joystick: add CLI utilty to scan display events to make it easier to add new joyticks

Signed-off-by: deadprogram <ron@hybridgroup.com>

platforms/joystick/README.md

@@ -235,3 +235,25 @@ func main() {
 	robot.Start()
 }
 ```
+
+## How to Add A New Joystick
+
+In the `bin` directory for this package is a CLI utility program that scans for SDL joystick events, and displays the ID and value:
+
+```
+$ go run ./platforms/joystick/bin/scanner.go 
+Joystick 0 connected
+[6625 ms] Axis: 1       value:-22686
+[6641 ms] Axis: 1       value:-32768
+[6836 ms] Axis: 1       value:-18317
+[6852 ms] Axis: 1       value:0
+[8663 ms] Axis: 3       value:-32768
+[8873 ms] Axis: 3       value:0
+[10183 ms] Axis: 0      value:-24703
+[10183 ms] Axis: 0      value:-32768
+[10313 ms] Axis: 1      value:-3193
+[10329 ms] Axis: 1      value:0
+[10345 ms] Axis: 0      value:0
+```
+
+You can use the output from this program to create a JSON file for the various buttons and axes on your joystick/gamepad.

platforms/joystick/bin/scanner.go

@@ -0,0 +1,68 @@
+// Joystick scanner
+// Based on original code from Jacky Boen
+// https://github.com/veandco/go-sdl2/blob/master/examples/events/events.go
+
+package main
+
+import (
+	"fmt"
+	"os"
+
+	"github.com/veandco/go-sdl2/sdl"
+)
+
+var joysticks [16]*sdl.Joystick
+
+func run() int {
+	var event sdl.Event
+	var running bool
+
+	sdl.Init(sdl.INIT_JOYSTICK)
+	defer sdl.Quit()
+
+	sdl.JoystickEventState(sdl.ENABLE)
+
+	running = true
+	for running {
+		for event = sdl.PollEvent(); event != nil; event = sdl.PollEvent() {
+			switch t := event.(type) {
+			case *sdl.QuitEvent:
+				running = false
+			case *sdl.JoyAxisEvent:
+				fmt.Printf("[%d ms] Axis: %d\tvalue:%d\n",
+					t.Timestamp, t.Axis, t.Value)
+			case *sdl.JoyBallEvent:
+				fmt.Printf("[%d ms] Ball:%d\txrel:%d\tyrel:%d\n",
+					t.Timestamp, t.Ball, t.XRel, t.YRel)
+			case *sdl.JoyButtonEvent:
+				fmt.Printf("[%d ms] Button:%d\tstate:%d\n",
+					t.Timestamp, t.Button, t.State)
+			case *sdl.JoyHatEvent:
+				fmt.Printf("[%d ms] Hat:%d\tvalue:%d\n",
+					t.Timestamp, t.Hat, t.Value)
+			case *sdl.JoyDeviceEvent:
+				if t.Type == sdl.JOYDEVICEADDED {
+					joysticks[int(t.Which)] = sdl.JoystickOpen(t.Which)
+					if joysticks[int(t.Which)] != nil {
+						fmt.Printf("Joystick %d connected\n", t.Which)
+					}
+				} else if t.Type == sdl.JOYDEVICEREMOVED {
+					if joystick := joysticks[int(t.Which)]; joystick != nil {
+						joystick.Close()
+					}
+					fmt.Printf("Joystick %d disconnected\n", t.Which)
+				}
+			default:
+				fmt.Printf("Unknown event\n")
+			}
+		}
+
+		sdl.Delay(16)
+	}
+
+	return 0
+}
+
+func main() {
+	os.Exit(run())
+}