3D view rendering in the background I'm writing an addon, which let the user the option to see the dynamics of its data. The user can create an offline movie, or try to run it online.
In this addon, there is quite a complex mesh, with thousands of vertices. In a modal timer operator, something like this one, I'm painting different vertices each timer tick:

vcol_layer = mesh.vertex_colors.new()


And inside a loop:

vcol_layer.data[loop_ind].color = some_color


The problem is that it takes about a second to render the image in the 3D view, and until the rendering is completed, the image is quite blurry, like in the following screenshot: 

Is there a way to change this behavior, so the rendering will be be done in the background, and the image will be updated only when it's completed?
If I got your question right you want to use the 3d view port preview rendering to data flow visualization. However it's purpose is completely different: check how your scene will be rendered by one of the NON REAL TIME rendering engines.

For this propose you should use a real time rendering engine. You have two choices:

Blender Game Engine for offline visualization, (programmable in python via BGE API)

blend4web for online visualization. (Programmable in JavaScript with blend4web sdk)

Both of them are capable to render complex scenes in realtime, morover they can be interactive.