Is there auto font size like in Unity

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Here is an improved, iterative algorithm relying on the same method, just using the divide and conquer approach. This approach results in us getting between 1-9 iterations at any time, with any size value and any text size length, while also not having a constant iteration factor like 20 in the previous comment. It also supports a minimum font size.

I used RichTextLabel here, but you quite literally only need to change the extends RichTextLabel to extends Label and you would be ready to go.


AutoSizer.gd:

# AutoSizer is just a class to remove the hassle of code duplication. Feel free to remove it, if you only need one type of Label.
class_name AutoSizer

static func update_font_size_label(label: AutoSizeLabel) -> void:
	_update_font_size(label, "font", "font_size", Vector2i(label.min_font_size, label.max_font_size), label.text)

static func update_font_size_richlabel(label: AutoSizeRichLabel) -> void:
	_update_font_size(label, "normal_font", "normal_font_size", Vector2i(label.min_font_size, label.max_font_size), label.text)

static func _update_font_size(label: Control, font_name: StringName, font_style_name: StringName, font_size_range: Vector2i, text: String) -> void:
	var font := label.get_theme_font(font_name)

	var line := TextLine.new()
	line.direction = label.text_direction as TextServer.Direction
	line.flags = TextServer.JUSTIFICATION_NONE
	line.alignment = HORIZONTAL_ALIGNMENT_LEFT
	
	while true:
		line.clear()
		
		var mid_font_size := font_size_range.x + roundi((font_size_range.y - font_size_range.x) * 0.5)
		if !line.add_string(text, font, mid_font_size):
			push_warning("Could not create a string!")
			return
		
		var text_width := line.get_line_width()
		if text_width >= floori(label.size.x):
			if font_size_range.y == mid_font_size:
				break
			
			font_size_range.y = mid_font_size
		
		if text_width < floori(label.size.x):
			if font_size_range.x == mid_font_size:
				break
			
			font_size_range.x = mid_font_size
	
	label.add_theme_font_size_override(font_style_name, font_size_range.x)



AutoSizeLabel.gd:

@tool
class_name AutoSizeLabel extends Label

@export var min_font_size := 8 :
	set(v):
		min_font_size = clampi(v, 1, max_font_size)
		update()

@export var max_font_size := 56 :
	set(v):
		max_font_size = clampi(v, min_font_size, 191)
		update()

func _ready() -> void:
	clip_text = true
	item_rect_changed.connect(update)

func _set(property: StringName, value: Variant) -> bool:
	# Listen for changes to text
	if property == "text":
		text = value
		update()
		return true
	
	return false

func update() -> void:
	return AutoSizer.update_font_size_label(self)



AutoSizeRichLabel.gd:

@tool
class_name AutoSizeRichLabel extends RichTextLabel

@export var min_font_size := 8 :
	set(v):
		min_font_size = clampi(v, 1, max_font_size)
		update()

@export var max_font_size := 56 :
	set(v):
		max_font_size = clampi(v, min_font_size, 191)
		update()

func _ready() -> void:
	item_rect_changed.connect(update)

func _set(property: StringName, value: Variant) -> bool:
	# Listen for changes to text
	if property == "text":
		text = value
		update()
		return true
	
	return false

func update() -> void:
	return AutoSizer.update_font_size_richlabel(self)



PS: Sorry for necroposting, but searching on Google for “Godot Font Autosize” returns this back as the top result and I wanted to share a better solution.

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