Fix negative temperature rounding

src/components/ble/SimpleWeatherService.h

@@ -34,6 +34,7 @@
 #include "components/datetime/DateTimeController.h"
 #include <lvgl/lvgl.h>
 #include "displayapp/InfiniTimeTheme.h"
+#include "utility/Math.h"
 
 int WeatherCallback(uint16_t connHandle, uint16_t attrHandle, struct ble_gatt_access_ctxt* ctxt, void* arg);
 
@@ -77,11 +78,11 @@ namespace Pinetime {
         }
 
         [[nodiscard]] int16_t Celsius() const {
-          return (PreciseCelsius() + 50) / 100;
+          return Utility::RoundedDiv(PreciseCelsius(), static_cast<int16_t>(100));
         }
 
         [[nodiscard]] int16_t Fahrenheit() const {
-          return (PreciseFahrenheit() + 50) / 100;
+          return Utility::RoundedDiv(PreciseFahrenheit(), static_cast<int16_t>(100));
         }
 
         [[nodiscard]] lv_color_t Color() const {

src/displayapp/DisplayApp.cpp

@@ -53,10 +53,13 @@
 #include "displayapp/screens/settings/SettingBluetooth.h"
 #include "displayapp/screens/settings/SettingOTA.h"
 
+#include "utility/Math.h"
+
 #include "libs/lv_conf.h"
 #include "UserApps.h"
 
 #include <algorithm>
+#include <limits>
 
 using namespace Pinetime::Applications;
 using namespace Pinetime::Applications::Display;
@@ -167,18 +170,15 @@ TickType_t DisplayApp::CalculateSleepTime() {
   // Calculates how many system ticks DisplayApp should sleep before rendering the next AOD frame
   // Next frame time is frame count * refresh period (ms) * tick rate
 
-  auto RoundedDiv = [](uint32_t a, uint32_t b) {
-    return ((a + (b / 2)) / b);
-  };
-  // RoundedDiv overflows when numerator + (denominator floordiv 2) > uint32 max
-  // in this case around 9 hours (=overflow frame count / always on refresh period)
-  constexpr TickType_t overflowFrameCount = (UINT32_MAX - (1000 / 16)) / ((configTICK_RATE_HZ / 8) * alwaysOnRefreshPeriod);
+  // Avoid overflow when numerator would be > uint32 max
+  // in this case around 18 hours (=overflow frame count / always on refresh period)
+  constexpr TickType_t overflowFrameCount = std::numeric_limits<TickType_t>::max() / ((configTICK_RATE_HZ / 8) * alwaysOnRefreshPeriod);
 
   TickType_t ticksElapsed = xTaskGetTickCount() - alwaysOnStartTime;
   // Divide both the numerator and denominator by 8 (=GCD(1000,1024))
   // to increase the number of ticks (frames) before the overflow tick is reached
-  TickType_t targetRenderTick = RoundedDiv((configTICK_RATE_HZ / 8) * alwaysOnFrameCount * alwaysOnRefreshPeriod, 1000 / 8);
-
+  TickType_t targetRenderTick =
+    Utility::RoundedDiv((configTICK_RATE_HZ / 8) * alwaysOnFrameCount * alwaysOnRefreshPeriod, static_cast<uint32_t>(1000 / 8));
   // Assumptions
 
   // Tick rate is multiple of 8
@@ -188,7 +188,8 @@ TickType_t DisplayApp::CalculateSleepTime() {
   // Frame count must always wraparound more often than the system tick count does
   // Always on overflow time (ms) < system tick overflow time (ms)
   // Using 64bit ints here to avoid overflow
-  static_assert((uint64_t) overflowFrameCount * (uint64_t) alwaysOnRefreshPeriod < (uint64_t) UINT32_MAX * 1000ULL / configTICK_RATE_HZ);
+  static_assert((uint64_t) overflowFrameCount * (uint64_t) alwaysOnRefreshPeriod <
+                (uint64_t) std::numeric_limits<TickType_t>::max() * 1000ULL / configTICK_RATE_HZ);
 
   if (alwaysOnFrameCount == overflowFrameCount) {
     alwaysOnFrameCount = 0;

src/heartratetask/HeartRateTask.cpp

@@ -3,16 +3,12 @@
 #include <components/heartrate/HeartRateController.h>
 #include <limits>
 
+#include "utility/Math.h"
+
 using namespace Pinetime::Applications;
 
 namespace {
   constexpr TickType_t backgroundMeasurementTimeLimit = 30 * configTICK_RATE_HZ;
-
-  // dividend + (divisor / 2) must be less than the max T value
-  template <std::unsigned_integral T>
-  constexpr T RoundedDiv(T dividend, T divisor) {
-    return (dividend + (divisor / static_cast<T>(2))) / divisor;
-  }
 }
 
 std::optional<TickType_t> HeartRateTask::BackgroundMeasurementInterval() const {
@@ -48,9 +44,9 @@ TickType_t HeartRateTask::CurrentTaskDelay() {
                       static_cast<uint64_t>((Pinetime::Controllers::Ppg::deltaTms)) <
                     std::numeric_limits<uint32_t>::max(),
                   "Overflow");
-    TickType_t elapsedTarget = RoundedDiv(static_cast<uint32_t>(configTICK_RATE_HZ / 2) * (static_cast<uint32_t>(count) + 1U) *
-                                            static_cast<uint32_t>((Pinetime::Controllers::Ppg::deltaTms)),
-                                          static_cast<uint32_t>(1000 / 2));
+    TickType_t elapsedTarget = Utility::RoundedDiv(static_cast<uint32_t>(configTICK_RATE_HZ / 2) * (static_cast<uint32_t>(count) + 1U) *
+                                                     static_cast<uint32_t>((Pinetime::Controllers::Ppg::deltaTms)),
+                                                   static_cast<uint32_t>(1000 / 2));
 
     // On count overflow, reset both count and start time
     // Count is 16bit to avoid overflow in elapsedTarget

src/utility/Math.h

@@ -1,10 +1,33 @@
 #pragma once
 
 #include <cstdint>
+#include <concepts>
 
 namespace Pinetime {
   namespace Utility {
     // returns the arcsin of `arg`. asin(-32767) = -90, asin(32767) = 90
     int16_t Asin(int16_t arg);
+
+    // Round half away from zero integer division
+    // If T signed, divisor cannot be std::numeric_limits<T>::min()
+    // Adapted from https://github.com/lucianpls/rounding_integer_division
+    // Under the MIT license
+    template <std::integral T>
+    constexpr T RoundedDiv(T dividend, T divisor) {
+      bool neg = divisor < 0;
+      if (neg) {
+        // overflows if divisor is minimum value for T
+        divisor = -divisor;
+      }
+
+      T m = dividend % divisor;
+      T h = divisor / 2 + divisor % 2;
+      T res = (dividend / divisor) + (!(dividend < 0) & (m >= h)) - ((dividend < 0) & ((m + h) <= 0));
+
+      if (neg) {
+        res = -res;
+      }
+      return res;
+    }
   }
 }