Rework update_ui_scale() logic

src/autoload/HandlerGUI.gd

@@ -274,30 +274,22 @@ func update_ui_scale() -> void:
 	# How much can the default size be increased before it takes all usable screen space.
 	var max_expansion := Vector2(usable_screen_size) / Vector2(window_default_size)
 	var max_scale := snappedf(minf(max_expansion.x, max_expansion.y) - 0.125, 0.25)
-	var min_scale := snappedf(max_scale / 2.0 - 0.125, 0.25)
-
-	var final_scale := Configs.savedata.ui_scale
-	if Configs.savedata.auto_ui_scale:
-		# The wider the screen, the bigger the automatically chosen UI scale.
-		var aspect_ratio := float(usable_screen_size.x) / usable_screen_size.y
-		var auto_scale := max_scale * clampf(aspect_ratio * 0.375, 0.6, 0.8)
-		if OS.get_name() == "Android":
-			auto_scale *= 1.1  # Default to giving mobile a bit more space.
-		final_scale = snappedf(final_scale * auto_scale, 0.25)
-	final_scale = clampf(final_scale, min_scale, max_scale)
-
+	if OS.get_name() == "Android":
+		# This is a temporary fix for smaller UI scale on Android.
+		# TODO Update this logic after moving to Godot 4.4
+		max_scale *= 1.1
+	var final_scale := minf(Configs.savedata.ui_scale * _calculate_auto_scale(), max_scale)
 	var resize_factor := final_scale / old_scale_factor
+
 	if not OS.get_name() in ["Android", "Web"]:
-		if window.mode == Window.MODE_WINDOWED:
+		# TODO Check later if this workaround is still necessary for Windows.
+		if OS.get_name() != "Windows" or window.mode == Window.MODE_WINDOWED:
 			# The window's minimum size can mess with the size change, so we set it to zero.
 			window.min_size = Vector2i.ZERO
-			window.size = Vector2i(mini(int(window.size.x * resize_factor),
-					usable_screen_size.x), mini(int(window.size.y * resize_factor),
-					usable_screen_size.y))
+			window.size *= resize_factor
 		window.min_size = window_default_size * final_scale
 	window.content_scale_factor = final_scale
 
-
 func open_update_checker() -> void:
 	var confirmation_dialog = ConfirmDialog.instantiate()
 	add_menu(confirmation_dialog)
@@ -332,6 +324,45 @@ func open_export() -> void:
 				"The graphic can only be exported as SVG because its size is not defined. Do you want to proceed?"),
 				Translator.translate("Export"), FileUtils.open_export_dialog.bind(svg_export_data))
 
+func _calculate_auto_scale() -> float:
+	if not Configs.savedata.auto_ui_scale:
+		return 1.0
+
+	# Credit: Godots (MIT, by MakovWait and contributors)
+
+	var screen := DisplayServer.window_get_current_screen()
+	if DisplayServer.screen_get_size(screen) == Vector2i():
+		return 1.0
+
+	# Use the smallest dimension to use a correct display scale on portrait displays.
+	var smallest_dimension := mini(DisplayServer.screen_get_size(screen).x,
+			DisplayServer.screen_get_size(screen).y)
+
+	var dpi :=  DisplayServer.screen_get_dpi(screen)
+	if dpi != 72:
+		if dpi < 72:
+			return 0.75
+		elif dpi <= 96:
+			return 1.0
+		elif dpi <= 120:
+			return 1.25
+		elif dpi <= 160:
+			return 1.5
+		elif dpi <= 200:
+			return 2.0
+		elif dpi <= 240:
+			return 2.5
+		elif dpi <= 320:
+			return 3.0
+		elif dpi <= 480:
+			return 4.0
+		else:  # dpi > 480
+			return 5.0
+	elif smallest_dimension >= 1700:
+		# Likely a hiDPI display, but we aren't certain due to the returned DPI.
+		# Use an intermediate scale to handle this situation.
+		return 1.5
+	return 1.0
 
 # Helpers