From 2facbe0d535733a4011a394f77ccdfba3d6a0c61 Mon Sep 17 00:00:00 2001
From: Paul Licameli <paul.licameli@audacityteam.org>
Date: Sun, 6 Jun 2021 08:15:35 -0400
Subject: [PATCH] Define BasicUI::WindowPlacement and subclass for wxWidgets...

... An elaborate way to hold a wxWindow* as parent of a window, but avoiding
mention of wxWindow* in the member functions of BasicUI::Services, to be defined
next
---
 libraries/lib-basic-ui/BasicUI.cpp |  2 ++
 libraries/lib-basic-ui/BasicUI.h   | 14 ++++++++++++++
 src/widgets/wxWidgetsBasicUI.cpp   | 12 ++++++++++++
 src/widgets/wxWidgetsBasicUI.h     | 14 ++++++++++++++
 4 files changed, 42 insertions(+)

diff --git a/libraries/lib-basic-ui/BasicUI.cpp b/libraries/lib-basic-ui/BasicUI.cpp
index bd5ab3db27..aa5fe38900 100644
--- a/libraries/lib-basic-ui/BasicUI.cpp
+++ b/libraries/lib-basic-ui/BasicUI.cpp
@@ -13,6 +13,8 @@ Paul Licameli
 #include <vector>
 
 namespace  BasicUI {
+WindowPlacement::~WindowPlacement() = default;
+
 Services::~Services() = default;
 
 static Services *theInstance = nullptr;
diff --git a/libraries/lib-basic-ui/BasicUI.h b/libraries/lib-basic-ui/BasicUI.h
index ff1ac2a284..26802d0e6d 100644
--- a/libraries/lib-basic-ui/BasicUI.h
+++ b/libraries/lib-basic-ui/BasicUI.h
@@ -20,6 +20,20 @@ namespace BasicUI {
 
 using Action = std::function<void()>;
 
+//! Subclasses may hold information such as a parent window pointer for a dialog.
+/*! The default-constructed empty value of this base class must be accepted by overrides of methods of
+ Services */
+class BASIC_UI_API WindowPlacement {
+public:
+   WindowPlacement() = default;
+
+   //! Don't slice
+   WindowPlacement( const WindowPlacement& ) PROHIBITED;
+   //! Don't slice
+   WindowPlacement &operator=( const WindowPlacement& ) PROHIBITED;
+   virtual ~WindowPlacement();
+};
+
 //! @}
 
 //! Abstract class defines a few user interface services, not mentioning particular toolkits
diff --git a/src/widgets/wxWidgetsBasicUI.cpp b/src/widgets/wxWidgetsBasicUI.cpp
index 25c9384d3d..3eb6cc0387 100644
--- a/src/widgets/wxWidgetsBasicUI.cpp
+++ b/src/widgets/wxWidgetsBasicUI.cpp
@@ -12,6 +12,8 @@ Paul Licameli
 
 using namespace BasicUI;
 
+wxWidgetsWindowPlacement::~wxWidgetsWindowPlacement() = default;
+
 wxWidgetsBasicUI::~wxWidgetsBasicUI() = default;
 
 void wxWidgetsBasicUI::DoCallAfter(const Action &action)
@@ -23,3 +25,13 @@ void wxWidgetsBasicUI::DoYield()
 {
    wxTheApp->Yield();
 }
+
+namespace {
+wxWindow *GetParent(const BasicUI::WindowPlacement &placement)
+{
+   if (auto *pPlacement =
+       dynamic_cast<const wxWidgetsWindowPlacement*>(&placement))
+      return pPlacement->pWindow;
+   return nullptr;
+}
+}
diff --git a/src/widgets/wxWidgetsBasicUI.h b/src/widgets/wxWidgetsBasicUI.h
index d203a045eb..9973110b7f 100644
--- a/src/widgets/wxWidgetsBasicUI.h
+++ b/src/widgets/wxWidgetsBasicUI.h
@@ -13,6 +13,20 @@ Paul Licameli
 
 #include "BasicUI.h"
 
+class wxWindow;
+
+//! Window placement information for wxWidgetsBasicUI can be constructed from a wxWindow pointer
+struct AUDACITY_DLL_API wxWidgetsWindowPlacement final
+: BasicUI::WindowPlacement {
+   wxWidgetsWindowPlacement() = default;
+   explicit wxWidgetsWindowPlacement( wxWindow *pWindow )
+      : pWindow{ pWindow }
+   {}
+
+   ~wxWidgetsWindowPlacement() override;
+   wxWindow *pWindow{};
+};
+
 //! An implementation of BasicUI::Services in terms of the wxWidgets toolkit
 /*! This is a singleton that doesn't need AUDACITY_DLL_API visibility */
 class wxWidgetsBasicUI final : public BasicUI::Services {