screen

The screen object represents a physical or virtual display. Each monitor connected to your system is a screen.

Upstream documentation: AwesomeWM screen docs

Accessing Screens

-- Primary screen
local s = screen.primary

-- Currently focused screen
local s = awful.screen.focused()

-- Iterate all screens
for s in screen do
    print(s.index, s.geometry.width)
end

-- Get screen by index (1-based)
local s = screen[1]

-- Total screen count
local count = screen.count()

Properties

Geometry & Layout

Property	Type	Access	Description
geometry	table	read	Screen bounds {x, y, width, height} in logical pixels
workarea	table	read	Usable area after panels/struts {x, y, width, height}
index	number	read	1-based screen index
padding	table	read/write	Manual padding {top, right, bottom, left}

Output Information

Property	Type	Access	Description
outputs	table	read	Physical output info (see below)
name	string	read/write	User-assignable screen name

The outputs table is keyed by output name:

-- Example outputs table
{
    ["DP-1"] = {
        name = "DP-1",
        mm_width = 600,   -- Physical width in millimeters
        mm_height = 340,  -- Physical height in millimeters
        viewport_id = 1,
    }
}

Scaling & DPI somewm-only

Property	Type	Access	Description
scale	number	read/write	Output scale factor (0.1 to 10.0)
dpi	number	read	Screen DPI (computed from physical size)
minimum_dpi	number	read	Lowest DPI across outputs
maximum_dpi	number	read	Highest DPI across outputs
preferred_dpi	number	read	Recommended DPI for this screen

-- Get current scale
print(screen.primary.scale)  -- e.g., 1.5

-- Set fractional scale for HiDPI display
screen.primary.scale = 1.5

-- Check DPI
print(screen.primary.dpi)  -- e.g., 144

When you change scale, the geometry and workarea update to reflect logical pixel dimensions. For example, a 3840x2160 display at scale 2.0 reports geometry of 1920x1080.

Tags & Clients

Property	Type	Access	Description
tags	table	read	All tags on this screen
selected_tags	table	read	Currently visible tags
selected_tag	tag	read	First selected tag (or nil)
clients	table	read	All clients on this screen
tiled_clients	table	read	Non-floating, non-minimized clients

Lifetime

Property	Type	Access	Description
valid	boolean	read	false once the screen has been removed

A screen object outlives the monitor it came from: your handlers, timers and closures can still hold one after the monitor is unplugged or fake_remove() is called. Once that happens, valid is the only property you can read. Every other read raises invalid object, and screen[s] gives you nil.

Check it before touching a screen you captured earlier:

gears.timer.delayed_call(function()
    if not s.valid then return end
    -- safe to use s here
end)

Methods

Screen Management

-- Get total screen count
local count = screen.count()

-- Get bounding geometry (respects workarea and padding)
local geo = s:get_bounding_geometry({
    honor_workarea = true,
    honor_padding = true,
})

-- Swap two screens' positions
screen[1]:swap(screen[2])

Virtual Screens

Not functional

screen.fake_add creates a real screen object: screen.count() goes up, added fires, and tags and wibars get created for it. But the screen does not work as a screen. Clients moved to it are hidden, wibars cannot attach to it, and layouts never run in its region, because window management is keyed to physical monitors (#561). Making a carved-out monitor region behave as a screen is planned as part of the 2.2 layout work.

-- Create a virtual screen object
local fake = screen.fake_add(0, 0, 1920, 1080)

-- Resize it
fake:fake_resize(0, 0, 2560, 1440)

-- Remove it
fake:fake_remove()

Signals

Signal	Arguments	Description
added	s	New screen connected
removed	s	Screen disconnected
list	(none)	Screen list changed
primary_changed	s	Primary screen changed
property::geometry	s, old_geometry	Screen geometry changed
property::workarea	s, old_workarea	Workarea changed (panel added/removed)
property::scale	s	Output scale changed somewm-only
property::outputs	s	Output metadata changed
property::index	s	Screen index changed

property::geometry and property::workarea pass the previous value as a second argument, so you can work out what moved rather than only that something did:

screen.connect_signal("property::geometry", function(s, old_geometry)
    local dx = s.geometry.x - old_geometry.x
    local dy = s.geometry.y - old_geometry.y
    -- dx/dy is how far the screen moved
end)

When a monitor is plugged or unplugged, added and removed reach you immediately, while the others are queued and arrive at the next frame. So inside an added handler the screen already exists, but list has not fired yet. See Signals Reference: Dispatch for the full list.

Example: React to Scale Changes

screen.connect_signal("property::scale", function(s)
    -- Refresh widgets when scale changes
    print("Screen " .. s.index .. " scale is now " .. s.scale)
end)

Example: Handle Monitor Hotplug

screen.connect_signal("added", function(s)
    -- Set up new monitor with appropriate scale
    if s.geometry.width > 3000 then
        s.scale = 1.5  -- 4K display
    end

    -- Create tags
    awful.tag({ "1", "2", "3" }, s, awful.layout.layouts[1])
end)

Common Patterns

Auto-Scale Based on Resolution

awful.screen.connect_for_each_screen(function(s)
    if s.geometry.width > 3000 then
        s.scale = 1.5
    elseif s.geometry.width > 2000 then
        s.scale = 1.25
    else
        s.scale = 1.0
    end
end)

Get Screen Under Mouse

local s = awful.screen.focused()  -- Follows focus
-- or
local s = mouse.screen  -- Screen containing mouse pointer

Find Screen by Output Name

for s in screen do
    for name, _ in pairs(s.outputs) do
        if name == "HDMI-A-1" then
            return s
        end
    end
end

See Also

• Fractional Scaling Guide - Configure HiDPI displays
• Multi-Monitor Setup - Per-screen configuration
• Tag Persistence - How tags survive monitor hotplug
• Display Scaling Concepts - How scaling works
• Object Model - How screens relate to tags and clients