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BRUH Automation

Labels, Stock & the Designer

One rendering, two consumers

There is exactly one route from a label to dots. The preview PNG and the raster sent to the printer are the same bitmap with different endings.

A preview drawn a second way would look right while the label came out blank — which is the kind of bug you only find standing at a printer.

Nothing is anti-aliased anywhere. A thermal head is one bit deep, so a 50% pixel is a black one, and an anti-aliased hairline comes out solid.

Text is fitted by its ink

Not by the font’s metrics. textlength is the advance width — where the next glyph starts, not where this one ends — and the font’s line box reserves room for ascenders and descenders the word may not have (DejaVu’s is about 1.29em against a cap height of 0.73em).

Fitting to those is how a word comes out touching one edge and filling barely half its box at the same time. Measured on “Rice” in a 40 × 12mm box: 0.60 of the height before, 0.96 after.

The margin is 2mm

A LabelWriter’s registration wanders, and the 450’s head is three dot columns short of a 2.25″ label. At 1mm you get text at the die cut every other label.

It is a default — a saved stock carries its own margin and keeps it, which is what lets the default move without undoing anybody’s measurement.

Barcodes are never scaled down to fit

This is the one thing that must not happen. A barcode’s module width has to be a whole number of dots: at 1.4 dots per module each bar rounds independently, so five equal bars come out 1, 1, 2, 1, 2 — and the scanner reads the wrong widths.

So a symbol that cannot fit at one whole dot per module is reported, never drawn smaller. An unreadable barcode looks exactly like a readable one until somebody scans it.

Same rule for QR.

The 2.25″ note

The 450’s head is 672 dots at 300dpi, which is 2.24″ — and the cryo stock is 2.25″. The three extra dot columns are clipped, not scaled away, and a note says so. Scaling everything down half a percent to hide it is what makes a module width fractional.

The designer

Drag elements around a canvas with snapping (drawable edges and centres, then other boxes, then a 1mm grid), alignment tools and nudge. Elements that can rotate have a ⟳ in the properties pane — it acts on the selected element, which is why it lives there and not on the toolbar.

Anything that will not print correctly gets a red outline, collected by watching the notes list grow per element, so a new drawer cannot forget to report.

The font picker’s rows are rendered by the same text drawer the label uses — a CSS font-family preview would show you the browser’s idea of a monospace font beside a label that prints in DejaVu Sans Mono.

The designer previews the canvas; everything else previews the sheet

A 90°-turned tube wrap is a tall strip with its words on their side once it reaches the sheet — the right picture on the Quick and Templates tabs, and the wrong one under a drag overlay whose coordinates are the canvas’s.

Templates

A template is a saved label with blanks in it.

Its fields come from the label, never from the request. The placeholders in the document are the truth about what it needs; a declared field that no longer appears anywhere is a box on the form that fills nothing.

Substitution is plain string replacement, with no expression language. A template that can evaluate is one that can be made to evaluate something else by whoever sends the automation payload, and the value of a label expression language is close to zero against that.

An empty field warns in the panel and refuses through the API — deliberately different: the panel has somebody looking at the preview, and the API call is usually an automation about to print fifty labels with a hole in them.

The remaining count is a control, not a readout

Nothing on a LabelWriter reports a real level, so the count is an estimate and says so everywhere it appears. It drifts the moment somebody prints from another machine.

A number you can see and cannot correct is a number you stop reading — so the bar is the button. Press it to set it right.

You can turn the whole thing off (track_remaining), and when you do the count stops moving as well as stops showing. A hidden count that kept counting would be worse than none: turning it back on would reveal a number that had been quietly wrong for a month.

Two settings on the Printer tab, both sent to the printer in the order the CUPS DYMO path has sent them for twenty years:

  • Density — how dark. On ordinary thermal stock the printer’s own default reads as faint.
  • Quality — text speed, or the barcodes-and-graphics mode. Graphics mode is 300 × 600, so the printer steps the paper twice as finely and every raster line is sent twice.

There is also a bare mode that sends the minimum. It exists because whether a given firmware accepts every command in the preamble is not something an add-on in a container can find out, and a printer that takes a job and prints nothing is otherwise a guessing game played one release at a time.