Image objects' appearance updates don't seem to be synchronized by the frame. I can't explain it much better than this, but I would expect every single added/removed/changed appearance to appear during the same render frame, rather than the visual flickering that's happening to me with certain objects.
It seems like changing image appearances works fine, but when you change the object that the appearance is linked to after changing the image, the old image appearance is used for one frame, and then the next frame, the new object's appearance changes are processed.
EDIT: I've found the source of this problem: Image objects' appearance changes are communicated and cause render updates on the client immediately, even if it's between frames. Meanwhile, atomic appearance updates wait until the next frame to change.
Numbered Steps to Reproduce Problem:
Lummox, PM me for the source code that demonstrates the problem. Basically, you need to update multiple image objects in a single frame to get this to happen.
Expected Results:
All changes to image objects during the frame should update instantaneously.
Actual Results:
Some objects update before others.
Image of problem in action at 40fps:
Image of the problem in action at 1fps:
I lowered the FPS of the world to 1fps to more clearly demonstrate the problem. The ticker at the top of the screen is updated once per frame. You'll notice that any object location/appearance updates wait until the next frame to render, while appearance updates on images are instantaneous.
The last gif shows the problem, as the color of the image objects is being changed on mouseover of a valid move destination, and the direction of the corner object that two /image objects are linked to is being changed in the same frame. This results in the direction being changed later than all the colors.
The first two gifs show the problem of image updates occurring in the color and icon_state changes to existing image objects, while their root objects being relocated from my object pool onto the map waits for the next frame.
This demo should show the problem. The demo runs at 1FPS to demonstrate that FPS is not respected at all by image updates.
This is not an issue of the object appearance updates being late. It is an issue of the image appearance updates triggering a redraw instantaneously.
It should also be noted that smooth tile gliding also triggers redraws at 1FPS, so I think image objects' appearances are actually tied to the glide redraw, and not the actual frame redraw.