How do you enlarge a group of shapes without stretching them?

[Alzahim]

First of all, I apologize if everything I say is not clear. I don't necessarily have all the terms I need in English, but I'll do my best.

Well, I've got a bit of a problem; I've set up a group, based on a few, shall we say “complex” shapes, to work out this sort of frame. 
Now I'd like to be able to enlarge it, either lengthwise or widthwise (ideally both), without the shapes stretching strangely.

To make things clearer, here's a small image:
First, the shape I've created, detailed in the layers panel on the right.
Below, the result I get when I try to enlarge it all at once (by whatever means I've tried).
Finally, again below, the result I'd like to obtain (obtained here by enlarging the shapes one by one).

So I'd like to know if there's a simpler and more effective way of achieving this result. I've been looking everywhere for a while now, and everything I've tried so far hasn't worked.

I'll give you the file if it helps.

Thanks in advance.

Alzahim.afpub

[GarryP]

Welcome to the forums @Alzahim

Because the Curves in the Group are not the same width (the ‘thick’ one is shorter), the width of each shape in the Group will change relative to the change in the width of the Group.

The same sort of thing goes for their height – different relative sizes will give different results upon resizing.

You might be able to ‘get round’ this with Constraints in Designer but I don’t have time to experiment at the moment, and it might be tricky.

Another way would be to use the Transform Panel to manually add a value (e.g. w+100, or h+200, etc.) to the width/height of each shape individually.

[Alzahim]

@GarryP 

Now I understand why.
I didn't really understand how the “constraints” panel worked (vaguely in theory, but I'm certainly getting it wrong in practice). If you get a chance to elaborate on what you have in mind later, that would be great.

Adding a fixed value directly to the transform pannel works more precisely, although it's not the most practical solution, until I find something better I'll take it.

In any case, thank you for the start of a solution.

[GarryP]

It’s been a while since I last used Constraints for anything useful so it might take me a while to get round to checking as I’ll probably have to re-educate myself as to how they work.

In the meantime, you might want to have a look at this where I used Constraints to create simple ‘dimension lines’: https://forum.affinity.serif.com/index.php?/topic/102574-very-simple-dimensioning-objects/

I think you might be able to use something similar but you will need to ‘dig in’ to the details to find out how I did it as I can’t remember.

[Alzahim]

Ok then, I downloaded your document, simply copied the settings, and it seems to work. I don't really understand what I've done, but I've done it. 

The only small problem is that when I group all the layers, the edges get eaten away when the constraint is applied. I managed to avoid this problem by creating a sort of invisible, larger box around them. It distorts the alignment a little, but progress is being made.

[Alzahim]

Alzahim.afpub
I'm updating the document, so if anyone has time to spare to improve the method, or to put more concrete words to what I've done, I'd be grateful. 
(The 3 groups are the same, only tests).

[Old Bruce]

@Alzahim,

Here is a Designer document, it will open in Publisher. You need access to the Apperance panel from Designer so I hope you have that application too. I set the strokes to the Inside of the shapes. One stroke is given a blend mode of Erase to make the thing appear smaller than it is.

Alzahim by bruce.afdesign

[Alzahim]

Yes @Old Bruce, I have all three app. 

It took me a while to figure it out, but to be sure, you created an “invisible outline” on the smallest of the shapes, so that it would be the same size as the others, and “trick” the software into enlarging the group without distorting it, right?

If so, it's interesting. I hadn't heard of this designer feature before.

[Old Bruce]

2 minutes ago, Alzahim said:

... “trick” the software into enlarging the group without distorting it, right?

Right.

[Alzahim]

Well, I've managed to figure out how best to make the constraint work. I wouldn't be able to explain exactly how it works, but if it helps people in the future :

The “constraint frame” applies to the strict border of the group, which means that, contours in the “center” or “outside” position as well as FX like drop shadows (any visual that would go outside the strict border) will be cut off by the constraint, so you'll have to set these parameters beforehand.

However, it is possible to add effects, etc., directly to the group, after applying the constraint, without the risk of being cut off.

I don't know if this is very clear, but in any case it solves my problem perfectly, thank you all.