From 51d98d36f5a366a2c80a08469da18a4438834c9d Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Michal=20Hornick=C3=BD?= <semtexzv@gmail.com>
Date: Thu, 19 Jul 2018 09:08:21 +0200
Subject: [PATCH 1/3] [x11-backend] Retrieve DPI from Xft.dpi XResource

---
 src/platform/linux/x11/util/randr.rs | 31 ++++++++++++++++++++++++----
 1 file changed, 27 insertions(+), 4 deletions(-)

diff --git a/src/platform/linux/x11/util/randr.rs b/src/platform/linux/x11/util/randr.rs
index f0b69d9b94..db0e002875 100644
--- a/src/platform/linux/x11/util/randr.rs
+++ b/src/platform/linux/x11/util/randr.rs
@@ -79,6 +79,24 @@ impl From<*mut ffi::XRRCrtcInfo> for MonitorRepr {
 }
 
 impl XConnection {
+    // Retrieve DPI from Xft.dpi property
+    pub unsafe fn get_xft_dpi(&self) -> Option<f64> {
+        (self.xlib.XrmInitialize)();
+        let resource_manager_str = (self.xlib.XResourceManagerString)(self.display);
+        if resource_manager_str == ptr::null_mut() {
+            return None;
+        }
+        if let Ok(res) = ::std::ffi::CStr::from_ptr(resource_manager_str).to_str() {
+            let name : &str = "Xft.dpi:\t";
+            for pair in res.split("\n") {
+                if pair.starts_with(&name) {
+                    let res = &pair[name.len()..];
+                    return f64::from_str(&res).ok();
+                }
+            }
+        }
+        None
+    }
     pub unsafe fn get_output_info(&self, resources: *mut ffi::XRRScreenResources, repr: &MonitorRepr) -> (String, f64) {
         let output_info = (self.xrandr.XRRGetOutputInfo)(
             self.display,
@@ -90,10 +108,15 @@ impl XConnection {
             (*output_info).nameLen as usize,
         );
         let name = String::from_utf8_lossy(name_slice).into();
-        let hidpi_factor = calc_dpi_factor(
-            repr.get_dimensions(),
-            ((*output_info).mm_width as u64, (*output_info).mm_height as u64),
-        );
+        let hidpi_factor = if let Some(dpi) = self.get_xft_dpi() {
+            dpi / 96.
+        } else {
+            calc_dpi_factor(
+                repr.get_dimensions(),
+                ((*output_info).mm_width as u64, (*output_info).mm_height as u64),
+            )
+        };
+
         (self.xrandr.XRRFreeOutputInfo)(output_info);
         (name, hidpi_factor)
     }

From 209789469af806912b0c962fef53cadf0e7e20fc Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Michal=20Hornick=C3=BD?= <semtexzv@gmail.com>
Date: Thu, 19 Jul 2018 09:19:00 +0200
Subject: [PATCH 2/3] Update CHANGELOG.md

---
 CHANGELOG.md | 1 +
 1 file changed, 1 insertion(+)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 6e6c4bfdba..2a60f3882c 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,6 +2,7 @@
 
 - On iOS, the view is now set correctly. This makes it possible to render things (instead of being stuck on a black screen), and touch events work again.
 - Added NetBSD support.
+- X11 - Dpi scaling factor behavior changed. First, winit tries to read it from "Xft.dpi" XResource, and uses DPI calculation from xrandr dimensions as fallback behavior.
 
 # Version 0.16.2 (2018-07-07)
 

From 13dd191fccba3fc22d05ac7bdd97968bfb42fb28 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Michal=20Hornick=C3=BD?= <semtexzv@gmail.com>
Date: Thu, 19 Jul 2018 09:21:04 +0200
Subject: [PATCH 3/3] Update window.rs

---
 src/window.rs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/window.rs b/src/window.rs
index cf36044880..1bc0dbf618 100644
--- a/src/window.rs
+++ b/src/window.rs
@@ -485,7 +485,7 @@ impl MonitorId {
     ///
     /// ## Platform-specific
     ///
-    /// - **X11:** Can be overridden using the `WINIT_HIDPI_FACTOR` environment variable.
+    /// - **X11:** This respects Xft.dpi XResource, and can be overridden using the `WINIT_HIDPI_FACTOR` environment variable.
     /// - **Android:** Always returns 1.0.
     #[inline]
     pub fn get_hidpi_factor(&self) -> f64 {