Allow adaptive width for UILayout with multiline text

arcade/gui/widgets/text.py

@@ -87,6 +87,14 @@ def __init__(
         size_hint_max=None,
         **kwargs,
     ):
+        # If multiline is enabled and no width is given, we need to fit the
+        # size to the text. This is done by setting the width to a very
+        # large value and then fitting the size.
+        adaptive_multiline = False
+        if multiline and not width:
+            width = 999999
+            adaptive_multiline = True
+
         # Use Arcade Text wrapper of pyglet.Label for text rendering
         self.label = arcade.Text(
             start_x=0,
@@ -99,10 +107,13 @@ def __init__(
             bold=bold,
             italic=italic,
             align=align,
-            anchor_y="bottom",   # Position text bottom left to fit into scissor
-            multiline=multiline, # area
+            anchor_y="bottom",   # Position text bottom left to fit into scissor area
+            multiline=multiline,
             **kwargs,
         )
+        if adaptive_multiline:
+            # +1 is required to prevent line wrap
+            width = self.label.content_width + 1
 
         super().__init__(
             x=x,

tests/unit/gui/test_uilabel.py

@@ -56,3 +56,12 @@ def test_uilabel_fixes_internal_text_to_pos_0_0(window):
     assert label.label.position == (0, 0)
     assert label.position == (10, 10)
 
+def test_adaptive_width_support_for_multiline_text(window):
+    """
+    This test is a bit tricky. Enabling multiline without a width
+    should fit the size to the text. This is not natively supported by either arcade.Text or pyglet.Label.
+    Because text length variates between different os, we can only test boundaries, which indicate a proper implementation.
+    """
+    label = UILabel(text="Multiline\ntext\nwhich\n", multiline=True)
+    assert label.width < 100
+    assert label.height > 20