ui(raylib): reduce spinner rotation artifact

A visual artifact (white pixel fringe) appeared on the edge of the
rotating spinner track texture, likely due to RGB color bleed during
bilinear filtering in Raylib.

Pre-multiplying the alpha channel of the spinner track image using
`rl.image_alpha_premultiply` significantly reduces the visibility of the
artifact.

system/ui/lib/application.py

@@ -50,9 +50,10 @@ class GuiApplication:
     self._set_styles()
     self._load_fonts()
 
-  def load_texture_from_image(self, file_name: str, width: int, height: int):
+  def load_texture_from_image(self, file_name: str, width: int, height: int, alpha_premultiply = False):
     """Load and resize a texture, storing it for later automatic unloading."""
     image = rl.load_image(file_name)
+    if alpha_premultiply: rl.image_alpha_premultiply(image)
     rl.image_resize(image, width, height)
     texture = rl.load_texture_from_image(image)
     # Set texture filtering to smooth the result

system/ui/spinner.py

@@ -23,7 +23,8 @@ def clamp(value, min_value, max_value):
 class Spinner:
   def __init__(self):
     self._comma_texture = gui_app.load_texture_from_image(os.path.join(BASEDIR, "selfdrive/assets/img_spinner_comma.png"), TEXTURE_SIZE, TEXTURE_SIZE)
-    self._spinner_texture = gui_app.load_texture_from_image(os.path.join(BASEDIR, "selfdrive/assets/img_spinner_track.png"), TEXTURE_SIZE, TEXTURE_SIZE)
+    self._spinner_texture = gui_app.load_texture_from_image(os.path.join(BASEDIR, "selfdrive/assets/img_spinner_track.png"), TEXTURE_SIZE, TEXTURE_SIZE,
+                                                            alpha_premultiply=True)
     self._rotation = 0.0
     self._text: str = ""
     self._progress: int | None = None