Zoom Steps in diagrams


In the above image you can see Zoom In and Zoom Out along with the percentage dropdown which is dependent on each other.

I want this functionality to Zoom In or Zoom Out (+25% or -25%) on every click like 50% to 75% on clicking + button, 75% to 50% on clicking - button and so on.

Can you help me to solve this?

I think you want to set the Diagram.scaleComputation property to a function that returns the value for Diagram.scale that you want. There is an example at:
GoJS Coordinate Systems-- Northwoods Software

Thanks Walter