kicad-developers team mailing list archive

["NHays Terrace" <nhays@xxxxxxxxxxxxxxx>]

It seems to me that the coordinate origin being up and left of the sheet is
rather arbitrary.
I can understand that you must start somewhere and that the system needs an
absolute origin.
But when I relocate the grid origin, I would think that the XY status bar
report should move with it.
I am used to placing a fiducial on the board (or off if needed)  and having
everything relative to that point.
That makes it easier when I am given a mechanical spec for connector
placement, etc..
The absolute XY report seems completely useless to the designer, unless they
are comparing objects to statements in the files directly.
If the origin is bumped around and a return to abs 0,0 is desired, there
could be a command to do so.
Using the spacebar and relative coordinates are highly useful for short term
measurements and placements.
But having to relocate to the fiducial is problematic - the grid location
isn't reported, so what to do?
When bumping from mm to mil and back, I find I can't drop the grid right on
the old fiducial unless I make the grid ridiculously fine.
Even then it is not accurate, just really close.
What is missing is a selectable 'snap' to both grid and/or graphic element.
Can someone elucidate the rationale for not displaying grid coordinates?

Perhaps a simple solution would be to have three coordinate reports:
absolute, grid, and relative(spacebar).

And while I'm on the subject, the long list of grid spacing choices should
display both "0.1mil" and "0.1mm" because "0.437259" is meaningless.
I think I would like to have the proposed three coordinate status reports to
tag the numbers with the units.
For example, if the global selection is in mm, but the grid is in mil and
relocated, then you might have on the status bar:
   ABS X:28.5750mm Y:12.0000mm   GRID x:1.1250mil x:2.5000mil   REL
dx:0.4239mm dy:1.3890mm

With this functionality, I am aware of both unit systems.
I never have to piece together in my head the current modality.
I don't have to do strange things to anchor grid or relative measurements in
mixed coordinate designs.
And I posit that many if not most boards have mixed coordinates since the
parts themselves are often in different unit systems.

Of course as a software engineer, I have an opinion about coordinates in
general.
Coordinates should be of a class VECTOR that is based on self-scaling units.
Every object maintains its 'true' Vectors in its own unit, mm or mil.
Vectors convert as needed to other units without the object or any other
code needing to care.
Vectors have overrides for +,-,*,/,etc... so again, code that uses them
doesn't care about the units.
Vectors also have methods for rotation, scaling, and polar/cartesian access.
Units should exist for mm, mil, pixels, plotting, etc..., but mm and mil are
the only absolutes.
When you ask an object for its location for plotting, etc..., you specify
the units and its Vectors convert for you (and remembers the calc for next
time).
This eliminates the rounding errors that are still in the program.
When you convert for display or output, the answer always has greater
resolution than the display device/output file.
The errors occur only when you convert, discard the source unit, then try to
convert back.

In the file, modules should specify the units local to their definition.
Parts in metric stay metric, those in imperial stay imperial.
Or any file coordinate can have the form, "0.1234mm" or "5.2mil" and that is
how it is remembered and written back to the file.
This way no odd-balls show up like 0.3 becoming 0.29999999.
This is annoying when working in the files - type in a 0.3 but it changes
when the file is saved.
Direct file editing is SO useful for creating arrays, many similar parts, or
converting part specs to kicad format.

So can we have grid coordinates in the status bar and grid resolution
selection units?

I am _so_ going to contribute cool code before long...
Nate