I am trying to draw a detailed dataflow diagram with a border representing the process I'm detailing; data stores outside the border are also used elsewhere, while those inside are not (Gane and Sarsen notation). In Photoshop Elements a lower layer is depicted behind a higher layer, so a shape can enclose other shapes without covering them. How can I do this here? I also tried "Send to back" with a rounded rectangle but it has no effect.
The elements are added to the active layer. You have to select the active layer in the Layers sidebar clicking on it. All elements you will add to the diagram canvas will be added to the active layer. The layers are rendered as follows: the last layer in the list (in the Layers sidebar) is rendered first, the first layer is rendered last. If you want to move elements from a layer to another one, select them, right-click on one of select elements and choose Move To Layer / Target Layer.
Send to Back and Bring to Front work only within a layer and cannot move an element to another layer.
I figured out that a good strategy is to put the enclosing rounded rectangle in its own layer, and move this layer behind the default layer that contains the rest of the diagram. This way I can make the enclosure invisible with the eyeball layer tool when I'm working on the rest of the diagram. I have to keep track of which layer is the current one, or objects I draw disappear from view.
I read your instructions, but I have no idea of the actual use of a layer. I assume that you could use them in a variety of ways. For example, one could do a use case and then break down the bubbles into activity diagrams. However, I don't know how best to use layers to create workable code. An example would be very useful.
I will add an example soon.
Layers allow to work with many levels of details in a single diagram. They allow to show/hide only some parts of the diagram. In the current version, source code generator does not take into account the layers, they are used only in visual manner.
I had the impression it was a way of nesting lower levels. If I'm doing an activity diagram where each Activity represents the roll up of lower level activities, do I handle the lower levels as separate projects rather than layers?
You can associate an activity diagram from the same project (right-click on the activity/Add Existing Diagram) or you can associate a new diagram (right-click on the activity/Add New Diagram). Then the activity will be linked with this diagram and you can navigate to this diagram each time you double-click on this activity.
I can add linking to other projects in one of next versions.
Thanks. That's exactly what I was looking for.