ebiten: Support updating the gamepad mapping (#1775)

This is only supported on desktops yet (on mobile standard layout isn't
implemented yet, and on the web this is the browser's responsibility).

Closes #1723

input.go

@@ -234,6 +234,27 @@ func IsStandardGamepadLayoutAvailable(id GamepadID) bool {
 	return uiDriver().Input().IsStandardGamepadLayoutAvailable(id)
 }
 
+// UpdateStandardGamepadLayoutMappings updates the gamepad layout definitions using a set of definitions in SDL_GameControllerDB format.
+//
+// Multiple input definitions can be provided separated by newlines.
+// In particular, it is valid to pass an entire gamecontrollerdb.txt file.
+//
+// Note though that Ebiten already includes its own copy of this file,
+// so this call should only be necessary to add mappings for hardware not supported yet;
+// ideally games using the StandardGamepad functions should allow the user to provide mappings and then call this function if provided.
+// When using this facility to support new hardware, please also send a pull request to https://github.com/gabomdq/SDL_GameControllerDB to make your mapping available to everyone else.
+//
+// UpdateStandardGamepadLayoutMappings reports whether the mappings were applied, and returns an error in case any occurred while parsing the mappings.
+//
+// On platforms where gamepad mappings are not managed by Ebiten, this always returns false and nil.
+//
+// UpdateStandardGamepadLayoutMappings must be called on the main thread before ebiten.Run, and is concurrent-safe after ebiten.Run.
+//
+// Updated mappings take effect immediately even for already connected gamepads.
+func UpdateStandardGamepadLayoutMappings(mappings string) (bool, error) {
+	return uiDriver().Input().UpdateStandardGamepadLayoutMappings(mappings)
+}
+
 // TouchID represents a touch's identifier.
 type TouchID = driver.TouchID
 

internal/driver/input.go

@@ -34,6 +34,7 @@ type Input interface {
 	IsStandardGamepadButtonPressed(id GamepadID, button StandardGamepadButton) bool
 	IsStandardGamepadLayoutAvailable(id GamepadID) bool
 	StandardGamepadAxisValue(id GamepadID, button StandardGamepadAxis) float64
+	UpdateStandardGamepadLayoutMappings(mapping string) (bool, error)
 	TouchPosition(id TouchID) (x, y int)
 	Wheel() (xoff, yoff float64)
 }

internal/uidriver/glfw/input.go

@@ -452,3 +452,26 @@ func standardButtonToGLFWButton(button driver.StandardGamepadButton) glfw.Gamepa
 		panic(fmt.Sprintf("glfw: invalid or inconvertible StandardGamepadButton: %d", button))
 	}
 }
+
+// UpdateStandardGamepadLayoutMappings can be used to provide new gamepad mappings to Ebiten.
+// The string must be in the format of SDL_GameControllerDB.
+func (i *Input) UpdateStandardGamepadLayoutMappings(mapping string) (bool, error) {
+	var err error
+	if i.ui.isRunning() {
+		err = i.ui.t.Call(func() error {
+			return i.updateStandardGamepadLayoutMappings(mapping)
+		})
+	} else {
+		err = i.updateStandardGamepadLayoutMappings(mapping)
+	}
+	return err == nil, err
+}
+
+func (i *Input) updateStandardGamepadLayoutMappings(mapping string) error {
+	if !glfw.UpdateGamepadMappings(mapping) {
+		// Would be nice if we could actually get the error string.
+		// However, go-gl currently does not provide it in any way.
+		return fmt.Errorf("glfw: could not parse or update gamepad mappings")
+	}
+	return nil
+}

internal/uidriver/js/input_js.go

@@ -496,3 +496,9 @@ func (i *Input) IsStandardGamepadButtonPressed(id driver.GamepadID, button drive
 	}
 	return g.standardButtonPressed[button]
 }
+
+// UpdateStandardGamepadLayoutMappings is not supported for JS - the browser maintains the mappings.
+func (i *Input) UpdateStandardGamepadLayoutMappings(mapping string) (bool, error) {
+	// All OK - browser owns this though.
+	return false, nil
+}

internal/uidriver/mobile/input.go

@@ -147,6 +147,13 @@ func (i *Input) StandardGamepadAxisValue(id driver.GamepadID, axis driver.Standa
 	return 0
 }
 
+// UpdateStandardGamepadLayoutMappings is not supported on mobile - this still needs to be implemented.
+func (i *Input) UpdateStandardGamepadLayoutMappings(mapping string) (bool, error) {
+	// TODO: Implement this (#1557)
+	// Note: NOT returning an error, as mappings also do not matter right now (all functions above return nothing is pressed anyway).
+	return false, nil
+}
+
 func (i *Input) AppendTouchIDs(touchIDs []driver.TouchID) []driver.TouchID {
 	i.ui.m.RLock()
 	defer i.ui.m.RUnlock()