Add an FPS timer

cmd/view-map/main.go

@@ -7,6 +7,7 @@ import (
 	"math"
 	"os"
 	"path/filepath"
+	"time"
 
 	"github.com/faiface/pixel"
 	"github.com/faiface/pixel/pixelgl"
@@ -35,7 +36,8 @@ type env struct {
 type state struct {
 	env *env
 
-	step int
+	step      int
+	fpsTicker <-chan time.Time
 
 	cam    pixel.Matrix
 	camPos pixel.Vec
@@ -78,14 +80,19 @@ func main() {
 		objects[name] = conv.ConvertObject(obj, name)
 	}
 
-	env := &env{gameMap: gameMap, set: mapSet, objects: objects}
+	env := &env{
+		gameMap: gameMap,
+		set:     mapSet,
+		objects: objects,
+	}
 
 	// The main thread now belongs to pixelgl
 	pixelgl.Run(env.run)
 }
 
 func (e *env) run() {
-	win, err := ui.NewWindow("View Map " + *mapFile)
+	title := "View Map " + *mapFile
+	win, err := ui.NewWindow(title + " | FPS: ?")
 	if err != nil {
 		log.Fatal("Couldn't create window: %v", err)
 	}
@@ -95,8 +102,10 @@ func (e *env) run() {
 		env: e,
 		//		camPos: pixel.V(0, float64(-pWin.Bounds().Size().Y)),
 		//		camPos: pixel.V(float64(3700), float64(0)),
-		zoom: 1.0,
-		rot:  0.785,
+		zoom:      1.0,
+		rot:       0.785,
+		step:      -1,
+		fpsTicker: time.Tick(time.Second),
 	}
 	pWin.SetSmooth(true)
 
@@ -104,12 +113,19 @@ func (e *env) run() {
 		oldState := *state
 		state = state.runStep(pWin)
 
-		if oldState != *state || oldState.step == 0 {
+		if oldState != *state || oldState.step == -1 {
 			log.Printf("zoom=%.2f rot=%.4f zIdx=%v camPos=%#v", state.zoom, state.rot, state.zIdx, state.camPos)
 			state.present(pWin)
 		}
 
 		state.step += 1
+		select {
+		case <-state.fpsTicker:
+			pWin.SetTitle(fmt.Sprintf("%s | FPS: %d", title, state.step))
+			state.step = 0
+		default:
+		}
+
 	})
 }