Add a only_on_screen container widget

Fixes: https://github.com/awesomeWM/awesome/issues/1565
Signed-off-by: Uli Schlachter <psychon@znc.in>

lib/awful/widget/init.lua

@@ -19,6 +19,7 @@ return
     textclock = require("awful.widget.textclock");
     keyboardlayout = require("awful.widget.keyboardlayout");
     watch = require("awful.widget.watch");
+    only_on_screen = require("awful.widget.only_on_screen");
 }
 
 -- vim: filetype=lua:expandtab:shiftwidth=4:tabstop=8:softtabstop=4:textwidth=80

lib/awful/widget/only_on_screen.lua

@@ -0,0 +1,147 @@
+---------------------------------------------------------------------------
+--
+-- A container that makes a widget display only on a specified screen.
+--
+-- @author Uli Schlachter
+-- @copyright 2017 Uli Schlachter
+-- @classmod awful.widget.only_on_screen
+---------------------------------------------------------------------------
+
+local type = type
+local pairs = pairs
+local setmetatable = setmetatable
+local base = require("wibox.widget.base")
+local util = require("awful.util")
+local capi = {
+    screen = screen,
+    awesome = awesome
+}
+
+local only_on_screen = { mt = {} }
+
+local instances = setmetatable({}, { __mode = "k" })
+
+local function should_display_on(self, s)
+    if not self._private.widget then
+        return false
+    end
+    local success, own_s = pcall(function()
+        return capi.screen[self._private.screen]
+    end)
+    return success and own_s == s
+end
+
+-- Layout this layout
+function only_on_screen:layout(context, ...)
+    if not should_display_on(self, context.screen) then return end
+    return { base.place_widget_at(self._private.widget, 0, 0, ...) }
+end
+
+-- Fit this layout into the given area
+function only_on_screen:fit(context, ...)
+    if not should_display_on(self, context.screen) then
+        return 0, 0
+    end
+    return base.fit_widget(self, context, self._private.widget, ...)
+end
+
+--- The widget to be displayed
+-- @property widget
+-- @tparam widget widget The widget
+
+function only_on_screen:set_widget(widget)
+    if widget then
+        base.check_widget(widget)
+    end
+    self._private.widget = widget
+    self:emit_signal("widget::layout_changed")
+end
+
+function only_on_screen:get_widget()
+    return self._private.widget
+end
+
+--- Get the number of children element
+-- @treturn table The children
+function only_on_screen:get_children()
+    return {self._private.widget}
+end
+
+--- Replace the layout children
+-- This layout only accept one children, all others will be ignored
+-- @tparam table children A table composed of valid widgets
+function only_on_screen:set_children(children)
+    self:set_widget(children[1])
+end
+
+--- The screen to display on. Can be a screen object, a screen index, a screen
+-- name ("VGA1") or the string "primary" for the primary screen.
+-- @property screen
+-- @tparam screen|string|integer screen The screen.
+
+function only_on_screen:set_screen(s)
+    self._private.screen = s
+    self:emit_signal("widget::layout_changed")
+end
+
+function only_on_screen:get_screen()
+    return self._private.screen
+end
+
+--- Returns a new only_on_screen container.
+-- This widget makes some other widget visible on just some screens. Use
+-- `:set_widget()` to set the widget and `:set_screen()` to set the screen.
+-- @param[opt] widget The widget to display.
+-- @param[opt] s The screen to display on.
+-- @treturn table A new only_on_screen container
+-- @function wibox.container.only_on_screen
+local function new(widget, s)
+    local ret = base.make_widget(nil, nil, {enable_properties = true})
+
+    util.table.crush(ret, only_on_screen, true)
+
+    ret:set_widget(widget)
+    ret:set_screen(s or "primary")
+
+    instances[ret] = true
+
+    return ret
+end
+
+function only_on_screen.mt:__call(...)
+    return new(...)
+end
+
+-- Handle lots of cases where a screen changes and thus this widget jumps around
+
+capi.screen.connect_signal("primary_changed", function()
+    for widget in pairs(instances) do
+        if widget._private.widget and widget._private.screen == "primary" then
+            widget:emit_signal("widget::layout_changed")
+        end
+    end
+end)
+
+capi.screen.connect_signal("list", function()
+    for widget in pairs(instances) do
+        if widget._private.widget and type(widget._private.screen) == "number" then
+            widget:emit_signal("widget::layout_changed")
+        end
+    end
+end)
+
+capi.screen.connect_signal("property::outputs", function()
+    for widget in pairs(instances) do
+        if widget._private.widget and type(widget._private.screen) == "string" then
+            widget:emit_signal("widget::layout_changed")
+        end
+    end
+end)
+
+--@DOC_widget_COMMON@
+
+--@DOC_object_COMMON@
+
+return setmetatable(only_on_screen, only_on_screen.mt)
+
+-- vim: filetype=lua:expandtab:shiftwidth=4:tabstop=8:softtabstop=4:textwidth=80

tests/test-awful-widget-only_on_screen.lua

@@ -0,0 +1,155 @@
+-- Test that awful.widget.only_on_screen works correctly
+
+local runner = require("_runner")
+local wibox = require("wibox")
+local awful = require("awful")
+
+-- Make sure we have at least two screens to test this on
+screen.fake_add(-100, -100, 50, 50)
+assert(screen.count() == 2)
+
+-- Each screen gets a wibox displaying our only_on_screen widget
+local inner_widget = wibox.widget.textbox("This is only visible on some screen")
+local only_widget = awful.widget.only_on_screen()
+awful.screen.connect_for_each_screen(function(s)
+    local geo = s.geometry
+    -- Just so that :fit() also gets code coverage, we use an align layout
+    local widget = wibox.layout.align.horizontal(only_widget)
+    s.testwibox = wibox{
+        x = geo.x + geo.width / 4,
+        y = geo.y + geo.height / 4,
+        width = geo.width / 2,
+        height = geo.height / 2,
+        widget = widget,
+        visible = true,
+    }
+end)
+
+-- Check if the inner_widget is visible on the given screen
+local function widget_visible_on(s)
+    for _, entry in ipairs(s.testwibox:find_widgets(1, 1)) do
+        if entry.widget == inner_widget then
+            return true
+        end
+    end
+    return false
+end
+
+-- Test the widget's constructor
+do
+    local widget = awful.widget.only_on_screen()
+    assert(widget.screen == "primary")
+    assert(widget.widget == nil)
+
+    widget = awful.widget.only_on_screen(inner_widget, 42)
+    assert(widget.screen == 42)
+    assert(widget.widget == inner_widget)
+end
+
+local steps = {}
+
+-- Test that the widget "does nothing" when no widget is set
+table.insert(steps, function()
+    -- Idle step so that the testwibox added above is drawn
+    return true
+end)
+table.insert(steps, function()
+    for s in screen do
+        local res = s.testwibox:find_widgets(1, 1)
+        assert(#res == 1, #res)
+    end
+    return true
+end)
+
+-- Test that the widget by default is displayed on the primary screen
+table.insert(steps, function()
+    only_widget.widget = inner_widget
+    return true
+end)
+table.insert(steps, function()
+    assert(only_widget.screen == "primary", only_widget.screen)
+    for s in screen do
+        if s == screen.primary then
+            assert(widget_visible_on(s))
+        else
+            assert(not widget_visible_on(s))
+        end
+    end
+    return true
+end)
+
+-- Test setting the screen
+for s in screen do
+    local index = s.index
+    local function check_result()
+        for t in screen do
+            assert(widget_visible_on(t) == (t.index == index))
+        end
+        return true
+    end
+
+    -- Test by screen object
+    table.insert(steps, function()
+        only_widget.screen = s
+        return true
+    end)
+    table.insert(steps, check_result)
+
+    -- Test by index
+    table.insert(steps, function()
+        only_widget.screen = index
+        return true
+    end)
+    table.insert(steps, check_result)
+end
+
+-- Test that the widget is correctly updated when screen "2" is removed
+table.insert(steps, function()
+    only_widget.screen = 2
+    return true
+end)
+table.insert(steps, function()
+    screen[2]:fake_remove()
+    return true
+end)
+table.insert(steps, function()
+    for s in screen do
+        assert(not widget_visible_on(s))
+    end
+    screen.fake_add(-100, -100, 50, 50)
+    return true
+end)
+table.insert(steps, function()
+    for s in screen do
+        assert(widget_visible_on(s) == (s.index == 2))
+    end
+    return true
+end)
+
+-- Test what happens when the primary screen is removed
+table.insert(steps, function()
+    only_widget.screen = "primary"
+    return true
+end)
+table.insert(steps, function()
+    local s, s2 = screen.primary, screen[2]
+    assert(s.index == 1)
+    s:fake_remove()
+    assert(screen.primary == s2)
+    return true
+end)
+table.insert(steps, function()
+    assert(only_widget.screen == "primary", only_widget.screen)
+    for s in screen do
+        if s == screen.primary then
+            assert(widget_visible_on(s))
+        else
+            assert(not widget_visible_on(s))
+        end
+    end
+    return true
+end)
+
+runner.run_steps(steps)
+
+-- vim: filetype=lua:expandtab:shiftwidth=4:tabstop=8:softtabstop=4:textwidth=80