Pickers

Pickers let the user choose a structured value, such as a date, a time or a font, without typing it in a particular format.

Which one to use

Date and time pickers

DatePicker is a month calendar. Selected holds the chosen date and OnChanged receives each new one.

calendar := widget.NewDatePicker(time.Now(), func(d time.Time) {
	status.SetText("Date: " + d.Format("2006-01-02"))
})

With the keyboard, the arrow keys move between days (and into the next or previous month), Home and End jump to the edges of the week, Page Up and Page Down move a month, and Enter or Space selects.

TimePicker is the MD3 clock dial. Hour and Minute hold the time, and Use24Hour switches between the 24-hour dial and AM/PM. The user can also type digits into the hour and minute fields.

DateTimePicker puts a date picker and a time picker on two tabs, switched with Date and Time buttons above them.

Each picker has a Show function that opens it in a modal dialog with OK and Cancel buttons. Your function runs only when the user presses OK:

pickTime := widget.NewButton("Pick a time", func() {
	now := time.Now()
	widget.ShowAutoTimePicker(now.Hour(), now.Minute(), func(h, m int) {
		status.SetText(fmt.Sprintf("Time: %02d:%02d", h, m))
	}, w.Canvas())
})

pickBoth := widget.NewButton("Pick date and time", func() {
	widget.ShowAutoDateTimePicker(time.Now(), func(t time.Time) {
		status.SetText("When: " + t.Format(time.RFC822))
	}, w.Canvas())
})

The Auto variants choose 12-hour or 24-hour mode from the user’s locale. The others take a use24h argument.

Date entries

DateEntry and DateTimeEntry are entries for forms. The user types a date in the locale’s format, or taps the button at the end of the field to open a calendar. Characters that cannot be part of a date are ignored, including in pasted text.

birthday := widget.NewDateEntry()
birthday.SetPlaceHolder("Birthday")
birthday.OnChanged = func(d time.Time) {
	status.SetText("Birthday " + d.Format("2 Jan 2006"))
}

meeting := widget.NewDateTimeEntry()
meeting.SetDateTime(time.Now().Add(24 * time.Hour))
meeting.OnChanged = func(t time.Time) {
	status.SetText("Meeting " + t.Format(time.Kitchen))
}

• Use the entry’s own OnChanged, which receives a time.Time. The embedded Entry.OnChanged receives the raw text instead.
• Selected holds the last valid value. Date() and DateTime() parse the current text and return an error if it is not valid.
• SetDate and SetDateTime write a value in the locale’s format.
• DateTimeEntry.Use24Hour is set from the locale and controls the time picker it opens.

Font picker

FontPicker combines controls for a font family, size, weight and style. It reports a FontPickerConfig with Family, Size, Weight, Bold, Italic and Underline. TextStyle() turns that into a bellui.TextStyle for a label or rich text.

font := widget.NewFontPickerWithSystemFonts(
	widget.FontPickerConfig{Size: 14},
	func(cfg widget.FontPickerConfig) {
		preview.TextStyle = cfg.TextStyle()
		preview.SetText(fmt.Sprintf("%s, %.0f pt", cfg.Family, cfg.Size))
	})

NewFontPickerWithSystemFonts lists the fonts installed on the system, loading the list in the background. NewFontPicker takes your own FontFamily list, each with a name and the font file as a resource. ShowFontPickerPopup opens a picker in a modal dialog with OK and Cancel buttons.

Theme selector

ThemeSelector is a ready-made appearance setting: System, Light or Dark above a row of primary colour swatches. It only reports the user’s choice. Call ThemeSelection.Apply to re-theme the app and SaveThemeSelection to remember it:

appearance := widget.NewThemeSelector(func(sel widget.ThemeSelection) {
	sel.Apply()
	widget.SaveThemeSelection(sel, a.Preferences())
})
// Restore the choice saved last time.
if sel, ok := widget.LoadThemeSelection(a.Preferences()); ok {
	sel.Apply()
	appearance.Selection = sel
}

Theme selector in the Theming section covers it in more detail.