ebiten: Add CursorShape/SetCursorShape/CursorShapeType

This change adds APIs to enable to use system cursor shapes other
than the default shape (an arrow).

This change doesn't add these cursors since they seem a little
different on macOS from the other platforms.

 * GLFW_HRESIZE_CURSOR
 * GLFW_VRESIZE_CURSOR

Closes #995

cursor.go

@@ -16,12 +16,23 @@ package ebiten
 
 import "github.com/hajimehoshi/ebiten/v2/internal/driver"
 
-// CursorModeType represents
-// a render and coordinate mode of a mouse cursor.
+// CursorModeType represents a render and coordinate mode of a mouse cursor.
 type CursorModeType int
 
+// CursorModeTypes
 const (
 	CursorModeVisible  CursorModeType = CursorModeType(driver.CursorModeVisible)
 	CursorModeHidden   CursorModeType = CursorModeType(driver.CursorModeHidden)
 	CursorModeCaptured CursorModeType = CursorModeType(driver.CursorModeCaptured)
 )
+
+// CursorShapeType represents a shape of a mouse cursor.
+type CursorShapeType int
+
+// CursorShapeTypes
+const (
+	CursorShapeDefault   CursorShapeType = CursorShapeType(driver.CursorShapeDefault)
+	CursorShapeText      CursorShapeType = CursorShapeType(driver.CursorShapeText)
+	CursorShapeCrosshair CursorShapeType = CursorShapeType(driver.CursorShapeCrosshair)
+	CursorShapePointer   CursorShapeType = CursorShapeType(driver.CursorShapePointer)
+)

examples/cursor/main.go

@@ -0,0 +1,94 @@
+// Copyright 2021 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.
+
+// +build example
+
+package main
+
+import (
+	"image"
+	"image/color"
+	"log"
+
+	"github.com/hajimehoshi/ebiten/v2"
+	"github.com/hajimehoshi/ebiten/v2/ebitenutil"
+)
+
+const (
+	screenWidth  = 640
+	screenHeight = 480
+)
+
+type Game struct {
+	grids      map[image.Rectangle]ebiten.CursorShapeType
+	gridColors map[image.Rectangle]color.Color
+}
+
+func (g *Game) Update() error {
+	pt := image.Pt(ebiten.CursorPosition())
+	for r, c := range g.grids {
+		if pt.In(r) {
+			ebiten.SetCursorShape(c)
+			return nil
+		}
+	}
+	ebiten.SetCursorShape(ebiten.CursorShapeDefault)
+	return nil
+}
+
+func (g *Game) Draw(screen *ebiten.Image) {
+	for r, c := range g.gridColors {
+		ebitenutil.DrawRect(screen, float64(r.Min.X), float64(r.Min.Y), float64(r.Dx()), float64(r.Dy()), c)
+	}
+
+	switch ebiten.CursorShape() {
+	case ebiten.CursorShapeDefault:
+		ebitenutil.DebugPrint(screen, "CursorShape: Default")
+	case ebiten.CursorShapeText:
+		ebitenutil.DebugPrint(screen, "CursorShape: Text")
+	case ebiten.CursorShapeCrosshair:
+		ebitenutil.DebugPrint(screen, "CursorShape: Crosshair")
+	case ebiten.CursorShapePointer:
+		ebitenutil.DebugPrint(screen, "CursorShape: Pointer")
+	}
+}
+
+func (g *Game) Layout(outsideWidth, outsideHeight int) (int, int) {
+	return screenWidth, screenHeight
+}
+
+func main() {
+	g := &Game{
+		grids: map[image.Rectangle]ebiten.CursorShapeType{
+			image.Rect(100, 100, 200, 300): ebiten.CursorShapeDefault,
+			image.Rect(200, 100, 300, 300): ebiten.CursorShapeText,
+			image.Rect(300, 100, 400, 300): ebiten.CursorShapeCrosshair,
+			image.Rect(400, 100, 500, 300): ebiten.CursorShapePointer,
+		},
+		gridColors: map[image.Rectangle]color.Color{},
+	}
+	for rect, c := range g.grids {
+		a := byte(0x40)
+		if c%2 == 0 {
+			a += 0x40
+		}
+		g.gridColors[rect] = color.Alpha{a}
+	}
+
+	ebiten.SetWindowSize(screenWidth, screenHeight)
+	ebiten.SetWindowTitle("Cursor (Ebiten Demo)")
+	if err := ebiten.RunGame(g); err != nil {
+		log.Fatal(err)
+	}
+}

internal/driver/cursor.go

@@ -21,3 +21,12 @@ const (
 	CursorModeHidden
 	CursorModeCaptured
 )
+
+type CursorShape int
+
+const (
+	CursorShapeDefault CursorShape = iota
+	CursorShapeText
+	CursorShapeCrosshair
+	CursorShapePointer
+)

internal/driver/ui.go

@@ -45,6 +45,9 @@ type UI interface {
 	CursorMode() CursorMode
 	SetCursorMode(mode CursorMode)
 
+	CursorShape() CursorShape
+	SetCursorShape(shape CursorShape)
+
 	IsFullscreen() bool
 	SetFullscreen(fullscreen bool)
 

internal/glfw/const.go

@@ -30,6 +30,7 @@ type (
 	ModifierKey     int
 	MouseButton     int
 	PeripheralEvent int
+	StandardCursor  int
 )
 
 const (
@@ -142,3 +143,12 @@ func (e ErrorCode) String() string {
 		return fmt.Sprintf("GLFW error code (%d)", e)
 	}
 }
+
+const (
+	ArrowCursor     = StandardCursor(0x00036001)
+	IBeamCursor     = StandardCursor(0x00036002)
+	CrosshairCursor = StandardCursor(0x00036003)
+	HandCursor      = StandardCursor(0x00036004)
+	HResizeCursor   = StandardCursor(0x00036005)
+	VResizeCursor   = StandardCursor(0x00036006)
+)

internal/glfw/glfw_notwindows.go

@@ -58,6 +58,15 @@ func (w windows) get(win *glfw.Window) *Window {
 	return ww
 }
 
+type Cursor struct {
+	c *glfw.Cursor
+}
+
+func CreateStandardCursor(shape StandardCursor) *Cursor {
+	c := glfw.CreateStandardCursor(glfw.StandardCursor(shape))
+	return &Cursor{c: c}
+}
+
 type Monitor struct {
 	m *glfw.Monitor
 }
@@ -163,6 +172,14 @@ func (w *Window) SetCharModsCallback(cbfun CharModsCallback) (previous CharModsC
 	return nil // TODO
 }
 
+func (w *Window) SetCursor(cursor *Cursor) {
+	var c *glfw.Cursor
+	if cursor != nil {
+		c = cursor.c
+	}
+	w.w.SetCursor(c)
+}
+
 func (w *Window) SetFramebufferSizeCallback(cbfun FramebufferSizeCallback) (previous FramebufferSizeCallback) {
 	var gcb glfw.FramebufferSizeCallback
 	if cbfun != nil {

internal/glfw/glfw_windows.go

@@ -65,6 +65,16 @@ func (w glfwWindows) get(win uintptr) *Window {
 	return ww
 }
 
+type Cursor struct {
+	c uintptr
+}
+
+func CreateStandardCursor(shape StandardCursor) *Cursor {
+	c := glfwDLL.call("glfwCreateStandardCursor", uintptr(shape))
+	panicError()
+	return &Cursor{c: c}
+}
+
 type Monitor struct {
 	m uintptr
 }
@@ -192,6 +202,14 @@ func (w *Window) SetCharModsCallback(cbfun CharModsCallback) (previous CharModsC
 	return nil // TODO
 }
 
+func (w *Window) SetCursor(cursor *Cursor) {
+	var c uintptr
+	if cursor != nil {
+		c = cursor.c
+	}
+	glfwDLL.call("glfwSetCursor", w.w, c)
+}
+
 func (w *Window) SetFramebufferSizeCallback(cbfun FramebufferSizeCallback) (previous FramebufferSizeCallback) {
 	var gcb uintptr
 	if cbfun != nil {

internal/uidriver/glfw/ui.go

@@ -64,6 +64,7 @@ type UserInterface struct {
 	runnableOnUnfocused bool
 	vsync               bool
 	iconImages          []image.Image
+	cursorShape         driver.CursorShape
 
 	// err must be accessed from the main thread.
 	err error
@@ -143,10 +144,13 @@ func init() {
 	cacheMonitors()
 }
 
+var glfwSystemCursors = map[driver.CursorShape]*glfw.Cursor{}
+
 func initialize() error {
 	if err := glfw.Init(); err != nil {
 		return err
 	}
+
 	glfw.WindowHint(glfw.Visible, glfw.False)
 	glfw.WindowHint(glfw.ClientAPI, glfw.NoAPI)
 
@@ -168,6 +172,12 @@ func initialize() error {
 	theUI.initFullscreenWidthInDP = int(fromGLFWMonitorPixel(float64(v.Width), scale))
 	theUI.initFullscreenHeightInDP = int(fromGLFWMonitorPixel(float64(v.Height), scale))
 
+	// Create system cursors. These cursors are destroyed at glfw.Terminate().
+	glfwSystemCursors[driver.CursorShapeDefault] = nil
+	glfwSystemCursors[driver.CursorShapeText] = glfw.CreateStandardCursor(glfw.IBeamCursor)
+	glfwSystemCursors[driver.CursorShapeCrosshair] = glfw.CreateStandardCursor(glfw.CrosshairCursor)
+	glfwSystemCursors[driver.CursorShapePointer] = glfw.CreateStandardCursor(glfw.HandCursor)
+
 	return nil
 }
 
@@ -271,6 +281,21 @@ func (u *UserInterface) setInitCursorMode(mode driver.CursorMode) {
 	u.m.Unlock()
 }
 
+func (u *UserInterface) getCursorShape() driver.CursorShape {
+	u.m.RLock()
+	v := u.cursorShape
+	u.m.RUnlock()
+	return v
+}
+
+func (u *UserInterface) setCursorShape(shape driver.CursorShape) driver.CursorShape {
+	u.m.Lock()
+	old := u.cursorShape
+	u.cursorShape = shape
+	u.m.Unlock()
+	return old
+}
+
 func (u *UserInterface) isInitWindowDecorated() bool {
 	u.m.RLock()
 	v := u.initWindowDecorated
@@ -557,6 +582,24 @@ func (u *UserInterface) SetCursorMode(mode driver.CursorMode) {
 	})
 }
 
+func (u *UserInterface) CursorShape() driver.CursorShape {
+	return u.getCursorShape()
+}
+
+func (u *UserInterface) SetCursorShape(shape driver.CursorShape) {
+	old := u.setCursorShape(shape)
+	if old == shape {
+		return
+	}
+	if !u.isRunning() {
+		return
+	}
+	_ = u.t.Call(func() error {
+		u.window.SetCursor(glfwSystemCursors[shape])
+		return nil
+	})
+}
+
 func (u *UserInterface) DeviceScaleFactor() float64 {
 	if !u.isRunning() {
 		return devicescale.GetAt(u.initMonitor.GetPos())
@@ -615,6 +658,7 @@ func (u *UserInterface) createWindow() error {
 	u.window.SetInputMode(glfw.StickyMouseButtonsMode, glfw.True)
 	u.window.SetInputMode(glfw.StickyKeysMode, glfw.True)
 	u.window.SetInputMode(glfw.CursorMode, driverCursorModeToGLFWCursorMode(u.getInitCursorMode()))
+	u.window.SetCursor(glfwSystemCursors[u.getCursorShape()])
 	u.window.SetTitle(u.title)
 	// TODO: Set icons
 

internal/uidriver/js/ui_js.go

@@ -31,11 +31,27 @@ var (
 	stringTransparent = js.ValueOf("transparent")
 )
 
+func driverCursorShapeToCSSCursor(cursor driver.CursorShape) string {
+	switch cursor {
+	case driver.CursorShapeDefault:
+		return "default"
+	case driver.CursorShapeText:
+		return "text"
+	case driver.CursorShapeCrosshair:
+		return "crosshair"
+	case driver.CursorShapePointer:
+		return "pointer"
+	}
+	return "auto"
+}
+
 type UserInterface struct {
 	runnableOnUnfocused bool
 	vsync               bool
 	running             bool
 	initFocused         bool
+	cursorHidden        bool
+	cursorShape         driver.CursorShape
 
 	sizeChanged bool
 	contextLost bool
@@ -107,10 +123,10 @@ func (u *UserInterface) CursorMode() driver.CursorMode {
 		return driver.CursorModeHidden
 	}
 
-	if jsutil.Equal(canvas.Get("style").Get("cursor"), stringNone) {
-		return driver.CursorModeVisible
-	}
+	if u.cursorHidden {
 		return driver.CursorModeHidden
+	}
+	return driver.CursorModeVisible
 }
 
 func (u *UserInterface) SetCursorMode(mode driver.CursorMode) {
@@ -118,20 +134,45 @@ func (u *UserInterface) SetCursorMode(mode driver.CursorMode) {
 		return
 	}
 
-	var visible bool
 	switch mode {
 	case driver.CursorModeVisible:
-		visible = true
+		if u.cursorHidden {
+			return
+		}
+		u.cursorHidden = false
 	case driver.CursorModeHidden:
-		visible = false
+		if !u.cursorHidden {
+			return
+		}
+		u.cursorHidden = true
 	default:
 		return
 	}
 
-	if visible {
-		canvas.Get("style").Set("cursor", "auto")
+	if u.cursorHidden {
+		canvas.Get("style").Set("cursor", stringNone)
 	} else {
-		canvas.Get("style").Set("cursor", "none")
+		canvas.Get("style").Set("cursor", driverCursorShapeToCSSCursor(u.cursorShape))
+	}
+}
+
+func (u *UserInterface) CursorShape() driver.CursorShape {
+	if !canvas.Truthy() {
+		return driver.CursorShapeDefault
+	}
+	return u.cursorShape
+}
+
+func (u *UserInterface) SetCursorShape(shape driver.CursorShape) {
+	if !canvas.Truthy() {
+		return
+	}
+	if u.cursorShape == shape {
+		return
+	}
+	u.cursorShape = shape
+	if !u.cursorHidden {
+		canvas.Get("style").Set("cursor", driverCursorShapeToCSSCursor(u.cursorShape))
 	}
 }
 

internal/uidriver/mobile/ui.go

@@ -370,6 +370,14 @@ func (u *UserInterface) SetCursorMode(mode driver.CursorMode) {
 	// Do nothing
 }
 
+func (u *UserInterface) CursorShape() driver.CursorShape {
+	return driver.CursorShapeDefault
+}
+
+func (u *UserInterface) SetCursorShape(shape driver.CursorShape) {
+	// Do nothing
+}
+
 func (u *UserInterface) IsFullscreen() bool {
 	return false
 }

run.go

@@ -241,6 +241,14 @@ func SetCursorMode(mode CursorModeType) {
 	uiDriver().SetCursorMode(driver.CursorMode(mode))
 }
 
+func CursorShape() CursorShapeType {
+	return CursorShapeType(uiDriver().CursorShape())
+}
+
+func SetCursorShape(shape CursorShapeType) {
+	uiDriver().SetCursorShape(driver.CursorShape(shape))
+}
+
 // IsFullscreen reports whether the current mode is fullscreen or not.
 //
 // IsFullscreen always returns false on browsers or mobiles.