rework MultiFieldReview to use less stack

ledger_device_sdk/examples/gadgets.rs

@@ -4,7 +4,7 @@
 use core::panic::PanicInfo;
 #[panic_handler]
 fn panic(_: &PanicInfo) -> ! {
-    loop {}
+    ledger_device_sdk::exit_app(1);
 }
 
 use ledger_device_sdk::buttons::*;

ledger_device_sdk/examples/review.rs

@@ -0,0 +1,40 @@
+#![no_std]
+#![no_main]
+
+use core::panic::PanicInfo;
+#[panic_handler]
+fn panic(_: &PanicInfo) -> ! {
+    ledger_device_sdk::exit_app(1);
+}
+
+use ledger_device_sdk::ui::bitmaps::*;
+use ledger_device_sdk::ui::gadgets::{Field, MultiFieldReview};
+
+#[no_mangle]
+extern "C" fn sample_main() {
+    let fields = [
+            Field {
+                name: "Amount",
+                value: "CRAB 666",
+            },
+            Field {
+                name: "Destination",
+                value: "0xde0b295669a9fd93d5f28d9ec85e40f4cb697bae",
+            },
+            Field {
+                name: "Memo",
+                value: "This is a very long memo. It will force the app client to send the serialized transaction to be sent in chunk. As the maximum chunk size is 255 bytes we will make this memo greater than 255 characters. Lorem ipsum dolor sit amet, consectetur adipiscing elit. Sed non risus. Suspendisse lectus tortor, dignissim sit amet, adipiscing nec, ultricies sed, dolor. Cras elementum ultrices diam.",
+            },
+    ];
+    let review = MultiFieldReview::new(
+        &fields,
+        &["Review ", "Transaction"],
+        Some(&EYE),
+        "Approve",
+        Some(&VALIDATE_14),
+        "Reject",
+        Some(&CROSSMARK),
+    );
+    review.show();
+    ledger_device_sdk::exit_app(0);
+}

ledger_device_sdk/src/ui/bagls/mcu.rs

@@ -134,6 +134,7 @@ pub enum Font {
     Symbols1,
 }
 
+#[derive(Clone, Copy)]
 pub struct Label<'a> {
     pub loc: Location,
     pub layout: Layout,
@@ -142,6 +143,18 @@ pub struct Label<'a> {
     pub text: &'a str,
 }
 
+impl Default for Label<'_> {
+    fn default() -> Self {
+        Label {
+            text: "",
+            bold: false,
+            dims: (128, 11),
+            loc: Location::Middle,
+            layout: Layout::Centered,
+        }
+    }
+}
+
 impl<'a> Label<'a> {
     pub const fn new() -> Self {
         Label {

ledger_device_sdk/src/ui/bagls/se.rs

@@ -3,13 +3,25 @@ use crate::ui::fonts::OPEN_SANS;
 use crate::ui::layout::*;
 use ledger_secure_sdk_sys;
 
+#[derive(Clone, Copy)]
 pub struct Label<'a> {
     pub text: &'a str,
     pub bold: bool,
     pub loc: Location,
     layout: Layout,
 }
 
+impl Default for Label<'_> {
+    fn default() -> Self {
+        Label {
+            text: "",
+            bold: false,
+            loc: Location::Middle,
+            layout: Layout::Centered,
+        }
+    }
+}
+
 impl<'a> From<&'a str> for Label<'a> {
     fn from(s: &'a str) -> Label<'a> {
         Label {