Lesson 4

Connections and layout

Connections are not decoration — they are the network the calculation walks. This lesson covers making them, forcing them to go your way, and moving everything around afterwards without tearing the scheme apart.

Time about 25 minutes You need the scheme from lesson 1 You finish with the lesson 1 scheme, tidied, and the editing moves at your fingertips

How a connection is made

Items are joined at connection points. Point at an item: the cursor turns into a target and its points light up, coloured by kind — red an outlet, green an inlet, yellow a false connector. Each point holds one connection at a time. Press the left button on the outlet and release it on the inlet.

The line is routed automatically: an orthogonal path with the fewest bends, going around the objects in the way. Where two lines cross, the horizontal one is drawn with a bridge, as pipework drawings require.

Releasing the button over the body of an item instead of over a dot also works — the program takes the first free point of the matching kind, an input for your output and the other way round.

Crossing lines: the horizontal one gets a bridge.

When the automatic route is wrong

Draw it yourself:

Start from a free point

Ctrl+click the free connection point you want to begin at. That point becomes the start of a hand-drawn line. (Ctrl+click on the body of an object does something else — it adds the object to the selection, see below.)
Drop the nodes

Click the sheet for each node. Every segment is horizontal or vertical — the direction is chosen by the longer projection of your mouse move, so lead with the axis you want.
Finish on the destination

Click the destination connection point. Whatever gap is left is routed automatically. The right button during drawing cancels the whole line.

A finished polyline is a single undo step. Cancelling with the right button leaves no step at all — the scheme is back exactly where it started.

A hand-drawn polyline taking the route you want.

To break a connection, right-click a point that is taken — it is released together with the hand-drawn line, if there was one. Deleting an object releases everything that led to it.

Selecting and moving

Action	Result
Click an object	Makes it current. If it belongs to a group, the whole group is taken.
Drag over empty space	Rubber band: everything inside the frame is captured.
`Ctrl`+click	Adds an object to the selection or removes it.
`Ctrl`+`A`	Every object of the scheme.
Click empty space	Drops the selection.
`Shift`+arrows	Nudges by one unit. A whole run of nudges is one undo step.
Double-click an object with a free input	Pulls it up to the item it is connected to, until the two points meet.

An object carrying a hand-drawn line moves in whole scheme units even with Snap off. Polyline nodes are stored as integers, and that is what keeps the line strictly orthogonal while the object travels. Objects without hand-drawn lines are positioned freely.

Rotating, mirroring, scaling

The item bar at the bottom of the sheet rotates by 45° either way ( rotate left rotate right ), mirrors about the vertical axis ( mirror ), and sets the scale of the current object; Ctrl+Shift+wheel over the sheet does the scaling too.

Rotation is refused for an object whose hand-drawn lines the turn would break. Delete the line, turn the object, draw the line again — in that order.

Drawing order

Command	Shortcut
Bring forward	`Alt`+click the object
Send backward	`Shift`+`Ctrl`+click the object
Raise a single object without touching its group	`Shift`+click

Groups

A group is several objects handled as one; an item with its caption is already a small group. Build a bigger one by rubber band or Ctrl+click — a selection of more than one object is drawn with a dash-dotted frame.

A selection moves, rotates and mirrors as a unit, and the connections between its members travel with it. The rotation centre is fixed when the gesture starts and does not drift as you keep turning.

Clicking any member selects the whole group. To work on one object inside it, take it out of the selection with Ctrl+click first.

Copy, duplicate, delete

Command	Keys	What it does
Copy	`Ctrl`+`C`	The current object or the whole selection into the clipboard.
Paste	`Ctrl`+`V`	From the keyboard the copy appears offset from the original; from the context menu of the sheet, at the cursor.
Duplicate	—	A copy beside the original, without touching the clipboard.
Delete	`Del`	The object or the selection, together with the connections that led to it.

Copies get fresh IDs, and connections inside the copied fragment are recreated between the new objects. A connection that led out of the fragment is dropped — there is nothing on the other end to attach it to. The clipboard uses a private format, so a fragment can be pasted into another running copy of EasyCAS (File → Launching a copy).

Check

Select the open pipe, copy and paste. The copy keeps the green values of the original — Diameter, Length, Pin — but has no connection. Calculate: the copy works out its own flow, yet the compressor still shows 1048.25 NL/min, because nothing joins the copy to it. The copy gets a break badge on the sheet, and the Problems panel says The element is not linked into the network. Delete it with Del and calculate again.

The context menu

A right click on an object opens its menu. On a catalog element it starts with what concerns the element itself — Recommended substitutions… (when it has a list of replacements, lesson 3), Variant calculation… (lesson 8) and Rename ID… (F2, lesson 5) — followed by the editing commands of this lesson:

Command	Same as
Rotate left, Rotate right, Mirror	The item bar.
Duplicate, Copy	See the table above.
Bring forward, Send backward	`Alt`+click, `Shift`+`Ctrl`+click.
Auto-signature, Untie all texts	Captions of the item — lesson 5.
Delete	`Del`.
Help, Close	The help topic of the object; close the menu.

A text or a picture has a shorter menu with the same editing commands; a picture also has Pin as background (lesson 5). On empty space the menu offers Paste when the clipboard holds a fragment, and on a taken connection point the right button breaks the connection instead of opening a menu.

Undo and redo

Ctrl+Z steps back, Ctrl+Y (or Ctrl+Shift+Z) repeats what was undone. A step is a completed action, not a mouse event: a whole drag is one step, a polyline is one step, a run of nudges is one step, and an action that changed nothing adds no step at all.

The history holds about thirty steps, and File → New or loading a scheme clears it — those snapshots belong to the scheme you have just closed.

Reading the lines after a calculation

View → Pipe display can colour the lines by air velocity or by pressure loss, and Flow animation sets a dash running in the direction the air actually travels. The direction comes from the scheme — from which end of the line is an outlet — not from the geometry, so a line drawn right to left animates right to left if that is the way the air goes.

Two things stay still on purpose: a branch carrying no flow, because a dash crawling along a dead branch is exactly the wrong thing to see, and the inside of a ring calculated with the simplified model, where there is no single direction to draw.

When it does not work

What you see	Why	What to do
The connection will not start	The point is taken — it already holds a connection.	Right-click it to release it, or use another point.
The route goes the long way round	Something is in the way of the straight path.	Move the obstacle, or draw the line by hand with `Ctrl`+click.
Rotate does nothing	A hand-drawn line on that object would break.	Delete the line first, then turn, then redraw.
A pasted fragment lost a connection	That connection led outside the fragment.	Join it to the scheme by hand.
Redo is greyed out	You made a new change after undoing — the undone branch is gone.	Normal behaviour of a linear history, not a fault.