From 0d00185d9f1c83084b9d438c3c8819e74d7fe8fb Mon Sep 17 00:00:00 2001
From: AlexxxRu <IceAlexxx@gmail.com>
Date: Thu, 27 Jan 2022 00:04:24 +0300
Subject: [PATCH] Bugfix/drag window (#1108)

Call .drag_window() only after Left mouse btn clicked

Co-authored-by: Emil Ernerfeldt <emil.ernerfeldt@gmail.com>
---
 CHANGELOG.md            |  2 ++
 egui-winit/CHANGELOG.md |  1 +
 egui-winit/src/epi.rs   | 22 ++++++++++++++++------
 3 files changed, 19 insertions(+), 6 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 69ad2f99..494412e7 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -38,10 +38,12 @@ NOTE: [`epaint`](epaint/CHANGELOG.md), [`eframe`](eframe/CHANGELOG.md), [`egui_w
 ### Fixed 🐛
 * Context menu now respects the theme ([#1043](https://github.com/emilk/egui/pull/1043))
 * Plot `Orientation` was not public, although fields using this type were ([#1130](https://github.com/emilk/egui/pull/1130))
+* Fixed `enable_drag` for Windows ([#1108](https://github.com/emilk/egui/pull/1108)).
 
 ### Contributors 🙏
 * [danielkeller](https://github.com/danielkeller): [#1050](https://github.com/emilk/egui/pull/1050).
 * [juancampa](https://github.com/juancampa): [#1147](https://github.com/emilk/egui/pull/1147).
+* [AlexxxRu](https://github.com/alexxxru): [#1108](https://github.com/emilk/egui/pull/1108).
 
 
 ## 0.16.1 - 2021-12-31 - Add back `CtxRef::begin_frame,end_frame`
diff --git a/egui-winit/CHANGELOG.md b/egui-winit/CHANGELOG.md
index 258e6a85..426fbc6a 100644
--- a/egui-winit/CHANGELOG.md
+++ b/egui-winit/CHANGELOG.md
@@ -8,6 +8,7 @@ All notable changes to the `egui-winit` integration will be noted in this file.
 * Replaced `std::time::Instant` with `instant::Instant` for WebAssembly compatability ([#1023](https://github.com/emilk/egui/pull/1023))
 * Shift-scroll will now result in horizontal scrolling on all platforms ([#1136](https://github.com/emilk/egui/pull/1136)).
 * Require knowledge about max texture side (e.g. `GL_MAX_TEXTURE_SIZE`)) ([#1154](https://github.com/emilk/egui/pull/1154)).
+* Fixed `enable_drag` for Windows. Now called only once just after left click ([#1108](https://github.com/emilk/egui/pull/1108)).
 
 
 ## 0.16.0 - 2021-12-29
diff --git a/egui-winit/src/epi.rs b/egui-winit/src/epi.rs
index 46f0eed1..f9eeaece 100644
--- a/egui-winit/src/epi.rs
+++ b/egui-winit/src/epi.rs
@@ -193,6 +193,7 @@ pub struct EpiIntegration {
     pub app: Box<dyn epi::App>,
     /// When set, it is time to quit
     quit: bool,
+    can_drag_window: bool,
 }
 
 impl EpiIntegration {
@@ -227,6 +228,7 @@ impl EpiIntegration {
             egui_winit: crate::State::new(max_texture_side, window),
             app,
             quit: false,
+            can_drag_window: false,
         };
 
         slf.setup(window);
@@ -264,11 +266,17 @@ impl EpiIntegration {
     }
 
     pub fn on_event(&mut self, event: &winit::event::WindowEvent<'_>) {
-        use winit::event::WindowEvent;
-        if *event == WindowEvent::CloseRequested {
-            self.quit = self.app.on_exit_event();
-        } else if *event == WindowEvent::Destroyed {
-            self.quit = true;
+        use winit::event::{ElementState, MouseButton, WindowEvent};
+
+        match event {
+            WindowEvent::CloseRequested => self.quit = self.app.on_exit_event(),
+            WindowEvent::Destroyed => self.quit = true,
+            WindowEvent::MouseInput {
+                button: MouseButton::Left,
+                state: ElementState::Pressed,
+                ..
+            } => self.can_drag_window = true,
+            _ => {}
         }
 
         self.egui_winit.on_event(&self.egui_ctx, event);
@@ -291,7 +299,9 @@ impl EpiIntegration {
             .egui_winit
             .handle_output(window, &self.egui_ctx, egui_output);
 
-        let app_output = self.frame.take_app_output();
+        let mut app_output = self.frame.take_app_output();
+        app_output.drag_window &= self.can_drag_window; // Necessary on Windows; see https://github.com/emilk/egui/pull/1108
+        self.can_drag_window = false;
 
         if app_output.quit {
             self.quit = self.app.on_exit_event();