Calendar now checks ever second for a date change

main.go

@@ -2,6 +2,7 @@ package main
 
 import "fmt"
 import "time"
+import "sync"
 import "bytes"
 import "image"
 import _ "embed"
@@ -14,9 +15,10 @@ var iconBytes []byte
 
 var application = &stone.Application { }
 
-var now time.Time
 var viewingMonth int
+var currentMonth int
 var columns, rows int
+var drawMutex sync.Mutex
 
 var shortMonthNames = []string {
 	"",
@@ -43,7 +45,7 @@ func main () {
 	application.SetIcon([]image.Image { icon })
 	
 	application.OnStart(onStart)
-	application.OnResize(redraw)
+	application.OnResize(onResize)
 	application.OnPress(onPress)
 	application.OnScroll(onScroll)
 	
@@ -52,6 +54,9 @@ func main () {
 }
 
 func onScroll (x, y int) {
+	drawMutex.Lock()
+	defer drawMutex.Unlock()
+	
 	viewingMonth += y * columns
 	application.Clear()
 	redraw()
@@ -61,50 +66,98 @@ func onScroll (x, y int) {
 func onPress (button stone.Button, modifiers stone.Modifiers) {
 	switch button {
 	case stone.KeyUp:
+		drawMutex.Lock()
+		defer drawMutex.Unlock()
+	
 		viewingMonth -= columns
 		application.Clear()
 		redraw()
 		application.Draw()
+		
 	case stone.KeyDown:
+		drawMutex.Lock()
+		defer drawMutex.Unlock()
+	
 		viewingMonth += columns
 		application.Clear()
 		redraw()
 		application.Draw()
+		
 	case stone.KeyPageUp:
+		drawMutex.Lock()
+		defer drawMutex.Unlock()
+	
 		viewingMonth -= columns * rows
 		application.Clear()
 		redraw()
 		application.Draw()
+		
 	case stone.KeyPageDown:
+		drawMutex.Lock()
+		defer drawMutex.Unlock()
+		
 		viewingMonth += columns * rows
 		application.Clear()
 		redraw()
 		application.Draw()
+		
 	}
 }
 
 func onStart () {
-	now = time.Now()
-	viewingMonth = int(now.Month() - 1) + now.Year() * 12
+	currentMonth = canonMonth(time.Now())
+	viewingMonth = currentMonth
 	redraw()
+	go tick()
+}
+
+func onResize () {
+	drawMutex.Lock()
+	defer drawMutex.Unlock()
+	
+	redraw()
+}
+
+func tick () {
+	for {
+		time.Sleep(time.Second)
+		drawMutex.Lock()
+
+		newMonth := canonMonth(time.Now())
+		if currentMonth != newMonth {
+			currentMonth = newMonth
+
+			pageSize := columns * rows
+			if currentMonth < viewingMonth {
+				viewingMonth -= pageSize
+			} else if currentMonth >= viewingMonth + pageSize {
+				viewingMonth += pageSize
+			}
+			
+			application.Clear()
+			redraw()
+			application.Draw()
+		}
+		
+		drawMutex.Unlock()
+	}
 }
 
 func redraw () {
 	width, height := application.Size()
+	columns = (width - 20) / 23 + 1
+	rows    = height / 10 + 1
 
 	monthIter := viewingMonth
-	rows = 0
-	columns = (width - 20) / 23 + 1
 	xOffset := (width - columns * 23) / 2 + 1
-	for y := 0; y < height; y += 10 {
-		for x := 0; x < width - 19;  x += 23 {
+	for y := 0; y < rows; y ++ {
+		for x := 0; x < columns;  x ++ {
 			drawMonth (
-				x + xOffset, y,
+				x * 23 + xOffset, y * 10,
 				monthIter / 12,
 				time.Month(wrap(monthIter, 12) + 1))
 			monthIter ++
 		}
-		rows ++
 	}
 }
 
@@ -118,7 +171,7 @@ func wrap (value, around int) (wrapped int) {
 }
 
 func drawMonth (xOffset, yOffset, year int, month time.Month) {
-	current := month == now.Month() && year == now.Year()
+	current := int(month) - 1 + year * 12 == currentMonth
 
 	bce := year < 0
 	if bce { year *= -1 }
@@ -159,7 +212,7 @@ func drawMonth (xOffset, yOffset, year int, month time.Month) {
 			fmt.Fprint(application, dayIter)
 		}
 
-		if current && dayIter == int(now.Day()) {
+		if current && dayIter == int(time.Now().Day()) {
 			application.SetColor(x,     y, stone.ColorRed)
 			application.SetColor(x + 1, y, stone.ColorRed)
 		} else if weekday == 0 || weekday == 6 {
@@ -205,3 +258,8 @@ func daysInMonth (year int, month time.Month) (days int) {
 
 	return
 }
+
+func canonMonth (when time.Time) (month int) {
+	month = int(when.Month() - 1) + when.Year() * 12
+	return
+}