previewing too is good

src/cascadia/TerminalApp/ActionPreviewHandlers.cpp

@@ -49,8 +49,9 @@ namespace winrt::TerminalApp::implementation
         switch (_lastPreviewedCommand.ActionAndArgs().Action())
         {
         case ShortcutAction::SetColorScheme:
+        case ShortcutAction::AdjustOpacity:
         {
-            _EndPreviewColorScheme();
+            _RunRestorePreviews();
             break;
         }
         }
@@ -65,7 +66,7 @@ namespace winrt::TerminalApp::implementation
     // - <none>
     // Return Value:
     // - <none>
-    void TerminalPage::_EndPreviewColorScheme()
+    void TerminalPage::_RunRestorePreviews()
     {
         for (const auto& f : _restorePreviewFuncs)
         {
@@ -109,6 +110,30 @@ namespace winrt::TerminalApp::implementation
         }
     }
 
+    void TerminalPage::_PreviewAdjustOpacity(const Settings::Model::AdjustOpacityArgs& args)
+    {
+        // if (const auto& scheme{ _settings.GlobalSettings().ColorSchemes().TryLookup(args.SchemeName()) })
+        // {
+        // Clear the saved preview funcs because we don't need to add a restore each time
+        // the preview color changes, we only need to be able to restore the last one.
+        _restorePreviewFuncs.clear();
+
+        _ApplyToActiveControls([&](const auto& control) {
+            // Stash a copy of the original scheme.
+            auto originalOpacity{ control.BackgroundOpacity() };
+
+            // Apply the new opacity
+            control.AdjustOpacity(args.Opacity(), args.Relative());
+
+            _restorePreviewFuncs.emplace_back([=]() {
+                // On dismiss:
+                // Don't adjust relatively, just set outright.
+                control.AdjustOpacity(::base::saturated_cast<int>(originalOpacity*100), false);
+            });
+        });
+        // }
+    }
+
     // Method Description:
     // - Handler for the CommandPalette::PreviewAction event. The Command
     //   Palette will raise this even when an action is selected, but _not_
@@ -140,6 +165,11 @@ namespace winrt::TerminalApp::implementation
                 _PreviewColorScheme(args.ActionAndArgs().Args().try_as<SetColorSchemeArgs>());
                 break;
             }
+            case ShortcutAction::AdjustOpacity:
+            {
+                _PreviewAdjustOpacity(args.ActionAndArgs().Args().try_as<AdjustOpacityArgs>());
+                break;
+            }
             }
 
             // GH#9818 Other ideas for actions that could be preview-able:

src/cascadia/TerminalApp/TerminalPage.h

@@ -383,8 +383,9 @@ namespace winrt::TerminalApp::implementation
 
         void _PreviewActionHandler(const IInspectable& sender, const Microsoft::Terminal::Settings::Model::Command& args);
         void _EndPreview();
-        void _EndPreviewColorScheme();
+        void _RunRestorePreviews();
         void _PreviewColorScheme(const Microsoft::Terminal::Settings::Model::SetColorSchemeArgs& args);
+        void _PreviewAdjustOpacity(const Microsoft::Terminal::Settings::Model::AdjustOpacityArgs& args);
         winrt::Microsoft::Terminal::Settings::Model::Command _lastPreviewedCommand{ nullptr };
         std::vector<std::function<void()>> _restorePreviewFuncs{};
 

src/cascadia/TerminalControl/ICoreState.idl

@@ -24,5 +24,6 @@ namespace Microsoft.Terminal.Control
         Microsoft.Terminal.TerminalConnection.ConnectionState ConnectionState { get; };
 
         Microsoft.Terminal.Core.Scheme ColorScheme { get; set; };
+
     };
 }

src/cascadia/TerminalControl/TermControl.cpp

@@ -2658,4 +2658,12 @@ namespace winrt::Microsoft::Terminal::Control::implementation
         _core.AdjustOpacity(opacity, relative);
     }
 
+    // - You'd think this should just be "Opacity", but UIElement already
+    //   defines an "Opacity", which we're actually not setting at all. We're
+    //   not overriding or changing _that_ value. Callers that want the opacity
+    //   set by the settings should call this instead.
+    double TermControl::BackgroundOpacity() const
+    {
+        return _core.Opacity();
+    }
 }

src/cascadia/TerminalControl/TermControl.h

@@ -58,6 +58,8 @@ namespace winrt::Microsoft::Terminal::Control::implementation
         int BufferHeight() const;
 
         bool BracketedPasteEnabled() const noexcept;
+
+        double BackgroundOpacity() const;
 #pragma endregion
 
         void ScrollViewport(int viewTop);

src/cascadia/TerminalControl/TermControl.idl

@@ -74,5 +74,12 @@ namespace Microsoft.Terminal.Control
         String ReadEntireBuffer();
 
         void AdjustOpacity(Int32 Opacity, Boolean relative);
+
+        // You'd think this should just be "Opacity", but UIElement already
+        // defines an "Opacity", which we're actually not setting at all. We're
+        // not overriding or changing _that_ value. Callers that want the
+        // opacity set by the settings should call this instead.
+        Double BackgroundOpacity { get; };
+
     }
 }