from mojo.UI import CurrentFontWindow

v = CurrentFontWindow().fontOverview.getGlyphCollection()

v.getGlyphCellView().setCellSize_((40.5, 40.5))

cs = v.getCellSize()
vw = v.getGlyphCellView().frameSize().width
vh = v.getGlyphCellView().frameSize().height

print(cs)
print(vw, vh)

it returns the following. Cell size is a whole number while frame size can be float.

(40, 40)
479.0 561.5

Since the cells are within the frame, I think it'd be useful for their dimensions to be more precise than that of the frame.

Thanks!

the cell size must be an int because it is the number of pixels in the bitmap representations.

cheers!

from mojo.UI import CurrentFontWindow

'''
trying to perfectly fit 16 columns of cells across the font overview
'''

gc = CurrentFontWindow().fontOverview.getGlyphCollection()
v = gc.getGlyphCellView()

# get the width of the cell view
vw = v.frameSize().width

cells_across = 16
cw = vw / cells_across

print("frame width is ", vw)
print("and the amount of cells I want across is ",  cells_across)
print("so: ")
print("desired cell size is ",  cw)

# do it
v.setCellSize_([cw, cw])

new_cw = gc.getCellSize()[0]

print("but resulting cell size is ", new_cw)
print("so: ")
print("leftover padding on right side of font overview is ", ((cw - new_cw) * cells_across))

frame width is  536.0
and the amount of cells I want across is  16
so: 
desired cell size is  33.5
but resulting cell size is  33
so: 
leftover padding on right side of font overview is  8.0

Resulting font overview with leftover space on the right is shown below. I've also tried resizing the font overview itself, but for some reason it needs to be re-run a few times before it almost hits flush with the cells. I'd love to be able to solve this without resizing the font overview itself.

See https://github.com/robotools/defconAppKit/blob/master/Lib/defconAppKit/representationFactories/glyphCellFactory.py#L12

Resize the window by 8? (Untested..)

If I go with the window resizing thing, there's another problem where the script needs to be run multiple times. I thought it had to do with the scrollbar at first, but I changed my settings, and it's not there anymore.
Video here.
Code here.

I gave it a try, this seems to work (very nice btw :)

from mojo.UI import CurrentFontWindow

cells = 8

fontWindow = CurrentFontWindow()
fontOverview = fontWindow.fontOverview
cellView = fontOverview.getGlyphCollection().getGlyphCellView()
frameWidth = cellView.frameSize().width

cellSize = int(frameWidth / cells)

# set cell size
cellView.setCellSize_([cellSize, cellSize])

# resize cell view
frameWidthNew = cells * cellSize
xDiff = frameWidth % cellSize
L, T, W, H = fontWindow.window().getPosSize()

if fontWindow.doodleWindowName == 'SingleFontWindow':
    x, y, w, h = fontOverview.getPosSize()
    fontWindow.editor.splitView.setDimension('fontOverview', frameWidthNew)
    fontWindow.editor.splitView.setDimension('glyphView', W - frameWidthNew)
    fontWindow.centerGlyphInView()

else: # FontWindow
    fontWindow.window().setPosSize((L, T, W - xDiff, H), False)

to do: update the cell size slider at the bottom

cheers!

And yes the main tool has fontOverview.views.sizeSlider.set() :))

I've flowed in your solve. Feel free to play with the real tool here.