move GUI code and unit conversion coefficients to corresponding separate files

gui.h

@@ -0,0 +1,91 @@
+#ifndef VELOMETER_GUI_H
+#define VELOMETER_GUI_H
+#include "config.h"
+#include <pico/stdlib.h>
+
+enum ButtonInputType {
+  BUTTON_SHORT_PRESS,
+  BUTTON_LONG_PRESS,
+};
+
+enum GUIScreen {
+  MAIN_SCREEN,
+  MENU_SCREEN,
+};
+
+enum DisplayMode {
+  DISPLAY_MODE_SPEED,
+  DISPLAY_MODE_DISTANCE_FROM_POWER_ON,
+  DISPLAY_MODE_TOTAL_DISTANCE,
+};
+
+enum MenuOptionType {
+  MENU_OPTION_NUMBER,
+  MENU_OPTION_ONOFF,
+  MENU_OPTION_TEXT,
+  MENU_OPTION_LINK,
+};
+
+#define TEXT_EDIT_STATIC_BUFFER_SIZE 18
+struct TextEditState {
+  uint textLength;     // number of characters in input
+  uint textByteLength; // number of bytes occupied by characters
+
+  // fixed-size buffers for most cases
+  char staticTextBuffer[TEXT_EDIT_STATIC_BUFFER_SIZE];
+  uint8_t staticCharWidthBuffer[TEXT_EDIT_STATIC_BUFFER_SIZE];
+
+  // the same thing but in heap for longer input
+  bool heapBufferInUse;
+  char *heapTextBuffer;
+  uint8_t *heapCharWidthBuffer;
+  uint heapTextBufferCapacity;
+  uint heapCharWidthBufferCapacity;
+
+  // visual edit field properties
+  uint cursorPos;           // in characters
+  uint cursorPosCharOffset; // for quicker character addressing inside a UTF-8 string
+  uint scrollOffset;        // in pixels
+};
+
+struct MenuScreenState {
+  enum {
+    MENU_SCREEN_STATE_CHOOSING_OPTION,
+    MENU_SCREEN_STATE_EDITING_OPTION,
+  } subState;
+  union {
+    struct {
+      uint chosenOptionIndex;
+      short scrollAnimationProgress;
+    } choosingOption;
+    struct {
+      uint optionIndex;
+      enum MenuOptionType optionType;
+      union {
+        uint numberValue;
+        bool onOffValue;
+        struct TextEditState textEditState;
+      };
+    } editingOption;
+  };
+};
+
+struct GUIState {
+  uint screen;
+  union {
+    struct {
+      uint displayMode;
+      bool displayModeChanged;
+    } mainScreen;
+    struct MenuScreenState menuScreen;
+  } screenState;
+  uint8_t drawnTimeHours;
+  uint8_t drawnTimeMinutes;
+  uint16_t drawnTimeTextWidth;
+};
+
+void gui_init();
+void on_button_input(short button, enum ButtonInputType type, uint heldButtons);
+void update_lcd();
+
+#endif