Attempt to draw less often

zig/sdl/hello_sdl.zig

    var skip: i32 = 0;
    var skip_horizontal: usize = 0;
    var num_lines: i32 = 0;
    var output_length: usize = 0;
    var changed = false;
    var hasChanged = false;
    var lastChange: u32 = 0;
    while (!quit) {
            changed = false;
            lastChange = c.SDL_GetTicks();
            hasChanged = true;
            skip = 0;
            skip_horizontal = 0;
        }
        // do not render if nothing has changed
        for (commands) |*command| {
            if (command.isActive(cmd)) {
                const out = try command.output();
                if (!hasChanged and out.len == output_length) {
                    continue;
                }
            }
        }
        _ = c.SDL_SetRenderDrawColor(renderer, 0, 0, 0, 100);
        //_ = c.SDL_SetRenderDrawBlendMode(renderer, c.SDL_BlendMode.SDL_BLENDMODE_BLEND);
        _ = c.SDL_RenderClear(renderer);
                continue;
            }
            const output = try command.output();
            output_length = output.len;
            // TODO: indicate if command is still running
            {
            }
            //std.debug.print("{s} {d} {d}\n", .{ command.process.is_running(), command.process.stdout_buf.items.len, command.process.stdout_buf.capacity });
            var lines = std.mem.split(u8, try command.output(), "\n");
            var lines = std.mem.split(u8, output, "\n");
            var line = lines.next();
            {
                var skipped: i32 = 0;