From 28250c4dca108ca65e90c99ccbca66d101766a48 Mon Sep 17 00:00:00 2001
From: Tarek Ismail <tarek.ismail@canonical.com>
Date: Fri, 6 Dec 2024 18:06:47 +0200
Subject: [PATCH] Hack around alt+tab for focus stealing prevented apps.

---
 src/miral/application_selector.cpp | 13 +++++++++----
 src/miral/basic_window_manager.cpp | 12 +++++++++++-
 src/miral/mru_window_list.cpp      |  9 +++++++++
 src/miral/mru_window_list.h        |  1 +
 4 files changed, 30 insertions(+), 5 deletions(-)

diff --git a/src/miral/application_selector.cpp b/src/miral/application_selector.cpp
index 1d4e8d5de5b..3a50e4ea606 100644
--- a/src/miral/application_selector.cpp
+++ b/src/miral/application_selector.cpp
@@ -19,6 +19,7 @@
 #include <miral/application.h>
 #include <mir/log.h>
 #include <mir/scene/session.h>
+#include <unordered_set>
 
 using namespace miral;
 
@@ -212,6 +213,7 @@ auto ApplicationSelector::advance(bool reverse, bool within_app) -> Window
     auto it = find(selected);
 
     std::optional<Window> next_window = std::nullopt;
+    auto should_continue = true;
     do {
         if (reverse)
         {
@@ -236,9 +238,10 @@ auto ApplicationSelector::advance(bool reverse, bool within_app) -> Window
         if (within_app)
         {
             if (it->application() == (*originally_selected_it).application() && tools.can_select_window(*it))
+            {
                 next_window = *it;
-            else
-                next_window = std::nullopt;
+                should_continue = false;
+            }
         }
         else
         {
@@ -251,15 +254,17 @@ auto ApplicationSelector::advance(bool reverse, bool within_app) -> Window
 
                 if (prev_it->application() == it->application())
                 {
-                    next_window = std::nullopt;
                     already_encountered = true;
                     break;
                 }
             }
             if (!already_encountered)
+            {
                 next_window = tools.window_to_select_application(it->application());
+                should_continue = !next_window.has_value();
+            }
         }
-    } while (next_window == std::nullopt);
+    } while (should_continue);
 
     if (next_window == std::nullopt)
         return selected;
diff --git a/src/miral/basic_window_manager.cpp b/src/miral/basic_window_manager.cpp
index c4490d0e38c..b2a1cba04b9 100644
--- a/src/miral/basic_window_manager.cpp
+++ b/src/miral/basic_window_manager.cpp
@@ -196,6 +196,16 @@ void miral::BasicWindowManager::surface_ready(std::shared_ptr<scene::Surface> co
 {
     Locker lock{this};
     policy->handle_window_ready(info_for(surface));
+
+    // Need to push onto the MRU list for alt+tab to work correctly.
+    //
+    // Originally, applications were pushed only when selected, but due to
+    // focus stealing prevention, they were not activated and thus weren't
+    // selected nor added to mru_active_windows, breaking alt+tab
+    auto window = info_for(surface).window();
+    auto const top = mru_active_windows.top();
+    if(top && top != window)
+        mru_active_windows.push_unfocused(window);
 }
 
 void miral::BasicWindowManager::modify_surface(
@@ -2993,4 +3003,4 @@ void miral::BasicWindowManager::move_cursor_to(mir::geometry::PointF point)
             sink->handle_input(std::move(event));
         });
     });
-}
\ No newline at end of file
+}
diff --git a/src/miral/mru_window_list.cpp b/src/miral/mru_window_list.cpp
index 1ee0b7b5832..25c63ae79e6 100644
--- a/src/miral/mru_window_list.cpp
+++ b/src/miral/mru_window_list.cpp
@@ -35,6 +35,15 @@ void miral::MRUWindowList::push(Window const& window)
     windows.push_back(window);
 }
 
+void miral::MRUWindowList::push_unfocused(Window const& window)
+{
+    windows.erase(remove(begin(windows), end(windows), window), end(windows));
+    if(!windows.empty())
+        windows.insert(windows.end()-1, window);
+    else
+        windows.push_back(window);
+}
+
 void miral::MRUWindowList::erase(Window const& window)
 {
     windows.erase(remove(begin(windows), end(windows), window), end(windows));
diff --git a/src/miral/mru_window_list.h b/src/miral/mru_window_list.h
index fc799f17a2e..132838a713c 100644
--- a/src/miral/mru_window_list.h
+++ b/src/miral/mru_window_list.h
@@ -29,6 +29,7 @@ class MRUWindowList
 public:
 
     void push(Window const& window);
+    void push_unfocused(Window const& window);
     void erase(Window const& window);
     auto top() const -> Window;