ofParameter feature discussion.

[openframeworks]

This is a feature discussion issue for what ofParameter and its utility clases should be. What you see below is Work In Progress!! - discussion and comments are especially welcome! I will edit and add pseudo code below as the structure of ofParameter and its utility classes gets more flushed out.

Once we are all agreed - this issue will become the reference page for the code development.

Goal: The idea is that ofParameter essentially can act like a variable within your app. Unlike a typical variable an ofParam has a name, a type and a range.

ofParameter will have several advantages when used in your app. They are:

• you can load and save them to disk ( in a variety of file formats ).
• they can be easily sent over the network ( osc / udp / tcp / http )
• they can be used to auto generate a gui to allow them to be changed.
• they can be printed out in a more friendly way for debugging

Current State:

• Currently ofParameter has a name, a min, a max and events for when the value has changed.
• ofParameter is being used with ofxGui.
• There is an osc parameter, which extends ofParameter.

ToDo's

• Have an ofParameterList or ofParameterGroup, or an ofBaseHasParams, which allows an app to expose a list of params, grouped together by a string based namespace ( of sorts ). This would mean that if a gui had multiple tabs, all the params which were added under the "computer-vision" namespace would be on one panel, while params added in another namespace would be grouped on another gui panel.
• Have a param serializer or stream type system for ofParameterList where a param list could be streamed out to either a network or file i/o . This stream based system could work in reverse and set/load values from a network connection or file.
• Have a stream based system for individual params which could allow printing of values to console.
• String Namespace based system for ofParameter so you can get a ofParameter via string query. IE paramList.getParam("global", "volume"); paramList.getParam("vision", "threshold");
• Test and develop this with a simple gui system to make sure ofParam has all the features needed to build guis on top of.

[markpitchless]

Thinking about meta data on the params like min and max for numbers. We could store this as a ParamGroup on the actual parameter. We then have an arbitrary store of named, typed meta data which other addons and your own app code can use.

ofxParameter<int> blur;
blur.meta.set<int>("min", 0);
blur.meta.set<int>("max", 50);

meta is the ParamGroup, set() auto-vivifies a param of the given type if that name does not exist or updates an existing param. Then GUI code etc can just get those values. blur.meta.get("min"). Different addons can doc the names and types of meta params they will use. We get nice extensibility without having to build a big hierarchy of Param classes. Works for the request for a different name to show in the GUI ie a "title" param that the GUI uses if set and falls back to name if not set. GUIs could look for "tooltips", "description" etc. XMLSettings could look for "xml_name", OSC for "osc_name".

[ofTheo]

@arturoc I just took a look at the latest in your branch and I think overall its a really good approach. I just barely understand all the craziness in the ofParameter classes :) but in terms of usage it behaves how I would hope/expect.

I think it would be really great to get this and ofxGui in the next release. It seems really close.

There were a few issues I ran into which I posted as a sep issue here: ( #1692 )

There are also some things which we could add at a later stage like an ofBaseHasParams and potentially a global param register for an app. ie: ofRegisterParameters.

But for now I think what is there is already really useful and could allow for a lot to be built off of it.

[arturoc]

haha, yes ofParameter is crazy, i still need to polish a couple of things and there's some others that i'm kind of dubious. mainly that for ofParameters of an object like ofParameter now you can do:

ofParameter p; p->x;

to access it's properties or methods but thats read only cause we need to make the parameter trigger the event whenever is changed, it works pretty much ok but it can be confusing sometimes when you try to change the values since the correct syntax is kind of weird:

p = ofVec3f(p->x+1,p->y)

instead of p->x++

but haven't found anyway you could detect you are writing to a property of an object from the object itself

[ofTheo]

ohh - I see. hmm could we just force people to use p.get() and p.set() ?

I feel like it could be fair to assume that if you access and modify the objects properties directly that it wouldn't trigger change events.

[arturoc]

even calling methods won't trigger any event since the object is encapsulated in ofParameter, we can overload the -> operator to return a reference to the internal object but once you have that reference you can't detect if it has changed anymore no matter if it's by calling the property directly or using a method, so it's kind of a tough one, most of the time probably we don't need to trigger events but it would be weird if you attach an event to a parameter and sometimes is not triggered

[bilderbuchi]

now that ofParameter has been merged, should we close this or just continue any emerging discussion in this issue?

[arturoc]

i think we can close this, if there are any problems or comments we can open new issues