Feat: draw stock contours in preview

[alex-pres]

Usual .ngc program does not have an idea what the stock is and where it is located.

However, many [ if not most ] customers now uses CAM tools to generate .ngc

I propose to define format of .ngc comment that will define workpiece size and position. This comment can be easily generated by post-processor ( I checked at least for Autodesk Fusion and SoldiCam - both can do that).

If this comment is present, GlCanon will see it during program parse and render it.

It will allow user to visually see stock contours and make less mistakes when preparing to program run.

If this idea is generally accepted, I am ready to develop this feature and submit PR.

[grandixximo]

Is there an industry standard for these comments? Support for block XYZ size, and 3D files?

[NoGare]

As a user, I'd personally find this a useful feature to limit my 'user' error mistakes... so up vote from me.
If memory serves each implementation is control specific, with Heidenhein TNC 7['Workpiece blank'] having been the easiest to work with. At least with the other controls(admittedly limited experience), most of them had this feature as entirely UI based experience.

[alex-scott]

Is there an industry standard for these comments? Support for block XYZ size, and 3D files?

Sorry for AI slot, but there is what I've found

Heidenhain TNC (Klartext) — BLK FORM

Closest thing to a de-facto standard, and mandatory for the control's graphics. Cuboid form is two corner points:

0 BEGIN PGM PART MM
1 BLK FORM 0.1 Z X+0 Y+0 Z-40      ; spindle axis + MIN point
2 BLK FORM 0.2 X+100 Y+100 Z+0     ; MAX point

BLK FORM 0.1 carries the spindle axis and the MIN point (smallest X/Y/Z, absolute); BLK FORM 0.2 carries the MAX point (largest X/Y/Z, absolute or incremental), and the blank is described relative to the active preset. MIN is left/front/bottom, MAX is right/rear/top.
ManualsLib + 2

Non-box variants exist:

BLK FORM CYLINDER — rotation axis X/Y/Z, R radius, L length, DIST shift along the rotation axis, RI inner radius for a hollow cylinder.
ManualsDir
BLK FORM ROTATION DIM_R LBL n — arbitrary rotationally-symmetric blank whose profile is a labelled contour placed after M30.
CNC Of Course
BLK FORM FILE — STL mesh as blank (option #152 on TNC 640), for second-op stock.

Siemens SINUMERIK Operate — WORKPIECE(...)

The control needs blank shape and size for graphical simulation; it can be defined via the UI or directly in the NC program. A real example:
ManualsLib

WORKPIECE(,"",,"BOX",112,0,-50,-80,0,0,100,100)
Positional argument list, roughly: (name, designation, , blank_type, flags, ZA, ZI, ZB, X0, Y0, X1, Y1) — ZA = top plane, ZI = blank bottom, ZB = clamping/base reference, then the two XY corners. Blank types are strings: BOX, CYLINDER, PIPE, N-CORNER, CENTERED BOX.

Two things to note as anti-patterns: the argument list is positional with empty slots and an opaque numeric flag field, and it's genuinely error-prone — a Fusion user reported the Siemens post omitting parameter 8, which hung Sinutrain until it was manually set to -80.
Autodesk Community

Fanuc MANUAL GUIDE i — G19xx blank blocks

Not comments, real G-codes reserved for the simulation subsystem. Blank form blocks: G1902 rectangular solid, G1900 column, G1906 column around X, G1901 column with a hole, G1907 column with a hole around X, G1903 prism, G1904 prism with a hole. For G1902: B = width (X length), D = depth (Y length). For G1900: D = diameter, L = length, K = Z work origin / face allowance.
Cncmanuals

Real-world lathe line: G1900 D2.3 L5. K0.2. G2900 defines the blank for graphic simulation.

What nobody does

I found no control or CAM ecosystem that puts stock in a comment. The comment-as-metadata precedent lives in FFF slicing (;MINX:, ;MAXX:, ;PRINT.SIZE) and in LinuxCNC itself — (MSG,...), (DEBUG,...), (PRINT,...), (PROBEOPEN ...), (AXIS,hide) are already parsed active comments, which is the precedent to cite in your proposal. Mazak/Okuma/Hurco define stock in conversational/setup data rather than in posted ISO output as far as I can tell — I didn't verify those directly.

Design points worth stealing / avoiding

Named keys, not positional. (STOCK,BOX,XMIN=0,YMIN=0,ZMIN=-40,XMAX=100,YMAX=100,ZMAX=0) — Siemens' positional form with empty slots is exactly the failure mode you don't want in posts.
Name the coordinate frame explicitly. Heidenhain implicitly uses the active preset. Since GlCanon sees your comment at parse time but G54/G92 can change mid-program, put the frame in the comment (FRAME=G54 or FRAME=MACHINE) instead of "whatever is current".
Units token, or state that it follows G20/G21 modal state at the point of the comment.
Shape enum from day one, even if you only implement BOX: BOX | CYLINDER | TUBE | MESH=file.stl. All three vendors needed cylinders for turning/second-op, and Heidenhain eventually needed a mesh reference.

We could start with supporting Box, Cylinder and Tube, mesh file seems to be overkilll for this goal, but may be useful too because seems both Fusion and SolidCAM postprocessors only can generate Box shape.

[grandixximo]

I like the comments because wether you have a version that supports or doesn't, at most you don't have the material, but the gcode still runs.

[grandixximo]

The conversation/setup thing also sounds very interesting, could be a versioned thing, let us play with more stuff in the future, but probably larger scope