From a1376557917a8859222c49f59ba42373c02905c7 Mon Sep 17 00:00:00 2001
From: Uli Schlachter <psychon@znc.in>
Date: Sun, 8 Oct 2017 12:30:21 +0200
Subject: [PATCH] Add & use a dpi property on screen objects

Once upon a time, beautiful.xresources.get_dpi was added to query
Xft.dpi. That made sense since this queried an xresources property. Over
time, other, non-xresources-based ways to query DPI were added to this
function. Now, it makes no more sense to have this function here.

Also, recently it became possible to add new properties to C objects
from Lua code. Thus, we no longer need to have a get_dpi() function
somewhere, but can add s.dpi directly.

Thus, this commit adds s.dpi and makes everything use it. No functional
changes are intended.

Signed-off-by: Uli Schlachter <psychon@znc.in>
---
 lib/awful/screen.lua                | 34 +++++++++++++++++++++++++++++
 lib/awful/widget/calendar_popup.lua |  2 +-
 lib/beautiful/xresources.lua        |  8 +++----
 lib/wibox/drawable.lua              |  2 +-
 lib/wibox/widget/textbox.lua        |  4 ++--
 5 files changed, 41 insertions(+), 9 deletions(-)

diff --git a/lib/awful/screen.lua b/lib/awful/screen.lua
index c6c88f73..91487518 100644
--- a/lib/awful/screen.lua
+++ b/lib/awful/screen.lua
@@ -504,6 +504,40 @@ function screen.object.get_selected_tag(s)
     return screen.object.get_selected_tags(s)[1]
 end
 
+--- The number of pixels per inch of the screen.
+-- @property dpi
+-- @treturn number the DPI value.
+
+local xft_dpi, fallback_dpi
+
+function screen.object.get_dpi(s)
+    local mm_per_inch = 25.4
+
+    if s.data.dpi then
+        return s.data.dpi
+    end
+
+    -- Xft.dpi is explicit user configuration, so honor it
+    if not xft_dpi and awesome and awesome.xrdb_get_value then
+        xft_dpi = tonumber(awesome.xrdb_get_value("", "Xft.dpi")) or false
+    end
+    if xft_dpi then
+        return xft_dpi
+    end
+
+    -- We have no outputs, so guess based on the size of the root window.
+    if root and not fallback_dpi then
+        local _, h = root.size()
+        local _, hmm = root.size_mm()
+        fallback_dpi = hmm ~= 0 and h * mm_per_inch / hmm
+    end
+    return fallback_dpi or 96
+end
+
+function screen.object.set_dpi(s, dpi)
+    s.data.dpi = dpi
+end
+
 
 --- When the tag history changed.
 -- @signal tag::history::update
diff --git a/lib/awful/widget/calendar_popup.lua b/lib/awful/widget/calendar_popup.lua
index b3afe302..da5cefab 100644
--- a/lib/awful/widget/calendar_popup.lua
+++ b/lib/awful/widget/calendar_popup.lua
@@ -173,7 +173,7 @@ local function get_geometry(widget, screen, position)
     local pos, s = position or "cc", screen or ascreen.focused()
     local margin = widget._calendar_margin or 0
     local wa = s.workarea
-    local width, height = widget:fit({screen=s, dpi=beautiful.xresources.get_dpi(s)}, wa.width, wa.height)
+    local width, height = widget:fit({screen=s, dpi=s.dpi}, wa.width, wa.height)
 
     width  = width  < wa.width  and width  or wa.width
     height = height < wa.height and height or wa.height
diff --git a/lib/beautiful/xresources.lua b/lib/beautiful/xresources.lua
index ce6e78ea..fae96b16 100644
--- a/lib/beautiful/xresources.lua
+++ b/lib/beautiful/xresources.lua
@@ -64,8 +64,6 @@ function xresources.get_current_theme()
 end
 
 
-local dpi_per_screen = {}
-
 local function get_screen(s)
     return s and screen[s]
 end
@@ -75,8 +73,8 @@ end
 -- @treturn number DPI value.
 function xresources.get_dpi(s)
     s = get_screen(s)
-    if dpi_per_screen[s] then
-        return dpi_per_screen[s]
+    if s then
+        return s.dpi
     end
     if not xresources.dpi then
         -- Might not be present when run under unit tests
@@ -115,7 +113,7 @@ function xresources.set_dpi(dpi, s)
     if not s then
         xresources.dpi = dpi
     else
-        dpi_per_screen[s] = dpi
+        s.dpi = dpi
     end
 end
 
diff --git a/lib/wibox/drawable.lua b/lib/wibox/drawable.lua
index e3e3eb50..cf9a129e 100644
--- a/lib/wibox/drawable.lua
+++ b/lib/wibox/drawable.lua
@@ -44,7 +44,7 @@ local function get_widget_context(self)
     end
 
     local context = self._widget_context
-    local dpi = beautiful.xresources.get_dpi(s)
+    local dpi = s.dpi
     if (not context) or context.screen ~= s or context.dpi ~= dpi then
         context = {
             screen = s,
diff --git a/lib/wibox/widget/textbox.lua b/lib/wibox/widget/textbox.lua
index 87039d88..628dccd8 100644
--- a/lib/wibox/widget/textbox.lua
+++ b/lib/wibox/widget/textbox.lua
@@ -73,7 +73,7 @@ end
 -- @treturn number The preferred width.
 -- @treturn number The preferred height.
 function textbox:get_preferred_size(s)
-    return self:get_preferred_size_at_dpi(beautiful.xresources.get_dpi(s))
+    return self:get_preferred_size_at_dpi(screen[s].dpi)
 end
 
 --- Get the preferred height of a textbox at a given width.
@@ -83,7 +83,7 @@ end
 -- @tparam integer|screen s The screen on which the textbox will be displayed.
 -- @treturn number The needed height.
 function textbox:get_height_for_width(width, s)
-    return self:get_height_for_width_at_dpi(width, beautiful.xresources.get_dpi(s))
+    return self:get_height_for_width_at_dpi(width, screen[s].dpi)
 end
 
 --- Get the preferred size of a textbox.