I also experimented since there are about 4 different factors in play when we change the scale of a Drawing placed on a Layout. It will be long, but I tried to write down everything that I found.
I have created a little matrix that shows the results with all the combinations of these various factors:
Let me explain all that is on the above image. First, the scale of a Drawing placed on a Layout can be modified in 2 different ways:
Method 1 (upper half of the above image): By modifying the Scale field of the Source View of the Drawing. This affects all Drawings with this View as their Source View.
Method 2 (lower half of the above image): By changing the Drawing Scale of the Drawing placed on the Layout. This does not modify the Scale set for its Source View. It affects only the Drawing elements for which the settings are modified.
To test how setting the various relevant fields affects the result, I created a very simple geometry consisting of a few lines, plus a large red cross marking the Project Origin, and saved a View with a Scale of 1:100. This is how it looks on the Floor Plan:
Then I placed this saved View as a Drawing on a Layout, which looks like this:
Here I added a few viewing aids for easier tracking of what happens.
The GREEN SOLID LINES are elements located in the Source View.
The RED X is also located in the Source View and designates where the Project Origin is located.
The RED DASHED LINE is the boundary of the Drawing.
The BLUE SOLID LINES mark the corners of the Drawing to help indicate the size of the Drawing before the change of Scale.
The intersection of the two diagonal BLUE DASHED LINES marks the position of the Project Origin in the Drawing.
The BLACK CIRCLE designates where the Anchor is located based on the Anchor setting of the Drawing.
Method 1
Let us first look at scale change method 1, where we open the Drawing's Source View setting and change the scale from 1:100 to 1:200. The upper left quadrant shows the state before the scale change and the upper right quadrant after the scale change.
When we change the scale of the Source View, naturally, all content of that source view will be resized.
A) The Drawing Frame's behavior is set to "Fit to Frame" (top row):
In this case, we will see that the Drawing Frame is resized to half its previous size because of the scale change. This is because, with the "Fit to Frame" option, the Frame is always as large as the boundary of the Drawing's content's bounding box. If the content changes to half its size, the Frame will also shrink to half its size.
Also, we can see that the position of the Drawing will be different based on the Anchor Settings.
1) If the Anchor is set to "Use Internal Origin", then the Project Origin of the Drawing will stay put.
2) If the Anchor is set to the "Middle Point", then the Middle Point of the Drawing will stay put.
3) If the Anchor is set to the "Lower Left Point", then the Lower Left Point of the Drawing will stay put.
B) The Drawing Frame's behavior is set to "Manually Resized Frame" (second row from top):
In this case, we will see that the Drawing Frame was not resized, which is the expected behavior. Here, Archicad assumes that you have set the size and shape of the Drawing Frame and you do not want it to change just because the size and/or position of the content it displays has changed.
However, in this case, the position of the Drawing content does not vary based on the Anchor Settings.
1), 2), and 3) (Anchor is set to "Use Internal Origin", "Middle Point", and "Lower Left Point", respectively.) Regardless of what we set for Anchor, the Project Origin of the Drawing will stay put in all 3 cases.
I think that this is not correct behavior. It should reposition the Drawing's content the same way as in A) above so that the Anchor stays put, wherever it is located. I will report this to Graphisoft because I think that this is a BUG: when Frame's behavior is set to "Manually Resized Frame", the Drawing's content does not take into consideration the "Anchor" setting.
Method 2
Let us now look at scale change method 2, where we select the Drawings we want to resize, open the Drawing Setting Dialog, and change the "Scale" field from 1:100 to 1:200. The lower left quadrant shows the state before the scale change, the lower right quadrant, after the scale change.
With this method, the change is made to the Drawing settings, so we have to select all Drawings to which we want to apply the scale change.
A) The Drawing Frame's behavior is set to "Fit to Frame" (third row from top):
We can see that both the behavior of the Drawing Frame and the position of the Drawing's content will be the same as with Method 1.
However, with this Method, Archicad arrived at the same result by taking a different path.
In Method 1, it resized the Source View content, generated the Frame around it, then positioned it so the Anchor stays put, whatever position is defined for it ("Use Internal Origin", "Middle Point", and "Lower Left Point", or other).
In Method 2, the boundary box of the Source View content defines the Frame, and when the Drawing's scale changes, the Drawing is resized (not its Source View), including its contents and its Frame, making sure that the Anchor stays put, wherever it is.
B) The Drawing Frame's behavior is set to "Manually Resized Frame" (bottom row):
We get the same result as in A) of Method 2 above.
Here, the Manually Resized Frame is defined by the user, and when the Drawing's scale changes, the whole Drawing is resized, including its contents and its Manually Resized Frame, making sure that the Anchor stays put.
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