Re: Question about handles

["Fred Morcos" <fred morcos gmail com>]

I still don't get it... I thought I did by Hans' last reply to Andrew,
but now it seems all fuzzy again to me.

On Tue, Jul 29, 2008 at 9:12 AM, Hans Breuer <hans breuer org> wrote:
> Am 29.07.2008 00:51, Don Blaheta schrieb:
>>
>> I'm trying to understand handles and connection points too, and having
>> some difficulty.
>>
>> Quoth Hans Breuer:
>>>
>>> Am 23.07.2008 10:41, Andrew M. Botros schrieb:
>>>>
>>>> One other thing, let me rephrase my question @ the very beginning,
>>>> How can I know the objects connected to a Standard - Line?
>>>>
>>> So lets try once more ;)
>>>
>>> There are two specialized objects involved in building a connection. One
>>> is a Handle, the other one is a ConnectionPoint. In an existing connection
>>> between two DiaObject the Handle belongs to the first ("connected to") and
>>> the ConnectionPoint belongs to second ("connected by").
>>
>> So the only things that have handles are the line-ish things (line, arc,
>> zigzagline, etc),
>
> No. There are handles on every object. They are represented by the little
> squares. Some of them are connectable (see lib/handle.h:HandleConnectType)
> and some of them are non-movable (lib/handle.h:HandleType).
>
> Non-movable handles - as in "UML - Class" - drawn in (almost) black.
> Movable, not connected handles are drawn in green. Connected handles are
> drawn in red.
>
>> for which you can actually drag and endpoint and
>> create a connection?  And then a lot of objects have ConnectionPoints,
>> marked by the little blue x (when that option is turned on)?
>>
> Yes.
>
>>> The "Standard - Line" DiaObject is special because it is one of only few
>>> objects which can be "connected to" (has Handles) and also "connected by"
>>> (has a ConnectionPoint). Thus I still have problems understanding your
>>> question. Note: there is an important difference between the active and the
>>> passive form.
>>
>> Note: the word "connected" is passive in both "connected to" and
>> "connected by".  Part of what I found confusing about the exchange was
>> that Hans seems to find the to/by distinction obvious, whereas to me it
>> seems rather arbitrary and *quite* at odds with the natural English
>> interpretations of those phrases.
>
> Indded for me it looks obvious that the active part in a connection is the
> Handle. It gets moved around until it meets a ConnectionPoint, which then is
> stored in Handle::connected_to.
>
>> For instance, if I had two boxes with
>> a line between them as in the following ASCII art:
>>
>>  +---+   +---+
>>  |   +---+   |
>>  +---+   +---+
>>
>> an _English_ description would say that the line is "connected to" both
>> boxes, each box is "connected to" the line, and box 1 and box 2 are
>> "connected by" the line that runs between them (but only as a pair;
>> "box 1 is connected by the line" is nonsensical as English).
>
> Luckily it is not English to compile. If you can not descrive the connection
> of just a line and a box, than English is just not expressive enough to
> describe Dia's reality.
>
>> In fact, I would (in English) say that box 1 is connected *to* box 2, *by*
>> the
>> line.
>>
>> By my current understanding, the _Dia_ description would say that the
>> line has two Handles, one at each endpoint, each of which is "connected
>> to" a ConnectionPoint on one of the boxes; meanwhile the boxes each have
>> many ConnectionPoints, one (per box) of which is "connected by" the
>> line.  The boxes are connected neither to nor by each other.
>>
>> Is that about right?
>>
> Yes.
>
> -------- Hans "at" Breuer "dot" Org -----------
> Tell me what you need, and I'll tell you how to
> get along without it.                -- Dilbert
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>



-- 
Fred Morcos
http://fredmorcos.blogspot.com/
http://fredmorcos.googlecode.com/