From 0db15ecaf46bcb04f6c6156e34668f36fc5e7c16 Mon Sep 17 00:00:00 2001
From: Wez Furlong <wez@wezfurlong.org>
Date: Thu, 2 Jan 2020 11:01:41 -0800
Subject: [PATCH] wayland: fix spurious resize event on focus change

The resize event would be fine except that it happens to trigger
the scroll position to reset to the bottom.
---
 window/src/lib.rs               |  2 +-
 window/src/os/wayland/window.rs | 19 ++++++++++++-------
 2 files changed, 13 insertions(+), 8 deletions(-)

diff --git a/window/src/lib.rs b/window/src/lib.rs
index b8c1dbd5e..d4e9ee6db 100644
--- a/window/src/lib.rs
+++ b/window/src/lib.rs
@@ -48,7 +48,7 @@ pub enum Operator {
     MultiplyThenOver(Color),
 }
 
-#[derive(Debug, Clone, Copy)]
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
 pub struct Dimensions {
     pub pixel_width: usize,
     pub pixel_height: usize,
diff --git a/window/src/os/wayland/window.rs b/window/src/os/wayland/window.rs
index 344e13300..1bf3a81bf 100644
--- a/window/src/os/wayland/window.rs
+++ b/window/src/os/wayland/window.rs
@@ -454,18 +454,23 @@ impl WaylandWindowInner {
                 // Update the window decoration size
                 self.window.as_mut().unwrap().resize(w, h);
 
-                // Store the new pixel dimensions
-                self.dimensions = Dimensions {
+                // Compute the new pixel dimensions
+                let new_dimensions = Dimensions {
                     pixel_width: pixel_width.try_into().unwrap(),
                     pixel_height: pixel_height.try_into().unwrap(),
                     dpi: factor as usize * 96,
                 };
+                // Only trigger a resize if the new dimensions are different;
+                // this makes things more efficient and a little more smooth
+                if new_dimensions != self.dimensions {
+                    self.dimensions = new_dimensions;
 
-                self.callbacks.resize(self.dimensions);
-                #[cfg(feature = "opengl")]
-                {
-                    if let Some(wegl_surface) = self.wegl_surface.as_mut() {
-                        wegl_surface.resize(pixel_width, pixel_height, 0, 0);
+                    self.callbacks.resize(self.dimensions);
+                    #[cfg(feature = "opengl")]
+                    {
+                        if let Some(wegl_surface) = self.wegl_surface.as_mut() {
+                            wegl_surface.resize(pixel_width, pixel_height, 0, 0);
+                        }
                     }
                 }