awful.screen: extract screen:get_next_in_direction() (#1597)

This extracts the code for finding the next screen
from focus_bydirection to a separate method on
the screen object.

The main reason was to use the finding code without
actually changing the screen focus but this should
incidentally make the code slightly easier to test
as well since both concerns can be tested in
isolation.

Signed-off-by: Christoph Mertz <chris@nimel.de>

lib/awful/screen.lua

@@ -122,6 +122,28 @@ function screen.focus(_screen)
     end
 end
 
+--- Get the next screen in a specific direction.
+--
+-- This gets the next screen relative to this one in
+-- the specified direction.
+--
+-- @function screen:get_next_in_direction
+-- @param self Screen.
+-- @param dir The direction, can be either "up", "down", "left" or "right".
+function screen.object.get_next_in_direction(self, dir)
+    local sel = get_screen(self)
+    if not sel then
+        return
+    end
+
+    local geomtbl = {}
+    for s in capi.screen do
+        geomtbl[s] = s.geometry
+    end
+
+    return grect.get_in_direction(dir, geomtbl, sel.geometry)
+end
+
 --- Move the focus to a screen in a specific direction.
 --
 -- This moves the mouse pointer to the last known position on the new screen,
@@ -131,15 +153,10 @@ end
 -- @param _screen Screen.
 function screen.focus_bydirection(dir, _screen)
     local sel = get_screen(_screen or screen.focused())
-    if sel then
-        local geomtbl = {}
-        for s in capi.screen do
-            geomtbl[s] = s.geometry
-        end
-        local target = grect.get_in_direction(dir, geomtbl, sel.geometry)
+    local target = sel:get_next_in_direction(dir)
+
     if target then
-            return screen.focus(target)
-        end
+        return target:focus()
     end
 end
 

lib/gears/geometry.lua

@@ -117,7 +117,7 @@ local function calculate_distance(dir, _gA, _gB)
         gAx = _gA.x + _gA.width
     end
 
-    return math.sqrt(math.pow(gBx - gAx, 2) + math.pow(gBy - gAy, 2))
+    return math.sqrt((gBx - gAx) ^ 2 + (gBy - gAy) ^ 2)
 end
 
 --- Get the nearest rectangle in the given direction. Every rectangle is specified as a table

spec/awful/screen_spec.lua

@@ -76,6 +76,40 @@ describe("awful.screen", function()
         end)
     end)
 
+    describe("get_next_in_direction", function()
+        before_each(function()
+            fake_screens = {
+                { geometry = { x = 0, y = 0, width = 1, height = 1 }, index = 1 },
+                { geometry = { x = 1, y = 0, width = 1, height = 1 }, index = 2 },
+                { geometry = { x = 0, y = 1, width = 1, height = 1 }, index = 3 },
+                { geometry = { x = 1, y = 1, width = 1, height = 1 }, index = 4 },
+            }
+        end)
+
+        it("gets screens to the left", function()
+            assert.is.equal(fake_screens[1], ascreen.object.get_next_in_direction(fake_screens[2], "left"))
+        end)
+
+        it("gets screens to the right", function()
+            assert.is.equal(fake_screens[2], ascreen.object.get_next_in_direction(fake_screens[1], "right"))
+        end)
+
+        it("gets screens to the top", function()
+            assert.is.equal(fake_screens[2], ascreen.object.get_next_in_direction(fake_screens[4], "up"))
+        end)
+
+        it("gets screens to the bottom", function()
+            assert.is.equal(fake_screens[4], ascreen.object.get_next_in_direction(fake_screens[2], "down"))
+        end)
+
+        it("gets no screens if none exist in the direction", function()
+            assert.is_nil(ascreen.object.get_next_in_direction(fake_screens[2], "up"))
+            assert.is_nil(ascreen.object.get_next_in_direction(fake_screens[4], "down"))
+            assert.is_nil(ascreen.object.get_next_in_direction(fake_screens[2], "right"))
+            assert.is_nil(ascreen.object.get_next_in_direction(fake_screens[1], "left"))
+        end)
+    end)
+
     describe("no screens", function()
         before_each(function()
             fake_screens = {}