ofDirectory Version Ordering

I propose an improvement on ofDirectory::sort() regarding ofDirectory natural sort order. The following code is a bit longer, but it can deal with prefix + ofToInt(n) + extension style files like ls -v.

ofFileUtils.cpp:

bool natural(const ofFile& a, const ofFile& b) {
    string aname = a.getBaseName();
    string bname = b.getBaseName();

    string aPrefix;
    string bPrefix;
    int aPrefixLength = 0;
    int bPrefixLength = 0;

    for(int i = 0; i < aname.length(); i++){
        if(isdigit(aname.at(i))){
            break;
        }
        aPrefixLength++;
    }
    for(int i = 0; i < bname.length(); i++){
        if(isdigit(bname.at(i))){
            break;
        }
        bPrefixLength++;
    }

    aPrefix = aname.substr(0, aPrefixLength);
    bPrefix = bname.substr(0, bPrefixLength);

    // if prefixes are different
    if(aPrefix.compare(bPrefix) != 0) {
        return aPrefix.compare(bPrefix) < 0;
    }

    // if prefixes are the same, result is ascending version
    int aVersionLength = 0;
    int bVersionLength = 0;

    for(int i = aPrefixLength; i < aname.length(); i++){
        if(!isdigit(aname.at(i))){
            break;
        }
        aVersionLength++;
    }
    for(int i = bPrefixLength; i < bname.length(); i++){
        if(!isdigit(bname.at(i))){
            break;
        }
        bVersionLength++;
    }

    int aVersion = ofToInt(aname.substr(aPrefixLength, aVersionLength));
    int bVersion = ofToInt(bname.substr(bPrefixLength, bVersionLength));

    if(aVersion != bVersion){
        return aVersion < bVersion;
    }else{
        return a.getFileName().compare(b.getFileName()) < 0;
    }
}

Original output:

[notice ] file 1 = DSC09302.jpg
[notice ] file 2 = DSC09305.jpg
[notice ] file 3 = DSC09307.jpg
[notice ] file 4 = DSC09310.jpg
[notice ] file 5 = DSC09311.jpg
[notice ] file 6 = DSC09315.jpeg
[notice ] file 7 = DSC09315.jpg
[notice ] file 8 = DSC09315abc.jpg
[notice ] file 9 = DSC09316.jpg
[notice ] file 10 = DSC09318.jpg
[notice ] file 11 = DSC09320.jpg
[notice ] file 12 = DSC09322.jpg
[notice ] file 13 = DSC09324.jpg
[notice ] file 14 = DSC09326.jpg
[notice ] file 15 = DSC09327.jpg
[notice ] file 16 = DSC09329.jpg
[notice ] file 17 = DSC09330.jpg
[notice ] file 18 = DSC09334.jpg
[notice ] file 19 = DSC09336.jpg
[notice ] file 20 = DSC09337.jpg
[notice ] file 21 = DSC09341.jpg
[notice ] file 22 = DSC09343.jpg
[notice ] file 23 = DSC09344.jpg
[notice ] file 24 = DSC09347.jpg
[notice ] file 25 = DSC11.jpg
[notice ] file 26 = DSC900.jpg
[notice ] file 27 = a200.jpg

After change:

[notice ] file 1 = DSC11.jpg
[notice ] file 2 = DSC900.jpg
[notice ] file 3 = DSC09302.jpg
[notice ] file 4 = DSC09305.jpg
[notice ] file 5 = DSC09307.jpg
[notice ] file 6 = DSC09310.jpg
[notice ] file 7 = DSC09311.jpg
[notice ] file 8 = DSC09315.jpeg
[notice ] file 9 = DSC09315.jpg
[notice ] file 10 = DSC09315abc.jpg
[notice ] file 11 = DSC09316.jpg
[notice ] file 12 = DSC09318.jpg
[notice ] file 13 = DSC09320.jpg
[notice ] file 14 = DSC09322.jpg
[notice ] file 15 = DSC09324.jpg
[notice ] file 16 = DSC09326.jpg
[notice ] file 17 = DSC09327.jpg
[notice ] file 18 = DSC09329.jpg
[notice ] file 19 = DSC09330.jpg
[notice ] file 20 = DSC09334.jpg
[notice ] file 21 = DSC09336.jpg
[notice ] file 22 = DSC09337.jpg
[notice ] file 23 = DSC09341.jpg
[notice ] file 24 = DSC09343.jpg
[notice ] file 25 = DSC09344.jpg
[notice ] file 26 = DSC09347.jpg
[notice ] file 27 = a200.jpg

Start in ofFileUtils.cpp at ofDirectory::sort() and review the proposed natural() comparator. Check how filenames such as DSC11.jpg, DSC900.jpg, and DSC09302.jpg should be ordered, including equal numeric prefixes and differing extensions. Done means sorting produces the natural-order output shown in the issue without changing unrelated ordering.