From 2cc68fb98780e2fc98ee12342a98b18b1c737307 Mon Sep 17 00:00:00 2001
From: Jakub <106778416+MarekZegare4@users.noreply.github.com>
Date: Tue, 9 Jun 2026 17:00:00 +0200
Subject: [PATCH] fix(trail,batt): GPX NUL in stream + battery curve top at
 4170 mV
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- Trail.h gpxWaypoints/gpxPoint: snprintf truncation clamp was `> sizeof`
  (writing the NUL terminator into the XML stream); corrected to
  `>= sizeof - 1` at all 3 sites (<wpt>, <time>, <trkpt>).
- UITask.cpp battMvToPercent: raise 100% ceiling from 4200 → 4170 mV —
  the board never charges to 4200, so the indicator was stuck at ~97%.
- Trail.h header comment: corrected RAM cost from "256×12 B=3 KB" to
  actual CAPACITY(512)×16 B=8 KB.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
---
 examples/companion_radio/Trail.h           | 11 ++++++-----
 examples/companion_radio/ui-new/UITask.cpp |  2 +-
 2 files changed, 7 insertions(+), 6 deletions(-)

diff --git a/examples/companion_radio/Trail.h b/examples/companion_radio/Trail.h
index 356666ae..9639a5b5 100644
--- a/examples/companion_radio/Trail.h
+++ b/examples/companion_radio/Trail.h
@@ -6,8 +6,9 @@
 #include <time.h>
 
 // RAM-only GPS trail ring buffer.
-// Storage cost: 256 × 12 B = 3 KB. The trail survives auto-off (only the
-// display blanks) but is lost on reboot — user explicitly snapshots to a
+// Storage cost: CAPACITY(512) × sizeof(TrailPoint)(16 B, padded) = 8 KB,
+// always resident (UITask::_trail member). The trail survives auto-off (only
+// the display blanks) but is lost on reboot — user explicitly snapshots to a
 // LittleFS slot before powering down to keep it.
 
 struct TrailPoint {
@@ -265,7 +266,7 @@ public:
         "<wpt lat=\"%.6f\" lon=\"%.6f\"><name>%s</name>",
         w.lat_1e6 / 1.0e6, w.lon_1e6 / 1.0e6, esc);
       if (len > 0) {
-        if ((size_t)len > sizeof(buf)) len = sizeof(buf);
+        if ((size_t)len >= sizeof(buf)) len = sizeof(buf) - 1;  // truncated: emit chars only, not the NUL
         n += out.write((const uint8_t*)buf, (size_t)len);
       }
       if (w.ts > 1000000000UL) {                 // append <time> when the RTC was set
@@ -276,7 +277,7 @@ public:
             "<time>%04d-%02d-%02dT%02d:%02d:%02dZ</time>",
             gt->tm_year + 1900, gt->tm_mon + 1, gt->tm_mday,
             gt->tm_hour, gt->tm_min, gt->tm_sec);
-          if (len > 0) { if ((size_t)len > sizeof(buf)) len = sizeof(buf);
+          if (len > 0) { if ((size_t)len >= sizeof(buf)) len = sizeof(buf) - 1;
                          n += out.write((const uint8_t*)buf, (size_t)len); }
         }
       }
@@ -314,7 +315,7 @@ public:
       gt->tm_year + 1900, gt->tm_mon + 1, gt->tm_mday,
       gt->tm_hour, gt->tm_min, gt->tm_sec);
     if (len < 0) return n;
-    if ((size_t)len > sizeof(buf)) len = sizeof(buf);  // snprintf returns intended size
+    if ((size_t)len >= sizeof(buf)) len = sizeof(buf) - 1;  // truncated: emit chars only, not the NUL
     n += out.write((const uint8_t*)buf, (size_t)len);
     return n;
   }
diff --git a/examples/companion_radio/ui-new/UITask.cpp b/examples/companion_radio/ui-new/UITask.cpp
index 6547975c..c1fa7cab 100644
--- a/examples/companion_radio/ui-new/UITask.cpp
+++ b/examples/companion_radio/ui-new/UITask.cpp
@@ -134,7 +134,7 @@ static int battMvToPercent(int mv, int low_mv) {
   static const struct { uint16_t mv; uint8_t pct; } CURVE[] = {
     {3200,  0}, {3300,  3}, {3400,  8}, {3500, 15},
     {3600, 25}, {3650, 33}, {3700, 45}, {3750, 58},
-    {3800, 68}, {3900, 77}, {4000, 86}, {4100, 93}, {4200, 100}
+    {3800, 68}, {3900, 77}, {4000, 86}, {4100, 93}, {4170, 100}
   };
   static const int CURVE_LEN = sizeof(CURVE) / sizeof(CURVE[0]);
   auto curveAt = [&](int v) -> int {