Keep create_text_sprite text through texture atlas rebuilds

CHANGELOG.md

@@ -11,6 +11,7 @@ Arcade [PyPi Release History](https://pypi.org/project/arcade/#history) page.
   - `anchor_x="center"` cut off the left half of the text, and `anchor_x="right"` made an empty sprite.
   - The sprite was placed too high. It now covers the same area as an `arcade.Text` with the same arguments at the same position.
   - An empty string raised `ValueError`. It now makes a transparent sprite, as documented.
+  - Text sprites went blank when the texture atlas rebuilt itself, which happens when it fills up after some textures were freed. The atlas redraws textures from their images, and a text sprite's image was empty. `sprite.texture.image` now also contains the text.
 
 ### New Features
 - Added `arcade.sweep_sprite(sprite, dx, dy, sprite_list)`, which checks the whole path of a moving sprite and returns a `SweepInfo` for the first sprite it would hit (the `sprite`, how far along the move as a `fraction` and `distance`, and the surface `normal`), or `None`. Fast sprites can't pass through thin walls this way. A sprite that already overlaps one is an immediate hit. Added the `sprite_bullets_sweep` example comparing it with a plain collision check.

arcade/text.py

@@ -939,6 +939,10 @@ def create_text_sprite(
     with texture_atlas.render_into(texture) as fbo:
         fbo.clear(color=background_color or arcade.color.TRANSPARENT_BLACK)
         text_object.draw()
+    # Keep a copy of the pixels in the texture's image. The atlas redraws
+    # textures from their images when it rebuilds itself, which would
+    # otherwise leave the sprite blank.
+    texture_atlas.update_texture_image_from_atlas(texture)
 
     # Place the sprite where the Text object was drawn
     return arcade.Sprite(

tests/unit/text/test_text_sprite.py

@@ -76,6 +76,19 @@ def test_same_text_different_style(window):
     assert red[1] > 200 and blue[1] == 0
 
 
+def test_survives_atlas_rebuild(window):
+    """The text is kept when the atlas rebuilds itself from the textures' images"""
+    atlas = window.ctx.default_atlas
+    sprite = arcade.create_text_sprite("Hello World", color=arcade.color.RED, font_size=20)
+    image = atlas.read_texture_image_from_atlas(sprite.texture)
+    assert _ink(image) > 0
+    # The texture's own image has the text too
+    assert sprite.texture.image.tobytes() == image.tobytes()
+
+    atlas.rebuild()
+    assert atlas.read_texture_image_from_atlas(sprite.texture).tobytes() == image.tobytes()
+
+
 def test_empty_text(window):
     """An empty string makes a transparent sprite instead of failing"""
     sprite = arcade.create_text_sprite("")