screen: Show placeholder when no signal groups available

src/main.rs

@@ -384,5 +384,5 @@ fn log_screen_error<E>(error: &E)
 where
     E: core::fmt::Debug,
 {
-    error!("TODO: {error:?}");
+    error!("graphics failed: {error:?}");
 }

src/screen.rs

@@ -1,7 +1,5 @@
 //! Screen Output
 
-use alloc::vec;
-
 use embedded_graphics::prelude::*;
 use embedded_graphics::{geometry, mono_font, pixelcolor, primitives, text};
 
@@ -46,13 +44,6 @@ where
 {
     let num_signals = data.len();
 
-    if num_signals == 0 {
-        return clear(target);
-    }
-
-    #[allow(clippy::cast_possible_truncation, clippy::cast_possible_wrap)]
-    let sig_width = (WIDTH as i32) / (num_signals as i32);
-
     let text_style =
         mono_font::MonoTextStyle::new(&profont::PROFONT_24_POINT, pixelcolor::Rgb565::WHITE);
     let blank_style = primitives::PrimitiveStyleBuilder::new()
@@ -79,6 +70,21 @@ where
     .into_styled(style)
     .draw(target)?;
 
+    if num_signals == 0 {
+        text::Text::with_alignment(
+            "No upcoming SGs",
+            geometry::Point::new(i32::from(WIDTH) / 2, 130),
+            text_style,
+            text::Alignment::Center,
+        )
+        .draw(target)?;
+
+        return Ok(());
+    }
+
+    #[allow(clippy::cast_possible_truncation, clippy::cast_possible_wrap)]
+    let sig_width = i32::from(WIDTH) / (num_signals as i32);
+
     for (idx, sig) in data.iter().enumerate() {
         #[allow(clippy::cast_possible_truncation, clippy::cast_possible_wrap)]
         let offset = (idx as i32) * sig_width;
@@ -96,7 +102,7 @@ where
         };
         primitives::Circle::new(
             geometry::Point::new(offset + circle_margin, 10),
-            circle_dia as u32,
+            circle_dia.cast_unsigned(),
         )
         .into_styled(style)
         .draw(target)?;
@@ -105,7 +111,7 @@ where
 
         // draw maneuver
         text::Text::with_alignment(
-            &alloc::format!("{}", maneuver_to_str(&sig.maneuver)),
+            &maneuver_to_str(sig.maneuver),
             geometry::Point::new(centerline, 130),
             text_style,
             text::Alignment::Center,
@@ -149,24 +155,24 @@ where
 
     clear(target)?;
 
-    let sig_width = (WIDTH as i32) / 3;
+    let sig_width = i32::from(WIDTH) / 3;
     let circle_dia = 50;
     let circle_margin = (sig_width - circle_dia) / 2;
 
-    for (idx, style) in vec![rd_style, ye_style, gn_style].iter().enumerate() {
+    for (idx, style) in [rd_style, ye_style, gn_style].iter().enumerate() {
         #[allow(clippy::cast_possible_truncation, clippy::cast_possible_wrap)]
         let offset = (idx as i32) * sig_width;
 
         primitives::Circle::new(
             geometry::Point::new(offset + circle_margin, 10),
-            circle_dia as u32,
+            circle_dia.cast_unsigned(),
         )
         .into_styled(*style)
         .draw(target)?;
     }
 
     // draw welcome text
-    let centerline = (WIDTH as i32) / 2;
+    let centerline = i32::from(WIDTH) / 2;
     text::Text::with_alignment(
         "C-ITS Signal Phase Display\nWaiting for GNSS fix...",
         geometry::Point::new(centerline, 130),
@@ -178,7 +184,7 @@ where
     Ok(())
 }
 
-fn maneuver_to_str(value: &applogic::v2x::map::Maneuvers) -> alloc::string::String {
+fn maneuver_to_str(value: applogic::v2x::map::Maneuvers) -> alloc::string::String {
     alloc::format!(
         "{}{}{}",
         if value.left_allowed { "<" } else { " " },