Alt+click-drag window resizing on a Mac? (Similar to X-Windows)

"I found this the other day, might be useful:

Although not Alt + left-click-drag but this would give you Ctrl + Cmd + Click natively
(High Sierra or later), no 3rd party app required:

Run this command in terminal to enable Ctrl + Cmd + Click in any window to move. Restart after.

# to add
defaults write -g NSWindowShouldDragOnGesture -bool true

Run this command in terminal to remove this functionality. Restart after.

# to remove
defaults delete -g NSWindowShouldDragOnGesture

sourced from web:.mackungfu.org/UsabilityhackClickdraganywhereinmacOSwindowstomovethem"

"Try holding fn + option and then move your mouse (10.6.4 2010 MBP)

My old mac used to do it using just option key along (10.6.2 MBA)

Oh and try the window snapping function on BetterTouchTool.
If you've not used that app, its the greatest thing to happen to Apple Trackpads (and Magic Mouse) > lets you configure over 40+ different gestures to lots of different commands!

And its free too"

There is also Maxsnap (10 USD), which I found to be smoother in movement than BTT.

With the Afloat utility installed, holding control+Command moves a window.