Summary of Schematic Editor Operations

ISSIE features developed over several years to help you create readable schematics very quickly.

Keys below are given for Windows and Linux. On macOS Ctrl is usually Cmd, and a few chords differ. The authoritative list for your platform is generated from the code: press Info → Keyboard Shortcuts. The same actions are also on the Edit and View menus, and on the right-click menus, each labelled with its key.

Placing and editing components

Feature	How	Explanation
Place a component	Click it in the Catalogue, then click the canvas — or drag it straight from the Catalogue and drop it where you want it	While you drag, a ghost of the real symbol follows the cursor. A drop onto space already occupied by another symbol is refused rather than overlapping them
Component tooltips	Hover any Catalogue entry, or any field label in Properties	Every component explains what it is for, and every field explains what it sets, and gives you immediate explanatory error feedback
Find a component	Type in the Catalogue's search box	Matches the explanations as well as the names, so "subtract" finds the N bits XOR. Sections holding a match open themselves
Size-to-fit	`Ctrl-0`	Most often used keyboard shortcut: zooms and centres the schematic so it all fits on screen
Zoom the canvas	`Ctrl`+`+` / `Ctrl`+`-`; `Ctrl`+mouse wheel	`Ctrl` with `+` `-` `0` zooms whatever you are looking at — the schematic, or the waveforms in the wave simulator. Add `Alt` to zoom the whole application instead
Pan the canvas	`Space`+drag or `Shift`+drag (or two-finger scroll)
Rotate and flip components	`Ctrl`+`Right`: rotate clockwise `Ctrl`+`Left`: rotate anti-clockwise `Ctrl`+`Up`: flip vertically `Ctrl`+`Down`: flip horizontally	Also on the Edit menu and on a component's right-click menu
Undo / redo	`Ctrl-Z` / `Ctrl-Y`, or the on-screen buttons
Copy / paste	`Ctrl-C` / `Ctrl-V`, or the on-screen buttons	Duplicates keep the label with an incremented number. Works across sheets
Paste as array	on-screen button or `Edit` menu	Quickly create horizontal or vertical copies of any selected circuitry
Move a component's label	Drag the label; `Ctrl-Shift-Right` rotates it
Change port location on custom components	Use Move ports on the component's right-click menu and drag ports to rearrange	Custom components can have a lot of ports; move them to make a readable symbol
Resize a custom component	Use Resize symbol on its right-click menu and drag a corner, or set `Width Scale` / `Height Scale` in Properties	Auto-sizing keeps port legends from overlapping; override it when you want a particular shape
Change anything about a component	Select it and use the Properties tab	Labels, bus widths, number of gate inputs, MUX input order, optional adder/counter ports, memory contents, Verilog source
Align / distribute	`Ctrl-Shift-A` / `Ctrl-Shift-D`; rotate a label with `Ctrl-Shift-R`	Same-type components in the selection are aligned or evenly spaced; other types are left alone
Rotate or scale a block	Drag a selection rectangle, then use the handles on the selection box	`Shift`-click adds or removes one component from the selection
Snapping	Automatic while dragging	A symbol sticks to the edges of other symbols, and to the positions that make its wires straight

Wires and connections

Feature	How	Explanation
Auto-routing with fixed segments	Automatic	Issie will nearly always route and separate all schematic connections neatly with no manual routing required. Any wire segment can be manually dragged to a desired position and "fixed", with other segments and wires auto-routed around it
Unfix a wire	Right-click the wire → Unfix Wire	Returns a hand-routed wire to auto-routing
Separate manual routing / redraw all	Edit menu	Applies the auto-routing and separation to everything, or keeps manual routing

and spreads it out evenly | | Wire type | View → Wire Type | Jump, Radiussed or Modern wires. Purely a display choice — choose what you prefer | | Wire arrows | View → Toggle Wire Arrows | Show the direction of signals at wire end-points | | Net labels | Catalogue → Input / Output → Net Label | Every net label with the same name is one net, joined without wires. Use for long connections and high fan-out. Exactly one label in a same-name set must be driven - all other labels follow it | | Terminate an unused output | Not Connected component, or a Viewer | Issie will otherwise report the dangling output — and offer to insert the Not Connected for you |

Sheets, hierarchy and the project

Feature	How	Explanation
Custom components	Catalogue → `This project`	Any design sheet can be placed in another sheet, any number of times
Design hierarchy tree	The Sheet menu	The whole project drawn as a tree with connector lines, showing which sheet contains which. The same tree appears in the waveform simulator
Sheet right-click menu	Right-click a sheet in that tree	Rename, Duplicate, Delete, Save as library component, Write design as Verilog — and Set as top only where two designs share a sheet and disagree about its parameter values, which is the one case where the choice settles anything
Add a description to a sheet	De-select everything, open Properties, click `Add Description`	The description appears against the sheet as an ⓘ button, and is shown in Properties wherever the sheet is used as a custom component
Sheet parameters	Properties with nothing selected → `Add Parameter`	Named integer parameters, used in arithmetic expressions for bus widths and constants. Each instance of the sheet supplies its own values. Memory address and word widths are not yet parameterisable. See Parameter System
Component libraries	Catalogue → `Library`	Ready-made parameterised components. Choosing one copies its sheet into your project and asks for its parameter values, so it stays an ordinary editable sheet
Array components	Catalogue → `Array components`	Advanced feature. Write a design sheet that is copied as an array component. Special components create carry chains, multiplexed or concatenated outputs, etc. The equivalent of a Verilog for loop.
Export a library	Right-click a library in Catalogue → `Library`	Copies it to a folder you choose, as a subdirectory named after the library — created if it is not there, brought up to date if it is. What lands is the library: a component you have since deleted goes from the copy too
Create or use a library	`Open project`, then the library's folder	A folder of `.ldgm` components opens as a project, each component a sheet — a multi-sheet component brings all of its sheets — and saving writes back into the library in place. Keep the library you are working on in a folder of your own: the shipped ones, and the store your saved and imported libraries land in, are not edited where they are
Import a sheet	`Sheet` → `Import Sheet`	Copy a sheet, or set of sheets, in from another project
Project browser	`Project` → `New project` / `Open project`	An in-app file browser: the projects inside a folder are listed and can be opened with the arrow keys and `Enter`
Automatic backups	Automatic	Every sheet is continuously snapshotted into a `backup/` subdirectory of the project

Simulation, appearance and help

Feature	How	Explanation
Step simulation	`Simulations` → `Step Simulation`	Set inputs and read outputs immediately. `Viewer` components expose signals from any subsheet
Truth table for combinational logic	`Simulations` → `Truth Table`	For a full sheet, or for just the components you select. Reduce it with input constraints, hidden columns, redundancy removal, or algebraic inputs
Waveform simulation	`Simulations` → `Wave Simulation`	See Features for what it can do
Add waveforms from the schematic	Right-click a component while a wave simulation is running → Add waveforms to viewer
Read a value off the schematic	Rest the mouse on a wire while either simulator is running	The value that wire carries appears beside the pointer — at the waveform cursor's cycle, or at the step simulator's current clock tick — in that simulator's radix. Nothing is shown for a wire on a sheet the simulation holds more than one copy of, since there would be no single answer
Themes	`View` → `Theme`	`Grayscale`, `Light` or `Colourful`
Grid	`View` → `Toggle grid`
Right-click context menus	Right-click a component, a custom component, a wire, the canvas, a sheet in the tree, or the project path	Each offers exactly the actions that apply there, labelled with their shortcuts
Keyboard shortcuts	Info → Keyboard Shortcuts	Generated from the same table the app dispatches keys with, for your platform, so it is always correct
Errors	Automatic	Every error names what is wrong and how to correct it, highlights the components and connections responsible on the canvas, and where the fix is unambiguous offers a button that applies it and restarts the simulation

Why the wire display types look different

Wires can be drawn as radial, modern or old-style jump; switching between them at any time changes nothing about the design. Radial is usually the most readable: a bend is drawn as a small quadrant, which distinguishes a wire crossing another from a wire joining it, so connectivity can be followed by eye. A bend is squared off only where the straight run beside it is too short to fit the radius.

How wires are routed and then separated across the sheet — and why a segment has a signed length and no position — is described in How a wire gets its shape.

Why symbols are the size they are

A custom component is sized from its ports: its height comes from whichever of the left and right edges carries more ports, and its width from the longest port labels on the top and bottom edges together with the component's own label. Ports on one edge are always equally spaced. This is what keeps port legends from overlapping as you move ports between edges. Use Resize symbol on the right-click menu, or the Width Scale and Height Scale fields in Properties, to override it.