feat(core): show the preview of default homescreen image

[no changelog]

core/embed/rust/src/ui/model_tr/component/homescreen.rs

@@ -28,6 +28,15 @@ const LABEL_OUTSET: i16 = 3;
 const NOTIFICATION_FONT: Font = Font::NORMAL;
 const NOTIFICATION_ICON: Icon = theme::ICON_WARNING;
 
+fn paint_default_image() {
+    theme::ICON_LOGO.draw(
+        TOP_CENTER + Offset::y(LOGO_ICON_TOP_MARGIN),
+        Alignment2D::TOP_CENTER,
+        theme::FG,
+        theme::BG,
+    );
+}
+
 pub struct Homescreen<T>
 where
     T: StringType,
@@ -58,12 +67,7 @@ where
             let toif_data = unwrap!(Toif::new(user_custom_image.as_ref()));
             toif_data.draw(TOP_CENTER, Alignment2D::TOP_CENTER, theme::FG, theme::BG);
         } else {
-            theme::ICON_LOGO.draw(
-                TOP_CENTER + Offset::y(LOGO_ICON_TOP_MARGIN),
-                Alignment2D::TOP_CENTER,
-                theme::FG,
-                theme::BG,
-            );
+            paint_default_image();
         }
     }
 
@@ -273,8 +277,13 @@ where
 
     fn paint(&mut self) {
         // Drawing the image full-screen first and then other things on top
-        let toif_data = unwrap!(Toif::new((self.buffer_func)()));
-        toif_data.draw(TOP_CENTER, Alignment2D::TOP_CENTER, theme::FG, theme::BG);
+        let buffer = (self.buffer_func)();
+        if buffer.is_empty() {
+            paint_default_image();
+        } else {
+            let toif_data = unwrap!(Toif::new(buffer));
+            toif_data.draw(TOP_CENTER, Alignment2D::TOP_CENTER, theme::FG, theme::BG);
+        };
         // Need to make all the title background black, so the title text is well
         // visible
         let title_area = self.title.inner().area();

core/embed/rust/src/ui/model_tt/layout.rs

@@ -703,16 +703,25 @@ extern "C" fn new_confirm_homescreen(n_args: usize, args: *const Obj, kwargs: *m
 
         // Layout needs to hold the Obj to play nice with GC. Obj is resolved to &[u8]
         // in every paint pass.
-        // SAFETY: We expect no existing mutable reference. Resulting reference is
-        //         discarded before returning to micropython.
-        let buffer_func = move || unsafe { unwrap!(get_buffer(data)) };
+        let buffer_func = move || {
+            // SAFETY: We expect no existing mutable reference. Resulting reference is
+            //         discarded before returning to micropython.
+            let buffer = unsafe { unwrap!(get_buffer(data)) };
+            // Incoming data may be empty, meaning we should display default homescreen
+            // image.
+            if buffer.is_empty() {
+                theme::IMAGE_HOMESCREEN
+            } else {
+                buffer
+            }
+        };
 
         let size = match jpeg_info(buffer_func()) {
             Some(info) => info.0,
             _ => return Err(value_error!("Invalid image.")),
         };
 
-        let buttons = Button::cancel_confirm_text(None, Some("CONFIRM"));
+        let buttons = Button::cancel_confirm_text(None, Some("CHANGE"));
         let obj = LayoutObj::new(Frame::centered(
             theme::label_title(),
             title,

core/src/apps/management/apply_settings.py

@@ -153,15 +153,7 @@ async def apply_settings(msg: ApplySettings) -> Success:
 async def _require_confirm_change_homescreen(homescreen: bytes) -> None:
     from trezor.ui.layouts import confirm_homescreen
 
-    if homescreen == b"":
-        await confirm_action(
-            "set_homescreen",
-            "Set homescreen",
-            description="Do you really want to set default homescreen image?",
-            br_code=BRT_PROTECT_CALL,
-        )
-    else:
-        await confirm_homescreen(homescreen)
+    await confirm_homescreen(homescreen)
 
 
 async def _require_confirm_change_label(label: str) -> None:

core/src/trezor/ui/layouts/tt/__init__.py

@@ -393,7 +393,7 @@ async def confirm_homescreen(
         interact(
             RustLayout(
                 trezorui2.confirm_homescreen(
-                    title="SET HOMESCREEN",
+                    title="CHANGE HOMESCREEN",
                     image=image,
                 )
             ),