Custom G-code Editor

The Custom G-code module lets you import, edit, analyze, and debug real G-code inside 3dSynth. Whether you need to tweak slicer output, hand-author toolpaths, or understand exactly what a G-code file does before printing, this module gives you professional-grade tools without leaving the app.

Core philosophy

Three principles guide the Custom G-code Editor:

G-code is the single source of truth. The editor always works directly on the G-code text. There is no hidden intermediate format. What you see is what the printer receives.
Bidirectional editing. Select lines in the editor and see them highlighted in the 3D viewer. Click a toolpath in 3D and the editor scrolls to that line. Text and visualization are always in sync.
Motion-first thinking. The system understands movement, extrusion, temperature, and time -- not meshes or slicer intent. This makes it useful for any G-code, regardless of which slicer generated it.

What you can do

Import G-code files from any slicer (.gcode, .gco, .g, .nc), Prusa binary G-code (.bgcode), ZIP containers (.3mf, .ufp, .zip), and thin mesh contours (.stl, .obj)
Edit with syntax highlighting, autocomplete, and hover documentation
Analyze structure (layers, perimeters, infill), metrics (time, filament, flow), and warnings
Visualize toolpaths with color modes (speed, flow, temperature, fan, layer, bead)
Debug by stepping through commands line-by-line and inspecting full machine state
Modify with precision tools (change speed, flow, temperature on any selection)
Reorder sections safely with dependency analysis and automatic transition generation
Snapshot versions of your edits and compare them with a built-in diff viewer

Supported firmware dialects

The editor auto-detects the firmware dialect from file headers and command patterns:

Dialect	Detection	Notes
Marlin	Slicer headers, M900/M205 commands	Most common. Full support.
Klipper	`printer.cfg` references, `{expression}` syntax	Macro string parameters parsed; macros are never rewritten.
RepRap/Duet	RRF headers, M552/M586 commands	RepRapFirmware conventions.
Bambu	Profile name / dialect	Pause uses `M400 U1`, never `M600`.

If the dialect can't be determined, the editor defaults to Marlin-compatible parsing. Unknown commands are flagged but never modified -- nothing is silently rewritten.

Supported file formats

Extension	Description
`.gcode`	Standard G-code (most slicers)
`.gco`	Shortened G-code extension
`.g`	RepRapFirmware convention
`.nc`	Numerical control (CNC/legacy)
`.3mf` / `.ufp` / `.zip`	Container — G-code entry extracted; original bytes are not stored
`.bgcode`	Prusa binary G-code (deflate / heatshrink decode; encode uncompressed or deflate)
`.stl` / `.obj`	Thin mesh → planar contours (no supports)

Interface layout

When you select Custom G-code from the module picker, the left dock shows:

Toolbar -- import, read-only, color mode (including fan, acceleration, extrusion rate, bead), travels/retractions/Z-hops, warning count, startup/end toggle
Outline sidebar -- hierarchical section tree (startup, objects when present, layers, regions, shutdown)
Monaco editor -- the same source the tools edit (displaySource); drag-and-drop .gcode / .bgcode / .3mf onto the tab
Dock tools -- metrics (with charts), snapshots (diff), precision tools, diagnostics, resume-from-Z

The 3D viewer is overlay-only for this module: click/hover a segment, isolate a range, measure two hits, and use the action HUD. Playback clips the overlay with setDrawRange (it does not rebuild geometry every tick).

Getting started

New to the G-code editor? Start with the Tutorial for a guided walkthrough, or jump to any of these pages:

Editor features -- syntax highlighting, autocomplete, selection, themes
Analysis and visualization -- outline, metrics, color modes, playback
Tools and debugging -- precision editing, batch operations, reordering, debugger
Warnings reference -- warning codes explained with examples
G-code command reference -- every G/M command the editor recognizes