Only iterate panes one time when updating settings

src/cascadia/TerminalApp/Pane.cpp

@@ -1049,48 +1049,32 @@ void Pane::_FocusFirstChild()
 }
 
 // Method Description:
-// - Attempts to update the settings of this pane or any children of this pane.
-//   * If this pane is a leaf, and our profile guid matches the parameter, then
-//     we'll apply the new settings to our control.
-//   * If we're not a leaf, we'll recurse on our children.
+// - Updates the settings of this pane, presuming that it is a leaf.
 // Arguments:
 // - settings: The new TerminalSettings to apply to any matching controls
 // - profile: The profile from which these settings originated.
 // Return Value:
 // - <none>
 void Pane::UpdateSettings(const TerminalSettingsCreateResult& settings, const Profile& profile)
 {
-    if (!_IsLeaf())
-    {
-        _firstChild->UpdateSettings(settings, profile);
-        _secondChild->UpdateSettings(settings, profile);
-    }
-    else
+    assert(_IsLeaf());
+
+    _profile = profile;
+    auto controlSettings = _control.Settings().as<TerminalSettings>();
+    // Update the parent of the control's settings object (and not the object itself) so
+    // that any overrides made by the control don't get affected by the reload
+    controlSettings.SetParent(settings.DefaultSettings());
+    auto unfocusedSettings{ settings.UnfocusedSettings() };
+    if (unfocusedSettings)
     {
-        // Because this call may be coming in with a different settings tree,
-        // we want to map the incoming profile based on its GUID.
-        // Failure to find a matching profile will result in a pane holding
-        // a reference to a deleted profile (which is okay!).
-        if (profile.Guid() == _profile.Guid())
-        {
-            _profile = profile;
-            auto controlSettings = _control.Settings().as<TerminalSettings>();
-            // Update the parent of the control's settings object (and not the object itself) so
-            // that any overrides made by the control don't get affected by the reload
-            controlSettings.SetParent(settings.DefaultSettings());
-            auto unfocusedSettings{ settings.UnfocusedSettings() };
-            if (unfocusedSettings)
-            {
-                // Note: the unfocused settings needs to be entirely unchanged _except_ we need to
-                // set its parent to the settings object that lives in the control. This is because
-                // the overrides made by the control live in that settings object, so we want to make
-                // sure the unfocused settings inherit from that.
-                unfocusedSettings.SetParent(controlSettings);
-            }
-            _control.UnfocusedAppearance(unfocusedSettings);
-            _control.UpdateSettings();
-        }
+        // Note: the unfocused settings needs to be entirely unchanged _except_ we need to
+        // set its parent to the settings object that lives in the control. This is because
+        // the overrides made by the control live in that settings object, so we want to make
+        // sure the unfocused settings inherit from that.
+        unfocusedSettings.SetParent(controlSettings);
     }
+    _control.UnfocusedAppearance(unfocusedSettings);
+    _control.UpdateSettings();
 }
 
 // Method Description:

src/cascadia/TerminalApp/Pane.h

@@ -55,6 +55,14 @@ class Pane : public std::enable_shared_from_this<Pane>
     winrt::Microsoft::Terminal::Control::TermControl GetTerminalControl();
     winrt::Microsoft::Terminal::Settings::Model::Profile GetFocusedProfile();
 
+    // Method Description:
+    // - If this is a leaf pane, return its profile.
+    // - If this is a branch/root pane, return nullptr.
+    winrt::Microsoft::Terminal::Settings::Model::Profile GetProfile() const
+    {
+        return _profile;
+    }
+
     winrt::Windows::UI::Xaml::Controls::Grid GetRootElement();
 
     bool WasLastFocused() const noexcept;

src/cascadia/TerminalApp/TerminalPage.cpp

@@ -1996,36 +1996,56 @@ namespace winrt::TerminalApp::implementation
         _HookupKeyBindings(_settings.ActionMap());
 
         // Refresh UI elements
-        auto profiles = _settings.ActiveProfiles();
-        for (const auto& profile : profiles)
+
+        // Mapping by GUID isn't _excellent_ because the defaults profile doesn't have a stable GUID; however,
+        // when we stabilize its guid this will become fully safe.
+        std::unordered_map<winrt::guid, std::pair<Profile, TerminalSettingsCreateResult>> profileGuidSettingsMap;
+        const auto profileDefaults{ _settings.ProfileDefaults() };
+        const auto allProfiles{ _settings.AllProfiles() };
+
+        profileGuidSettingsMap.reserve(allProfiles.Size() + 1);
+
+        // Include the Defaults profile for consideration
+        profileGuidSettingsMap.insert_or_assign(profileDefaults.Guid(), std::pair{ profileDefaults, nullptr });
+        for (const auto& newProfile : allProfiles)
         {
-            try
+            // Avoid creating a TerminalSettings right now. They're not totally cheap, and we suspect that users with many
+            // panes may not be using all of their profiles at the same time. Lazy evaluation is king!
+            profileGuidSettingsMap.insert_or_assign(newProfile.Guid(), std::pair{ newProfile, nullptr });
+        }
+
+        for (const auto& tab : _tabs)
+        {
+            if (auto terminalTab{ _GetTerminalTabImpl(tab) })
             {
-                auto settings{ TerminalSettings::CreateWithProfile(_settings, profile, *_bindings) };
+                terminalTab->UpdateSettings();
 
-                for (auto tab : _tabs)
-                {
-                    if (auto terminalTab = _GetTerminalTabImpl(tab))
+                // Manually enumerate the panes in each tab; this will let us recycle TerminalSettings
+                // objects but only have to iterate one time.
+                terminalTab->GetRootPane()->WalkTree([&](auto&& pane) {
+                    if (const auto profile{ pane->GetProfile() })
                     {
-                        terminalTab->UpdateSettings(settings, profile);
+                        const auto found{ profileGuidSettingsMap.find(profile.Guid()) };
+                        // GH#2455: If there are any panes with controls that had been
+                        // initialized with a Profile that no longer exists in our list of
+                        // profiles, we'll leave it unmodified. The profile doesn't exist
+                        // anymore, so we can't possibly update its settings.
+                        if (found != profileGuidSettingsMap.cend())
+                        {
+                            auto& pair{ found->second };
+                            if (!pair.second)
+                            {
+                                pair.second = TerminalSettings::CreateWithProfile(_settings, pair.first, *_bindings);
+                            }
+                            pane->UpdateSettings(pair.second, pair.first);
+                        }
                     }
-                }
-            }
-            CATCH_LOG();
-        }
-
-        // GH#2455: If there are any panes with controls that had been
-        // initialized with a Profile that no longer exists in our list of
-        // profiles, we'll leave it unmodified. The profile doesn't exist
-        // anymore, so we can't possibly update its settings.
+                    return false;
+                });
 
-        // Update the icon of the tab for the currently focused profile in that tab.
-        // Only do this for TerminalTabs. Other types of tabs won't have multiple panes
-        // and profiles so the Title and Icon will be set once and only once on init.
-        for (auto tab : _tabs)
-        {
-            if (auto terminalTab = _GetTerminalTabImpl(tab))
-            {
+                // Update the icon of the tab for the currently focused profile in that tab.
+                // Only do this for TerminalTabs. Other types of tabs won't have multiple panes
+                // and profiles so the Title and Icon will be set once and only once on init.
                 _UpdateTabIcon(*terminalTab);
 
                 // Force the TerminalTab to re-grab its currently active control's title.

src/cascadia/TerminalApp/TerminalTab.cpp

@@ -263,16 +263,13 @@ namespace winrt::TerminalApp::implementation
     }
 
     // Method Description:
-    // - Attempts to update the settings of this tab's tree of panes.
-    // Arguments:
-    // - settings: The new TerminalSettingsCreateResult to apply to any matching controls
-    // - profile: The GUID of the profile these settings should apply to.
+    // - Attempts to update the settings that apply to this tab.
+    // - Panes are handled elsewhere, by somebody who can establish broader knowledge
+    //   of the settings that apply to all tabs.
     // Return Value:
     // - <none>
-    void TerminalTab::UpdateSettings(const TerminalSettingsCreateResult& settings, const Profile& profile)
+    void TerminalTab::UpdateSettings()
     {
-        _rootPane->UpdateSettings(settings, profile);
-
         // The tabWidthMode may have changed, update the header control accordingly
         _UpdateHeaderControlMaxWidth();
     }

src/cascadia/TerminalApp/TerminalTab.h

@@ -62,7 +62,7 @@ namespace winrt::TerminalApp::implementation
         bool SwapPane(const winrt::Microsoft::Terminal::Settings::Model::FocusDirection& direction);
         bool FocusPane(const uint32_t id);
 
-        void UpdateSettings(const Microsoft::Terminal::Settings::Model::TerminalSettingsCreateResult& settings, const winrt::Microsoft::Terminal::Settings::Model::Profile& profile);
+        void UpdateSettings();
         winrt::fire_and_forget UpdateTitle();
 
         void Shutdown() override;
@@ -90,6 +90,8 @@ namespace winrt::TerminalApp::implementation
         std::shared_ptr<Pane> GetActivePane() const;
         winrt::TerminalApp::TaskbarState GetCombinedTaskbarState() const;
 
+        std::shared_ptr<Pane> GetRootPane() const { return _rootPane; }
+
         winrt::TerminalApp::TerminalTabStatus TabStatus()
         {
             return _tabStatus;