Method drawInternal

Code/Arduino_libraries/SSD1306/OLEDDisplay.cpp:1037–1105

}

void inline OLEDDisplay::drawInternal(int16_t xMove, int16_t yMove, int16_t width, int16_t height, const uint8_t *data, uint16_t offset, uint16_t bytesInData) {
  if (width < 0 || height < 0) return;
  if (yMove + height < 0 || yMove > this->height())  return;
  if (xMove + width  < 0 || xMove > this->width())   return;

  uint8_t  rasterHeight = 1 + ((height - 1) >> 3); // fast ceil(height / 8.0)
  int8_t   yOffset      = yMove & 7;

  bytesInData = bytesInData == 0 ? width * rasterHeight : bytesInData;

  int16_t initYMove   = yMove;
  int8_t  initYOffset = yOffset;


  for (uint16_t i = 0; i < bytesInData; i++) {

    // Reset if next horizontal drawing phase is started.
    if ( i % rasterHeight == 0) {
      yMove   = initYMove;
      yOffset = initYOffset;
    }

    uint8_t currentByte = pgm_read_byte(data + offset + i);

    int16_t xPos = xMove + (i / rasterHeight);
    int16_t yPos = ((yMove >> 3) + (i % rasterHeight)) * this->width();

//    int16_t yScreenPos = yMove + yOffset;
    int16_t dataPos    = xPos  + yPos;

    if (dataPos >=  0  && dataPos < displayBufferSize &&
        xPos    >=  0  && xPos    < this->width() ) {

      if (yOffset >= 0) {
        switch (this->color) {
          case WHITE:   buffer[dataPos] |= currentByte << yOffset; break;
          case BLACK:   buffer[dataPos] &= ~(currentByte << yOffset); break;
          case INVERSE: buffer[dataPos] ^= currentByte << yOffset; break;
        }

        if (dataPos < (displayBufferSize - this->width())) {
          switch (this->color) {
            case WHITE:   buffer[dataPos + this->width()] |= currentByte >> (8 - yOffset); break;
            case BLACK:   buffer[dataPos + this->width()] &= ~(currentByte >> (8 - yOffset)); break;
            case INVERSE: buffer[dataPos + this->width()] ^= currentByte >> (8 - yOffset); break;
          }
        }
      } else {
        // Make new offset position
        yOffset = -yOffset;

        switch (this->color) {
          case WHITE:   buffer[dataPos] |= currentByte >> yOffset; break;
          case BLACK:   buffer[dataPos] &= ~(currentByte >> yOffset); break;
          case INVERSE: buffer[dataPos] ^= currentByte >> yOffset; break;
        }

        // Prepare for next iteration by moving one block up