tests: Implement mouse.screen properly

tests/examples/shims/mouse.lua

@@ -62,6 +62,13 @@ return setmetatable(mouse, {
                 forced_screen = nil
             end
 
+            for s in screen do
+                if coords.x > s.geometry.x and coords.x < s.geometry.x +s.geometry.width
+                  and coords.y > s.geometry.y and coords.y < s.geometry.y +s.geometry.height then
+                    return s
+                end
+            end
+
             -- Using capi.mouse.screen is *not* supported when there is zero
             -- screen. Nearly all the code uses `mouse.screen` as its ultimate
             -- fallback. Having no screens is tolerated during early

tests/examples/shims/screen.lua

@@ -35,12 +35,6 @@ local function create_screen(args)
 
     local wa = args.workarea_sides or 10
 
-    -- This will happen if `clear()` is called
-    if mouse and (screen.count() > 0 and not mouse.screen) then
-        screen[s] = s
-        mouse.screen = s
-    end
-
     return setmetatable(s,{ __index = function(_, key)
             assert(s.valid)