Input events on non-input clients pass straight through to the surface below

[Daniel van Vugt]

Input events on non-input clients pass straight through to the surface below (if any). This is particularly confusing when the non-input app on top is opaque and you can't see that you're interacting with the surface below it.

Test case:
  1. Start mir_demo_server_shell
  2. Start mir_demo_client_fingerpaint
  3. Start mir_demo_client_egltriangle or any other non-input client, on top of fingerpaint
  4. Click and drag in the egltriangle window. Nothing happens (correctly).
  5. Alt-Tab to see fingerpaint that was below.
Expected: Fingerpaint shows nothing.
Observed: Fingerpaint shows markings from clicking and dragging on the egltriangle window.

Obviously we're passing input events down to the first surface that consumes them. However for simple opaque non-input surfaces, this is very confusing and misleading. We need to ensure touch/mouse events don't get sent to obscured client surfaces below.

[Alan Griffiths (alan-griffiths)]

Sometime in the past three years this got fixed.