Library: Port 'Text Colors' to Python (#735)

Co-authored-by: Marco Capypara Köpcke <hello@capypara.de>

src/Library/demos/Text Colors/main.py

@@ -0,0 +1,59 @@
+# Pango is a text layout library. It can e.g. be used for formatting text
+# https://gjs-docs.gnome.org/pango10~1.0/
+import gi
+
+gi.require_version("Gtk", "4.0")
+gi.require_version("Pango", "1.0")
+from gi.repository import Gtk, Pango
+import workbench
+
+label: Gtk.Label = workbench.builder.get_object("label")
+
+
+def update_attributes():
+    # A Pango Attribute List is used to style the label
+    label.set_attributes(rainbow_attributes(label.get_label()))
+
+
+# Generates an Attribute List that styles the label in rainbow colors.
+# The `text` parameter is needed to detect string length + position of spaces
+def rainbow_attributes(text):
+    rainbow_colors = (
+        "#D00",
+        "#C50",
+        "#E90",
+        "#090",
+        "#24E",
+        "#55E",
+        "#C3C",
+    )
+
+    # Create a color array with the length needed to color all the letters
+    color_array = []
+    i = 0
+    while i < len(text):
+        color_array += rainbow_colors
+        i = len(color_array)
+
+    # Independent variable from `i` in the following loop to avoid spaces "consuming" a color
+    color_idx = 0
+
+    attr_list_string = ""
+    for i in range(len(text)):
+        # Skip space characters
+        if text[i] != " ":
+            start_idx = i
+            end_idx = i + 1
+
+            color = color_array[color_idx]
+            color_idx += 1
+            # See comment below
+            attr_list_string += f"{start_idx} {end_idx} foreground {color},"
+
+    # For more info about the syntax for this function, see:
+    # https://docs.gtk.org/Pango/method.AttrList.to_string.html
+    return Pango.attr_list_from_string(attr_list_string)
+
+
+label.connect("notify::label", lambda _, __: update_attributes())
+update_attributes()