Method BitmapRow

src/Display/Lcd/MonoLcd.cpp:192–236

Draw a single bitmap row. 'left' and 'width' do not need to be divisible by 8.

// Draw a single bitmap row. 'left' and 'width' do not need to be divisible by 8.
void MonoLcd::BitmapRow(PixelNumber top, PixelNumber left, PixelNumber width, const uint8_t data[], bool invert) noexcept
{
	if (left + width > numCols)
	{
		width = numCols - left;										// avoid overflowing the buffer
	}

	if (width != 0 && top < numRows)									// avoid possible arithmetic underflow or overflowing the buffer
	{
		const uint8_t inv = (invert) ? 0xFF : 0;
		uint8_t firstColIndex = left/8;									// column index of the first byte to write
		const uint8_t lastColIndex = (left + width - 1)/8;				// column index of the last byte to write
		const unsigned int firstDataShift = left % 8;					// number of bits in the first byte that we leave alone
		uint8_t *_ecv_array p = image + (top * numCols/8) + firstColIndex;

		// Do all bytes except the last one
		uint8_t accumulator = *p & (0xFF << (8 - firstDataShift));		// prime the accumulator
		while (firstColIndex < lastColIndex)
		{
			const uint8_t invData = *data ^ inv;
			const uint8_t newVal = accumulator | (invData >> firstDataShift);
			if (newVal != *p)
			{
				*p = newVal;
				SetPixelDirty(top, 8 * firstColIndex);
			}
			accumulator = invData << (8 - firstDataShift);
			++p;
			++data;
			++firstColIndex;
		}

		// Do the last byte. 'accumulator' contains up to 'firstDataShift' of the most significant bits.
		const unsigned int lastDataShift = 7 - ((left + width - 1) % 8);	// number of trailing bits in the last byte that we leave alone, 0 to 7
		const uint8_t lastMask = (1u << lastDataShift) - 1;					// mask for bits we want to keep;
		accumulator |= (*data ^ inv) >> firstDataShift;
		accumulator &= ~lastMask;
		accumulator |= *p & lastMask;
		if (accumulator != *p)
		{
			*p = accumulator;
			SetPixelDirty(top, 8 * firstColIndex);
		}
	}
}

#endif