1 files changed, 83 insertions, 0 deletions
diff --git a/src/displayapp/screens/Calculator.h b/src/displayapp/screens/Calculator.h
new file mode 100644
index 00000000..9971f275
--- /dev/null
+++ b/src/displayapp/screens/Calculator.h
@@ -0,0 +1,83 @@
+#pragma once
+
+#include "displayapp/screens/Screen.h"
+#include "displayapp/apps/Apps.h"
+#include "displayapp/Controllers.h"
+#include "Symbols.h"
+
+namespace {
+  constexpr int64_t powi(int64_t base, uint8_t exponent) {
+    int64_t value = 1;
+    while (exponent) {
+      value *= base;
+      exponent--;
+    }
+    return value;
+  }
+}
+
+namespace Pinetime {
+  namespace Applications {
+    namespace Screens {
+      class Calculator : public Screen {
+      public:
+        ~Calculator() override;
+
+        Calculator();
+
+        void OnButtonEvent(lv_obj_t* obj, lv_event_t event);
+
+      private:
+        lv_obj_t* buttonMatrix {};
+        lv_obj_t* valueLabel {};
+        lv_obj_t* resultLabel {};
+
+        void Eval();
+        void ResetInput();
+        void HandleInput();
+        void UpdateValueLabel();
+        void UpdateResultLabel() const;
+        void UpdateOperation() const;
+
+        // change this if you want to change the number of decimals
+        // keep in mind, that we only have 12 digits in total (see MAX_DIGITS)
+        // due to the fixed point implementation
+        static constexpr uint8_t N_DECIMALS = 3;
+        // this is the constant default offset
+        static constexpr int64_t FIXED_POINT_OFFSET = powi(10, N_DECIMALS);
+        // this is the current offset, may vary after pressing '.'
+        int64_t offset = FIXED_POINT_OFFSET;
+
+        // the screen can show 12 chars
+        // but two are needed for '.' and '-'
+        static constexpr uint8_t MAX_DIGITS = 12;
+        static constexpr int64_t MAX_VALUE = powi(10, MAX_DIGITS) - 1;
+        // this is assumed in the multiplication overflow!
+        static constexpr int64_t MIN_VALUE = -MAX_VALUE;
+
+        int64_t value = 0;
+        int64_t result = 0;
+        char operation = ' ';
+        bool equalSignPressedBefore = false;
+
+        enum Error {
+          TooLarge,
+          ZeroDivision,
+          None,
+        };
+
+        Error error = Error::None;
+      };
+    }
+
+    template <>
+    struct AppTraits<Apps::Calculator> {
+      static constexpr Apps app = Apps::Calculator;
+      static constexpr const char* icon = Screens::Symbols::calculator;
+
+      static Screens::Screen* Create(AppControllers& /* controllers */) {
+        return new Screens::Calculator();
+      };
+    };
+  }
+}