writer.py

import framebuf

class Writer():
    text_row = 0        # attributes common to all Writer instances
    text_col = 0
    row_clip = False    # Clip or scroll when screen full
    col_clip = False    # Clip or new line when row is full

    @classmethod
    def set_textpos(cls, col, row):
        cls.text_row = row
        cls.text_col = col

    @classmethod
    def set_clip(cls, col_clip, row_clip):
        cls.row_clip = row_clip
        cls.col_clip = col_clip

    def __init__(self, device, font, verbose=True):
        self.device = device
        self.font = font
        # Allow to work with any font mapping
        if font.hmap():
            self.map = framebuf.MONO_HMSB if font.reverse() \
                else framebuf.MONO_HLSB
        else:
            raise ValueError('Font must be horizontally mapped.')
        if verbose:
            print('Orientation: {} Reversal: {}'.format('horiz' \
                if font.hmap() else 'vert', font.reverse()))
        self.screenwidth = device.width  # In pixels
        self.screenheight = device.height

    def _newline(self):
        height = self.font.height()
        Writer.text_row += height
        Writer.text_col = 0
        margin = self.screenheight - (Writer.text_row + height)
        if margin < 0:
            if not Writer.row_clip:
                self.device.scroll(0, margin)
                Writer.text_row += margin

    def printstring(self, string):
        for char in string:
            self._printchar(char)

    # Method using blitting. Efficient rendering for monochrome displays.
    # Tested on SSD1306. Invert is for black-on-white rendering.
    def _printchar(self, char, invert=False):
        if char == '\n':
            self._newline()
            return
        glyph, char_height, char_width = self.font.get_ch(char)
        if Writer.text_row + char_height > self.screenheight:
            if Writer.row_clip:
                return
            self._newline()
        if Writer.text_col + char_width > self.screenwidth:
            if Writer.col_clip:
                return
            else:
                self._newline()
        buf = bytearray(glyph)
        if invert:
            for i, v in enumerate(buf):
                buf[i] = 0xFF & ~ v
        fbc = framebuf.FrameBuffer(buf, char_width, char_height, self.map)
        self.device.blit(fbc, Writer.text_col, Writer.text_row)
        Writer.text_col += char_width

    def stringlen(self, string):
        l = 0
        for char in string:
            l += self._charlen(char)
        return l

    def _charlen(self, char):
        if char == '\n':
            char_width = 0
        else:
            _, _, char_width = self.font.get_ch(char)
        return char_width