internal/gamepad: refactor standard layout support to allow remapping in the per-platform implementations. (#2588)

Refactors native standard layout so standard axes and buttons can be implemented using any of axes, buttons or hats.

This is required to be able to implement a native standard layout mapping for Linux, as e.g. shoulder buttons can be
backed either by an analog or digital input.

Precedes #2587

Updates #2052

internal/gamepad/gamepad.go

@@ -187,11 +187,59 @@ type Gamepad struct {
 	native nativeGamepad
 }
 
+type mappingInput interface {
+	Pressed() bool
+	Value() float64 // Normalized to range: 0..1.
+}
+
+type axisMappingInput struct {
+	g    nativeGamepad
+	axis int
+}
+
+func (a axisMappingInput) Pressed() bool {
+	return a.g.axisValue(a.axis) > gamepaddb.ButtonPressedThreshold
+}
+
+func (a axisMappingInput) Value() float64 {
+	return a.g.axisValue(a.axis)*0.5 + 0.5
+}
+
+type buttonMappingInput struct {
+	g      nativeGamepad
+	button int
+}
+
+func (b buttonMappingInput) Pressed() bool {
+	return b.g.isButtonPressed(b.button)
+}
+
+func (b buttonMappingInput) Value() float64 {
+	return b.g.buttonValue(b.button)
+}
+
+type hatMappingInput struct {
+	g         nativeGamepad
+	hat       int
+	direction int
+}
+
+func (h hatMappingInput) Pressed() bool {
+	return h.g.hatState(h.hat)&h.direction != 0
+}
+
+func (h hatMappingInput) Value() float64 {
+	if h.Pressed() {
+		return 1
+	}
+	return 0
+}
+
 type nativeGamepad interface {
 	update(gamepads *gamepads) error
 	hasOwnStandardLayoutMapping() bool
-	isStandardAxisAvailableInOwnMapping(axis gamepaddb.StandardAxis) bool
-	isStandardButtonAvailableInOwnMapping(button gamepaddb.StandardButton) bool
+	standardAxisInOwnMapping(axis gamepaddb.StandardAxis) mappingInput
+	standardButtonInOwnMapping(button gamepaddb.StandardButton) mappingInput
 	axisCount() int
 	buttonCount() int
 	hatCount() int
@@ -291,7 +339,7 @@ func (g *Gamepad) IsStandardAxisAvailable(axis gamepaddb.StandardAxis) bool {
 	if gamepaddb.HasStandardLayoutMapping(g.sdlID) {
 		return gamepaddb.HasStandardAxis(g.sdlID, axis)
 	}
-	return g.native.isStandardAxisAvailableInOwnMapping(axis)
+	return g.native.standardAxisInOwnMapping(axis) != nil
 }
 
 // IsStandardButtonAvailable is concurrent safe.
@@ -302,7 +350,7 @@ func (g *Gamepad) IsStandardButtonAvailable(button gamepaddb.StandardButton) boo
 	if gamepaddb.HasStandardLayoutMapping(g.sdlID) {
 		return gamepaddb.HasStandardButton(g.sdlID, button)
 	}
-	return g.native.isStandardButtonAvailableInOwnMapping(button)
+	return g.native.standardButtonInOwnMapping(button) != nil
 }
 
 // StandardAxisValue is concurrent-safe.
@@ -310,8 +358,8 @@ func (g *Gamepad) StandardAxisValue(axis gamepaddb.StandardAxis) float64 {
 	if gamepaddb.HasStandardLayoutMapping(g.sdlID) {
 		return gamepaddb.AxisValue(g.sdlID, axis, g)
 	}
-	if g.native.hasOwnStandardLayoutMapping() {
-		return g.native.axisValue(int(axis))
+	if m := g.native.standardAxisInOwnMapping(axis); m != nil {
+		return m.Value()*2 - 1
 	}
 	return 0
 }
@@ -321,8 +369,8 @@ func (g *Gamepad) StandardButtonValue(button gamepaddb.StandardButton) float64 {
 	if gamepaddb.HasStandardLayoutMapping(g.sdlID) {
 		return gamepaddb.ButtonValue(g.sdlID, button, g)
 	}
-	if g.native.hasOwnStandardLayoutMapping() {
-		return g.native.buttonValue(int(button))
+	if m := g.native.standardButtonInOwnMapping(button); m != nil {
+		return m.Value()
 	}
 	return 0
 }
@@ -332,8 +380,8 @@ func (g *Gamepad) IsStandardButtonPressed(button gamepaddb.StandardButton) bool
 	if gamepaddb.HasStandardLayoutMapping(g.sdlID) {
 		return gamepaddb.IsButtonPressed(g.sdlID, button, g)
 	}
-	if g.native.hasOwnStandardLayoutMapping() {
-		return g.native.isButtonPressed(int(button))
+	if m := g.native.standardButtonInOwnMapping(button); m != nil {
+		return m.Pressed()
 	}
 	return false
 }

internal/gamepad/gamepad_android.go

@@ -53,12 +53,12 @@ func (*nativeGamepadImpl) hasOwnStandardLayoutMapping() bool {
 	return false
 }
 
-func (*nativeGamepadImpl) isStandardAxisAvailableInOwnMapping(axis gamepaddb.StandardAxis) bool {
-	return false
+func (*nativeGamepadImpl) standardAxisInOwnMapping(axis gamepaddb.StandardAxis) mappingInput {
+	return nil
 }
 
-func (*nativeGamepadImpl) isStandardButtonAvailableInOwnMapping(button gamepaddb.StandardButton) bool {
-	return false
+func (*nativeGamepadImpl) standardButtonInOwnMapping(button gamepaddb.StandardButton) mappingInput {
+	return nil
 }
 
 func (g *nativeGamepadImpl) axisCount() int {
@@ -87,8 +87,11 @@ func (g *nativeGamepadImpl) isButtonPressed(button int) bool {
 	return g.buttons[button]
 }
 
-func (*nativeGamepadImpl) buttonValue(button int) float64 {
-	panic("gamepad: buttonValue is not implemented")
+func (g *nativeGamepadImpl) buttonValue(button int) float64 {
+	if g.isButtonPressed(button) {
+		return 1
+	}
+	return 0
 }
 
 func (g *nativeGamepadImpl) hatState(hat int) int {

internal/gamepad/gamepad_darwin.go

@@ -372,12 +372,12 @@ func (g *nativeGamepadImpl) hasOwnStandardLayoutMapping() bool {
 	return false
 }
 
-func (g *nativeGamepadImpl) isStandardAxisAvailableInOwnMapping(axis gamepaddb.StandardAxis) bool {
-	return false
+func (*nativeGamepadImpl) standardAxisInOwnMapping(axis gamepaddb.StandardAxis) mappingInput {
+	return nil
 }
 
-func (g *nativeGamepadImpl) isStandardButtonAvailableInOwnMapping(button gamepaddb.StandardButton) bool {
-	return false
+func (*nativeGamepadImpl) standardButtonInOwnMapping(button gamepaddb.StandardButton) mappingInput {
+	return nil
 }
 
 func (g *nativeGamepadImpl) axisCount() int {
@@ -400,7 +400,10 @@ func (g *nativeGamepadImpl) axisValue(axis int) float64 {
 }
 
 func (g *nativeGamepadImpl) buttonValue(button int) float64 {
-	panic("gamepad: buttonValue is not implemented")
+	if g.isButtonPressed(button) {
+		return 1
+	}
+	return 0
 }
 
 func (g *nativeGamepadImpl) isButtonPressed(button int) bool {

internal/gamepad/gamepad_desktop_windows.go

@@ -572,12 +572,12 @@ func (*nativeGamepadDesktop) hasOwnStandardLayoutMapping() bool {
 	return false
 }
 
-func (*nativeGamepadDesktop) isStandardAxisAvailableInOwnMapping(axis gamepaddb.StandardAxis) bool {
-	return false
+func (*nativeGamepadDesktop) standardAxisInOwnMapping(axis gamepaddb.StandardAxis) mappingInput {
+	return nil
 }
 
-func (*nativeGamepadDesktop) isStandardButtonAvailableInOwnMapping(button gamepaddb.StandardButton) bool {
-	return false
+func (*nativeGamepadDesktop) standardButtonInOwnMapping(button gamepaddb.StandardButton) mappingInput {
+	return nil
 }
 
 func (g *nativeGamepadDesktop) usesDInput() bool {
@@ -757,7 +757,10 @@ func (g *nativeGamepadDesktop) isButtonPressed(button int) bool {
 }
 
 func (g *nativeGamepadDesktop) buttonValue(button int) float64 {
-	panic("gamepad: buttonValue is not implemented")
+	if g.isButtonPressed(button) {
+		return 1
+	}
+	return 0
 }
 
 func (g *nativeGamepadDesktop) hatState(hat int) int {

internal/gamepad/gamepad_ios.go

@@ -58,12 +58,12 @@ func (*nativeGamepadImpl) hasOwnStandardLayoutMapping() bool {
 	return false
 }
 
-func (*nativeGamepadImpl) isStandardAxisAvailableInOwnMapping(axis gamepaddb.StandardAxis) bool {
-	return false
+func (*nativeGamepadImpl) standardAxisInOwnMapping(axis gamepaddb.StandardAxis) mappingInput {
+	return nil
 }
 
-func (*nativeGamepadImpl) isStandardButtonAvailableInOwnMapping(button gamepaddb.StandardButton) bool {
-	return false
+func (*nativeGamepadImpl) standardButtonInOwnMapping(button gamepaddb.StandardButton) mappingInput {
+	return nil
 }
 
 func (g *nativeGamepadImpl) axisCount() int {
@@ -92,8 +92,11 @@ func (g *nativeGamepadImpl) isButtonPressed(button int) bool {
 	return g.buttons[button]
 }
 
-func (*nativeGamepadImpl) buttonValue(button int) float64 {
-	panic("gamepad: buttonValue is not implemented")
+func (g *nativeGamepadImpl) buttonValue(button int) float64 {
+	if g.isButtonPressed(button) {
+		return 1
+	}
+	return 0
 }
 
 func (g *nativeGamepadImpl) hatState(hat int) int {

internal/gamepad/gamepad_js.go

@@ -116,18 +116,24 @@ func (g *nativeGamepadImpl) hasOwnStandardLayoutMapping() bool {
 	return g.mapping == "standard"
 }
 
-func (g *nativeGamepadImpl) isStandardAxisAvailableInOwnMapping(axis gamepaddb.StandardAxis) bool {
+func (g *nativeGamepadImpl) standardAxisInOwnMapping(axis gamepaddb.StandardAxis) mappingInput {
 	if !g.hasOwnStandardLayoutMapping() {
-		return false
+		return nil
 	}
-	return axis >= 0 && int(axis) < g.axisCount()
+	if axis < 0 || int(axis) >= g.axisCount() {
+		return nil
+	}
+	return axisMappingInput{g: g, axis: int(axis)}
 }
 
-func (g *nativeGamepadImpl) isStandardButtonAvailableInOwnMapping(button gamepaddb.StandardButton) bool {
+func (g *nativeGamepadImpl) standardButtonInOwnMapping(button gamepaddb.StandardButton) mappingInput {
 	if !g.hasOwnStandardLayoutMapping() {
-		return false
+		return nil
 	}
-	return button >= 0 && int(button) < g.buttonCount()
+	if button < 0 || int(button) >= g.buttonCount() {
+		return nil
+	}
+	return buttonMappingInput{g: g, button: int(button)}
 }
 
 func (g *nativeGamepadImpl) update(gamepads *gamepads) error {

internal/gamepad/gamepad_linux.go

@@ -423,12 +423,12 @@ func (*nativeGamepadImpl) hasOwnStandardLayoutMapping() bool {
 	return false
 }
 
-func (*nativeGamepadImpl) isStandardAxisAvailableInOwnMapping(axis gamepaddb.StandardAxis) bool {
-	return false
+func (g *nativeGamepadImpl) standardAxisInOwnMapping(axis gamepaddb.StandardAxis) mappingInput {
+	return nil
 }
 
-func (*nativeGamepadImpl) isStandardButtonAvailableInOwnMapping(button gamepaddb.StandardButton) bool {
-	return false
+func (g *nativeGamepadImpl) standardButtonInOwnMapping(button gamepaddb.StandardButton) mappingInput {
+	return nil
 }
 
 func (g *nativeGamepadImpl) axisCount() int {
@@ -457,8 +457,11 @@ func (g *nativeGamepadImpl) isButtonPressed(button int) bool {
 	return g.buttons[button]
 }
 
-func (*nativeGamepadImpl) buttonValue(button int) float64 {
-	panic("gamepad: buttonValue is not implemented")
+func (g *nativeGamepadImpl) buttonValue(button int) float64 {
+	if g.isButtonPressed(button) {
+		return 1
+	}
+	return 0
 }
 
 func (g *nativeGamepadImpl) hatState(hat int) int {

internal/gamepad/gamepad_nintendosdk.go

@@ -118,14 +118,20 @@ func (g *nativeGamepadImpl) hasOwnStandardLayoutMapping() bool {
 	return g.standard
 }
 
-func (g *nativeGamepadImpl) isStandardAxisAvailableInOwnMapping(axis gamepaddb.StandardAxis) bool {
+func (g *nativeGamepadImpl) standardAxisInOwnMapping(axis gamepaddb.StandardAxis) mappingInput {
 	// TODO: Implement this on the C side.
-	return axis >= 0 && int(axis) < len(g.axisValues)
+	if axis < 0 || int(axis) >= len(g.axisValues) {
+		return nil
+	}
+	return axisMappingInput{g: g, axis: int(axis)}
 }
 
-func (g *nativeGamepadImpl) isStandardButtonAvailableInOwnMapping(button gamepaddb.StandardButton) bool {
+func (g *nativeGamepadImpl) standardButtonInOwnMapping(button gamepaddb.StandardButton) mappingInput {
 	// TODO: Implement this on the C side.
-	return button >= 0 && int(button) < len(g.buttonValues)
+	if button < 0 || int(button) >= len(g.buttonValues) {
+		return nil
+	}
+	return buttonMappingInput{g: g, button: int(button)}
 }
 
 func (g *nativeGamepadImpl) axisCount() int {

internal/gamepad/gamepad_null.go

@@ -46,12 +46,12 @@ func (*nativeGamepadImpl) hasOwnStandardLayoutMapping() bool {
 	return false
 }
 
-func (*nativeGamepadImpl) isStandardAxisAvailableInOwnMapping(axis gamepaddb.StandardAxis) bool {
-	return false
+func (*nativeGamepadImpl) standardAxisInOwnMapping(axis gamepaddb.StandardAxis) mappingInput {
+	return nil
 }
 
-func (*nativeGamepadImpl) isStandardButtonAvailableInOwnMapping(button gamepaddb.StandardButton) bool {
-	return false
+func (*nativeGamepadImpl) standardButtonInOwnMapping(button gamepaddb.StandardButton) mappingInput {
+	return nil
 }
 
 func (*nativeGamepadImpl) axisCount() int {
@@ -75,7 +75,7 @@ func (*nativeGamepadImpl) isButtonPressed(button int) bool {
 }
 
 func (*nativeGamepadImpl) buttonValue(button int) float64 {
-	panic("gamepad: buttonValue is not implemented")
+	return 0
 }
 
 func (*nativeGamepadImpl) hatState(hat int) int {

internal/gamepad/gamepad_xbox_windows.go

@@ -157,25 +157,27 @@ func (n *nativeGamepadXbox) hasOwnStandardLayoutMapping() bool {
 	return true
 }
 
-func (n *nativeGamepadXbox) isStandardAxisAvailableInOwnMapping(axis gamepaddb.StandardAxis) bool {
+func (n *nativeGamepadXbox) standardAxisInOwnMapping(axis gamepaddb.StandardAxis) mappingInput {
 	switch axis {
 	case gamepaddb.StandardAxisLeftStickHorizontal,
 		gamepaddb.StandardAxisLeftStickVertical,
 		gamepaddb.StandardAxisRightStickHorizontal,
 		gamepaddb.StandardAxisRightStickVertical:
-		return true
+		return axisMappingInput{g: n, axis: int(axis)}
 	}
-	return false
+	return nil
 }
 
-func (n *nativeGamepadXbox) isStandardButtonAvailableInOwnMapping(button gamepaddb.StandardButton) bool {
+func (n *nativeGamepadXbox) standardButtonInOwnMapping(button gamepaddb.StandardButton) mappingInput {
 	switch button {
 	case gamepaddb.StandardButtonFrontBottomLeft,
 		gamepaddb.StandardButtonFrontBottomRight:
-		return true
+		return buttonMappingInput{g: n, button: int(button)}
 	}
-	_, ok := standardButtonToGamepadInputGamepadButton(button)
-	return ok
+	if _, ok := standardButtonToGamepadInputGamepadButton(button); !ok {
+		return nil
+	}
+	return buttonMappingInput{g: n, button: int(button)}
 }
 
 func (n *nativeGamepadXbox) axisCount() int {
@@ -222,15 +224,11 @@ func (n *nativeGamepadXbox) buttonValue(button int) float64 {
 }
 
 func (n *nativeGamepadXbox) isButtonPressed(button int) bool {
-	// Use XInput's trigger dead zone.
-	// See https://source.chromium.org/chromium/chromium/src/+/main:device/gamepad/public/cpp/gamepad.h;l=22-23;drc=6997f8a177359bb99598988ed5e900841984d242
-	// TODO: Integrate this value with the same one in the package gamepaddb.
-	const threshold = 30.0 / 255.0
 	switch gamepaddb.StandardButton(button) {
 	case gamepaddb.StandardButtonFrontBottomLeft:
-		return n.state.leftTrigger >= threshold
+		return n.state.leftTrigger > gamepaddb.ButtonPressedThreshold
 	case gamepaddb.StandardButtonFrontBottomRight:
-		return n.state.rightTrigger >= threshold
+		return n.state.rightTrigger > gamepaddb.ButtonPressedThreshold
 	}
 
 	b, ok := standardButtonToGamepadInputGamepadButton(gamepaddb.StandardButton(button))

internal/gamepaddb/gamepaddb.go

@@ -519,11 +519,13 @@ func buttonValue(id string, button StandardButton, state GamepadState) float64 {
 	return 0
 }
 
-func IsButtonPressed(id string, button StandardButton, state GamepadState) bool {
-	// Use XInput's trigger dead zone.
+// ButtonPressedThreshold represents the value up to which a button counts as not yet pressed.
+// This has been set to match XInput's trigger dead zone.
 // See https://source.chromium.org/chromium/chromium/src/+/main:device/gamepad/public/cpp/gamepad.h;l=22-23;drc=6997f8a177359bb99598988ed5e900841984d242
-	const threshold = 30.0 / 255.0
+// Note: should be used with >, not >=, comparisons.
+const ButtonPressedThreshold = 30.0 / 255.0
 
+func IsButtonPressed(id string, button StandardButton, state GamepadState) bool {
 	mappingsM.RLock()
 	defer mappingsM.RUnlock()
 
@@ -540,7 +542,7 @@ func IsButtonPressed(id string, button StandardButton, state GamepadState) bool
 	switch mapping.Type {
 	case mappingTypeAxis:
 		v := buttonValue(id, button, state)
-		return v > threshold
+		return v > ButtonPressedThreshold
 	case mappingTypeButton:
 		return state.Button(mapping.Index)
 	case mappingTypeHat: