UX: redisplay HWM by pushing both buttons

To allow user to update the HWM screen

README.md

@@ -383,6 +383,9 @@ trust the computer. The current High Watermark (HWM) -- the highest level to
 have been baked so far -- is displayed on the device's screen, and is also
 persisted between runs of the device.
 
+For performance reasons, the HWM screen is not updated dynamically.
+On Nano devices, press both buttons to update.
+
 The sign operation will be sent to the hardware wallet by the baking daemon when
 configured to bake with a Ledger device key. The Ledger device uses the first byte of the
 information to be signed -- the magic number -- to tell whether it is a block

src/ui_bagl.c

@@ -38,6 +38,8 @@
 
 #define G_display global.dynamic_display
 
+static void ui_refresh_idle_hwm_screen(void);
+
 /**
  * @brief This structure represents a context needed for home screens navigation
  *
@@ -66,7 +68,10 @@ UX_STEP_NOCB(ux_app_is_ready_step, nn, {"Application", "is ready"});
 UX_STEP_NOCB(ux_version_step, bnnn_paging, {"Tezos Baking", APPVERSION});
 UX_STEP_NOCB(ux_chain_id_step, bnnn_paging, {"Chain", home_context.chain_id});
 UX_STEP_NOCB(ux_authorized_key_step, bnnn_paging, {"Public Key Hash", home_context.authorized_key});
-UX_STEP_NOCB(ux_hwm_step, bnnn_paging, {"High Watermark", home_context.hwm});
+UX_STEP_CB(ux_hwm_step,
+           bnnn_paging,
+           ui_refresh_idle_hwm_screen(),
+           {"High Watermark", home_context.hwm});
 UX_STEP_CB(ux_idle_quit_step, pb, exit_app(), {&C_icon_dashboard_x, "Quit"});
 
 UX_FLOW(ux_idle_flow,
@@ -154,6 +159,16 @@ void ui_initial_screen(void) {
     TZ_EXC_PRINT(exc);
 }
 
+/**
+ * @brief Refreshes the idle HWM screen
+ *
+ *        Used to update the HWM by pushing both buttons
+ *
+ */
+static void ui_refresh_idle_hwm_screen(void) {
+    ux_flow_init(0, ux_idle_flow, &ux_hwm_step);
+}
+
 void ux_prepare_confirm_callbacks(ui_callback_t ok_c, ui_callback_t cxl_c) {
     if (ok_c) {
         G_display.ok_callback = ok_c;

test/test_instructions.py

@@ -522,6 +522,11 @@ def test_sign_preattestation(
 
         tezos_navigator.assert_screen("hwm_before_sign", snap_path=snap_path)
 
+        if firmware.is_nano:
+            # No update for Stax
+            backend.both_click()
+            backend.wait_for_screen_change()
+        tezos_navigator.assert_screen("hwm_after_sign", snap_path=snap_path)
 
     tezos_navigator.check_app_context(
         account,
@@ -574,6 +579,12 @@ def test_sign_attestation(
 
         tezos_navigator.assert_screen("hwm_before_sign", snap_path=snap_path)
 
+        if firmware.is_nano:
+            # No update for Stax
+            backend.both_click()
+            backend.wait_for_screen_change()
+        tezos_navigator.assert_screen("hwm_after_sign", snap_path=snap_path)
+
     tezos_navigator.check_app_context(
         account,
         chain_id=main_chain_id,
@@ -625,6 +636,12 @@ def test_sign_attestation_dal(
 
         tezos_navigator.assert_screen("hwm_before_sign", snap_path=snap_path)
 
+        if firmware.is_nano:
+            # No update for Stax
+            backend.both_click()
+            backend.wait_for_screen_change()
+        tezos_navigator.assert_screen("hwm_after_sign", snap_path=snap_path)
+
     tezos_navigator.check_app_context(
         account,
         chain_id=main_chain_id,
@@ -676,6 +693,12 @@ def test_sign_block(
 
         tezos_navigator.assert_screen("hwm_before_sign", snap_path=snap_path)
 
+        if firmware.is_nano:
+            # No update for Stax
+            backend.both_click()
+            backend.wait_for_screen_change()
+        tezos_navigator.assert_screen("hwm_after_sign", snap_path=snap_path)
+
     tezos_navigator.check_app_context(
         account,
         chain_id=main_chain_id,