Implement horizontal scrolling and tabs!

zig/sdl/hello_sdl.zig

    var quit = false;
    var skip: i32 = 0;
    var skip_horizontal: usize = 0;
    var num_lines: i32 = 0;
    var changed = false;
                                    skip = num_lines - 10;
                                }
                            },
                            c.SDLK_LEFT => {
                                if (skip_horizontal > 0) {
                                    skip_horizontal -= 1;
                                }
                            },
                            c.SDLK_RIGHT => {
                                skip_horizontal += 1;
                            },
                            else => {},
                        }
                    }
            changed = false;
            lastChange = c.SDL_GetTicks();
            skip = 0;
            skip_horizontal = 0;
        }
        _ = c.SDL_SetRenderDrawColor(renderer, 0, 0, 0, 100);
        }
        var i: c_int = 1;
        var line_buf = [_]u8{0} ** 10000;
        for (commands) |*command| {
            if (!command.isActive(cmd)) {
                continue;
                }
            }
            while (line != null and i * glyph_height < window_height) {
                const line_c = try gpa.dupeZ(u8, line.?);
                // TODO: render tabs at correct width (or some width at least)
                const result_text = c.TTF_RenderUTF8_Shaded(font, line_c, white, black);
                gpa.free(line_c);
                const skipped_line = line.?[std.math.min(skip_horizontal, line.?.len)..];
                // fix tabs
                const repl_size = std.mem.replacementSize(u8, skipped_line, "\t", " " ** 8);
                _ = std.mem.replace(u8, skipped_line, "\t", " " ** 8, &line_buf);
                line_buf[repl_size] = 0;
                const result_text = c.TTF_RenderUTF8_Shaded(font, &line_buf, white, black);
                const result_texture = c.SDL_CreateTextureFromSurface(renderer, result_text);
                _ = c.SDL_RenderCopy(renderer, result_texture, null, &c.SDL_Rect{ .x = 0, .y = i * glyph_height, .w = @intCast(c_int, line.?.len) * glyph_width, .h = glyph_height });
                _ = c.SDL_RenderCopy(renderer, result_texture, null, &c.SDL_Rect{ .x = 0, .y = i * glyph_height, .w = @intCast(c_int, repl_size) * glyph_width, .h = glyph_height });
                c.SDL_FreeSurface(result_text);
                c.SDL_DestroyTexture(result_texture);