Host: Add 'Auxiliary Render Windows'

i.e. debugging windows

src/duckstation-qt/displaywidget.cpp

@@ -465,3 +465,177 @@ bool DisplayContainer::event(QEvent* event)
 
   return res;
 }
+
+AuxiliaryDisplayWidget::AuxiliaryDisplayWidget(QWidget* parent, u32 width, u32 height, const QString& title,
+                                               void* userdata)
+  : QWidget(parent), m_userdata(userdata)
+{
+  // We want a native window for both D3D and OpenGL.
+  setAutoFillBackground(false);
+  setAttribute(Qt::WA_NativeWindow, true);
+  setAttribute(Qt::WA_NoSystemBackground, true);
+  setAttribute(Qt::WA_PaintOnScreen, true);
+  setAttribute(Qt::WA_KeyCompression, false);
+  setFocusPolicy(Qt::StrongFocus);
+  setMouseTracking(true);
+  setWindowTitle(title);
+  resize(width, height);
+}
+
+AuxiliaryDisplayWidget::~AuxiliaryDisplayWidget() = default;
+
+QPaintEngine* AuxiliaryDisplayWidget::paintEngine() const
+{
+  return nullptr;
+}
+
+bool AuxiliaryDisplayWidget::event(QEvent* event)
+{
+  const QEvent::Type type = event->type();
+  switch (type)
+  {
+    case QEvent::KeyPress:
+    case QEvent::KeyRelease:
+    {
+      g_emu_thread->queueAuxiliaryRenderWindowInputEvent(
+        m_userdata,
+        (type == QEvent::KeyPress) ? Host::AuxiliaryRenderWindowEvent::KeyPressed :
+                                     Host::AuxiliaryRenderWindowEvent::KeyReleased,
+        Host::AuxiliaryRenderWindowEventParam{.uint_param =
+                                                static_cast<u32>(static_cast<const QKeyEvent*>(event)->key())});
+
+      return true;
+    }
+
+    case QEvent::MouseMove:
+    {
+      const qreal dpr = QtUtils::GetDevicePixelRatioForWidget(this);
+      const QPoint mouse_pos = static_cast<QMouseEvent*>(event)->pos();
+      const float scaled_x = static_cast<float>(static_cast<qreal>(mouse_pos.x()) * dpr);
+      const float scaled_y = static_cast<float>(static_cast<qreal>(mouse_pos.y()) * dpr);
+
+      g_emu_thread->queueAuxiliaryRenderWindowInputEvent(
+        m_userdata, Host::AuxiliaryRenderWindowEvent::MouseMoved,
+        Host::AuxiliaryRenderWindowEventParam{.float_param = scaled_x},
+        Host::AuxiliaryRenderWindowEventParam{.float_param = scaled_y});
+
+      return true;
+    }
+
+    case QEvent::MouseButtonPress:
+    case QEvent::MouseButtonDblClick:
+    case QEvent::MouseButtonRelease:
+    {
+      const u32 button_index = CountTrailingZeros(static_cast<u32>(static_cast<const QMouseEvent*>(event)->button()));
+      g_emu_thread->queueAuxiliaryRenderWindowInputEvent(
+        m_userdata,
+        (type == QEvent::MouseButtonRelease) ? Host::AuxiliaryRenderWindowEvent::MouseReleased :
+                                               Host::AuxiliaryRenderWindowEvent::MousePressed,
+        Host::AuxiliaryRenderWindowEventParam{.uint_param = button_index},
+        Host::AuxiliaryRenderWindowEventParam{.uint_param = BoolToUInt32(type == QEvent::MouseButtonRelease)});
+
+      return true;
+    }
+
+    case QEvent::Wheel:
+    {
+      const QWheelEvent* wheel_event = static_cast<QWheelEvent*>(event);
+      const QPoint delta = wheel_event->angleDelta();
+      if (delta.x() != 0 || delta.y())
+      {
+        g_emu_thread->queueAuxiliaryRenderWindowInputEvent(
+          m_userdata, Host::AuxiliaryRenderWindowEvent::MouseWheel,
+          Host::AuxiliaryRenderWindowEventParam{.float_param = static_cast<float>(delta.x())},
+          Host::AuxiliaryRenderWindowEventParam{.float_param = static_cast<float>(delta.y())});
+      }
+
+      return true;
+    }
+
+    case QEvent::Close:
+    {
+      if (m_destroying)
+        return QWidget::event(event);
+
+      g_emu_thread->queueAuxiliaryRenderWindowInputEvent(m_userdata, Host::AuxiliaryRenderWindowEvent::CloseRequest);
+      event->ignore();
+      return true;
+    }
+
+    case QEvent::Paint:
+    case QEvent::Resize:
+    {
+      QWidget::event(event);
+
+      const float dpr = QtUtils::GetDevicePixelRatioForWidget(this);
+      const u32 scaled_width =
+        static_cast<u32>(std::max(static_cast<int>(std::ceil(static_cast<qreal>(width()) * dpr)), 1));
+      const u32 scaled_height =
+        static_cast<u32>(std::max(static_cast<int>(std::ceil(static_cast<qreal>(height()) * dpr)), 1));
+
+      // avoid spamming resize events for paint events (sent on move on windows)
+      if (m_last_window_width != scaled_width || m_last_window_height != scaled_height || m_last_window_scale != dpr)
+      {
+        m_last_window_width = scaled_width;
+        m_last_window_height = scaled_height;
+        m_last_window_scale = dpr;
+        g_emu_thread->queueAuxiliaryRenderWindowInputEvent(
+          m_userdata, Host::AuxiliaryRenderWindowEvent::Resized,
+          Host::AuxiliaryRenderWindowEventParam{.uint_param = scaled_width},
+          Host::AuxiliaryRenderWindowEventParam{.uint_param = scaled_height},
+          Host::AuxiliaryRenderWindowEventParam{.float_param = dpr});
+      }
+
+      return true;
+    }
+
+    default:
+      return QWidget::event(event);
+  }
+}
+
+AuxiliaryDisplayWidget* AuxiliaryDisplayWidget::create(s32 pos_x, s32 pos_y, u32 width, u32 height,
+                                                       const QString& title, const QString& icon_name, void* userdata)
+{
+  QStackedWidget* parent = nullptr;
+  if (DisplayContainer::isNeeded(false, false))
+  {
+    parent = new QStackedWidget(nullptr);
+    parent->resize(width, height);
+    parent->setWindowTitle(title);
+  }
+
+  AuxiliaryDisplayWidget* widget = new AuxiliaryDisplayWidget(parent, width, height, title, userdata);
+  if (parent)
+    parent->addWidget(widget);
+
+  QWidget* window = parent ? static_cast<QWidget*>(parent) : static_cast<QWidget*>(widget);
+  if (!icon_name.isEmpty())
+  {
+    if (const QIcon icon(icon_name); !icon.isNull())
+      window->setWindowIcon(icon);
+    else
+      window->setWindowIcon(QtHost::GetAppIcon());
+  }
+  else
+  {
+    window->setWindowIcon(QtHost::GetAppIcon());
+  }
+
+  if (pos_x != std::numeric_limits<s32>::min() && pos_y != std::numeric_limits<s32>::min())
+    window->move(pos_x, pos_y);
+
+  window->show();
+  return widget;
+}
+
+void AuxiliaryDisplayWidget::destroy()
+{
+  m_destroying = true;
+
+  QWidget* container = static_cast<QWidget*>(parent());
+  if (!container)
+    container = this;
+  container->close();
+  container->deleteLater();
+}

src/duckstation-qt/displaywidget.h

@@ -89,3 +89,28 @@ protected:
 private:
   DisplayWidget* m_display_widget = nullptr;
 };
+
+class AuxiliaryDisplayWidget final : public QWidget
+{
+  Q_OBJECT
+
+public:
+  explicit AuxiliaryDisplayWidget(QWidget* parent, u32 width, u32 height, const QString& title, void* userdata);
+  ~AuxiliaryDisplayWidget();
+
+  QPaintEngine* paintEngine() const override;
+
+  static AuxiliaryDisplayWidget* create(s32 pos_x, s32 pos_y, u32 width, u32 height, const QString& title,
+                                        const QString& icon_name, void* userdata);
+  void destroy();
+
+protected:
+  bool event(QEvent* event) override;
+
+private:
+  void* m_userdata = nullptr;
+  u32 m_last_window_width = 0;
+  u32 m_last_window_height = 0;
+  float m_last_window_scale = 1.0f;
+  bool m_destroying = false;
+};

src/duckstation-qt/mainwindow.cpp

@@ -2044,6 +2044,10 @@ void MainWindow::connectSignals()
   connect(g_emu_thread, &EmuThread::achievementsChallengeModeChanged, this,
           &MainWindow::onAchievementsChallengeModeChanged);
   connect(g_emu_thread, &EmuThread::onCoverDownloaderOpenRequested, this, &MainWindow::onToolsCoverDownloaderTriggered);
+  connect(g_emu_thread, &EmuThread::onCreateAuxiliaryRenderWindow, this, &MainWindow::onCreateAuxiliaryRenderWindow,
+          Qt::BlockingQueuedConnection);
+  connect(g_emu_thread, &EmuThread::onDestroyAuxiliaryRenderWindow, this, &MainWindow::onDestroyAuxiliaryRenderWindow,
+          Qt::BlockingQueuedConnection);
 
   // These need to be queued connections to stop crashing due to menus opening/closing and switching focus.
   connect(m_game_list_widget, &GameListWidget::refreshProgress, this, &MainWindow::onGameListRefreshProgress);
@@ -2642,6 +2646,36 @@ void MainWindow::onAchievementsChallengeModeChanged(bool enabled)
   updateEmulationActions(false, System::IsValid(), enabled);
 }
 
+bool MainWindow::onCreateAuxiliaryRenderWindow(qint32 x, qint32 y, quint32 width, quint32 height, const QString& title,
+                                               const QString& icon_name, Host::AuxiliaryRenderWindowUserData userdata,
+                                               Host::AuxiliaryRenderWindowHandle* handle, WindowInfo* wi, Error* error)
+{
+  AuxiliaryDisplayWidget* widget = AuxiliaryDisplayWidget::create(x, y, width, height, title, icon_name, userdata);
+  if (!widget)
+    return false;
+
+  const std::optional<WindowInfo> owi = QtUtils::GetWindowInfoForWidget(widget, error);
+  if (!owi.has_value())
+  {
+    widget->destroy();
+    return false;
+  }
+
+  *handle = widget;
+  *wi = owi.value();
+  return true;
+}
+
+void MainWindow::onDestroyAuxiliaryRenderWindow(Host::AuxiliaryRenderWindowHandle handle, QPoint* pos, QSize* size)
+{
+  AuxiliaryDisplayWidget* widget = static_cast<AuxiliaryDisplayWidget*>(handle);
+  DebugAssert(widget);
+
+  *pos = widget->pos();
+  *size = widget->size();
+  widget->destroy();
+}
+
 void MainWindow::onToolsMemoryCardEditorTriggered()
 {
   openMemoryCardEditor(QString(), QString());

src/duckstation-qt/mainwindow.h

@@ -10,6 +10,7 @@
 
 #include "core/types.h"
 
+#include "util/imgui_manager.h"
 #include "util/window_info.h"
 
 #include <QtCore/QThread>
@@ -144,6 +145,11 @@ private Q_SLOTS:
   void onMediaCaptureStopped();
   void onAchievementsLoginRequested(Achievements::LoginRequestReason reason);
   void onAchievementsChallengeModeChanged(bool enabled);
+  bool onCreateAuxiliaryRenderWindow(qint32 x, qint32 y, quint32 width, quint32 height, const QString& title,
+                                     const QString& icon_name, Host::AuxiliaryRenderWindowUserData userdata,
+                                     Host::AuxiliaryRenderWindowHandle* handle, WindowInfo* wi, Error* error);
+  void onDestroyAuxiliaryRenderWindow(Host::AuxiliaryRenderWindowHandle handle, QPoint* pos, QSize* size);
+
   void onApplicationStateChanged(Qt::ApplicationState state);
 
   void onStartFileActionTriggered();

src/duckstation-qt/qthost.cpp

@@ -1700,6 +1700,58 @@ void Host::OpenHostFileSelectorAsync(std::string_view title, bool select_directo
   });
 }
 
+bool Host::CreateAuxiliaryRenderWindow(s32 x, s32 y, u32 width, u32 height, std::string_view title,
+                                       std::string_view icon_name, AuxiliaryRenderWindowUserData userdata,
+                                       AuxiliaryRenderWindowHandle* handle, WindowInfo* wi, Error* error)
+{
+  return emit g_emu_thread->onCreateAuxiliaryRenderWindow(x, y, width, height, QtUtils::StringViewToQString(title),
+                                                          QtUtils::StringViewToQString(icon_name), userdata, handle, wi,
+                                                          error);
+}
+
+void Host::DestroyAuxiliaryRenderWindow(AuxiliaryRenderWindowHandle handle, s32* pos_x, s32* pos_y, u32* width,
+                                        u32* height)
+{
+  QPoint pos;
+  QSize size;
+  emit g_emu_thread->onDestroyAuxiliaryRenderWindow(handle, &pos, &size);
+
+  if (pos_x)
+    *pos_x = pos.x();
+  if (pos_y)
+    *pos_y = pos.y();
+  if (width)
+    *width = size.width();
+  if (height)
+    *height = size.height();
+
+  // eat all pending events, to make sure we're not going to write input events back to a dead pointer
+  g_emu_thread->getEventLoop()->processEvents(QEventLoop::AllEvents);
+}
+
+void EmuThread::queueAuxiliaryRenderWindowInputEvent(Host::AuxiliaryRenderWindowUserData userdata,
+                                                     Host::AuxiliaryRenderWindowEvent event,
+                                                     Host::AuxiliaryRenderWindowEventParam param1,
+                                                     Host::AuxiliaryRenderWindowEventParam param2,
+                                                     Host::AuxiliaryRenderWindowEventParam param3)
+{
+  DebugAssert(isOnUIThread());
+  QMetaObject::invokeMethod(this, "processAuxiliaryRenderWindowInputEvent", Qt::QueuedConnection,
+                            Q_ARG(void*, userdata), Q_ARG(quint32, static_cast<quint32>(event)),
+                            Q_ARG(quint32, param1.uint_param), Q_ARG(quint32, param2.uint_param),
+                            Q_ARG(quint32, param3.uint_param));
+}
+
+void EmuThread::processAuxiliaryRenderWindowInputEvent(void* userdata, quint32 event, quint32 param1, quint32 param2,
+                                                       quint32 param3)
+{
+  DebugAssert(isOnThread());
+  ImGuiManager::ProcessAuxiliaryRenderWindowInputEvent(userdata, static_cast<Host::AuxiliaryRenderWindowEvent>(event),
+                                                       Host::AuxiliaryRenderWindowEventParam{.uint_param = param1},
+                                                       Host::AuxiliaryRenderWindowEventParam{.uint_param = param2},
+                                                       Host::AuxiliaryRenderWindowEventParam{.uint_param = param3});
+}
+
 void EmuThread::doBackgroundControllerPoll()
 {
   System::Internal::IdlePollUpdate();

src/duckstation-qt/qthost.h

@@ -11,6 +11,7 @@
 #include "core/types.h"
 
 #include "util/gpu_device.h"
+#include "util/imgui_manager.h"
 #include "util/input_manager.h"
 
 #include <QtCore/QByteArray>
@@ -119,6 +120,13 @@ public:
   /// This version is **only** for the system thread. UI thread should use the MainWindow variant.
   SystemLock pauseAndLockSystem();
 
+  /// Queues an input event for an additional render window to the emu thread.
+  void queueAuxiliaryRenderWindowInputEvent(Host::AuxiliaryRenderWindowUserData userdata,
+                                            Host::AuxiliaryRenderWindowEvent event,
+                                            Host::AuxiliaryRenderWindowEventParam param1 = {},
+                                            Host::AuxiliaryRenderWindowEventParam param2 = {},
+                                            Host::AuxiliaryRenderWindowEventParam param3 = {});
+
 Q_SIGNALS:
   void errorReported(const QString& title, const QString& message);
   bool messageConfirmed(const QString& title, const QString& message);
@@ -151,6 +159,11 @@ Q_SIGNALS:
   void mediaCaptureStarted();
   void mediaCaptureStopped();
 
+  bool onCreateAuxiliaryRenderWindow(qint32 x, qint32 y, quint32 width, quint32 height, const QString& title,
+                                     const QString& icon_name, Host::AuxiliaryRenderWindowUserData userdata,
+                                     Host::AuxiliaryRenderWindowHandle* handle, WindowInfo* wi, Error* error);
+  void onDestroyAuxiliaryRenderWindow(Host::AuxiliaryRenderWindowHandle handle, QPoint* pos, QSize* size);
+
   /// Big Picture UI requests.
   void onCoverDownloaderOpenRequested();
 
@@ -210,6 +223,8 @@ private Q_SLOTS:
   void onDisplayWindowTextEntered(const QString& text);
   void doBackgroundControllerPoll();
   void runOnEmuThread(std::function<void()> callback);
+  void processAuxiliaryRenderWindowInputEvent(void* userdata, quint32 event, quint32 param1, quint32 param2,
+                                              quint32 param3);
 
 protected:
   void run() override;

src/util/imgui_manager.cpp

@@ -9,6 +9,9 @@
 #include "imgui_glyph_ranges.inl"
 #include "input_manager.h"
 
+// TODO: Remove me when GPUDevice config is also cleaned up.
+#include "core/host.h"
+
 #include "common/assert.h"
 #include "common/easing.h"
 #include "common/error.h"
@@ -64,7 +67,7 @@ struct OSDMessage
 static_assert(std::is_same_v<WCharType, ImWchar>);
 
 static void UpdateScale();
-static void SetStyle();
+static void SetStyle(ImGuiStyle& style, float scale);
 static void SetKeyMap();
 static bool LoadFontData();
 static void ReloadFontDataIfActive();
@@ -91,6 +94,7 @@ static std::string s_font_path;
 static std::vector<WCharType> s_font_range;
 static std::vector<WCharType> s_emoji_range;
 
+static ImGuiContext* s_imgui_context;
 static ImFont* s_standard_font;
 static ImFont* s_osd_font;
 static ImFont* s_fixed_font;
@@ -235,9 +239,9 @@ bool ImGuiManager::Initialize(float global_scale, Error* error)
     (g_gpu_device->HasMainSwapChain() ? g_gpu_device->GetMainSwapChain()->GetScale() : 1.0f) * global_scale, 1.0f);
   s_scale_changed = false;
 
-  ImGui::CreateContext();
+  s_imgui_context = ImGui::CreateContext();
 
-  ImGuiIO& io = ImGui::GetIO();
+  ImGuiIO& io = s_imgui_context->IO;
   io.IniFilename = nullptr;
   io.BackendFlags |= ImGuiBackendFlags_HasGamepad | ImGuiBackendFlags_RendererHasVtxOffset;
   io.BackendUsingLegacyKeyArrays = 0;
@@ -259,7 +263,7 @@ bool ImGuiManager::Initialize(float global_scale, Error* error)
   io.DisplaySize = ImVec2(s_window_width, s_window_height);
 
   SetKeyMap();
-  SetStyle();
+  SetStyle(s_imgui_context->Style, s_global_scale);
 
   if (!AddImGuiFonts(false) || !g_gpu_device->UpdateImGuiFontTexture())
   {
@@ -269,7 +273,7 @@ bool ImGuiManager::Initialize(float global_scale, Error* error)
   }
 
   // don't need the font data anymore, save some memory
-  ImGui::GetIO().Fonts->ClearTexData();
+  io.Fonts->ClearTexData();
 
   NewFrame();
 
@@ -281,8 +285,11 @@ void ImGuiManager::Shutdown()
 {
   DestroySoftwareCursorTextures();
 
-  if (ImGui::GetCurrentContext())
-    ImGui::DestroyContext();
+  if (s_imgui_context)
+  {
+    ImGui::DestroyContext(s_imgui_context);
+    s_imgui_context = nullptr;
+  }
 
   s_standard_font = nullptr;
   s_fixed_font = nullptr;
@@ -291,6 +298,11 @@ void ImGuiManager::Shutdown()
   ImGuiFullscreen::SetFonts(nullptr, nullptr);
 }
 
+ImGuiContext* ImGuiManager::GetMainContext()
+{
+  return s_imgui_context;
+}
+
 float ImGuiManager::GetWindowWidth()
 {
   return s_window_width;
@@ -327,11 +339,7 @@ void ImGuiManager::UpdateScale()
     return;
 
   s_global_scale = scale;
-
-  ImGui::GetStyle() = ImGuiStyle();
-  ImGui::GetStyle().WindowMinSize = ImVec2(1.0f, 1.0f);
-  SetStyle();
-  ImGui::GetStyle().ScaleAllSizes(scale);
+  SetStyle(s_imgui_context->Style, s_global_scale);
 
   if (!AddImGuiFonts(HasFullscreenFonts()))
     Panic("Failed to create ImGui font text");
@@ -360,9 +368,8 @@ void ImGuiManager::NewFrame()
   s_imgui_wants_mouse.store(io.WantCaptureMouse, std::memory_order_release);
 }
 
-void ImGuiManager::SetStyle()
+void ImGuiManager::SetStyle(ImGuiStyle& style, float scale)
 {
-  ImGuiStyle& style = ImGui::GetStyle();
   style = ImGuiStyle();
   style.WindowMinSize = ImVec2(1.0f, 1.0f);
 
@@ -416,7 +423,7 @@ void ImGuiManager::SetStyle()
   colors[ImGuiCol_NavWindowingDimBg] = ImVec4(0.80f, 0.80f, 0.80f, 0.20f);
   colors[ImGuiCol_ModalWindowDimBg] = ImVec4(0.80f, 0.80f, 0.80f, 0.35f);
 
-  style.ScaleAllSizes(s_global_scale);
+  style.ScaleAllSizes(scale);
 }
 
 void ImGuiManager::SetKeyMap()
@@ -713,7 +720,7 @@ bool ImGuiManager::AddImGuiFonts(bool fullscreen_fonts)
 
 void ImGuiManager::ReloadFontDataIfActive()
 {
-  if (!ImGui::GetCurrentContext())
+  if (!s_imgui_context)
     return;
 
   ImGui::EndFrame();
@@ -1054,43 +1061,43 @@ bool ImGuiManager::WantsMouseInput()
 
 void ImGuiManager::AddTextInput(std::string str)
 {
-  if (!ImGui::GetCurrentContext())
+  if (!s_imgui_context)
     return;
 
   if (!s_imgui_wants_keyboard.load(std::memory_order_acquire))
     return;
 
-  ImGui::GetIO().AddInputCharactersUTF8(str.c_str());
+  s_imgui_context->IO.AddInputCharactersUTF8(str.c_str());
 }
 
 void ImGuiManager::UpdateMousePosition(float x, float y)
 {
-  if (!ImGui::GetCurrentContext())
+  if (!s_imgui_context)
     return;
 
-  ImGui::GetIO().MousePos = ImVec2(x, y);
+  s_imgui_context->IO.MousePos = ImVec2(x, y);
   std::atomic_thread_fence(std::memory_order_release);
 }
 
 bool ImGuiManager::ProcessPointerButtonEvent(InputBindingKey key, float value)
 {
-  if (!ImGui::GetCurrentContext() || key.data >= std::size(ImGui::GetIO().MouseDown))
+  if (!s_imgui_context || key.data >= std::size(ImGui::GetIO().MouseDown))
     return false;
 
   // still update state anyway
-  ImGui::GetIO().AddMouseButtonEvent(key.data, value != 0.0f);
+  s_imgui_context->IO.AddMouseButtonEvent(key.data, value != 0.0f);
 
   return s_imgui_wants_mouse.load(std::memory_order_acquire);
 }
 
 bool ImGuiManager::ProcessPointerAxisEvent(InputBindingKey key, float value)
 {
-  if (!ImGui::GetCurrentContext() || key.data < static_cast<u32>(InputPointerAxis::WheelX))
+  if (!s_imgui_context || key.data < static_cast<u32>(InputPointerAxis::WheelX))
     return false;
 
   // still update state anyway
   const bool horizontal = (key.data == static_cast<u32>(InputPointerAxis::WheelX));
-  ImGui::GetIO().AddMouseWheelEvent(horizontal ? value : 0.0f, horizontal ? 0.0f : value);
+  s_imgui_context->IO.AddMouseWheelEvent(horizontal ? value : 0.0f, horizontal ? 0.0f : value);
 
   return s_imgui_wants_mouse.load(std::memory_order_acquire);
 }
@@ -1098,11 +1105,11 @@ bool ImGuiManager::ProcessPointerAxisEvent(InputBindingKey key, float value)
 bool ImGuiManager::ProcessHostKeyEvent(InputBindingKey key, float value)
 {
   decltype(s_imgui_key_map)::iterator iter;
-  if (!ImGui::GetCurrentContext() || (iter = s_imgui_key_map.find(key.data)) == s_imgui_key_map.end())
+  if (!s_imgui_context || (iter = s_imgui_key_map.find(key.data)) == s_imgui_key_map.end())
     return false;
 
   // still update state anyway
-  ImGui::GetIO().AddKeyEvent(iter->second, value != 0.0);
+  s_imgui_context->IO.AddKeyEvent(iter->second, value != 0.0);
 
   return s_imgui_wants_keyboard.load(std::memory_order_acquire);
 }
@@ -1138,13 +1145,13 @@ bool ImGuiManager::ProcessGenericInputEvent(GenericInputBinding key, float value
     ImGuiKey_GamepadL2,        // R2
   };
 
-  if (!ImGui::GetCurrentContext())
+  if (!s_imgui_context)
     return false;
 
   if (static_cast<u32>(key) >= std::size(key_map) || key_map[static_cast<u32>(key)] == ImGuiKey_None)
     return false;
 
-  ImGui::GetIO().AddKeyAnalogEvent(key_map[static_cast<u32>(key)], (value > 0.0f), value);
+  s_imgui_context->IO.AddKeyAnalogEvent(key_map[static_cast<u32>(key)], (value > 0.0f), value);
   return s_imgui_wants_keyboard.load(std::memory_order_acquire);
 }
 
@@ -1275,3 +1282,213 @@ std::string ImGuiManager::StripIconCharacters(std::string_view str)
 
   return result;
 }
+
+#ifndef __ANDROID__
+
+bool ImGuiManager::CreateAuxiliaryRenderWindow(AuxiliaryRenderWindowState* state, std::string_view title,
+                                               std::string_view icon_name, const char* config_section,
+                                               const char* config_prefix, u32 default_width, u32 default_height,
+                                               Error* error)
+{
+  constexpr s32 DEFAULT_POSITION = std::numeric_limits<s32>::min();
+
+  // figure out where to position it
+  s32 pos_x = DEFAULT_POSITION;
+  s32 pos_y = DEFAULT_POSITION;
+  u32 width = default_width;
+  u32 height = default_height;
+  if (config_prefix)
+  {
+    pos_x = Host::GetBaseIntSettingValue(config_section, TinyString::from_format("{}PositionX", config_prefix),
+                                         DEFAULT_POSITION);
+    pos_y = Host::GetBaseIntSettingValue(config_section, TinyString::from_format("{}PositionY", config_prefix),
+                                         DEFAULT_POSITION);
+    width =
+      Host::GetBaseUIntSettingValue(config_section, TinyString::from_format("{}Width", config_prefix), default_width);
+    height =
+      Host::GetBaseUIntSettingValue(config_section, TinyString::from_format("{}Height", config_prefix), default_height);
+  }
+
+  WindowInfo wi;
+  if (!Host::CreateAuxiliaryRenderWindow(pos_x, pos_y, width, height, title, icon_name, state, &state->window_handle,
+                                         &wi, error))
+  {
+    return false;
+  }
+
+  state->swap_chain = g_gpu_device->CreateSwapChain(wi, GPUVSyncMode::Disabled, false, nullptr, std::nullopt, error);
+  if (!state->swap_chain)
+  {
+    Host::DestroyAuxiliaryRenderWindow(state->window_handle);
+    state->window_handle = nullptr;
+    return false;
+  }
+
+  state->imgui_context = ImGui::CreateContext(s_imgui_context->IO.Fonts);
+  state->imgui_context->IO.DisplaySize =
+    ImVec2(static_cast<float>(state->swap_chain->GetWidth()), static_cast<float>(state->swap_chain->GetHeight()));
+  state->imgui_context->IO.IniFilename = nullptr;
+  state->imgui_context->IO.BackendFlags |= ImGuiBackendFlags_HasGamepad;
+  state->imgui_context->IO.BackendUsingLegacyKeyArrays = 0;
+  state->imgui_context->IO.BackendUsingLegacyNavInputArray = 0;
+  state->imgui_context->IO.KeyRepeatDelay = 0.5f;
+  state->imgui_context->IO.ConfigFlags |= ImGuiConfigFlags_NoMouseCursorChange;
+
+  SetStyle(state->imgui_context->Style, state->swap_chain->GetScale());
+  state->imgui_context->Style.WindowBorderSize = 0.0f;
+
+  state->close_request = false;
+  return true;
+}
+
+void ImGuiManager::DestroyAuxiliaryRenderWindow(AuxiliaryRenderWindowState* state, const char* config_section,
+                                                const char* config_prefix)
+{
+  constexpr s32 DEFAULT_POSITION = std::numeric_limits<s32>::min();
+
+  if (!state->window_handle)
+    return;
+
+  s32 old_pos_x = DEFAULT_POSITION, old_pos_y = DEFAULT_POSITION;
+  u32 old_width = 0, old_height = 0;
+  if (config_section)
+  {
+    old_pos_x = Host::GetBaseIntSettingValue(config_section, TinyString::from_format("{}PositionX", config_prefix),
+                                             DEFAULT_POSITION);
+    old_pos_y = Host::GetBaseIntSettingValue(config_section, TinyString::from_format("{}PositionY", config_prefix),
+                                             DEFAULT_POSITION);
+    old_width = Host::GetBaseUIntSettingValue(config_section, TinyString::from_format("{}Width", config_prefix), 0);
+    old_height = Host::GetBaseUIntSettingValue(config_section, TinyString::from_format("{}Height", config_prefix), 0);
+  }
+
+  ImGui::DestroyContext(state->imgui_context);
+  state->imgui_context = nullptr;
+  state->swap_chain.reset();
+  state->close_request = false;
+
+  // store positioning for config
+  s32 new_pos_x = old_pos_x, new_pos_y = old_pos_y;
+  u32 new_width = old_width, new_height = old_height;
+  Host::DestroyAuxiliaryRenderWindow(std::exchange(state->window_handle, nullptr), &new_pos_x, &new_pos_y, &new_width,
+                                     &new_height);
+
+  if (config_section)
+  {
+    // update config if the window was moved
+    if (old_pos_x != new_pos_x || old_pos_y != new_pos_y || old_width != new_width || old_height != new_height)
+    {
+      Host::SetBaseIntSettingValue(config_section, TinyString::from_format("{}PositionX", config_prefix), new_pos_x);
+      Host::SetBaseIntSettingValue(config_section, TinyString::from_format("{}PositionY", config_prefix), new_pos_y);
+      Host::SetBaseUIntSettingValue(config_section, TinyString::from_format("{}Width", config_prefix), new_width);
+      Host::SetBaseUIntSettingValue(config_section, TinyString::from_format("{}Height", config_prefix), new_height);
+      Host::CommitBaseSettingChanges();
+    }
+  }
+}
+
+bool ImGuiManager::RenderAuxiliaryRenderWindow(AuxiliaryRenderWindowState* state, void (*draw_callback)(float scale))
+{
+  DebugAssert(state->window_handle);
+  if (state->close_request)
+    return false;
+
+  ImGui::SetCurrentContext(state->imgui_context);
+
+  ImGui::NewFrame();
+  ImGui::SetNextWindowPos(ImVec2(0.0f, 0.0f), ImGuiCond_Always);
+  ImGui::SetNextWindowSize(state->imgui_context->IO.DisplaySize, ImGuiCond_Always);
+  if (ImGui::Begin("AuxRenderWindowMain", nullptr,
+                   ImGuiWindowFlags_NoTitleBar | ImGuiWindowFlags_NoResize | ImGuiWindowFlags_NoMove |
+                     ImGuiWindowFlags_NoCollapse))
+  {
+    draw_callback(state->swap_chain->GetScale());
+  }
+
+  ImGui::End();
+
+  const GPUDevice::PresentResult pres = g_gpu_device->BeginPresent(state->swap_chain.get());
+  if (pres == GPUDevice::PresentResult::OK)
+  {
+    g_gpu_device->RenderImGui(state->swap_chain.get());
+    g_gpu_device->EndPresent(state->swap_chain.get(), false);
+  }
+  else
+  {
+    ImGui::EndFrame();
+  }
+
+  ImGui::SetCurrentContext(GetMainContext());
+  return true;
+}
+
+void ImGuiManager::ProcessAuxiliaryRenderWindowInputEvent(Host::AuxiliaryRenderWindowUserData userdata,
+                                                          Host::AuxiliaryRenderWindowEvent event,
+                                                          Host::AuxiliaryRenderWindowEventParam param1,
+                                                          Host::AuxiliaryRenderWindowEventParam param2,
+                                                          Host::AuxiliaryRenderWindowEventParam param3)
+{
+  // we can get bogus events here after the user closes it, so check we're not being destroyed
+  AuxiliaryRenderWindowState* state = static_cast<AuxiliaryRenderWindowState*>(userdata);
+  if (!state->window_handle) [[unlikely]]
+    return;
+
+  ImGuiIO& io = state->imgui_context->IO;
+
+  switch (event)
+  {
+    case Host::AuxiliaryRenderWindowEvent::CloseRequest:
+    {
+      state->close_request = true;
+    }
+    break;
+
+    case Host::AuxiliaryRenderWindowEvent::Resized:
+    {
+      Error error;
+      if (!state->swap_chain->ResizeBuffers(param1.uint_param, param2.uint_param, param3.float_param, &error))
+      {
+        ERROR_LOG("Failed to resize aux window swap chain to {}x{}: {}", param1.uint_param, param2.uint_param,
+                  error.GetDescription());
+        return;
+      }
+
+      state->imgui_context->IO.DisplaySize.x = static_cast<float>(param1.uint_param);
+      state->imgui_context->IO.DisplaySize.y = static_cast<float>(param2.uint_param);
+    }
+    break;
+
+    case Host::AuxiliaryRenderWindowEvent::KeyPressed:
+    case Host::AuxiliaryRenderWindowEvent::KeyReleased:
+    {
+      const auto iter = s_imgui_key_map.find(param1.uint_param);
+      if (iter != s_imgui_key_map.end())
+        io.AddKeyEvent(iter->second, (event == Host::AuxiliaryRenderWindowEvent::KeyPressed));
+    }
+    break;
+
+    case Host::AuxiliaryRenderWindowEvent::MouseMoved:
+    {
+      io.MousePos.x = param1.float_param;
+      io.MousePos.y = param2.float_param;
+    }
+    break;
+
+    case Host::AuxiliaryRenderWindowEvent::MousePressed:
+    case Host::AuxiliaryRenderWindowEvent::MouseReleased:
+    {
+      io.AddMouseButtonEvent(param1.uint_param, (event == Host::AuxiliaryRenderWindowEvent::MousePressed));
+    }
+    break;
+
+    case Host::AuxiliaryRenderWindowEvent::MouseWheel:
+    {
+      io.AddMouseWheelEvent(param1.float_param, param2.float_param);
+    }
+    break;
+
+    default:
+      break;
+  }
+}
+
+#endif // __ANDROID__

src/util/imgui_manager.h

@@ -4,17 +4,51 @@
 #pragma once
 
 #include "common/types.h"
+
+#include <memory>
 #include <span>
 #include <string>
 #include <vector>
 
 class Error;
+struct WindowInfo;
+
+class GPUSwapChain;
 
+struct ImGuiContext;
 struct ImFont;
 
 union InputBindingKey;
 enum class GenericInputBinding : u8;
 
+namespace Host {
+
+/// Handle representing an auxiliary render window in the host.
+using AuxiliaryRenderWindowHandle = void*;
+using AuxiliaryRenderWindowUserData = void*;
+
+enum class AuxiliaryRenderWindowEvent : u8
+{
+  CloseRequest,
+  Resized,
+  KeyPressed,
+  KeyReleased,
+  MouseMoved,
+  MousePressed,
+  MouseReleased,
+  MouseWheel,
+  MaxCount,
+};
+
+union AuxiliaryRenderWindowEventParam
+{
+  s32 int_param;
+  u32 uint_param;
+  float float_param;
+};
+
+} // namespace Host
+
 namespace ImGuiManager {
 
 using WCharType = u32;
@@ -42,6 +76,9 @@ bool Initialize(float global_scale, Error* error);
 /// Frees all ImGui resources.
 void Shutdown();
 
+/// Returns main ImGui context.
+ImGuiContext* GetMainContext();
+
 /// Returns the size of the display window. Can be safely called from any thread.
 float GetWindowWidth();
 float GetWindowHeight();
@@ -124,9 +161,45 @@ void RenderSoftwareCursors();
 
 /// Strips icon characters from a string.
 std::string StripIconCharacters(std::string_view str);
+
+#ifndef __ANDROID__
+
+/// Auxiliary imgui windows.
+struct AuxiliaryRenderWindowState
+{
+  Host::AuxiliaryRenderWindowHandle window_handle = nullptr;
+  std::unique_ptr<GPUSwapChain> swap_chain;
+  ImGuiContext* imgui_context = nullptr;
+  bool close_request = false;
+};
+
+/// Create a new aux render window. This creates the window itself, swap chain, and imgui context.
+/// Window position and dimensions are restored from the configuration file, under the specified section/key.
+bool CreateAuxiliaryRenderWindow(AuxiliaryRenderWindowState* state, std::string_view title, std::string_view icon_name,
+                                 const char* config_section, const char* config_prefix, u32 default_width,
+                                 u32 default_height, Error* error);
+
+/// Destroys a previously-created aux render window, optionally saving its position information.
+void DestroyAuxiliaryRenderWindow(AuxiliaryRenderWindowState* state, const char* config_section = nullptr,
+                                  const char* config_prefix = nullptr);
+
+/// Renders the specified aux render window. draw_callback will be invoked if the window is not hidden.
+/// Returns false if the user has closed the window.
+bool RenderAuxiliaryRenderWindow(AuxiliaryRenderWindowState* state, void (*draw_callback)(float scale));
+
+/// Processes input events from the host.
+void ProcessAuxiliaryRenderWindowInputEvent(Host::AuxiliaryRenderWindowUserData userdata,
+                                            Host::AuxiliaryRenderWindowEvent event,
+                                            Host::AuxiliaryRenderWindowEventParam param1,
+                                            Host::AuxiliaryRenderWindowEventParam param2,
+                                            Host::AuxiliaryRenderWindowEventParam param3);
+
+#endif
+
 } // namespace ImGuiManager
 
 namespace Host {
+
 /// Typical durations for OSD messages.
 static constexpr float OSD_CRITICAL_ERROR_DURATION = 20.0f;
 static constexpr float OSD_ERROR_DURATION = 15.0f;
@@ -143,4 +216,16 @@ void AddIconOSDWarning(std::string key, const char* icon, std::string message, f
 void RemoveKeyedOSDMessage(std::string key);
 void RemoveKeyedOSDWarning(std::string key);
 void ClearOSDMessages(bool clear_warnings);
+
+#ifndef __ANDROID__
+
+/// Auxiliary window management.
+bool CreateAuxiliaryRenderWindow(s32 x, s32 y, u32 width, u32 height, std::string_view title,
+                                 std::string_view icon_name, AuxiliaryRenderWindowUserData userdata,
+                                 AuxiliaryRenderWindowHandle* handle, WindowInfo* wi, Error* error);
+void DestroyAuxiliaryRenderWindow(AuxiliaryRenderWindowHandle handle, s32* pos_x = nullptr, s32* pos_y = nullptr,
+                                  u32* width = nullptr, u32* height = nullptr);
+
+#endif
+
 } // namespace Host