refactor(core/homescreen): load homescreen image on-demand

core/src/apps/homescreen/__init__.py

@@ -9,10 +9,12 @@ class HomescreenBase(ui.Layout):
     def __init__(self) -> None:
         super().__init__()
         self.label = storage.device.get_label() or "My Trezor"
-        self.image = storage.device.get_homescreen() or res.load(
+        self.repaint = storage.cache.homescreen_shown is not self.RENDER_INDICATOR
+
+    def get_image(self) -> bytes:
+        return storage.device.get_homescreen() or res.load(
             "apps/homescreen/res/bg.toif"
         )
-        self.repaint = storage.cache.homescreen_shown is not self.RENDER_INDICATOR
 
     def on_render(self) -> None:
         if not self.repaint:

core/src/apps/homescreen/homescreen.py

@@ -52,7 +52,7 @@ class Homescreen(HomescreenBase):
             ui.display.bar(0, 0, ui.WIDTH, ui.HEIGHT, ui.BG)
 
         # homescreen with shifted avatar and text on bottom
-        ui.display.avatar(48, 48 - 10, self.image, ui.WHITE, ui.BLACK)
+        ui.display.avatar(48, 48 - 10, self.get_image(), ui.WHITE, ui.BLACK)
         ui.display.text_center(ui.WIDTH // 2, 220, self.label, ui.BOLD, ui.FG, ui.BG)
 
     def on_touch_start(self, _x: int, _y: int) -> None:

core/src/apps/homescreen/lockscreen.py

@@ -41,7 +41,7 @@ class Lockscreen(HomescreenBase):
         ui.display.text_center(
             ui.WIDTH // 2, 35, self.label, ui.BOLD, ui.TITLE_GREY, ui.BG
         )
-        ui.display.avatar(48, 48, self.image, ui.WHITE, ui.BLACK)
+        ui.display.avatar(48, 48, self.get_image(), ui.WHITE, ui.BLACK)
 
         # lock bar
         ui.display.bar_radius(40, 100, 160, 40, ui.TITLE_GREY, ui.BG, 4)