Add calendar widget

calendar.go

@@ -0,0 +1,167 @@
+package objects
+
+import "fmt"
+import "time"
+import "git.tebibyte.media/tomo/tomo"
+import "git.tebibyte.media/tomo/tomo/event"
+import "git.tebibyte.media/tomo/objects/layouts"
+
+// Calendar is an object that can display a date and allow the user to change
+// it. It can display one month at a time.
+type Calendar struct {
+	tomo.ContainerBox
+	
+	grid tomo.ContainerBox
+	time time.Time
+	monthLabel *Label
+	
+	on struct {
+		edit event.FuncBroadcaster
+	}
+}
+
+// NewCalendar creates a new calendar with the specified date.
+func NewCalendar (tm time.Time) *Calendar {
+	calendar := &Calendar {
+		ContainerBox: tomo.NewContainerBox(),
+		time:         tm,
+	}
+	calendar.SetRole(tomo.R("objects", "Calendar", ""))
+	calendar.SetLayout(layouts.ContractVertical)
+	
+	prevButton := NewButton("")
+	prevButton.SetIcon(tomo.IconGoPrevious)
+	prevButton.OnClick(func () {
+		calendar.prevMonth()
+		calendar.on.edit.Broadcast()
+	})
+	nextButton := NewButton("")
+	nextButton.SetIcon(tomo.IconGoNext)
+	nextButton.OnClick(func () {
+		calendar.nextMonth()
+		calendar.on.edit.Broadcast()
+	})
+	calendar.monthLabel = NewLabel("")
+	calendar.monthLabel.SetAlign(tomo.AlignMiddle, tomo.AlignMiddle)
+	
+	calendar.grid = tomo.NewContainerBox()
+	calendar.grid.SetRole(tomo.R("objects", "CalendarGrid", ""))
+	calendar.grid.SetLayout(layouts.NewGrid (
+		[]bool { true, true, true, true, true, true, true },
+		[]bool { }))
+	calendar.Add(NewInnerContainer (
+		layouts.Row { false, true, false },
+		prevButton, calendar.monthLabel, nextButton))
+	calendar.Add(calendar.grid)
+	
+	calendar.OnScroll(calendar.handleScroll)
+	calendar.CaptureScroll(true)
+	
+	calendar.refresh()
+	return calendar
+}
+
+// SetTime sets the date the calendar will display.
+func (this *Calendar) SetTime (tm time.Time) {
+	if this.time == tm { return }
+	this.time = tm
+	this.refresh()
+}
+
+// OnEdit sets a function to be called when the user changes the date on the
+// calendar.
+func (this *Calendar) OnEdit (callback func ()) {
+	this.on.edit.Connect(callback)
+}
+
+func (this *Calendar) prevMonth () {
+	this.time = firstOfMonth(this.time.Add(24 * time.Hour * 40))
+	this.refresh()
+}
+
+func (this *Calendar) nextMonth () {
+	this.time = firstOfMonth(this.time.Add(24 * time.Hour * -20))
+	this.refresh()
+}
+
+var weekdayAbbreviations = []string {
+	"Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat",
+}
+
+func (this *Calendar) refresh () {
+	this.monthLabel.SetText(this.time.Format("2006 January"))
+
+	this.grid.Clear()
+	for _, day := range weekdayAbbreviations {
+		dayLabel := tomo.NewTextBox()
+		dayLabel.SetRole(tomo.R("objects", "CalendarWeekdayHeader", ""))
+		dayLabel.SetText(day)
+		dayLabel.SetAlign(tomo.AlignMiddle, tomo.AlignMiddle)
+		this.grid.Add(dayLabel)
+	}
+	
+	dayIter := 0 - int(firstOfMonth(this.time).Weekday())
+	if dayIter <= -6 {
+		dayIter = 1
+	}
+	weekday := 0
+	totalDays := daysInMonth(this.time)
+	for ; dayIter <= totalDays; dayIter ++ {
+		weekday = (weekday + 1) % 7
+		if dayIter > 0 {
+			day := tomo.NewTextBox()
+			day.SetText(fmt.Sprint(dayIter))
+			if weekday == 1 || weekday == 0 {
+				day.SetRole(tomo.R("objects", "CalendarDay", "weekend"))
+			} else {
+				day.SetRole(tomo.R("objects", "CalendarDay", "weekday"))
+			}
+			this.grid.Add(day)
+		} else {
+			this.grid.Add(tomo.NewBox())
+		}
+	}
+}
+
+func (this *Calendar) handleScroll (x, y float64) {
+	if y < 0 {
+		this.nextMonth()
+	} else {
+		this.prevMonth()
+	}
+}
+
+func firstOfMonth (tm time.Time) time.Time {
+	return time.Date(tm.Year(), tm.Month(), 0, 0, 0, 0, 0, time.Local)
+}
+
+func daysInMonth (tm time.Time) (days int) {
+	year  := tm.Year()
+	month := tm.Month()
+	switch month {
+	case 1:  days = 31
+	case 2:
+		// betcha didn't know this about leap years
+		if year % 4 == 0 && (year % 100 != 0 || year % 400 == 0) {
+			days = 29
+		} else {
+			days = 28
+		}
+	case 3:  days = 31
+	case 4:  days = 30
+	case 5:  days = 31
+	case 6:  days = 30
+	case 7:  days = 31
+	case 8:  days = 31
+	case 9:  days = 30
+	case 10: days = 31
+	case 11: days = 30
+	case 12: days = 31
+	}
+
+	return
+}
+
+func canonMonth (tm time.Time) int {
+	return int(tm.Month() - 1) + tm.Year() * 12
+}