Develop the background loader

[Marco Lazzaroni]

At the moment Luce preloads all the images to RAM. This is not a workable solution. The following algorithm runs a "mobile" cache around the current image:

http://luceimageviewer.wordpress.com/2011/03/10/the-background-loader-algorithm/

int N = number of image;
int cur = pointer to current image;
bool going_forward = current direction
int max_memory = maximum memory for luce
int cur_memory = current used memory
bool async_load = do async/sync load

flag_loadable_neighbours(cur_memory, max_memory);
next=cur;
prev=cur;
for(i=0;i<N/2;i++)
{
    async_load=!i;
    if(!ThumbIsLoaded(next) && ThumbIsLoadable(next) && !ThumbIsLoading(next))
        LoadThumb(next,async_load);
    async_load=1;
    if(!ScreenIsLoaded(next) && ScreenIsLoadable(next) && !ScreenIsLoading(next))
        LoadScreen(next,async_load);
    if(!ThumbIsLoaded(prev) && ThumbIsLoadable(prev) && !ThumbIsLoading(prev))
        LoadThumb(next,async_load);
    if(NeedToBreak())
        break; //usually triggered by a keypress
    if(going_forward())
        next=cur->next; prev=cur->prev;
    else
        next=cur->prev; prev=cur->next;
}

[Marco Lazzaroni (marcolazzaroni)]

Probably, only the the thumb with i=0 must be synchronous, the others asynchronous

[Marco Lazzaroni (marcolazzaroni)]

max_memory will be a part of system memory.
After a research, the /usr/bin/free utility of the procps package parses the content of the /proc/meminfo file.
It would be nice to dinamically shape max_memory in order not to overload the system, in the case that heavy processes are open when luce is already running.