u8g2_font_render.c

/*
 * u8g2_font_render.c
 *
 *  Created on: Nov 27, 2020
 *      Author: quard
 */
#include "u8g2_font_render.h"


uint8_t font_get_unsigned_bits(U8G2FontGlyph_t *glyph, uint8_t count);
int8_t font_get_signed_bits(U8G2FontGlyph_t *glyph, uint8_t count);
uint16_t font_get_start_symbol_search_postition(U8G2FontRender_t *font, char chr);
int8_t font_get_glyph(U8G2FontRender_t *font, U8G2FontGlyph_t *glyph, uint16_t search_position, char chr);
void font_parse_glyph_header(U8G2FontRender_t *font, U8G2FontGlyph_t *glyph);
uint8_t font_draw_start_x_position(U8G2FontRender_t *font, U8G2FontGlyph_t *glyph);
uint8_t font_draw_start_y_position(U8G2FontRender_t *font, U8G2FontGlyph_t *glyph);
void font_render_glyph(U8G2FontRender_t *font, U8G2FontGlyph_t *glyph, uint8_t x, uint8_t y);


U8G2FontRender_t U8G2FontRender(const uint8_t *data, fnDrawPixel drawFgPixel, fnDrawPixel drawBgPixel) {
	U8G2FontRender_t font = {
			.data = data,
			.drawFgPixel = drawFgPixel,
			.drawBgPixel = drawBgPixel,
	};

	font.header = U8G2FontRender_ParseHeader(&font);

	return font;
}

U8G2FontHeader_t U8G2FontRender_ParseHeader(U8G2FontRender_t *font) {
	U8G2FontHeader_t header;

	memcpy(&header, font->data, U8G2_FONT_HEADER_SIZE);
	header.offset_A = U8G2_FONT_HEADER_SIZE + (font->data[17] << 8 | font->data[18]);
	header.offset_a = U8G2_FONT_HEADER_SIZE + (font->data[19] << 8 | font->data[20]);
	header.offset_0x100 = U8G2_FONT_HEADER_SIZE + (font->data[21] << 8 | font->data[22]);

	return header;
}

void U8G2FontRender_PrintChar(U8G2FontRender_t *font, uint8_t *x, uint8_t y, char chr) {
	uint16_t search_position = font_get_start_symbol_search_postition(font, chr);

	U8G2FontGlyph_t glyph;
	if (font_get_glyph(font, &glyph, search_position, chr) != U8G2FontRender_OK) {
		return;
	}
	font_parse_glyph_header(font, &glyph);

	font_render_glyph(font, &glyph, *x, y);

	*x += glyph.pitch;
}

void U8G2FontRender_Print(U8G2FontRender_t *font, uint8_t x, uint8_t y, char *str) {
	while (*str) {
		char *chr = str++;
		if (*chr < 0x100) {
			U8G2FontRender_PrintChar(font, &x, y, *chr);
		}
	}
}

uint8_t font_get_unsigned_bits(U8G2FontGlyph_t *glyph, uint8_t count) {
  uint8_t val;
  uint8_t start = glyph->bit_pos;
  uint8_t end = start + count;

  val = pgm_read(glyph->data);
  val >>= start;

  if (end >= 8) {
    uint8_t cnt = 8 - start;
    glyph->data++;

    val |= pgm_read(glyph->data) << (cnt);

    end -= 8;
  }

  glyph->bit_pos = end;

  val &= (1U << count) - 1;

  return val;
}

int8_t font_get_signed_bits(U8G2FontGlyph_t *glyph, uint8_t count) {
  int8_t val = (int8_t)font_get_unsigned_bits(glyph, count);
  val -= 1 << (count - 1);

  return val;
}

uint16_t font_get_start_symbol_search_postition(U8G2FontRender_t *font, char chr) {
	uint16_t search_position = U8G2_FONT_HEADER_SIZE;
	if (chr >= 65 && chr <= 90) {
		search_position = font->header.offset_A;
	} else if (chr >= 97 && chr <= 122) {
		search_position = font->header.offset_a;
	}

	return search_position;
}

int8_t font_get_glyph(U8G2FontRender_t *font, U8G2FontGlyph_t *glyph, uint16_t search_position, char chr) {
	while (1) {
		memcpy(glyph, font->data + search_position, 2);
		if (glyph->character == chr) {
			glyph->data = font->data + search_position + 2;
			glyph->bit_pos = 0;

			return U8G2FontRender_OK;
		}

		search_position += glyph->next_glypth;
		if (glyph->next_glypth == 0) {
			break;
		}
	}

	return U8G2FontRender_ERR;
}

void font_parse_glyph_header(U8G2FontRender_t *font, U8G2FontGlyph_t *glyph) {
	glyph->width = font_get_unsigned_bits(glyph, font->header.glyph_width);
	glyph->height = font_get_unsigned_bits(glyph, font->header.glyph_height);
	glyph->x_offset = font_get_signed_bits(glyph, font->header.glyph_x_offset);
	glyph->y_offset = font_get_signed_bits(glyph, font->header.glyph_y_offset);
	glyph->pitch = font_get_signed_bits(glyph, font->header.glyph_pitch);
}

uint8_t font_draw_start_x_position(U8G2FontRender_t *font, U8G2FontGlyph_t *glyph) {
	return glyph->x_offset;
}

uint8_t font_draw_start_y_position(U8G2FontRender_t *font, U8G2FontGlyph_t *glyph) {
	return font->header.bounding_box_height - glyph->height - glyph->y_offset;
}

void font_render_glyph(U8G2FontRender_t *font, U8G2FontGlyph_t *glyph, uint8_t x, uint8_t y) {
	uint32_t pixels = 0;
	uint8_t y_pos = y + font_draw_start_y_position(font, glyph);
	uint8_t x_pos = x + font_draw_start_x_position(font, glyph);
	while (1) {
		uint8_t zeros = font_get_unsigned_bits(glyph, font->header.zero_bit_width);
		uint8_t ones = font_get_unsigned_bits(glyph, font->header.one_bit_width);
		int8_t repeat = 0;

		while (font_get_unsigned_bits(glyph, 1) == 1) {
			repeat++;
		}

		for (; repeat>=0; repeat--) {
			for (uint8_t i=0; i<zeros + ones; i++) {
				if (i <= zeros - 1) {
					font->drawBgPixel(x_pos, y_pos);
				} else {
					font->drawFgPixel(x_pos, y_pos);
				}
				x_pos++;

				pixels++;
				if (pixels % glyph->width == 0) {
					y_pos++;
					x_pos = x + font_draw_start_x_position(font, glyph);
				}
			}
		}

		if (pixels >= glyph->width * glyph->height) {
			break;
		}
	}
}