since I wanted to use DarkTheme I played around with TRMorph (since seeing giant white rectangle in dark theme is not very nice).

What I have done is moved the background color setting to `surface clear:` (instead of the original aCanvas fillRectangle).

And then if theme background luminance is dark (>0.5), I invert all the colors in the visualization.
For dark theme the background is black, and not the theme background - at least to me it seems that black is much clearer.

Is this something that could be incorporated?

And the modified code:
"protocol: drawing"
TRMorph>>drawOn: aCanvas
"aCanvas is a FormCanvas"
self checkSession.
"aCanvas fillRectangle: bounds color: trachelCanvas color."
trachelCanvas playAnimations.
"The drawing has to be done when a change in the shapes occured or when there is an animation."
surface drawDuring: [:cs |
surface clear: trachelCanvas color.
"We display the elements that are subject to the camera"
cs pathTransform
translateBy: (self extent / 2) asFloatPoint;
   scaleBy: trachelCanvas camera scale asFloat;
translateBy: trachelCanvas camera position negated asFloatPoint.
trachelCanvas shapes do: [ :trachelShape |
trachelShape drawOn: cs.
"We display the elements that are _NOT_ subject to the camera"
cs pathTransform loadIdentity scaleBy: 1.001.
trachelCanvas fixedShapes do: [ :trachelShape |
trachelShape drawOn: cs.
self theme backgroundColor luminance < 0.5 ifTrue: [
surface drawDuring: [ :cs |
cs paintMode restoreAfter: [
cs setPaint: Color white.
cs paintMode difference.
cs drawShape: (0 @ 0 extent: surface extent)
"aCanvas translucentImage: surface asForm at: self bounds origin."
"asForm creates a new Form, which is likely to be expensive. This can be cached"
aCanvas image: surface asForm at: self bounds origin sourceRect: (0 @ 0 extent: surface extent) rule: 34.