetPos())
		return nil
	})
	return f
}

func init() {
	// Lock the main thread.
	runtime.LockOSThread()
}

func (u *UserInterface) Run(width, height int, scale float64, title string, uicontext driver.UIContext, graphics driver.Graphics) error {
	// Initialize the main thread first so the thread is available at u.run (#809).
	u.t = thread.New()
	u.graphics = graphics
	u.graphics.SetThread(u.t)

	ctx, cancel := context.WithCancel(context.Background())

	ch := make(chan error, 1)
	go func() {
		defer cancel()
		defer close(ch)
		if err := u.run(width, height, scale, title, uicontext); err != nil {
			ch <- err
		}
	}()

	u.setRunning(true)
	u.t.Loop(ctx)
	u.setRunning(false)
	return <-ch
}

func (u *UserInterface) RunWithoutMainLoop(width, height int, scale float64, title string, context driver.UIContext, graphics driver.Graphics) <-chan error {
	panic("glfw: RunWithoutMainLoop is not implemented")
}

func (u *UserInterface) run(width, height int, scale float64, title string, context driver.UIContext) error {
	if err := u.t.Call(func() error {
		if u.graphics.IsGL() {
			glfw.WindowHint(glfw.ContextVersionMajor, 2)
			glfw.WindowHint(glfw.ContextVersionMinor, 1)
		} else {
			glfw.WindowHint(glfw.ClientAPI, glfw.NoAPI)
		}

		decorated := glfw.False
		if u.isInitWindowDecorated() {
			decorated = glfw.True
		}
		glfw.WindowHint(glfw.Decorated, decorated)

		transparent := glfw.False
		if u.isInitScreenTransparent() {
			transparent = glfw.True
		}
		glfw.WindowHint(glfw.TransparentFramebuffer, transparent)
		u.graphics.SetTransparent(u.isInitScreenTransparent())

		resizable := glfw.False
		if u.isInitWindowResizable() {
			resizable = glfw.True
		}
		glfw.WindowHint(glfw.Resizable, resizable)

		// Set the window visible explicitly or the application freezes on Wayland (#974).
		if os.Getenv("WAYLAND_DISPLAY") != "" {
			glfw.WindowHint(glfw.Visible, glfw.True)
		}

		// As a start, create a window with temporary size to create OpenGL context thread.
		window, err := glfw.CreateWindow(16, 16, "", nil, nil)
		if err != nil {
			return err
		}
		u.window = window

		if u.graphics.IsGL() {
			u.window.MakeContextCurrent()
		}

		u.window.SetInputMode(glfw.StickyMouseButtonsMode, glfw.True)
		u.window.SetInputMode(glfw.StickyKeysMode, glfw.True)

		// Solve the initial properties of the window.
		mode := glfw.CursorNormal
		if !u.isInitCursorVisible() {
			mode = glfw.CursorHidden
		}
		u.window.SetInputMode(glfw.CursorMode, mode)

		if i := u.getInitIconImages(); i != nil {
			u.window.SetIcon(i)
		}

		// Get the monitor before showing the window.
		//
		// On Windows, there are two types of windows:
		//
		//   active window:     The window that has input-focus and attached to the calling thread.
		//   foreground window: The window that has input-focus: this can be in another process
		//
		// currentMonitor returns the monitor for the active window when possible and then the monitor for
		// the foreground window as fallback. In the current situation, the current window is hidden and
		// there is not the active window but the foreground window. After showing the current window, the
		// current window will be the active window. Thus, currentMonitor result varies before and after
		// showing the window.
		m := u.currentMonitor()
		mx, my := m.GetPos()
		v := m.GetVideoMode()

		// The game is in window mode (not fullscreen mode) at the first state.
		// Don't refer u.initFullscreen here to avoid some GLFW problems.
		u.setScreenSize(width, height, scale, false, u.vsync)
		// Get the window size before showing since window.Show might change the current
		// monitor which affects glfwSize result.
		w, h := u.glfwSize()

		u.title = title
		u.window.SetTitle(title)
		u.window.Show()

		x, y := u.getInitWindowPosition()
		if x == invalidPos || y == invalidPos {
			x = mx + (v.Width-w)/2
			y = my + (v.Height-h)/3
		}
		// Adjusting the position is needed only when the monitor is primary. (#829)
		if mx == 0 && my == 0 {
			x, y = adjustWindowPosition(x, y)
		}
		u.window.SetPos(x, y)

		u.window.SetSizeCallback(func(_ *glfw.Window, width, height int) {
			if u.window.GetAttrib(glfw.Resizable) == glfw.False {
				return
			}
			if u.isFullscreen() {
				return
			}

			s := u.glfwScale()
			w := int(float64(width) / u.scale / s)
			h := int(float64(height) / u.scale / s)
			u.reqWidth = w
			u.reqHeight = h
		})
		return nil
	}); err != nil {
		return err
	}

	var w unsafe.Pointer
	_ = u.t.Call(func() error {
		w = u.nativeWindow()
		return nil
	})
	u.graphics.SetWindow(w)
	return u.loop(context)
}

// getSize must be called from the main thread.
func (u *UserInterface) glfwSize() (int, int) {
	w := int(float64(u.windowWidth) * u.getScale() * u.glfwScale())
	h := int(float64(u.height) * u.getScale() * u.glfwScale())
	return w, h
}

// getScale must be called from the main thread.
func (u *UserInterface) getScale() float64 {
	if !u.isFullscreen() {
		return u.scale
	}
	if u.fullscreenScale == 0 {
		v := u.window.GetMonitor().GetVideoMode()
		sw := float64(v.Width) / u.glfwScale() / float64(u.width)
		sh := float64(v.Height) / u.glfwScale() / float64(u.height)
		s := sw
		if s > sh {
			s = sh
		}
		u.fullscreenScale = s
	}
	return u.fullscreenScale
}

// actualScreenScale must be called from the main thread.
func (u *UserInterface) actualScreenScale() float64 {
	// Avoid calling monitor.GetPos if we have the monitor position cached already.
	if cm, ok := getCachedMonitor(u.window.GetPos()); ok {
		return u.getScale() * devicescale.GetAt(cm.x, cm.y)
	}
	return u.getScale() * devicescale.GetAt(u.currentMonitor().GetPos())
}

func (u *UserInterface) updateSize(context driver.UIContext) {
	actualScale := 0.0
	sizeChanged := false
	// TODO: Is it possible to reduce 'runOnMainThread' calls?
	_ = u.t.Call(func() error {
		actualScale = u.actualScreenScale()
		if u.lastActualScale != actualScale {
			u.forceSetScreenSize(u.width, u.height, u.scale, u.isFullscreen(), u.vsync)
		}
		u.lastActualScale = actualScale

		if !u.toChangeSize {
			return nil
		}

		u.toChangeSize = false
		sizeChanged = true
		return nil
	})
	if sizeChanged {
		context.SetSize(u.width, u.height, actualScale)
	}
}

func (u *UserInterface) update(context driver.UIContext) error {
	shouldClose := false
	_ = u.t.Call(func() error {
		shouldClose = u.window.ShouldClose()
		return nil
	})
	if shouldClose {
		return driver.RegularTermination
	}

	_ = u.t.Call(func() error {
		if u.isInitFullscreen() {
			u.setScreenSize(u.width, u.height, u.scale, true, u.vsync)
			u.setInitFullscreen(false)
		}
		return nil
	})

	// This call is needed for initialization.
	u.updateSize(context)

	_ = u.t.Call(func() error {
		glfw.PollEvents()

		u.input.update(u.window, u.getScale()*u.glfwScale())

		defer context.ResumeAudio()

		for !u.isRunnableInBackground() && u.window.GetAttrib(glfw.Focused) == 0 {
			context.SuspendAudio()
			// Wait for an arbitrary period to avoid busy loop.
			time.Sleep(time.Second / 60)
			glfw.PollEvents()
			if u.window.ShouldClose() {
				return nil
			}
		}
		return nil
	})
	if err := context.Update(func() {
		// The offscreens must be updated every frame (#490).
		u.updateSize(context)
	}); err != nil {
		return err
	}

	// Update the screen size when the window is resizable.
	_ = u.t.Call(func() error {
		w, h := u.reqWidth, u.reqHeight
		if w != 0 || h != 0 {
			u.setScreenSize(w, h, u.scale, u.isFullscreen(), u.vsync)
		}
		u.reqWidth = 0
		u.reqHeight = 0
		return nil
	})
	return nil
}

func (u *UserInterface) loop(context driver.UIContext) error {
	defer func() {
		_ = u.t.Call(func() error {
			glfw.Terminate()
			return nil
		})
	}()
	for {
		var unfocused bool

		// On Windows, the focusing state might be always false (#987).
		// On Windows, even if a window is in another workspace, vsync seems to work.
		// Then let's assume the window is alwasy 'focused' as a workaround.
		if runtime.GOOS != "windows" {
			unfocused = u.window.GetAttrib(glfw.Focused) == glfw.False
		}

		var t1, t2 time.Time

		if unfocused {
			t1 = time.Now()
		}
		if err := u.update(context); err != nil {
			return err
		}

		_ = u.t.Call(func() error {
			u.swapBuffers()
			return nil
		})
		if unfocused {
			t2 = time.Now()
		}

		// When a window is not focused, SwapBuffers might return immediately and CPU might be busy.
		// Mitigate this by sleeping (#982).
		if unfocused {
			d := t2.Sub(t1)
			const wait = time.Second / 60
			if d < wait {
				time.Sleep(wait - d)
			}
		}
	}
}

// swapBuffers must be called from the main thread.
func (u *UserInterface) swapBuffers() {
	if u.graphics.IsGL() {
		u.window.SwapBuffers()
	}
}

// setScreenSize must be called from the main thread.
func (u *UserInterface) setScreenSize(width, height int, scale float64, fullscreen bool, vsync bool) bool {
	if u.width == width && u.height == height && u.scale == scale && u.isFullscreen() == fullscreen && u.vsync == vsync {
		return false
	}
	u.forceSetScreenSize(width, height, scale, fullscreen, vsync)
	return true
}

// forceSetScreenSize must be called from the main thread.
func (u *UserInterface) forceSetScreenSize(width, height int, scale float64, fullscreen bool, vsync bool) {
	// On Windows, giving a too small width doesn't call a callback (#165).
	// To prevent hanging up, return asap if the width is too small.
	// 252 is an arbitrary number and I guess this is small enough.
	minWindowWidth := 252
	if u.window.GetAttrib(glfw.Decorated) == glfw.False {
		minWindowWidth = 1
	}

	if width < 1 {
		width = 1
	}
	if height < 1 {
		height = 1
	}

	u.width = width
	u.windowWidth = width
	s := scale * devicescale.GetAt(u.currentMonitor().GetPos())
	if int(float64(width)*s) < minWindowWidth {
		u.windowWidth = int(math.Ceil(float64(minWindowWidth) / s))
	}
	u.height = height
	u.scale = scale
	u.fullscreenScale = 0
	u.vsync = vsync

	// To make sure the current existing framebuffers are rendered,
	// swap buffers here before SetSize is called.
	u.swapBuffers()

	if fullscreen {
		if u.origPosX == invalidPos || u.origPosY == invalidPos {
			u.origPosX, u.origPosY = u.window.GetPos()
		}
		m := u.currentMonitor()
		v := m.GetVideoMode()
		u.window.SetMonitor(m, 0, 0, v.Width, v.Height, v.RefreshRate)
	} else {
		if u.window.GetMonitor() != nil {
			// Give dummy values as the window position and size.
			// The new window position should be specifying after SetSize.
			u.window.SetMonitor(nil, 0, 0, 16, 16, 0)
		}

		oldW, oldH := u.window.GetSize()
		newW, newH := u.glfwSize()
		if oldW != newW || oldH != newH {
			ch := make(chan struct{})
			u.window.SetFramebufferSizeCallback(func(_ *glfw.Window, _, _ int) {
				u.window.SetFramebufferSizeCallback(nil)
				close(ch)
			})
			u.window.SetSize(u.glfwSize())
		event:
			for {
				glfw.PollEvents()
				select {
				case <-ch:
					break event
				default:
				}
			}
		}

		if u.origPosX != invalidPos && u.origPosY != invalidPos {
			x := u.origPosX
			y := u.origPosY
			u.window.SetPos(x, y)
			u.origPosX = invalidPos
			u.origPosY = invalidPos
		}

		// Window title might be lost on macOS after coming back from fullscreen.
		u.window.SetTitle(u.title)
	}

	if u.graphics.IsGL() {
		// SwapInterval is affected by the current monitor of the window.
		// This needs to be called at least after SetMonitor.
		// Without SwapInterval after SetMonitor, vsynch doesn't work (#375).
		//
		// TODO: (#405) If triple buffering is needed, SwapInterval(0) should be called,
		// but is this correct? If glfw.SwapInterval(0) and the driver doesn't support triple
		// buffering, what will happen?
		if u.vsync {
			glfw.SwapInterval(1)
		} else {
			glfw.SwapInterval(0)
		}
	}
	u.graphics.SetVsyncEnabled(vsync)

	u.toChangeSize = true
}

// currentMonitor returns the monitor most suitable with the current window.
//
// currentMonitor must be called on the main thread.
func (u *UserInterface) currentMonitor() *glfw.Monitor {
	w := u.window
	if m := w.GetMonitor(); m != nil {
		return m
	}
	// Get the monitor which the current window belongs to. This requires OS API.
	return u.currentMonitorFromPosition()
}

func (u *UserInterface) SetWindowPosition(x, y int) {
	if !u.isRunning() {
		u.setInitWindowPosition(x, y)
		return
	}
	_ = u.t.Call(func() error {
		if u.isFullscreen() {
			return nil
		}
		u.window.SetPos(x, y)
		return nil
	})
}

func (u *UserInterface) WindowPosition() (int, int) {
	if !u.isRunning() {
		panic("glfw: WindowPosition can't be called before the main loop starts")
	}
	x, y := 0, 0
	_ = u.t.Call(func() error {
		if u.isFullscreen() {
			x, y = u.origPosX, u.origPosY
			return nil
		}
		x, y = u.window.GetPos()
		return nil
	})
	return x, y
}

func (u *UserInterface) SetScreenTransparent(transparent bool) {
	if !u.isRunning() {
		u.setInitScreenTransparent(transparent)
		return
	}
	panic("glfw: SetScreenTransparent can't be called after the main loop starts")
}

func (u *UserInterface) IsScreenTransparent() bool {
	if !u.isRunning() {
		return u.isInitScreenTransparent()
	}
	val := false
	_ = u.t.Call(func() error {
		val = u.window.GetAttrib(glfw.TransparentFramebuffer) == glfw.True
		return nil
	})
	return val
}

func (u *UserInterface) Input() driver.Input {
	return &u.input
}