Blocks and libraries and neightbouring things

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Blocks and libraries and neightbouring things

Postby kazmer » Thu Dec 26, 2013 10:10 pm

So I've been playing a bit with libraries (as in part libraries).

It seems that once you added an item from a library to a drawing, that item is set to stone wrt that drawing. This may or may not be desireable (arguments could be made pro and con), but there seems to be at least one corner case where it doesn't play out right.

Consider the following: drop some item from a library to a drawing. Change your mind, delete the item from the drawing. Change your mind altogether, edit the library item, then drop the now-changed item to the drawing. (Saving, exiting from QCAD, etc. is allowed any time.) What happens is you get back your unchanged library item on the drawing, even now that you've changed it. Even the library browser preview shows the thumbnail for the changed item, but as soon as you drop it on your drawing, it reverts to the original state. I would expect that when the last reference to a block is deleted, the block should be gone too, no?

In some ways the way Eagle CAD (electronics design package) handles this is more to my liking. They do it as follows: you have libraries, you have items in the libraries. As soon as you add an item to your drawing, the instance on the drawing is de-coupled from the library (ie. the drawing is complete on its own alone, without the library itself), but a "weak link" of some kind is maintained. This link is used so that later you can update the instance in the drawing from the library: change the library, drawing unaffected; hit the "update" button, drawing pulls in the new version of the item from the library.

Of course Eagle has the freedom of having a custom file format :)

Now, I'm not an experienced CAD person by any stretch of the imagination (I do have a quite a significant amount of experience with Eagle though), but if DXF isn't a limiting factor, it sounds like an approach to consider, doesn't it?

Thoughts?
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Re: Blocks and libraries and neightbouring things

Postby Clive » Fri Dec 27, 2013 12:24 am

Hi Kazmer and welcome.
I cannot reproduce your problem , what OS are you using please and what version of QCAD?

My test case is using QCAD 3.4.5 pro on Windows 8, however I will test this also on windows 7 and Vista and on Linux Mint!

Can you submit an example of your problem here on the forum?

* A little thing I've got used to doing every time I install/update QCAD is to set the permissions on all of the QCAD files to make then writeable, see if this makes a difference.
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Re: Blocks and libraries and neightbouring things

Postby Husky » Fri Dec 27, 2013 3:25 am

Hi kazmer - welcome in the Forum!

kazmer wrote:Consider the following: drop some item from a library to a drawing. Change your mind, delete the item from the drawing.

Only from the drawing or also the Block which has provided the block content for the drawing? Important for the next steps :wink:

kazmer wrote:Change your mind altogether, edit the library item, then drop the now-changed item to the drawing.

Is there still the old block-with the same name? Have you insert the changed Library item with or without the option to overwrite a possible existing block with the same name?

kazmer wrote:What happens is you get back your unchanged library item on the drawing, even now that you've changed it.

Yes - if you have already a block with the same name in your drawing and you haven't used the overwrite option :wink:

kazmer wrote:Even the library browser preview shows the thumbnail for the changed item, but as soon as you drop it on your drawing, it reverts to the original state.

After you change the library item did you update the Library Icon?

Husky-2013.12.26-01.png
Husky-2013.12.26-01.png (26.52 KiB) Viewed 1368 times


kazmer wrote:I would expect that when the last reference to a block is deleted, the block should be gone too, no?

No - from time to time it is important to keep the block - even it's an empty block. But you can Manuel force to clean the block list for empty blocks: --> Block --> Purge unused blocks --> done :wink:
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Re: Blocks and libraries and neightbouring things

Postby kazmer » Fri Dec 27, 2013 7:35 am

Husky wrote:
kazmer wrote:Change your mind altogether, edit the library item, then drop the now-changed item to the drawing.

Is there still the old block-with the same name? Have you insert the changed Library item with or without the option to overwrite a possible existing block with the same name?

Right, that was it, thanks -- the dynamic toolbars get me every time ;)
Husky wrote:
kazmer wrote:I would expect that when the last reference to a block is deleted, the block should be gone too, no?

No - from time to time it is important to keep the block - even it's an empty block. But you can Manuel force to clean the block list for empty blocks: --> Block --> Purge unused blocks --> done :wink:

I don't have such a menu item, neither in community (Git head) nor in the trial version.

block.png
block.png (39.08 KiB) Viewed 1363 times
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Re: Blocks and libraries and neightbouring things

Postby Husky » Fri Dec 27, 2013 8:43 am

kazmer wrote:I don't have such a menu item, neither in community (Git head) nor in the trial version.

You haven't mention your QCAD Version till now - sorry, you are right - the "purge unused Block" and the "purge unused Layer" is indeed only part of the Pro Version.

Here is the full feature list - written in Italic is only available in Pro ...
http://www.qcad.org/en/qcad-documentation/qcad-features
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Re: Blocks and libraries and neightbouring things

Postby kazmer » Fri Dec 27, 2013 10:31 am

Ah, ok - thanks, Husky.
For some reason I've been operating under the assumption that the downloadable binary trial includes all pro features :) That explains it, thank you.
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