1 files changed, 119 insertions, 0 deletions
diff --git a/kernel/src/misc/graphics.c b/kernel/src/misc/graphics.c
new file mode 100644
index 0000000..d4fc7c7
--- /dev/null
+++ b/kernel/src/misc/graphics.c
@@ -0,0 +1,119 @@
+#include <stdint.h>
+#include <multiboot2.h>
+#include <graphics.h>
+#include <font.h>
+
+uint64_t* pixel_offset(fb_t fb, uint32_t x, uint32_t y)
+{
+	return (uint64_t*)((char*)fb.addr + y * fb.pitch + x * fb.bpp / 8);
+}
+
+void fb_draw_pixel(fb_t fb, uint32_t x, uint32_t y, uint32_t col)
+{
+	if (x >= fb.width || y >= fb.height) return;
+
+	uint32_t* fb_offset = (uint32_t*)pixel_offset(fb, x, y);
+	*fb_offset = col;
+}
+
+/* https://en.wikipedia.org/wiki/Bresenham%27s_line_algorithm */
+
+void fb_draw_line_low(fb_t fb, uint32_t x0, uint32_t y0, uint32_t x1, uint32_t y1, uint32_t col)
+{
+	int32_t dx = x1 - x0;
+	int32_t dy = y1 - y0;
+	int32_t yi = 1;
+	if (dy < 0) {
+		yi = -1;
+		dy = -dy;
+	}
+	int32_t D = (2 * dy) - dx;
+	int32_t y = y0;
+
+	for (int32_t x = x0; x <= x1; x++) {
+		fb_draw_pixel(fb, x, y, col);
+		if (D > 0) {
+			y = y + yi;
+			D = D + (2 * (dy - dx));
+		} else {
+			D = D + 2 * dy;
+		}
+	}
+
+}
+
+void fb_draw_line_high(fb_t fb, int32_t x0, int32_t y0, int32_t x1, int32_t y1, int32_t col)
+{
+	int32_t dx = x1 - x0;
+	int32_t dy = y1 - y0;
+	int32_t xi = 1;
+	if (dx < 0) {
+		xi = -1;
+		dx = -dx;
+	}
+	int32_t D = (2 * dx) - dy;
+	int32_t x = x0;
+
+	for (int32_t y = y0; y <= y1; y++) {
+		fb_draw_pixel(fb, x, y, col);
+		if (D > 0) {
+			x = x + xi;
+			D = D + (2 * (dx - dy));
+		} else {
+			D = D + 2 * dx;
+		}
+	}
+}
+
+int32_t abs(int32_t val)
+{
+	if (val < 0) return -val;
+	return val;
+}
+
+void fb_draw_line(fb_t fb, int32_t x0, int32_t y0, int32_t x1, int32_t y1, int32_t col)
+{
+	if (abs(y1 - y0) < abs(x1 - x0)) {
+		if (x0 > x1)
+			fb_draw_line_low(fb, x1, y1, x0, y0, col);
+		else
+			fb_draw_line_low(fb, x0, y0, x1, y1, col);
+	} else {
+		if (y0 > y1)
+			fb_draw_line_high(fb, x1, y1, x0, y0, col);
+		else
+			fb_draw_line_high(fb, x0, y0, x1, y1, col);
+	}
+}
+
+void fb_draw_character(fb_t fb, char c, uint32_t x, uint32_t y, uint32_t char_col, uint32_t bg_col)
+{
+	if (c < 0) return;
+
+	uint32_t offset = 32 + c * 16;
+	for (uint32_t i = 0 ; i < 16; i++)
+	{
+		for (uint32_t j = 0 ; j < 8; j++)
+		{
+			if (font[offset + i] & (1 << (7 - j))) {
+				fb_draw_pixel(fb, x + j, y + i, char_col);
+			} else {
+				fb_draw_pixel(fb, x + j, y + i, bg_col);
+			}
+		}
+	}
+}
+
+uint32_t strlen(const char* s)
+{
+	char *p = (char*)s;
+	while (*p) p++;
+	return p - s;
+}
+
+void fb_draw_string(fb_t fb, const char* s, uint32_t x, uint32_t y, uint32_t char_col, uint32_t bg_col)
+{
+	for (uint32_t i = 0; i < strlen(s); i++) {
+		fb_draw_character(fb, s[i], x + i * 8, y, char_col, bg_col);
+	}
+}