DrawStr: made more efficient and renders newline characters

Before, DrawStr would copy all bytes into a []rune slice, and later
copy the rune slice (by accident) in the for i, v := range loop. Now,
it uses a []byte slice and iterates with for i := range slice.

ui/drawfunctions.go

@@ -18,9 +18,19 @@ func DrawRect(s tcell.Screen, x, y, width, height int, char rune, style tcell.St
 
 // DrawStr will render each character of a string at `x` and `y`.
 func DrawStr(s tcell.Screen, x, y int, str string, style tcell.Style) {
-	runes := []rune(str)
-	for idx, r := range runes {
-		s.SetContent(x+idx, y, r, nil, style)
+	var col int
+	bytes := []byte(str)
+	var i int
+	for i < len(bytes) {
+		r, size := utf8.DecodeRune(bytes[i:])
+		if r == '\n' {
+			col = 0
+			y++
+		} else {
+			s.SetContent(x+col, y, r, nil, style)
+		}
+		i += size
+		col++
 	}
 }
 

ui/messagedialog.go

@@ -0,0 +1,135 @@
+package ui
+
+import (
+	"strings"
+
+	"github.com/gdamore/tcell/v2"
+	"github.com/mattn/go-runewidth"
+)
+
+type MessageDialogKind uint8
+
+const (
+	MessageKindNormal MessageDialogKind = iota
+	MessageKindWarning
+	MessageKindError
+)
+
+// Index of messageDialogKindTitles is any MessageDialogKind.
+var messageDialogKindTitles [3]string = [3]string{
+	"Message",
+	"Warning!",
+	"Error!",
+}
+
+type MessageDialog struct {
+	Title    string
+	Kind     MessageDialogKind
+	Callback func(string)
+
+	message        string
+	messageWrapped string
+
+	x, y          int
+	width, height int
+	focused       bool
+	theme         *Theme
+
+	buttons     []*Button
+	selectedIdx int
+}
+
+func NewMessageDialog(title string, message string, kind MessageDialogKind, options []string, theme *Theme, callback func(string)) *MessageDialog {
+	if title == "" {
+		title = messageDialogKindTitles[kind] // Use default title
+	}
+
+	if options == nil || len(options) == 0 {
+		options = []string{"OK"}
+	}
+
+	dialog := MessageDialog{
+		Title: title,
+		Kind: kind,
+		Callback: callback,
+
+		theme: theme,
+	}
+
+	dialog.buttons = make([]*Button, len(options))
+	for i := range options {
+		dialog.buttons[i] = NewButton(options[i], theme, func() {
+			if dialog.Callback != nil {
+				dialog.Callback(dialog.buttons[dialog.selectedIdx].Text)
+			}
+		})
+	}
+
+	// Set the dialog's size to its minimum size
+	dialog.SetSize(0, 0)
+	dialog.SetMessage(message)
+
+	return &dialog
+}
+
+func (d *MessageDialog) SetMessage(message string) {
+	d.message = message
+	d.messageWrapped = runewidth.Wrap(message, d.width-2)
+	// Update height:
+	_, minHeight := d.GetMinSize()
+	d.height = Max(d.height, minHeight)
+}
+
+func (d *MessageDialog) Draw(s tcell.Screen) {
+	DrawWindow(s, d.x, d.y, d.width, d.height, d.Title, d.theme)
+
+	// DrawStr will handle '\n' characters and wrap for us.
+	DrawStr(s, d.x+1, d.y+2, d.messageWrapped, d.theme.GetOrDefault("Window"))
+
+	col := d.width // Start from the right side
+	for i := range d.buttons {
+		width, _ := d.buttons[i].GetSize()
+		col -= width + 1 // Move left enough for each button (1 for padding)
+		d.buttons[i].SetPos(d.x+col, d.y+d.height-2)
+		d.buttons[i].Draw(s)
+	}
+}
+
+func (d *MessageDialog) SetFocused(v bool) {
+	d.focused = v
+	d.buttons[d.selectedIdx].SetFocused(v)
+}
+
+func (d *MessageDialog) SetTheme(theme *Theme) {
+	d.theme = theme
+	for i := range d.buttons {
+		d.buttons[i].SetTheme(theme)
+	}
+}
+
+func (d *MessageDialog) GetPos() (int, int) {
+	return d.x, d.y
+}
+
+func (d *MessageDialog) SetPos(x, y int) {
+	d.x, d.y = x, y
+}
+
+func (d *MessageDialog) GetMinSize() (int, int) {
+	lines := strings.Count(d.messageWrapped, "\n") + 1
+	
+	return Max(len(d.Title)+2, 30), 2+lines+2
+}
+
+func (d *MessageDialog) GetSize() (int, int) {
+	return d.width, d.height
+}
+
+func (d *MessageDialog) SetSize(width, height int) {
+	minWidth, minHeight := d.GetMinSize()
+	d.width, d.height = Max(width, minWidth), Max(height, minHeight)
+}
+
+func (d *MessageDialog) HandleEvent(event tcell.Event) bool {
+	return d.buttons[d.selectedIdx].HandleEvent(event)
+}