Preferences
controls the appearance of the current schematic — line widths, colours and fonts.
Fig. 33 The Preferences dialog, grouped by element type.
Per-schematic styling
Styling works on two levels:
The application’s global defaults are the template for every new schematic.
When you change a setting in Preferences, it applies to the current schematic and is saved into its
<name>.inisidecar file (see Projects). Re-opening that schematic restores exactly the look it was saved with — independent of the machine’s global defaults.
This is what lets a book or report keep a consistent house style across all its figures.
What you can change
The dialog is grouped by element type, including:
Symbol — stroke and text colour.
Wire — colour and width.
Net label, Component refdes, Component parameters — colour, font and size.
Text annotations, Hyperlinks — fonts and colours.
Grid — minor and major line colours.
Wire handles / connections — the colour and size of wire selection handles, and the connection colour used for the unconnected-pin markers (see Wiring).
Junctions — colour and radius.
Rendering — turn LaTeX typesetting of labels on or off, and set the LaTeX scale of the schematic (see LaTeX scales below). Leave typesetting off in NGspice schematics: a simulator expression is code, not mathematics, and only the part of it that is also valid mathematics can be typeset. A value that cannot be typeset is shown as plain text — it is never rendered wrongly. If you want a typeset expression on an NGspice schematic, either accept the generated form, or hide the value and place the formula yourself with ; such a snippet is for display only and is not netlisted.
Every font family list offers the generic families sans-serif, serif and monospace. They render the same on every machine, in the editor and in the SVG and PDF export, because the viewer resolves a generic family to a font it has. A named font can be typed in the list, at the risk that another machine substitutes it.
Changes take effect immediately on the canvas.
LaTeX scales
A schematic has one LaTeX scale, in the Rendering group of the
preferences, 150 % by default. The GUI typesets LaTeX at 10 pt. At 100 %,
the text has that size in a drawing at 2 units per mm, the default of the
project setting sch_scale. The reference does not depend on the
project’s sch_scale, so a percentage gives the same text size relative
to the symbols in every project. On paper, in a figure that is included at
its natural size, the text is 10 pt × scale × 2 / sch_scale: at 150 %
this is 15 pt at 2 units per mm and 8.5 pt at 3.54 units per mm. The component
labels (reference designators and parameter values) always use this scale.
LaTeX fragments, parameter and model tables, and the analysis and library
blocks use it too, unless they have a scale of their own: their dialogs
have a LaTeX scale field with a Default box. With Default
checked, the item follows the schematic’s scale, and changing the scale in
the preferences resizes it. Without it, the item keeps its own percentage.
New items start at Default.
Schematics saved before this scale was introduced are converted on loading. The schematic’s scale becomes the scale at which the labels were drawn, and the tables, blocks and fragments get their old size as their own scale, so no drawing changes size.
Grid
Three grids: the minor lines (the grid step), the major lines (every eight minor cells) and the subgrid, a dot on every point of the fine grid, one fifth of the grid step, the grid that shapes snap to while Shift is held. Each has its colour; View subgrid switches the dots on, and they appear when the zoom keeps them apart.
Border
The Border group sets the look that a new border gets when it is placed (Place > Border): line colour, width and style (solid, dashed, dotted, dash-dot), background colour and opacity, and whether the line is drawn in the exported SVG/PDF. An existing border keeps its own values, edited in the Border dialog. A background at opacity 0 % is invisible; choosing a background colour in the Border dialog therefore sets the opacity to 100 % when it was 0 %.
The defaults are those of the figures in the book Structured Electronic
Design: a solid blue line, the light blue background #ecf3ff at 100 %
opacity, and no border line in the export, so an exported schematic is a
figure on a tinted panel. The same palette sets black symbol text, red net
labels and blue operating-point annotations. A schematic’s own values live
in the [border] and other sections of its .ini sidecar; give every
border the width of the document column (see the sch_scale setting
under Projects).
The Border formats table holds formats of your own, offered next to the
paper and screen formats in the Border dialog, the properties dialog and
the New poster dialog. A row is a name, a width and a height in mm. Leave
the width or the height empty for a free side: that side is not fixed, and
you size it by hand on the canvas. The row Column, 120, empty is a
figure of a book with a 120 mm column: a fixed width and a free height.
The table is the [border_presets] section of the sidecar, one line per
format, Column = 120 x.
Colour scheme
on the main window has a Colour scheme: system follows the desktop, light and dark force one. The window chrome follows through Qt. On a dark scheme the canvases draw on a dark background with every colour’s lightness inverted for the screen only: black wires show white, white fills dark, red stays red; LaTeX renders (labels, parameter table, model and analysis blocks, fragments) show their black as white. A change of the desktop scheme while SLiCAP runs is followed at once. The schematic style, and therefore every SVG and PDF export, keeps the document colours.