ceda2vga/src/draw_demo.c

#include "draw_demo.h"

#include "framebuffer.h"
#include "pico/platform.h"

#include <string.h>

static bool valid_coord(uint16_t x, uint16_t y)
{
	if (x < 0 || x >= HPIXEL)
		return false;
	if (y < 0 || y >= VPIXEL)
		return false;

	return true;
}

// just because i did not need all the letters
// and didn't want to fill a proper array :-)
const Letter letters[] = {
	{'A', 6, (Point[]){{0, 7}, {0, 0}, {7, 0}, {7, 7}, {7, 3}, {0, 3}}},
	{'G', 6, (Point[]){{7, 0}, {0, 0}, {0, 7}, {7, 7}, {7, 3}, {3, 3}}},
	{'L', 3, (Point[]){{0, 0}, {0, 7}, {7, 7}}},
	{'M', 5, (Point[]){{0, 7}, {0, 0}, {3, 3}, {7, 0}, {7, 7}}},
	{'O', 5, (Point[]){{0, 0}, {0, 7}, {7, 7}, {7, 0}, {0, 0}}},
	{'P', 5, (Point[]){{0, 7}, {0, 0}, {7, 0}, {7, 3}, {0, 3}}},
	{'R', 6, (Point[]){{0, 7}, {0, 0}, {7, 0}, {7, 3}, {0, 3}, {7, 7}}},
	{'S', 6, (Point[]){{0, 7}, {7, 7}, {7, 3}, {0, 3}, {0, 0}, {7, 0}}},
};

void draw_path(uint16_t x, uint16_t y, Point points[], size_t len)
{
	Point *old_point = &points[0];

	for (int i = 1; i < len; ++i)
	{
		Point *current_point = &points[i];
		draw_line(x + old_point->x, y + old_point->y, x + current_point->x, y + current_point->y,
		          true);
		old_point = current_point;
	}
}

void draw_letter(uint16_t x, uint16_t y, char c)
{
	for (int i = 0; i < count_of(letters); ++i)
	{
		if (letters[i].letter == c)
		{
			draw_path(x, y, letters[i].points, letters[i].len);
			break;
		}
	}
}

void draw_string(uint16_t x, uint16_t y, const char *s)
{
	while (*s != 0)
	{
		draw_letter(x, y, *s);
		s++;
		x += 9;
	}
}

void draw_demo(void)
{
	// draw a little demo

	// clear frame buffer
	memset(&frame[0], 0, sizeof(frame));

	// horizontal lines
	draw_line(0, 0, 640 - 1, 0, true);
	draw_line(0, 240 - 1, 640 - 1, 240 - 1, true);
	draw_line(0, 480 - 1, 640 - 1, 480 - 1, true);

	// vertical lines
	draw_line(0, 0, 0, 480 - 1, true);
	draw_line(320 - 1, 0, 320 - 1, 480 - 1, true);
	draw_line(638, 0, 638, 480 - 1, true); // last pixel of a line can't be set, see set_pixel()

	// cat eye
	for (uint16_t x = 0; x < 640; x += 20)
	{
		draw_line(x, 0, 0, (480 - x * 480 / 640), true);
		draw_line(640, x * 480 / 640, 640 - x, 480, true);
	}

	// string
	draw_string(200, 200, "GLG PROGRAMS");
}

void draw_simple_line(uint16_t x, uint16_t y, uint16_t len, bool horizontal)
{
	for (uint16_t i = 0; i < len; ++i)
	{
		if (horizontal)
			set_pixel(x + i, y);
		else
			set_pixel(x, y + i);
	}
}

void draw_line(uint16_t _x0, uint16_t _y0, uint16_t _x1, uint16_t _y1, bool fill)
{
	const float x0 = _x0;
	const float y0 = _y0;
	const float x1 = _x1;
	const float y1 = _y1;

	if (x0 != x1)
	{
		const uint16_t x_begin = MIN(x0, x1);
		const uint16_t x_end = MAX(x0, x1);

		for (uint16_t x = x_begin; x < x_end; ++x)
		{
			const uint16_t y = (y1 - y0) * (x - x0) / (x1 - x0) + y0;
			if (fill)
				set_pixel(x, y);
			else
				clear_pixel(x, y);
		}
	}
	else
	{
		const uint16_t y_begin = MIN(y0, y1);
		const uint16_t y_end = MAX(y0, y1);

		for (uint16_t y = y_begin; y < y_end; ++y)
		{
			if (fill)
				set_pixel(x0, y);
			else
				clear_pixel(x0, y);
		}
	}
}

void set_pixel(uint16_t x, uint16_t y)
{
	// ignore out of frame pixels
	if (!valid_coord(x, y))
		return;

	// Since there is not much space in PIO program memory,
	// it is not possible to set the last pixel of a line,
	// because there is not enough program space to unset it
	// in the hardware, and, if left set, will mess with
	// the sync signals.
	if (x == 639)
		return;

	// skip wasted blanking lines
	// (see frame struct declaration)
	y += VBBLANK + VSPULSE - 1;

	// set bit
	frame[y * 80 + x / 8] |= (1 << x % 8);
}

void clear_pixel(uint16_t x, uint16_t y)
{
	if (!valid_coord(x, y))
		return;

	y += VBBLANK + VSPULSE - 1;
	frame[y * 80 + x / 8] &= ~(1 << x % 8);
}