IronOS/source/Core/Src/ScrollMessage.cpp

#include "ScrollMessage.hpp"

#include "OLED.hpp"
#include "configuration.h"

/**
 * Counts the number of chars in the string excluding the null terminator.
 * This is a custom version of `strlen` which takes into account our custom
 * double-byte char encoding.
 * @param str The input string.
 * @return The length of the string.
 */
static uint16_t str_display_len(const char *const str) {
  const uint8_t *next  = reinterpret_cast<const uint8_t *>(str);
  uint16_t       count = 0;
  while (next[0]) {
    if (next[0] <= 0xF0) {
      count++;
      next++;
    } else {
      if (!next[1]) {
        break;
      }
      count++;
      next += 2;
    }
  }
  return count;
}

uint16_t ScrollMessage::messageWidth(const char *message) { return FONT_12_WIDTH * str_display_len(message); }

bool ScrollMessage::drawUpdate(const char *message, uint32_t currentTick) {
  bool lcdRefresh = false;

  if (messageStart == 0) {
    messageStart = currentTick;
    lcdRefresh   = true;
  }
  int16_t  messageOffset;
  uint16_t msgWidth = messageWidth(message);
  if (msgWidth > OLED_WIDTH) {
    messageOffset = ((currentTick - messageStart) / (getSettingValue(SettingsOptions::DescriptionScrollSpeed) == 1 ? TICKS_100MS / 10 : (TICKS_100MS / 5)));
    messageOffset %= msgWidth + OLED_WIDTH; // Roll around at the end
    if (messageOffset < OLED_WIDTH) {
      // Snap the message to the left edge.
      messageOffset = OLED_WIDTH;
    } else if (messageOffset > msgWidth) {
      // Snap the message to the right edge.
      messageOffset = msgWidth;
    }
  } else {
    // Centre the message without scrolling.
    messageOffset = (OLED_WIDTH - msgWidth) / 2 + msgWidth;
  }

  if (lastOffset != messageOffset) {
    OLED::clearScreen();

    //^ Rolling offset based on time
    OLED::setCursor((OLED_WIDTH - messageOffset), 0);
    OLED::print(message, FontStyle::LARGE);
    lastOffset = messageOffset;
    lcdRefresh = true;
  }

  return lcdRefresh;
}