Simple font rendering library

This forums is for OS project announcements including project openings, new releases, update notices, test requests, and job openings (both paying and volunteer).

Post Reply

Print view

45 posts

TLHorse: Posts: 1; Joined: Tue Aug 11, 2020 7:18 am

A question of the transform between .SFN and .O

Quote

Post by TLHorse » Tue Aug 11, 2020 7:53 am

Hello everyone,

I'm currently developing a really simple GUI for my operating system. And I've just found this 1-year-ago topic of SSFN from this post: https://wiki.osdev.org/Scalable_Screen_Font

Recently I want to add the ability of rendering text (more precisely, Unicode) on VRam, I've tried to use PSFs format & plain data written in array, but these method are too... clumsy and difficult to maintain, so I changed my plan and started to use SSFN library to render text.

Unfortunately, my OS is still in early-stage. I cannot use any file function such as

Code: Select all

fread()

, I couldn't read data from SFN file directly in my project directory.[/b] The only way to read data from SFN, is to convert .sfn to .o file via objcopy when building, after that I can link datas in my code.

I found that there are a few fonts attached to the SSFN directory, I moved one of them, FreeSans.sfn, into my project directory. I simply created fonts.c and packaged an API:

Code: Select all

#define SSFN_CONSOLEBITMAP_HICOLOR
#include "font.h"
#include "ssfn.h"
extern char _binary_drivers_FreeSans_sfn_start;
/*
 * @brief Plot a character on the VRam.
 * 
 * @param vram Video RAM,
 * @param bpr Bytes per row.
 * @param x X axis of the char.
 * @param y Y axis of the char.
 * @param w Width of the screen.
 * @param h Height of the screen.
 * @param fg Foreground color.
 * @param bg Background color.
 * @param unicode Unicode of the char.
 */
void plot_font(uint8_t *vram, uint16_t bpr, int x, int y, int w, int h,
 uint32_t fg, uint32_t bg, uint32_t unicode) {
 ssfn_src = &_binary_drivers_FreeSans_sfn_start;
 ssfn_dst.ptr = vram;
 ssfn_dst.p = bpr;
 ssfn_dst.fg = fg;
 ssfn_dst.bg = bg;
 ssfn_dst.x = x;
 ssfn_dst.y = y;
 ssfn_dst.w = w;
 ssfn_dst.h = h;
 ssfn_putc(unicode);
}

My Makefile:

Code: Select all

C_SOURCES = ......
HEADERS = ......
OBJ = ${C_SOURCES:.c=.o ...... drivers/FreeSans.o}
CC = /path/to/cc
GDB = /usr/local/bin/gdb
CFLAGS = -g -ffreestanding -Wall -Wextra -fno-exceptions -m32
.............(omitted)
%.o: %.sfn
	i386-elf-objcopy -O elf32-i386 -B i386 -I binary $< $@

My project was successfully built, however it couldn't print the character 'A' when I use it in kernel.c. So I started debug. And I found that, in int ssfn_putc(uint32_t unicode), there's a line of code:

Code: Select all

 if(!ssfn_src || ssfn_src->magic[0] != 'S' || ssfn_src->magic[1] != 'F' || ssfn_src->magic[2] != 'N' ||
 ssfn_src->magic[3] != '2' || !ssfn_dst.ptr || !ssfn_dst.p) return SSFN_ERR_INVINP;

The whole function was returned due to this if statement. I printed ssfn_src->magic via gdb and found that, there is no magic SFN number of my .O file.Hence, my transform from .SFN to .O wasn't correct.

So, my question is, how do I transform .sfn to .o correctly? If there is no such method, are there any alternatives :?: