Example: Qucs schematic → ROOM → round-trip

The qucs_to_room program — schematic import, save, reload, export

1. Run (VS Code)

Tasks: Run Task → Example: Qucs to ROOM

2. Run (command line)

.\build\qucs_to_room.exe examples\qucs_to_room\data\rc_lowpass.sch examples\qucs_to_room\output\schematic.room

Argument	Description
`input.sch`	Qucs schematic (default: `examples/qucs_to_room/data/rc_lowpass.sch`)
`output.room`	ROOM file — any path/name, e.g. `schematic.room`
`dump.txt`	Text dump (optional)
`roundtrip.sch`	Exported Qucs file after reload (optional)

3. Source code

examples/qucs_to_room/main.cpp

#include "database.h"
#include "qucs_importer.h"
#include "qucs_exporter.h"
#include "text_dump.h"

room::QucsImporter importer;
room::Database db = importer.importFile("rc_lowpass.sch");

db.saveToFile("schematic.room");

room::Database loaded = room::Database::loadFromFile("schematic.room");

room::QucsExporter exporter;
exporter.exportCell(loaded, "rc_lowpass", "schematic_roundtrip.sch");

4. Data flow

Qucs .sch (text) │ ▼ QucsImporter::importFile() │ Components → Instance, Wires → Net/Term ▼ Database → Cell → CellContent(schematic).payload.schematic.block │ ├─► Database::saveToFile() → schematic.room ├─► Database::loadFromFile() → reload check └─► QucsExporter::exportCell() → schematic_roundtrip.sch

5. Qucs → ROOM mapping

Qucs	ROOM
`<Components>` line	Instance (`cellName` = Qucs type, `qucs.instName` = R1, C1, …)
`<Wires>` label	Net name
Wire endpoints	Term positions; `dbuPerEditorUnit=1` (1 DBU = 1 Qucs grid unit)
Coordinate scale	`CellContent::dbuPerEditorUnit()` = `1`
View type	`ViewType::Schematic`

6. Attached primitive libraries (LibMan / Qucs-S)

When a project attaches tech or common libraries, LibMan sets environment variables consumed by PrimitiveResolver and QucsExporter::Options:

Variable	Purpose
`CORE_PRIMITIVE_LIBS_FILE`	Newline-separated list of `*.symbol.room` paths (preferred for large libraries)
`LIBMAN_TECH_LIBRARY`	Logical library names (`commonLib;sg13g2_pr`)
`QUCS_PRIMITIVE_LIB`	Qucs `<Lib>` name for PDK cells

On export to Qucs, passives map to native devices (res → R). PDK and hierarchy cells use <Lib> with ROOM symbol geometry. Xschem-only decorations (lab_wire, code_shown) are omitted in Qucs.

7. Sample text dump

cell "rc_lowpass"
  type schematic dbuPerMicron=1.000 dbuPerEditorUnit=1.000
  shapes=0 instances=4 nets=3
    instance -> "R" at (280,200)
    instance -> "C" at (480,200)
    net "N1" sig=signal terms=4

Limitations

Only schematic topology is mapped; simulation diagrams are stored but not interpreted
Implicit connectivity through unlabeled wire junctions uses endpoint union-find (anonymous nets N$N)
Qucs component libraries (.lib) are not imported yet