how to fix mesh objects rolling out of the base surface in scatter? 

Hi 

I believe you may be referring to objects appearing off the surface.

Have you tried clicking on Update All and Reseed - In the Distribute Mesh roll up.

https://docs.sinisoftware.com/scatter-ui

thank you. what I mean is for the objects inside the red region to be cut or move inside the surface or even the part out side the surface does not appear in render

OK. 

Do you have camera-clipping on? 
Try and switch it on and extend the extents. 

https://docs.sinisoftware.com/scatter-ui#1j-08-camera-clipping-rollup

for example if I want to put grass on a surface, the grass object would appear outside the surface, what to do in this case to control the grass remaining inside the surface region?

take a look at this forest tutorial 

http://vividdownload.ir/Free-Tutorials/2-Boundary_in_forest_pack.mp4

Have you used the paint brush to erase unwanted grass?

Keep in mind Scatter is not Forest Pack. It's a free tool and doesn't have as many features. 

tanks

color correct from scatter and disperse rollout is not working with Corona any help please

We are aware of the colour correction bug with Corona. It will be fixed in the next release.