From 9648b40d855b0dc6212af761842f0f59803ea7f1 Mon Sep 17 00:00:00 2001
From: dbr <dbr.onix@gmail.com>
Date: Sat, 19 Mar 2022 21:03:52 +1100
Subject: [PATCH] Handle window focus lost event

Avoids keys getting stuck when window loses focus (e.g alt+tab)

Closes #602
---
 imgui-winit-support/src/lib.rs | 23 ++++++++++++++++++++++-
 imgui/src/io.rs                |  2 +-
 2 files changed, 23 insertions(+), 2 deletions(-)

diff --git a/imgui-winit-support/src/lib.rs b/imgui-winit-support/src/lib.rs
index 3c2c65d..c733b80 100644
--- a/imgui-winit-support/src/lib.rs
+++ b/imgui-winit-support/src/lib.rs
@@ -941,7 +941,14 @@ impl WinitPlatform {
                     }
                     _ => (),
                 }
-            }
+            },
+            WindowEvent::Focused(newly_focused) => {
+                if !newly_focused {
+                    // Set focus-lost to avoid stuck keys (like 'alt'
+                    // when alt-tabbing)
+                    io.app_focus_lost = true;
+                }
+            },
             _ => (),
         }
     }
@@ -1052,6 +1059,13 @@ impl WinitPlatform {
                     _ => (),
                 }
             }
+            WindowEvent::Focused(newly_focused) => {
+                if !newly_focused {
+                    // Set focus-lost to avoid stuck keys (like 'alt'
+                    // when alt-tabbing)
+                    io.app_focus_lost = true;
+                }
+            }
             _ => (),
         }
     }
@@ -1161,6 +1175,13 @@ impl WinitPlatform {
                     _ => (),
                 }
             }
+            WindowEvent::Focused(newly_focused) => {
+                if !newly_focused {
+                    // Set focus-lost to avoid stuck keys (like 'alt'
+                    // when alt-tabbing)
+                    io.app_focus_lost = true;
+                }
+            }
             _ => (),
         }
     }
diff --git a/imgui/src/io.rs b/imgui/src/io.rs
index 2362c31..4bf8ba1 100644
--- a/imgui/src/io.rs
+++ b/imgui/src/io.rs
@@ -339,7 +339,7 @@ pub struct Io {
     nav_inputs_down_duration: [f32; NavInput::COUNT + NavInput::INTERNAL_COUNT],
     nav_inputs_down_duration_prev: [f32; NavInput::COUNT + NavInput::INTERNAL_COUNT],
     pen_pressure: f32,
-    app_focus_lost: bool,
+    pub app_focus_lost: bool,
     input_queue_surrogate: sys::ImWchar16,
     input_queue_characters: ImVector<sys::ImWchar>,
 }