Descriptive Problem Summary:
Using the 'Alt' placement (aka holding Alt when placing an object, or using Ctrl+Alt in the same way) to place it with pixel alignment results in crazy values depending on how far you moved the mouse, in the step_x/y pixel_x/y variables, even with Nudge as Pixels set.

For example, if I use this method to place an object and move the mouse very little, I will end up with something like:
step_x: 2
pixel_x: 3

step_y: 3
pixel_y: 2


But if I flail the mouse around and then place the object in the same spot on the screen I'll get something like...
step_x: -391
pixel_x: 396

step_y: -390
pixel_y: 395

It will appear to be in the same spot in the screen and in the game, but the values for these variables are a little nutty, not to mention it's adjusting step_x and step_y needlessly while I have 'Nudge as pixels' on, just to 'counter' the values of pixel_x and pixel_y. Feels like it's forgetting to just sum them and set pixel_x/y to those values.

Numbered Steps to Reproduce Problem:
Just place any object in DM using Alt (or Ctrl+Alt) and flail the mouse around before placing it where you want it. Observe resulting values.

Expected Results:
pixel_x and pixel_y to be set to some numbers based on offset from origin.

Actual Results:
step_x and step_y are also set, and seem to be used 'only' to counter the pixel_x and pixel_y values to 'normalize' them.

Does the problem occur:
Every time? Or how often? Every time.
In other games? Yes, any game.
In other user accounts? Yes, other accounts.
On other computers? Yes, on other computers.

When does the problem NOT occur?
Can't find a time it doesn't occur.

Did the problem NOT occur in any earlier versions? If so, what was the last version that worked? (Visit http://www.byond.com/download/build to download old versions for testing.)
Seems to occur in all 512 betas and 511.

Workarounds:
None, just don't use the mouse placement method, which is sad because it's pretty easy to use.