Adding upstream version 115.8.0esr.upstream/115.8.0esr

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 2150 insertions, 0 deletions

diff --git a/widget/nsIWidget.h b/widget/nsIWidget.h
new file mode 100644
index 0000000000..40752e07dd
--- /dev/null
+++ b/widget/nsIWidget.h
@@ -0,0 +1,2150 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef nsIWidget_h__
+#define nsIWidget_h__
+
+#include <cmath>
+#include <cstdint>
+#include "imgIContainer.h"
+#include "ErrorList.h"
+#include "Units.h"
+#include "mozilla/AlreadyAddRefed.h"
+#include "mozilla/Assertions.h"
+#include "mozilla/Attributes.h"
+#include "mozilla/EventForwards.h"
+#include "mozilla/Maybe.h"
+#include "mozilla/RefPtr.h"
+#include "mozilla/TimeStamp.h"
+#include "mozilla/UniquePtr.h"
+#include "mozilla/gfx/Matrix.h"
+#include "mozilla/gfx/Rect.h"
+#include "mozilla/layers/LayersTypes.h"
+#include "mozilla/layers/ScrollableLayerGuid.h"
+#include "mozilla/layers/ZoomConstraints.h"
+#include "mozilla/image/Resolution.h"
+#include "mozilla/widget/IMEData.h"
+#include "nsCOMPtr.h"
+#include "nsColor.h"
+#include "nsDebug.h"
+#include "nsID.h"
+#include "nsIObserver.h"
+#include "nsISupports.h"
+#include "nsITheme.h"
+#include "nsITimer.h"
+#include "nsIWidgetListener.h"
+#include "nsRect.h"
+#include "nsSize.h"
+#include "nsStringFwd.h"
+#include "nsTArray.h"
+#include "nsTHashMap.h"
+#include "mozilla/widget/InitData.h"
+#include "nsXULAppAPI.h"
+
+// forward declarations
+class nsIBidiKeyboard;
+class nsIRollupListener;
+class nsIContent;
+class ViewWrapper;
+class nsIRunnable;
+
+namespace mozilla {
+enum class NativeKeyBindingsType : uint8_t;
+class VsyncDispatcher;
+class WidgetGUIEvent;
+class WidgetInputEvent;
+class WidgetKeyboardEvent;
+struct FontRange;
+
+enum class StyleWindowShadow : uint8_t;
+enum class ColorScheme : uint8_t;
+enum class WindowButtonType : uint8_t;
+
+#if defined(MOZ_WIDGET_ANDROID)
+namespace ipc {
+class Shmem;
+}
+#endif  // defined(MOZ_WIDGET_ANDROID)
+namespace dom {
+class BrowserChild;
+enum class CallerType : uint32_t;
+}  // namespace dom
+class WindowRenderer;
+namespace layers {
+class AsyncDragMetrics;
+class Compositor;
+class CompositorBridgeChild;
+struct FrameMetrics;
+class LayerManager;
+class WebRenderBridgeChild;
+}  // namespace layers
+namespace widget {
+class TextEventDispatcher;
+class TextEventDispatcherListener;
+class CompositorWidget;
+class CompositorWidgetInitData;
+class Screen;
+}  // namespace widget
+namespace wr {
+class DisplayListBuilder;
+class IpcResourceUpdateQueue;
+enum class RenderRoot : uint8_t;
+}  // namespace wr
+}  // namespace mozilla
+
+/**
+ * Callback function that processes events.
+ *
+ * The argument is actually a subtype (subclass) of WidgetEvent which carries
+ * platform specific information about the event. Platform specific code
+ * knows how to deal with it.
+ *
+ * The return value determines whether or not the default action should take
+ * place.
+ */
+typedef nsEventStatus (*EVENT_CALLBACK)(mozilla::WidgetGUIEvent* aEvent);
+
+// Hide the native window system's real window type so as to avoid
+// including native window system types and APIs. This is necessary
+// to ensure cross-platform code.
+typedef void* nsNativeWidget;
+
+/**
+ * Values for the GetNativeData function
+ */
+#define NS_NATIVE_WINDOW 0
+#define NS_NATIVE_GRAPHIC 1
+#define NS_NATIVE_WIDGET 3
+#define NS_NATIVE_REGION 5
+#define NS_NATIVE_OFFSETX 6
+#define NS_NATIVE_OFFSETY 7
+#define NS_NATIVE_SCREEN 9
+// The toplevel GtkWidget containing this nsIWidget:
+#define NS_NATIVE_SHELLWIDGET 10
+#define NS_NATIVE_OPENGL_CONTEXT 12
+// This is available only with GetNativeData() in parent process.  Anybody
+// shouldn't access this pointer as a valid pointer since the result may be
+// special value like NS_ONLY_ONE_NATIVE_IME_CONTEXT.  So, the result is just
+// an identifier of distinguishing a text composition is caused by which native
+// IME context.  Note that the result is only valid in the process.  So,
+// XP code should use nsIWidget::GetNativeIMEContext() instead of using this.
+#define NS_RAW_NATIVE_IME_CONTEXT 14
+#define NS_NATIVE_WINDOW_WEBRTC_DEVICE_ID 15
+#ifdef XP_WIN
+#  define NS_NATIVE_TSF_THREAD_MGR 100
+#  define NS_NATIVE_TSF_CATEGORY_MGR 101
+#  define NS_NATIVE_TSF_DISPLAY_ATTR_MGR 102
+#  define NS_NATIVE_ICOREWINDOW 103  // winrt specific
+#endif
+#if defined(MOZ_WIDGET_GTK)
+#  define NS_NATIVE_EGL_WINDOW 106
+#endif
+#ifdef MOZ_WIDGET_ANDROID
+#  define NS_JAVA_SURFACE 100
+#endif
+
+#define MOZ_WIDGET_MAX_SIZE 16384
+#define MOZ_WIDGET_INVALID_SCALE 0.0
+
+// Must be kept in sync with xpcom/rust/xpcom/src/interfaces/nonidl.rs
+#define NS_IWIDGET_IID                               \
+  {                                                  \
+    0x06396bf6, 0x2dd8, 0x45e5, {                    \
+      0xac, 0x45, 0x75, 0x26, 0x53, 0xb1, 0xc9, 0x80 \
+    }                                                \
+  }
+
+/**
+ * Cursor types.
+ */
+
+enum nsCursor {  ///(normal cursor,       usually rendered as an arrow)
+  eCursor_standard,
+  ///(system is busy,      usually rendered as a hourglass or watch)
+  eCursor_wait,
+  ///(Selecting something, usually rendered as an IBeam)
+  eCursor_select,
+  ///(can hyper-link,      usually rendered as a human hand)
+  eCursor_hyperlink,
+  ///(north/south/west/east edge sizing)
+  eCursor_n_resize,
+  eCursor_s_resize,
+  eCursor_w_resize,
+  eCursor_e_resize,
+  ///(corner sizing)
+  eCursor_nw_resize,
+  eCursor_se_resize,
+  eCursor_ne_resize,
+  eCursor_sw_resize,
+  eCursor_crosshair,
+  eCursor_move,
+  eCursor_help,
+  eCursor_copy,  // CSS3
+  eCursor_alias,
+  eCursor_context_menu,
+  eCursor_cell,
+  eCursor_grab,
+  eCursor_grabbing,
+  eCursor_spinning,
+  eCursor_zoom_in,
+  eCursor_zoom_out,
+  eCursor_not_allowed,
+  eCursor_col_resize,
+  eCursor_row_resize,
+  eCursor_no_drop,
+  eCursor_vertical_text,
+  eCursor_all_scroll,
+  eCursor_nesw_resize,
+  eCursor_nwse_resize,
+  eCursor_ns_resize,
+  eCursor_ew_resize,
+  eCursor_none,
+  // This one is used for array sizing, and so better be the last
+  // one in this list...
+  eCursorCount,
+
+  // ...except for this one.
+  eCursorInvalid = eCursorCount + 1
+};
+
+enum nsTopLevelWidgetZPlacement {  // for PlaceBehind()
+  eZPlacementBottom = 0,           // bottom of the window stack
+  eZPlacementBelow,                // just below another widget
+  eZPlacementTop                   // top of the window stack
+};
+
+/**
+ * Before the OS goes to sleep, this topic is notified.
+ */
+#define NS_WIDGET_SLEEP_OBSERVER_TOPIC "sleep_notification"
+
+/**
+ * After the OS wakes up, this topic is notified.
+ */
+#define NS_WIDGET_WAKE_OBSERVER_TOPIC "wake_notification"
+
+/**
+ * Before the OS suspends the current process, this topic is notified.  Some
+ * OS will kill processes that are suspended instead of resuming them.
+ * For that reason this topic may be useful to safely close down resources.
+ */
+#define NS_WIDGET_SUSPEND_PROCESS_OBSERVER_TOPIC "suspend_process_notification"
+
+/**
+ * After the current process resumes from being suspended, this topic is
+ * notified.
+ */
+#define NS_WIDGET_RESUME_PROCESS_OBSERVER_TOPIC "resume_process_notification"
+
+/**
+ * When an app(-shell) is activated by the OS, this topic is notified.
+ * Currently, this only happens on Mac OSX.
+ */
+#define NS_WIDGET_MAC_APP_ACTIVATE_OBSERVER_TOPIC "mac_app_activate"
+
+namespace mozilla::widget {
+
+/**
+ * Size constraints for setting the minimum and maximum size of a widget.
+ * Values are in device pixels.
+ */
+struct SizeConstraints {
+  SizeConstraints()
+      : mMaxSize(MOZ_WIDGET_MAX_SIZE, MOZ_WIDGET_MAX_SIZE),
+        mScale(MOZ_WIDGET_INVALID_SCALE) {}
+
+  SizeConstraints(mozilla::LayoutDeviceIntSize aMinSize,
+                  mozilla::LayoutDeviceIntSize aMaxSize,
+                  mozilla::DesktopToLayoutDeviceScale aScale)
+      : mMinSize(aMinSize), mMaxSize(aMaxSize), mScale(aScale) {
+    if (mMaxSize.width > MOZ_WIDGET_MAX_SIZE) {
+      mMaxSize.width = MOZ_WIDGET_MAX_SIZE;
+    }
+    if (mMaxSize.height > MOZ_WIDGET_MAX_SIZE) {
+      mMaxSize.height = MOZ_WIDGET_MAX_SIZE;
+    }
+  }
+
+  mozilla::LayoutDeviceIntSize mMinSize;
+  mozilla::LayoutDeviceIntSize mMaxSize;
+
+  /*
+   * The scale used to convert from desktop to device dimensions.
+   * MOZ_WIDGET_INVALID_SCALE if the value is not known.
+   *
+   * Bug 1701109 is filed to revisit adding of 'mScale' and deal
+   * with multi-monitor scaling issues in more complete way across
+   * all widget implementations.
+   */
+  mozilla::DesktopToLayoutDeviceScale mScale;
+};
+
+struct AutoObserverNotifier {
+  AutoObserverNotifier(nsIObserver* aObserver, const char* aTopic)
+      : mObserver(aObserver), mTopic(aTopic) {}
+
+  void SkipNotification() { mObserver = nullptr; }
+
+  uint64_t SaveObserver() {
+    if (!mObserver) {
+      return 0;
+    }
+    uint64_t observerId = ++sObserverId;
+    sSavedObservers.InsertOrUpdate(observerId, mObserver);
+    SkipNotification();
+    return observerId;
+  }
+
+  ~AutoObserverNotifier() {
+    if (mObserver) {
+      mObserver->Observe(nullptr, mTopic, nullptr);
+    }
+  }
+
+  static void NotifySavedObserver(const uint64_t& aObserverId,
+                                  const char* aTopic) {
+    nsCOMPtr<nsIObserver> observer = sSavedObservers.Get(aObserverId);
+    if (!observer) {
+      MOZ_ASSERT(aObserverId == 0,
+                 "We should always find a saved observer for nonzero IDs");
+      return;
+    }
+
+    sSavedObservers.Remove(aObserverId);
+    observer->Observe(nullptr, aTopic, nullptr);
+  }
+
+ private:
+  nsCOMPtr<nsIObserver> mObserver;
+  const char* mTopic;
+
+ private:
+  static uint64_t sObserverId;
+  static nsTHashMap<uint64_t, nsCOMPtr<nsIObserver>> sSavedObservers;
+};
+
+}  // namespace mozilla::widget
+
+/**
+ * The base class for all the widgets. It provides the interface for
+ * all basic and necessary functionality.
+ */
+class nsIWidget : public nsISupports {
+ protected:
+  typedef mozilla::dom::BrowserChild BrowserChild;
+
+ public:
+  typedef mozilla::layers::CompositorBridgeChild CompositorBridgeChild;
+  typedef mozilla::layers::AsyncDragMetrics AsyncDragMetrics;
+  typedef mozilla::layers::FrameMetrics FrameMetrics;
+  typedef mozilla::layers::LayerManager LayerManager;
+  typedef mozilla::WindowRenderer WindowRenderer;
+  typedef mozilla::layers::LayersBackend LayersBackend;
+  typedef mozilla::layers::LayersId LayersId;
+  typedef mozilla::layers::ScrollableLayerGuid ScrollableLayerGuid;
+  typedef mozilla::layers::ZoomConstraints ZoomConstraints;
+  typedef mozilla::widget::IMEEnabled IMEEnabled;
+  typedef mozilla::widget::IMEMessage IMEMessage;
+  typedef mozilla::widget::IMENotification IMENotification;
+  typedef mozilla::widget::IMENotificationRequests IMENotificationRequests;
+  typedef mozilla::widget::IMEState IMEState;
+  typedef mozilla::widget::InputContext InputContext;
+  typedef mozilla::widget::InputContextAction InputContextAction;
+  typedef mozilla::widget::NativeIMEContext NativeIMEContext;
+  typedef mozilla::widget::SizeConstraints SizeConstraints;
+  typedef mozilla::widget::TextEventDispatcher TextEventDispatcher;
+  typedef mozilla::widget::TextEventDispatcherListener
+      TextEventDispatcherListener;
+  typedef mozilla::LayoutDeviceIntMargin LayoutDeviceIntMargin;
+  typedef mozilla::LayoutDeviceIntPoint LayoutDeviceIntPoint;
+  typedef mozilla::LayoutDeviceIntRect LayoutDeviceIntRect;
+  typedef mozilla::LayoutDeviceIntRegion LayoutDeviceIntRegion;
+  typedef mozilla::LayoutDeviceIntSize LayoutDeviceIntSize;
+  typedef mozilla::ScreenIntPoint ScreenIntPoint;
+  typedef mozilla::ScreenIntMargin ScreenIntMargin;
+  typedef mozilla::ScreenIntSize ScreenIntSize;
+  typedef mozilla::ScreenPoint ScreenPoint;
+  typedef mozilla::CSSToScreenScale CSSToScreenScale;
+  typedef mozilla::DesktopIntRect DesktopIntRect;
+  typedef mozilla::DesktopPoint DesktopPoint;
+  typedef mozilla::DesktopIntPoint DesktopIntPoint;
+  typedef mozilla::DesktopRect DesktopRect;
+  typedef mozilla::DesktopSize DesktopSize;
+  typedef mozilla::CSSPoint CSSPoint;
+  typedef mozilla::CSSRect CSSRect;
+
+  using InitData = mozilla::widget::InitData;
+  using WindowType = mozilla::widget::WindowType;
+  using PopupType = mozilla::widget::PopupType;
+  using PopupLevel = mozilla::widget::PopupLevel;
+  using BorderStyle = mozilla::widget::BorderStyle;
+  using TransparencyMode = mozilla::widget::TransparencyMode;
+  using Screen = mozilla::widget::Screen;
+
+  // Used in UpdateThemeGeometries.
+  struct ThemeGeometry {
+    // The ThemeGeometryType value for the themed widget, see
+    // nsITheme::ThemeGeometryTypeForWidget.
+    nsITheme::ThemeGeometryType mType;
+    // The device-pixel rect within the window for the themed widget
+    LayoutDeviceIntRect mRect;
+
+    ThemeGeometry(nsITheme::ThemeGeometryType aType,
+                  const LayoutDeviceIntRect& aRect)
+        : mType(aType), mRect(aRect) {}
+  };
+
+  NS_DECLARE_STATIC_IID_ACCESSOR(NS_IWIDGET_IID)
+
+  nsIWidget()
+      : mLastChild(nullptr),
+        mPrevSibling(nullptr),
+        mOnDestroyCalled(false),
+        mWindowType(WindowType::Child),
+        mZIndex(0)
+
+  {
+    ClearNativeTouchSequence(nullptr);
+  }
+
+  /**
+   * Create and initialize a widget.
+   *
+   * All the arguments can be null in which case a top level window
+   * with size 0 is created. The event callback function has to be
+   * provided only if the caller wants to deal with the events this
+   * widget receives.  The event callback is basically a preprocess
+   * hook called synchronously. The return value determines whether
+   * the event goes to the default window procedure or it is hidden
+   * to the os. The assumption is that if the event handler returns
+   * false the widget does not see the event. The widget should not
+   * automatically clear the window to the background color. The
+   * calling code must handle paint messages and clear the background
+   * itself.
+   *
+   * In practice at least one of aParent and aNativeParent will be null. If
+   * both are null the widget isn't parented (e.g. context menus or
+   * independent top level windows).
+   *
+   * The dimensions given in aRect are specified in the parent's
+   * device coordinate system.
+   * This must not be called for parentless widgets such as top-level
+   * windows, which use the desktop pixel coordinate system; a separate
+   * method is provided for these.
+   *
+   * @param     aParent       parent nsIWidget
+   * @param     aNativeParent native parent widget
+   * @param     aRect         the widget dimension
+   * @param     aInitData     data that is used for widget initialization
+   *
+   */
+  [[nodiscard]] virtual nsresult Create(nsIWidget* aParent,
+                                        nsNativeWidget aNativeParent,
+                                        const LayoutDeviceIntRect& aRect,
+                                        InitData* = nullptr) = 0;
+
+  /*
+   * As above, but with aRect specified in DesktopPixel units (for top-level
+   * widgets).
+   * Default implementation just converts aRect to device pixels and calls
+   * through to device-pixel Create, but platforms may override this if the
+   * mapping is not straightforward or the native platform needs to use the
+   * desktop pixel values directly.
+   */
+  [[nodiscard]] virtual nsresult Create(nsIWidget* aParent,
+                                        nsNativeWidget aNativeParent,
+                                        const DesktopIntRect& aRect,
+                                        InitData* aInitData = nullptr) {
+    LayoutDeviceIntRect devPixRect =
+        RoundedToInt(aRect * GetDesktopToDeviceScale());
+    return Create(aParent, aNativeParent, devPixRect, aInitData);
+  }
+
+  /**
+   * Allocate, initialize, and return a widget that is a child of
+   * |this|.  The returned widget (if nonnull) has gone through the
+   * equivalent of CreateInstance(widgetCID) + Create(...).
+   *
+   * |CreateChild()| lets widget backends decide whether to parent
+   * the new child widget to this, nonnatively parent it, or both.
+   * This interface exists to support the PuppetWidget backend,
+   * which is entirely non-native.  All other params are the same as
+   * for |Create()|.
+   *
+   * |aForceUseIWidgetParent| forces |CreateChild()| to only use the
+   * |nsIWidget*| this, not its native widget (if it exists), when
+   * calling |Create()|.  This is a timid hack around poorly
+   * understood code, and shouldn't be used in new code.
+   */
+  virtual already_AddRefed<nsIWidget> CreateChild(
+      const LayoutDeviceIntRect& aRect, InitData* = nullptr,
+      bool aForceUseIWidgetParent = false) = 0;
+
+  /**
+   * Attach to a top level widget.
+   *
+   * In cases where a top level chrome widget is being used as a content
+   * container, attach a secondary listener and update the device
+   * context. The primary widget listener will continue to be called for
+   * notifications relating to the top-level window, whereas other
+   * notifications such as painting and events will instead be called via
+   * the attached listener. SetAttachedWidgetListener should be used to
+   * assign the attached listener.
+   *
+   * aUseAttachedEvents if true, events are sent to the attached listener
+   * instead of the normal listener.
+   */
+  virtual void AttachViewToTopLevel(bool aUseAttachedEvents) = 0;
+
+  /**
+   * Accessor functions to get and set the attached listener. Used by
+   * nsView in connection with AttachViewToTopLevel above.
+   */
+  virtual void SetAttachedWidgetListener(nsIWidgetListener* aListener) = 0;
+  virtual nsIWidgetListener* GetAttachedWidgetListener() const = 0;
+  virtual void SetPreviouslyAttachedWidgetListener(
+      nsIWidgetListener* aListener) = 0;
+  virtual nsIWidgetListener* GetPreviouslyAttachedWidgetListener() = 0;
+
+  /**
+   * Notifies the root widget of a non-blank paint.
+   */
+  virtual void DidGetNonBlankPaint() {}
+
+  /**
+   * Accessor functions to get and set the listener which handles various
+   * actions for the widget.
+   */
+  //@{
+  virtual nsIWidgetListener* GetWidgetListener() const = 0;
+  virtual void SetWidgetListener(nsIWidgetListener* alistener) = 0;
+  //@}
+
+  /**
+   * Close and destroy the internal native window.
+   * This method does not delete the widget.
+   */
+
+  virtual void Destroy() = 0;
+
+  /**
+   * Destroyed() returns true if Destroy() has been called already.
+   * Otherwise, false.
+   */
+  bool Destroyed() const { return mOnDestroyCalled; }
+
+  /**
+   * Reparent a widget
+   *
+   * Change the widget's parent. Null parents are allowed.
+   *
+   * @param     aNewParent   new parent
+   */
+  virtual void SetParent(nsIWidget* aNewParent) = 0;
+
+  /**
+   * Return the parent Widget of this Widget or nullptr if this is a
+   * top level window
+   *
+   * @return the parent widget or nullptr if it does not have a parent
+   *
+   */
+  virtual nsIWidget* GetParent(void) = 0;
+
+  /**
+   * Return the top level Widget of this Widget
+   *
+   * @return the top level widget
+   */
+  virtual nsIWidget* GetTopLevelWidget() = 0;
+
+  /**
+   * Return the top (non-sheet) parent of this Widget if it's a sheet,
+   * or nullptr if this isn't a sheet (or some other error occurred).
+   * Sheets are only supported on some platforms (currently only macOS).
+   *
+   * @return the top (non-sheet) parent widget or nullptr
+   *
+   */
+  virtual nsIWidget* GetSheetWindowParent(void) = 0;
+
+  /**
+   * Return the physical DPI of the screen containing the window ...
+   * the number of device pixels per inch.
+   */
+  virtual float GetDPI() = 0;
+
+  /**
+   * Fallback DPI for when there's no widget available.
+   */
+  static float GetFallbackDPI();
+
+  /**
+   * Return the scaling factor between device pixels and the platform-
+   * dependent "desktop pixels" used to manage window positions on a
+   * potentially multi-screen, mixed-resolution desktop.
+   */
+  virtual mozilla::DesktopToLayoutDeviceScale GetDesktopToDeviceScale() = 0;
+
+  /**
+   * Return the scaling factor between device pixels and the platform-
+   * dependent "desktop pixels" by looking up the screen by the position
+   * of the widget.
+   */
+  virtual mozilla::DesktopToLayoutDeviceScale
+  GetDesktopToDeviceScaleByScreen() = 0;
+
+  /**
+   * Return the default scale factor for the window. This is the
+   * default number of device pixels per CSS pixel to use. This should
+   * depend on OS/platform settings such as the Mac's "UI scale factor"
+   * or Windows' "font DPI". This will take into account Gecko preferences
+   * overriding the system setting.
+   */
+  mozilla::CSSToLayoutDeviceScale GetDefaultScale();
+
+  /**
+   * Fallback default scale for when there's no widget available.
+   */
+  static mozilla::CSSToLayoutDeviceScale GetFallbackDefaultScale();
+
+  /**
+   * Return the first child of this widget.  Will return null if
+   * there are no children.
+   */
+  nsIWidget* GetFirstChild() const { return mFirstChild; }
+
+  /**
+   * Return the last child of this widget.  Will return null if
+   * there are no children.
+   */
+  nsIWidget* GetLastChild() const { return mLastChild; }
+
+  /**
+   * Return the next sibling of this widget
+   */
+  nsIWidget* GetNextSibling() const { return mNextSibling; }
+
+  /**
+   * Set the next sibling of this widget
+   */
+  void SetNextSibling(nsIWidget* aSibling) { mNextSibling = aSibling; }
+
+  /**
+   * Return the previous sibling of this widget
+   */
+  nsIWidget* GetPrevSibling() const { return mPrevSibling; }
+
+  /**
+   * Set the previous sibling of this widget
+   */
+  void SetPrevSibling(nsIWidget* aSibling) { mPrevSibling = aSibling; }
+
+  /**
+   * Show or hide this widget
+   *
+   * @param aState true to show the Widget, false to hide it
+   *
+   */
+  virtual void Show(bool aState) = 0;
+
+  /**
+   * Whether or not a widget must be recreated after being hidden to show
+   * again properly.
+   */
+  virtual bool NeedsRecreateToReshow() { return false; }
+
+  /**
+   * Make the window modal.
+   */
+  virtual void SetModal(bool aModal) = 0;
+
+  /**
+   * Make the non-modal window opened by modal window fake-modal, that will
+   * call SetFakeModal(false) on destroy on Cocoa.
+   */
+  virtual void SetFakeModal(bool aModal) { SetModal(aModal); }
+
+  /**
+   * Are we app modal. Currently only implemented on Cocoa.
+   */
+  virtual bool IsRunningAppModal() { return false; }
+
+  /**
+   * The maximum number of simultaneous touch contacts supported by the device.
+   * In the case of devices with multiple digitizers (e.g. multiple touch
+   * screens), the value will be the maximum of the set of maximum supported
+   * contacts by each individual digitizer.
+   */
+  virtual uint32_t GetMaxTouchPoints() const = 0;
+
+  /**
+   * Returns whether the window is visible
+   *
+   */
+  virtual bool IsVisible() const = 0;
+
+  /**
+   * Returns whether the window has allocated resources so
+   * we can paint into it.
+   * Recently it's used on Linux/Gtk where we should not paint
+   * to invisible window.
+   */
+  virtual bool IsMapped() const { return true; }
+
+  /**
+   * Perform platform-dependent sanity check on a potential window position.
+   * This is guaranteed to work only for top-level windows.
+   */
+  virtual void ConstrainPosition(DesktopIntPoint&) = 0;
+
+  /**
+   * NOTE:
+   *
+   * For a top-level window widget, the "parent's coordinate system" is the
+   * "global" display pixel coordinate space, *not* device pixels (which
+   * may be inconsistent between multiple screens, at least in the Mac OS
+   * case with mixed hi-dpi and lo-dpi displays). This applies to all the
+   * following Move and Resize widget APIs.
+   *
+   * The display-/device-pixel distinction becomes important for (at least)
+   * macOS with Hi-DPI (retina) displays, and Windows when the UI scale factor
+   * is set to other than 100%.
+   *
+   * The Move and Resize methods take floating-point parameters, rather than
+   * integer ones. This is important when manipulating top-level widgets,
+   * where the coordinate system may not be an integral multiple of the
+   * device-pixel space.
+   **/
+
+  /**
+   * Move this widget.
+   *
+   * Coordinates refer to the top-left of the widget.  For toplevel windows
+   * with decorations, this is the top-left of the titlebar and frame .
+   *
+   * @param aX the new x position expressed in the parent's coordinate system
+   * @param aY the new y position expressed in the parent's coordinate system
+   *
+   **/
+  virtual void Move(double aX, double aY) = 0;
+
+  /**
+   * Reposition this widget so that the client area has the given offset.
+   *
+   * @param aOffset  the new offset of the client area expressed as an
+   *                 offset from the origin of the client area of the parent
+   *                 widget (for root widgets and popup widgets it is in
+   *                 screen coordinates)
+   **/
+  virtual void MoveClient(const DesktopPoint& aOffset) = 0;
+
+  /**
+   * Resize this widget. Any size constraints set for the window by a
+   * previous call to SetSizeConstraints will be applied.
+   *
+   * @param aWidth  the new width expressed in the parent's coordinate system
+   * @param aHeight the new height expressed in the parent's coordinate
+   *                system
+   * @param aRepaint whether the widget should be repainted
+   */
+  virtual void Resize(double aWidth, double aHeight, bool aRepaint) = 0;
+
+  /**
+   * Lock the aspect ratio of a Window
+   *
+   * @param aShouldLock bool
+   *
+   */
+  virtual void LockAspectRatio(bool aShouldLock){};
+
+  /**
+   * Move or resize this widget. Any size constraints set for the window by
+   * a previous call to SetSizeConstraints will be applied.
+   *
+   * @param aX       the new x position expressed in the parent's coordinate
+   *                 system
+   * @param aY       the new y position expressed in the parent's coordinate
+   *                 system
+   * @param aWidth   the new width expressed in the parent's coordinate system
+   * @param aHeight  the new height expressed in the parent's coordinate
+   *                 system
+   * @param aRepaint whether the widget should be repainted if the size
+   *                 changes
+   *
+   */
+  virtual void Resize(double aX, double aY, double aWidth, double aHeight,
+                      bool aRepaint) = 0;
+
+  virtual mozilla::Maybe<bool> IsResizingNativeWidget() {
+    return mozilla::Nothing();
+  }
+
+  /**
+   * Resize the widget so that the inner client area has the given size.
+   *
+   * @param aSize    the new size of the client area.
+   * @param aRepaint whether the widget should be repainted
+   */
+  virtual void ResizeClient(const DesktopSize& aSize, bool aRepaint) = 0;
+
+  /**
+   * Resize and reposition the widget so tht inner client area has the given
+   * offset and size.
+   *
+   * @param aRect    the new offset and size of the client area. The offset is
+   *                 expressed as an offset from the origin of the client area
+   *                 of the parent widget (for root widgets and popup widgets it
+   *                 is in screen coordinates).
+   * @param aRepaint whether the widget should be repainted
+   */
+  virtual void ResizeClient(const DesktopRect& aRect, bool aRepaint) = 0;
+
+  /**
+   * Sets the widget's z-index.
+   */
+  virtual void SetZIndex(int32_t aZIndex) = 0;
+
+  /**
+   * Gets the widget's z-index.
+   */
+  int32_t GetZIndex() { return mZIndex; }
+
+  /**
+   * Position this widget just behind the given widget. (Used to
+   * control z-order for top-level widgets. Get/SetZIndex by contrast
+   * control z-order for child widgets of other widgets.)
+   * @param aPlacement top, bottom, or below a widget
+   *                   (if top or bottom, param aWidget is ignored)
+   * @param aWidget    widget to place this widget behind
+   *                   (only if aPlacement is eZPlacementBelow).
+   *                   null is equivalent to aPlacement of eZPlacementTop
+   * @param aActivate  true to activate the widget after placing it
+   */
+  virtual void PlaceBehind(nsTopLevelWidgetZPlacement aPlacement,
+                           nsIWidget* aWidget, bool aActivate) = 0;
+
+  /**
+   * Minimize, maximize or normalize the window size.
+   * Takes a value from nsSizeMode (see nsIWidgetListener.h)
+   */
+  virtual void SetSizeMode(nsSizeMode aMode) = 0;
+
+  virtual void GetWorkspaceID(nsAString& workspaceID) = 0;
+
+  virtual void MoveToWorkspace(const nsAString& workspaceID) = 0;
+
+  /**
+   * Suppress animations that are applied to a window by OS.
+   */
+  virtual void SuppressAnimation(bool aSuppress) {}
+
+  /**
+   * Return size mode (minimized, maximized, normalized).
+   * Returns a value from nsSizeMode (see nsIWidgetListener.h)
+   */
+  virtual nsSizeMode SizeMode() = 0;
+
+  /**
+   * Ask whether the window is tiled.
+   */
+  virtual bool IsTiled() const = 0;
+
+  /**
+   * Ask wether the widget is fully occluded
+   */
+  virtual bool IsFullyOccluded() const = 0;
+
+  /**
+   * Enable or disable this Widget
+   *
+   * @param aState true to enable the Widget, false to disable it.
+   */
+  virtual void Enable(bool aState) = 0;
+
+  /**
+   * Ask whether the widget is enabled
+   */
+  virtual bool IsEnabled() const = 0;
+
+  /*
+   * Whether we should request activation of this widget's toplevel window.
+   */
+  enum class Raise {
+    No,
+    Yes,
+  };
+
+  /**
+   * Request activation of this window or give focus to this widget.
+   */
+  virtual void SetFocus(Raise, mozilla::dom::CallerType aCallerType) = 0;
+
+  /**
+   * Get this widget's outside dimensions relative to its parent widget. For
+   * popup widgets the returned rect is in screen coordinates and not
+   * relative to its parent widget.
+   *
+   * @return the x, y, width and height of this widget.
+   */
+  virtual LayoutDeviceIntRect GetBounds() = 0;
+
+  /**
+   * Get this widget's outside dimensions in device coordinates. This
+   * includes any title bar on the window.
+   *
+   * @return the x, y, width and height of this widget.
+   */
+  virtual LayoutDeviceIntRect GetScreenBounds() = 0;
+
+  /**
+   * Similar to GetScreenBounds except that this function will always
+   * get the size when the widget is in the nsSizeMode_Normal size mode
+   * even if the current size mode is not nsSizeMode_Normal.
+   * This method will fail if the size mode is not nsSizeMode_Normal and
+   * the platform doesn't have the ability.
+   * This method will always succeed if the current size mode is
+   * nsSizeMode_Normal.
+   *
+   * @param aRect   On return it holds the  x, y, width and height of
+   *                this widget.
+   */
+  [[nodiscard]] virtual nsresult GetRestoredBounds(
+      LayoutDeviceIntRect& aRect) = 0;
+
+  /**
+   * Get this widget's client area bounds, if the window has a 3D border
+   * appearance this returns the area inside the border. The position is the
+   * position of the client area relative to the client area of the parent
+   * widget (for root widgets and popup widgets it is in screen coordinates).
+   *
+   * @return the x, y, width and height of the client area of this widget.
+   */
+  virtual LayoutDeviceIntRect GetClientBounds() = 0;
+
+  /**
+   * Sets the non-client area dimensions of the window. Pass -1 to restore
+   * the system default frame size for that border. Pass zero to remove
+   * a border, or pass a specific value adjust a border. Units are in
+   * pixels. (DPI dependent)
+   *
+   * Platform notes:
+   *  Windows: shrinking top non-client height will remove application
+   *  icon and window title text. Glass desktops will refuse to set
+   *  dimensions between zero and size < system default.
+   */
+  virtual nsresult SetNonClientMargins(const LayoutDeviceIntMargin&) = 0;
+
+  /**
+   * Sets the region around the edges of the window that can be dragged to
+   * resize the window. All four sides of the window will get the same margin.
+   */
+  virtual void SetResizeMargin(mozilla::LayoutDeviceIntCoord aResizeMargin) = 0;
+  /**
+   * Get the client offset from the window origin.
+   *
+   * @return the x and y of the offset.
+   */
+  virtual LayoutDeviceIntPoint GetClientOffset() = 0;
+
+  /**
+   * Returns the slop from the screen edges in device pixels.
+   * @see Window.screenEdgeSlop{X,Y}
+   */
+  virtual LayoutDeviceIntPoint GetScreenEdgeSlop() { return {}; }
+
+  /**
+   * Equivalent to GetClientBounds but only returns the size.
+   */
+  virtual LayoutDeviceIntSize GetClientSize() {
+    // Depending on the backend, overloading this method may be useful if
+    // requesting the client offset is expensive.
+    return GetClientBounds().Size();
+  }
+
+  /**
+   * Set the background color for this widget
+   *
+   * @param aColor the new background color
+   *
+   */
+
+  virtual void SetBackgroundColor(const nscolor& aColor) {}
+
+  /**
+   * If a cursor type is currently cached locally for this widget, clear the
+   * cached cursor to force an update on the next SetCursor call.
+   */
+
+  virtual void ClearCachedCursor() = 0;
+
+  struct Cursor {
+    // The system cursor chosen by the page. This is used if there's no custom
+    // cursor, or if we fail to use the custom cursor in some way (if the image
+    // fails to load, for example).
+    nsCursor mDefaultCursor = eCursor_standard;
+    // May be null, to represent no custom cursor image.
+    nsCOMPtr<imgIContainer> mContainer;
+    uint32_t mHotspotX = 0;
+    uint32_t mHotspotY = 0;
+    mozilla::ImageResolution mResolution;
+
+    bool IsCustom() const { return !!mContainer; }
+
+    bool operator==(const Cursor& aOther) const {
+      return mDefaultCursor == aOther.mDefaultCursor &&
+             mContainer.get() == aOther.mContainer.get() &&
+             mHotspotX == aOther.mHotspotX && mHotspotY == aOther.mHotspotY &&
+             mResolution == aOther.mResolution;
+    }
+
+    bool operator!=(const Cursor& aOther) const { return !(*this == aOther); }
+  };
+
+  /**
+   * Sets the cursor for this widget.
+   */
+  virtual void SetCursor(const Cursor&) = 0;
+
+  virtual void SetCustomCursorAllowed(bool) = 0;
+
+  static nsIntSize CustomCursorSize(const Cursor&);
+
+  /**
+   * Get the window type of this widget.
+   */
+  WindowType GetWindowType() const { return mWindowType; }
+
+  /**
+   * Set the transparency mode of the top-level window containing this widget.
+   * So, e.g., if you call this on the widget for an IFRAME, the top level
+   * browser window containing the IFRAME actually gets set. Be careful.
+   *
+   * This can fail if the platform doesn't support
+   * transparency/glass. By default widgets are not
+   * transparent.  This will also fail if the toplevel window is not
+   * a Mozilla window, e.g., if the widget is in an embedded
+   * context.
+   *
+   * After transparency/glass has been enabled, the initial alpha channel
+   * value for all pixels is 1, i.e., opaque.
+   * If the window is resized then the alpha channel values for
+   * all pixels are reset to 1.
+   * Pixel RGB color values are already premultiplied with alpha channel values.
+   */
+  virtual void SetTransparencyMode(TransparencyMode aMode) = 0;
+
+  /**
+   * Get the transparency mode of the top-level window that contains this
+   * widget.
+   */
+  virtual TransparencyMode GetTransparencyMode() = 0;
+
+  /**
+   * Set the shadow style of the window.
+   *
+   * Ignored on child widgets and on non-Mac platforms.
+   */
+  virtual void SetWindowShadowStyle(mozilla::StyleWindowShadow aStyle) = 0;
+
+  /**
+   * Set the opacity of the window.
+   * Values need to be between 0.0f (invisible) and 1.0f (fully opaque).
+   *
+   * Ignored on child widgets and on non-Mac platforms.
+   */
+  virtual void SetWindowOpacity(float aOpacity) {}
+
+  /**
+   * Set the transform of the window. Values are in device pixels,
+   * the origin is the top left corner of the window.
+   *
+   * Ignored on child widgets and on non-Mac platforms.
+   */
+  virtual void SetWindowTransform(const mozilla::gfx::Matrix& aTransform) {}
+
+  /**
+   * Set the preferred color-scheme for the widget.
+   * Ignored on non-Mac platforms.
+   */
+  virtual void SetColorScheme(const mozilla::Maybe<mozilla::ColorScheme>&) {}
+
+  /**
+   * Set whether the window should ignore mouse events or not, and if it should
+   * not, what input margin should it use.
+   *
+   * This is only used on popup windows. The margin is only implemented on
+   * Linux.
+   */
+  struct InputRegion {
+    bool mFullyTransparent = false;
+    mozilla::LayoutDeviceIntCoord mMargin = 0;
+  };
+  virtual void SetInputRegion(const InputRegion&) {}
+
+  /*
+   * On macOS, this method shows or hides the pill button in the titlebar
+   * that's used to collapse the toolbar.
+   *
+   * Ignored on child widgets and on non-Mac platforms.
+   */
+  virtual void SetShowsToolbarButton(bool aShow) = 0;
+
+  /*
+   * On macOS, this method determines whether we tell cocoa that the window
+   * supports native full screen. If we do so, and another window is in
+   * native full screen, this window will also appear in native full screen.
+   *
+   * We generally only want to do this for primary application windows.
+   *
+   * Ignored on child widgets and on non-Mac platforms.
+   */
+  virtual void SetSupportsNativeFullscreen(bool aSupportsNativeFullscreen) = 0;
+
+  enum WindowAnimationType {
+    eGenericWindowAnimation,
+    eDocumentWindowAnimation
+  };
+
+  /**
+   * Sets the kind of top-level window animation this widget should have. On
+   * macOS, this causes a particular kind of animation to be shown when the
+   * window is first made visible.
+   *
+   * Ignored on child widgets and on non-Mac platforms.
+   */
+  virtual void SetWindowAnimationType(WindowAnimationType aType) = 0;
+
+  /**
+   * Specifies whether the window title should be drawn even if the window
+   * contents extend into the titlebar. Ignored on windows that don't draw
+   * in the titlebar. Only implemented on macOS.
+   */
+  virtual void SetDrawsTitle(bool aDrawTitle) {}
+
+  /**
+   * Hide window chrome (borders, buttons) for this widget.
+   *
+   */
+  virtual void HideWindowChrome(bool aShouldHide) = 0;
+
+  enum FullscreenTransitionStage {
+    eBeforeFullscreenToggle,
+    eAfterFullscreenToggle
+  };
+
+  /**
+   * Prepares for fullscreen transition and returns whether the widget
+   * supports fullscreen transition. If this method returns false,
+   * PerformFullscreenTransition() must never be called. Otherwise,
+   * caller should call that method twice with "before" and "after"
+   * stages respectively in order. In the latter case, this method may
+   * return some data via aData pointer. Caller must pass that data to
+   * PerformFullscreenTransition() if any, and caller is responsible
+   * for releasing that data.
+   */
+  virtual bool PrepareForFullscreenTransition(nsISupports** aData) = 0;
+
+  /**
+   * Performs fullscreen transition. This method returns immediately,
+   * and will post aCallback to the main thread when the transition
+   * finishes.
+   */
+  virtual void PerformFullscreenTransition(FullscreenTransitionStage aStage,
+                                           uint16_t aDuration,
+                                           nsISupports* aData,
+                                           nsIRunnable* aCallback) = 0;
+
+  /**
+   * Perform any actions needed after the fullscreen transition has ended.
+   */
+  virtual void CleanupFullscreenTransition() = 0;
+
+  /**
+   * Return the screen the widget is in, or null if we don't know.
+   */
+  virtual already_AddRefed<Screen> GetWidgetScreen() = 0;
+
+  /**
+   * Put the toplevel window into or out of fullscreen mode.
+   *
+   * @return NS_OK if the widget is setup properly for fullscreen and
+   * FullscreenChanged callback has been or will be called. If other
+   * value is returned, the caller should continue the change itself.
+   */
+  virtual nsresult MakeFullScreen(bool aFullScreen) = 0;
+
+  /**
+   * Same as MakeFullScreen, except that, on systems which natively
+   * support fullscreen transition, calling this method explicitly
+   * requests that behavior.
+   * It is currently only supported on macOS 10.7+.
+   */
+  virtual nsresult MakeFullScreenWithNativeTransition(bool aFullScreen) {
+    return MakeFullScreen(aFullScreen);
+  }
+
+  /**
+   * Invalidate a specified rect for a widget so that it will be repainted
+   * later.
+   */
+  virtual void Invalidate(const LayoutDeviceIntRect& aRect) = 0;
+
+  enum LayerManagerPersistence {
+    LAYER_MANAGER_CURRENT = 0,
+    LAYER_MANAGER_PERSISTENT
+  };
+
+  /**
+   * Return the widget's LayerManager. The layer tree for that LayerManager is
+   * what gets rendered to the widget.
+   *
+   * Note that this tries to create a renderer if it doesn't exist.
+   */
+  virtual WindowRenderer* GetWindowRenderer() = 0;
+
+  /**
+   * Returns whether there's an existing window renderer.
+   */
+  virtual bool HasWindowRenderer() const = 0;
+
+  /**
+   * Called before each layer manager transaction to allow any preparation
+   * for DrawWindowUnderlay/Overlay that needs to be on the main thread.
+   *
+   * Always called on the main thread.
+   */
+  virtual void PrepareWindowEffects() = 0;
+
+  /**
+   * Called on the main thread at the end of WebRender display list building.
+   */
+  virtual void AddWindowOverlayWebRenderCommands(
+      mozilla::layers::WebRenderBridgeChild* aWrBridge,
+      mozilla::wr::DisplayListBuilder& aBuilder,
+      mozilla::wr::IpcResourceUpdateQueue& aResources) {}
+
+  /**
+   * Called when Gecko knows which themed widgets exist in this window.
+   * The passed array contains an entry for every themed widget of the right
+   * type (currently only StyleAppearance::Toolbar) within the window, except
+   * for themed widgets which are transformed or have effects applied to them
+   * (e.g. CSS opacity or filters).
+   * This could sometimes be called during display list construction
+   * outside of painting.
+   * If called during painting, it will be called before we actually
+   * paint anything.
+   */
+  virtual void UpdateThemeGeometries(
+      const nsTArray<ThemeGeometry>& aThemeGeometries) = 0;
+
+  /**
+   * Informs the widget about the region of the window that is opaque.
+   *
+   * @param aOpaqueRegion the region of the window that is opaque.
+   */
+  virtual void UpdateOpaqueRegion(const LayoutDeviceIntRegion& aOpaqueRegion) {}
+
+  /**
+   * Informs the widget about the region of the window that is draggable.
+   */
+  virtual void UpdateWindowDraggingRegion(
+      const LayoutDeviceIntRegion& aRegion) {}
+
+  /**
+   * Tells the widget whether the given input block results in a swipe.
+   * Should be called in response to a WidgetWheelEvent that has
+   * mFlags.mCanTriggerSwipe set on it.
+   */
+  virtual void ReportSwipeStarted(uint64_t aInputBlockId, bool aStartSwipe) {}
+
+  /**
+   * Internal methods
+   */
+
+  //@{
+  virtual void AddChild(nsIWidget* aChild) = 0;
+  virtual void RemoveChild(nsIWidget* aChild) = 0;
+  virtual void* GetNativeData(uint32_t aDataType) = 0;
+  virtual void FreeNativeData(void* data, uint32_t aDataType) = 0;  //~~~
+
+  //@}
+
+  /**
+   * Set the widget's title.
+   * Must be called after Create.
+   *
+   * @param aTitle string displayed as the title of the widget
+   */
+  virtual nsresult SetTitle(const nsAString& aTitle) = 0;
+
+  /**
+   * Set the widget's icon.
+   * Must be called after Create.
+   *
+   * @param aIconSpec string specifying the icon to use; convention is to
+   *                  pass a resource: URL from which a platform-dependent
+   *                  resource file name will be constructed
+   */
+  virtual void SetIcon(const nsAString& aIconSpec) = 0;
+
+  /**
+   * Return this widget's origin in screen coordinates.
+   *
+   * @return screen coordinates stored in the x,y members
+   */
+  virtual LayoutDeviceIntPoint WidgetToScreenOffset() = 0;
+
+  /**
+   * The same as WidgetToScreenOffset(), except in the case of
+   * PuppetWidget where this method omits the chrome offset.
+   */
+  virtual LayoutDeviceIntPoint TopLevelWidgetToScreenOffset() {
+    return WidgetToScreenOffset();
+  }
+
+  /**
+   * For a PuppetWidget, returns the transform from the coordinate
+   * space of the PuppetWidget to the coordinate space of the
+   * top-level native widget.
+   *
+   * Identity transform in other cases.
+   */
+  virtual mozilla::LayoutDeviceToLayoutDeviceMatrix4x4
+  WidgetToTopLevelWidgetTransform() {
+    return mozilla::LayoutDeviceToLayoutDeviceMatrix4x4();
+  }
+
+  mozilla::LayoutDeviceIntPoint WidgetToTopLevelWidgetOffset() {
+    return mozilla::LayoutDeviceIntPoint::Round(
+        WidgetToTopLevelWidgetTransform().TransformPoint(
+            mozilla::LayoutDevicePoint()));
+  }
+
+  /**
+   * Returns the margins that are applied to go from client sizes to window
+   * sizes (which includes window borders and titlebar).
+   * This method should work even when the window is not yet visible.
+   */
+  virtual LayoutDeviceIntMargin ClientToWindowMargin() { return {}; }
+
+  LayoutDeviceIntSize ClientToWindowSizeDifference();
+
+  /**
+   * Dispatches an event to the widget
+   */
+  virtual nsresult DispatchEvent(mozilla::WidgetGUIEvent* event,
+                                 nsEventStatus& aStatus) = 0;
+
+  /**
+   * Dispatches an event to APZ only.
+   * No-op in the child process.
+   */
+  virtual void DispatchEventToAPZOnly(mozilla::WidgetInputEvent* aEvent) = 0;
+
+  /*
+   * Dispatch a gecko event for this widget.
+   * Returns true if it's consumed.  Otherwise, false.
+   */
+  virtual bool DispatchWindowEvent(mozilla::WidgetGUIEvent& event) = 0;
+
+  // A structure that groups the statuses from APZ dispatch and content
+  // dispatch.
+  struct ContentAndAPZEventStatus {
+    // Either of these may not be set if the event was not dispatched
+    // to APZ or to content.
+    nsEventStatus mApzStatus = nsEventStatus_eIgnore;
+    nsEventStatus mContentStatus = nsEventStatus_eIgnore;
+  };
+
+  /**
+   * Dispatches an event that must be handled by APZ first, when APZ is
+   * enabled. If invoked in the child process, it is forwarded to the
+   * parent process synchronously.
+   */
+  virtual ContentAndAPZEventStatus DispatchInputEvent(
+      mozilla::WidgetInputEvent* aEvent) = 0;
+
+  /**
+   * Confirm an APZ-aware event target. This should be used when APZ will
+   * not need a layers update to process the event.
+   */
+  virtual void SetConfirmedTargetAPZC(
+      uint64_t aInputBlockId,
+      const nsTArray<ScrollableLayerGuid>& aTargets) const = 0;
+
+  /**
+   * Returns true if APZ is in use, false otherwise.
+   */
+  virtual bool AsyncPanZoomEnabled() const = 0;
+
+  /**
+   */
+  virtual void SwipeFinished() = 0;
+
+  /**
+   * Enables the dropping of files to a widget.
+   */
+  virtual void EnableDragDrop(bool aEnable) = 0;
+  virtual nsresult AsyncEnableDragDrop(bool aEnable) = 0;
+
+  /**
+   * Classify the window for the window manager. Mostly for X11.
+   *
+   *  @param xulWinType The window type. Characters other than [A-Za-z0-9_-] are
+   *                    converted to '_'. Anything before the first colon is
+   *                    assigned to name, anything after it to role. If there's
+   *                    no colon, assign the whole thing to both role and name.
+   *
+   * @param xulWinClass The window class. If set, overrides the normal value.
+   *                    Otherwise, the program class it used.
+   *
+   * @param xulWinName The window name. If set, overrides the value specified in
+   *                   window type. Otherwise, name from window type is used.
+   *
+   */
+  virtual void SetWindowClass(const nsAString& xulWinType,
+                              const nsAString& xulWinClass,
+                              const nsAString& xulWinName) = 0;
+
+  /**
+   * Enables/Disables system capture of any and all events that would cause a
+   * popup to be rolled up. aListener should be set to a non-null value for
+   * any popups that are not managed by the popup manager.
+   * @param aDoCapture true enables capture, false disables capture
+   *
+   */
+  virtual void CaptureRollupEvents(bool aDoCapture) = 0;
+
+  /**
+   * Bring this window to the user's attention.  This is intended to be a more
+   * gentle notification than popping the window to the top or putting up an
+   * alert.  See, for example, Win32 FlashWindow or the NotificationManager on
+   * the Mac.  The notification should be suppressed if the window is already
+   * in the foreground and should be dismissed when the user brings this window
+   * to the foreground.
+   * @param aCycleCount Maximum number of times to animate the window per system
+   *                    conventions. If set to -1, cycles indefinitely until
+   *                    window is brought into the foreground.
+   */
+  [[nodiscard]] virtual nsresult GetAttention(int32_t aCycleCount) = 0;
+
+  /**
+   * Ask whether there user input events pending.  All input events are
+   * included, including those not targeted at this nsIwidget instance.
+   */
+  virtual bool HasPendingInputEvent() = 0;
+
+  /**
+   * If set to true, the window will draw its contents into the titlebar
+   * instead of below it.
+   *
+   * Ignored on any platform that does not support it. Ignored by widgets that
+   * do not represent windows.
+   * May result in a resize event, so should only be called from places where
+   * reflow and painting is allowed.
+   *
+   * @param aState Whether drawing into the titlebar should be activated.
+   */
+  virtual void SetDrawsInTitlebar(bool aState) = 0;
+
+  /*
+   * Determine whether the widget shows a resize widget. If it does,
+   * aResizerRect returns the resizer's rect.
+   *
+   * Returns false on any platform that does not support it.
+   *
+   * @param aResizerRect The resizer's rect in device pixels.
+   * @return Whether a resize widget is shown.
+   */
+  virtual bool ShowsResizeIndicator(LayoutDeviceIntRect* aResizerRect) = 0;
+
+  // TODO: Make this an enum class with MOZ_MAKE_ENUM_CLASS_BITWISE_OPERATORS or
+  //       EnumSet class.
+  enum Modifiers : uint32_t {
+    NO_MODIFIERS = 0x00000000,
+    CAPS_LOCK = 0x00000001,  // when CapsLock is active
+    NUM_LOCK = 0x00000002,   // when NumLock is active
+    SHIFT_L = 0x00000100,
+    SHIFT_R = 0x00000200,
+    CTRL_L = 0x00000400,
+    CTRL_R = 0x00000800,
+    ALT_L = 0x00001000,  // includes Option
+    ALT_R = 0x00002000,
+    COMMAND_L = 0x00004000,
+    COMMAND_R = 0x00008000,
+    HELP = 0x00010000,
+    ALTGRAPH = 0x00020000,  // AltGr key on Windows.  This emulates
+                            // AltRight key behavior of keyboard
+                            // layouts which maps AltGr to AltRight
+                            // key.
+    FUNCTION = 0x00100000,
+    NUMERIC_KEY_PAD = 0x01000000  // when the key is coming from the keypad
+  };
+  /**
+   * Utility method intended for testing. Dispatches native key events
+   * to this widget to simulate the press and release of a key.
+   * @param aNativeKeyboardLayout a *platform-specific* constant.
+   * On Mac, this is the resource ID for a 'uchr' or 'kchr' resource.
+   * On Windows, it is converted to a hex string and passed to
+   * LoadKeyboardLayout, see
+   * http://msdn.microsoft.com/en-us/library/ms646305(VS.85).aspx
+   * @param aNativeKeyCode a *platform-specific* keycode.
+   * On Windows, this is the virtual key code.
+   * @param aModifiers some combination of the above 'Modifiers' flags;
+   * not all flags will apply to all platforms. Mac ignores the _R
+   * modifiers. Windows ignores COMMAND, NUMERIC_KEY_PAD, HELP and
+   * FUNCTION.
+   * @param aCharacters characters that the OS would decide to generate
+   * from the event. On Windows, this is the charCode passed by
+   * WM_CHAR.
+   * @param aUnmodifiedCharacters characters that the OS would decide
+   * to generate from the event if modifier keys (other than shift)
+   * were assumed inactive. Needed on Mac, ignored on Windows.
+   * @param aObserver the observer that will get notified once the events
+   * have been dispatched.
+   * @return NS_ERROR_NOT_AVAILABLE to indicate that the keyboard
+   * layout is not supported and the event was not fired
+   */
+  virtual nsresult SynthesizeNativeKeyEvent(
+      int32_t aNativeKeyboardLayout, int32_t aNativeKeyCode,
+      uint32_t aModifierFlags, const nsAString& aCharacters,
+      const nsAString& aUnmodifiedCharacters, nsIObserver* aObserver) = 0;
+
+  /**
+   * Utility method intended for testing. Dispatches native mouse events
+   * may even move the mouse cursor. On Mac the events are guaranteed to
+   * be sent to the window containing this widget, but on Windows they'll go
+   * to whatever's topmost on the screen at that position, so for
+   * cross-platform testing ensure that your window is at the top of the
+   * z-order.
+   * @param aPoint screen location of the mouse, in device
+   * pixels, with origin at the top left
+   * @param aNativeMessage abstract native message.
+   * @param aButton Mouse button defined by DOM UI Events.
+   * @param aModifierFlags Some values of nsIWidget::Modifiers.
+   *                       FYI: On Windows, Android and Headless widget on all
+   *                       platroms, this hasn't been handled yet.
+   * @param aObserver the observer that will get notified once the events
+   * have been dispatched.
+   */
+  enum class NativeMouseMessage : uint32_t {
+    ButtonDown,   // button down
+    ButtonUp,     // button up
+    Move,         // mouse cursor move
+    EnterWindow,  // mouse cursor comes into a window
+    LeaveWindow,  // mouse cursor leaves from a window
+  };
+  virtual nsresult SynthesizeNativeMouseEvent(
+      LayoutDeviceIntPoint aPoint, NativeMouseMessage aNativeMessage,
+      mozilla::MouseButton aButton, nsIWidget::Modifiers aModifierFlags,
+      nsIObserver* aObserver) = 0;
+
+  /**
+   * A shortcut to SynthesizeNativeMouseEvent, abstracting away the native
+   * message. aPoint is location in device pixels to which the mouse pointer
+   * moves to.
+   * @param aObserver the observer that will get notified once the events
+   * have been dispatched.
+   */
+  virtual nsresult SynthesizeNativeMouseMove(LayoutDeviceIntPoint aPoint,
+                                             nsIObserver* aObserver) = 0;
+
+  /**
+   * Utility method intended for testing. Dispatching native mouse scroll
+   * events may move the mouse cursor.
+   *
+   * @param aPoint            Mouse cursor position in screen coordinates.
+   *                          In device pixels, the origin at the top left of
+   *                          the primary display.
+   * @param aNativeMessage    Platform native message.
+   * @param aDeltaX           The delta value for X direction.  If the native
+   *                          message doesn't indicate X direction scrolling,
+   *                          this may be ignored.
+   * @param aDeltaY           The delta value for Y direction.  If the native
+   *                          message doesn't indicate Y direction scrolling,
+   *                          this may be ignored.
+   * @param aDeltaZ           The delta value for Z direction.  If the native
+   *                          message doesn't indicate Z direction scrolling,
+   *                          this may be ignored.
+   * @param aModifierFlags    Must be values of Modifiers, or zero.
+   * @param aAdditionalFlags  See nsIDOMWidnowUtils' consts and their
+   *                          document.
+   * @param aObserver         The observer that will get notified once the
+   *                          events have been dispatched.
+   */
+  virtual nsresult SynthesizeNativeMouseScrollEvent(
+      LayoutDeviceIntPoint aPoint, uint32_t aNativeMessage, double aDeltaX,
+      double aDeltaY, double aDeltaZ, uint32_t aModifierFlags,
+      uint32_t aAdditionalFlags, nsIObserver* aObserver) = 0;
+
+  /*
+   * TouchPointerState states for SynthesizeNativeTouchPoint. Match
+   * touch states in nsIDOMWindowUtils.idl.
+   */
+  enum TouchPointerState {
+    // The pointer is in a hover state above the digitizer
+    TOUCH_HOVER = (1 << 0),
+    // The pointer is in contact with the digitizer
+    TOUCH_CONTACT = (1 << 1),
+    // The pointer has been removed from the digitizer detection area
+    TOUCH_REMOVE = (1 << 2),
+    // The pointer has been canceled. Will cancel any pending os level
+    // gestures that would triggered as a result of completion of the
+    // input sequence. This may not cancel moz platform related events
+    // that might get tirggered by input already delivered.
+    TOUCH_CANCEL = (1 << 3),
+
+    // ALL_BITS used for validity checking during IPC serialization
+    ALL_BITS = (1 << 4) - 1
+  };
+  /*
+   * TouchpadGesturePhase states for SynthesizeNativeTouchPadPinch and
+   * SynthesizeNativeTouchpadPan. Match phase states in nsIDOMWindowUtils.idl.
+   */
+  enum TouchpadGesturePhase {
+    PHASE_BEGIN = 0,
+    PHASE_UPDATE = 1,
+    PHASE_END = 2
+  };
+  /*
+   * Create a new or update an existing touch pointer on the digitizer.
+   * To trigger os level gestures, individual touch points should
+   * transition through a complete set of touch states which should be
+   * sent as individual messages.
+   *
+   * @param aPointerId The touch point id to create or update.
+   * @param aPointerState one or more of the touch states listed above
+   * @param aPoint coords of this event
+   * @param aPressure 0.0 -> 1.0 float val indicating pressure
+   * @param aOrientation 0 -> 359 degree value indicating the
+   * orientation of the pointer. Use 90 for normal taps.
+   * @param aObserver The observer that will get notified once the events
+   * have been dispatched.
+   */
+  virtual nsresult SynthesizeNativeTouchPoint(uint32_t aPointerId,
+                                              TouchPointerState aPointerState,
+                                              LayoutDeviceIntPoint aPoint,
+                                              double aPointerPressure,
+                                              uint32_t aPointerOrientation,
+                                              nsIObserver* aObserver) = 0;
+  /*
+   * See nsIDOMWindowUtils.sendNativeTouchpadPinch().
+   */
+  virtual nsresult SynthesizeNativeTouchPadPinch(
+      TouchpadGesturePhase aEventPhase, float aScale,
+      LayoutDeviceIntPoint aPoint, int32_t aModifierFlags) = 0;
+
+  /*
+   * Helper for simulating a simple tap event with one touch point. When
+   * aLongTap is true, simulates a native long tap with a duration equal to
+   * ui.click_hold_context_menus.delay. This pref is compatible with the
+   * apzc long tap duration. Defaults to 1.5 seconds.
+   * @param aObserver The observer that will get notified once the events
+   * have been dispatched.
+   */
+  virtual nsresult SynthesizeNativeTouchTap(LayoutDeviceIntPoint aPoint,
+                                            bool aLongTap,
+                                            nsIObserver* aObserver);
+
+  virtual nsresult SynthesizeNativePenInput(uint32_t aPointerId,
+                                            TouchPointerState aPointerState,
+                                            LayoutDeviceIntPoint aPoint,
+                                            double aPressure,
+                                            uint32_t aRotation, int32_t aTiltX,
+                                            int32_t aTiltY, int32_t aButton,
+                                            nsIObserver* aObserver) = 0;
+
+  /*
+   * Cancels all active simulated touch input points and pending long taps.
+   * Native widgets should track existing points such that they can clear the
+   * digitizer state when this call is made.
+   * @param aObserver The observer that will get notified once the touch
+   * sequence has been cleared.
+   */
+  virtual nsresult ClearNativeTouchSequence(nsIObserver* aObserver);
+
+  /*
+   * Send a native event as if the user double tapped the touchpad with two
+   * fingers.
+   */
+  virtual nsresult SynthesizeNativeTouchpadDoubleTap(
+      LayoutDeviceIntPoint aPoint, uint32_t aModifierFlags) = 0;
+
+  /*
+   * See nsIDOMWindowUtils.sendNativeTouchpadPan().
+   */
+  virtual nsresult SynthesizeNativeTouchpadPan(TouchpadGesturePhase aEventPhase,
+                                               LayoutDeviceIntPoint aPoint,
+                                               double aDeltaX, double aDeltaY,
+                                               int32_t aModifierFlags,
+                                               nsIObserver* aObserver) = 0;
+
+  virtual void StartAsyncScrollbarDrag(
+      const AsyncDragMetrics& aDragMetrics) = 0;
+
+  /**
+   * Notify APZ to start autoscrolling.
+   * @param aAnchorLocation the location of the autoscroll anchor
+   * @param aGuid identifies the scroll frame to be autoscrolled
+   * @return true if APZ has been successfully notified
+   */
+  virtual bool StartAsyncAutoscroll(const ScreenPoint& aAnchorLocation,
+                                    const ScrollableLayerGuid& aGuid) = 0;
+
+  /**
+   * Notify APZ to stop autoscrolling.
+   * @param aGuid identifies the scroll frame which is being autoscrolled.
+   */
+  virtual void StopAsyncAutoscroll(const ScrollableLayerGuid& aGuid) = 0;
+
+  virtual LayersId GetRootLayerTreeId() = 0;
+
+  // If this widget supports out-of-process compositing, it can override
+  // this method to provide additional information to the compositor.
+  virtual void GetCompositorWidgetInitData(
+      mozilla::widget::CompositorWidgetInitData* aInitData) {}
+
+  /**
+   * Setter/Getter of the system font setting for testing.
+   */
+  virtual nsresult SetSystemFont(const nsCString& aFontName) {
+    return NS_ERROR_NOT_IMPLEMENTED;
+  }
+  virtual nsresult GetSystemFont(nsCString& aFontName) {
+    return NS_ERROR_NOT_IMPLEMENTED;
+  }
+
+  /**
+   * Wayland specific routines.
+   */
+  virtual LayoutDeviceIntSize GetMoveToRectPopupSize() const {
+    NS_WARNING("GetLayoutPopupRect implemented only for wayland");
+    return LayoutDeviceIntSize();
+  }
+
+  /**
+   * If this widget uses native pointer lock instead of warp-to-center
+   * (currently only GTK on Wayland), these methods provide access to that
+   * functionality.
+   */
+  virtual void SetNativePointerLockCenter(
+      const LayoutDeviceIntPoint& aLockCenter) {}
+  virtual void LockNativePointer() {}
+  virtual void UnlockNativePointer() {}
+
+  /*
+   * Get safe area insets except to cutout.
+   * See https://drafts.csswg.org/css-env-1/#safe-area-insets.
+   */
+  virtual mozilla::ScreenIntMargin GetSafeAreaInsets() const {
+    return mozilla::ScreenIntMargin();
+  }
+
+ private:
+  class LongTapInfo {
+   public:
+    LongTapInfo(int32_t aPointerId, LayoutDeviceIntPoint& aPoint,
+                mozilla::TimeDuration aDuration, nsIObserver* aObserver)
+        : mPointerId(aPointerId),
+          mPosition(aPoint),
+          mDuration(aDuration),
+          mObserver(aObserver),
+          mStamp(mozilla::TimeStamp::Now()) {}
+
+    int32_t mPointerId;
+    LayoutDeviceIntPoint mPosition;
+    mozilla::TimeDuration mDuration;
+    nsCOMPtr<nsIObserver> mObserver;
+    mozilla::TimeStamp mStamp;
+  };
+
+  static void OnLongTapTimerCallback(nsITimer* aTimer, void* aClosure);
+
+  static already_AddRefed<nsIBidiKeyboard> CreateBidiKeyboardContentProcess();
+  static already_AddRefed<nsIBidiKeyboard> CreateBidiKeyboardInner();
+
+  mozilla::UniquePtr<LongTapInfo> mLongTapTouchPoint;
+  nsCOMPtr<nsITimer> mLongTapTimer;
+  static int32_t sPointerIdCounter;
+
+ public:
+  /**
+   * If key events have not been handled by content or XBL handlers, they can
+   * be offered to the system (for custom application shortcuts set in system
+   * preferences, for example).
+   */
+  virtual void PostHandleKeyEvent(mozilla::WidgetKeyboardEvent* aEvent);
+
+  /**
+   * Activates a native menu item at the position specified by the index
+   * string. The index string is a string of positive integers separated
+   * by the "|" (pipe) character. The last integer in the string represents
+   * the item index in a submenu located using the integers preceding it.
+   *
+   * Example: 1|0|4
+   * In this string, the first integer represents the top-level submenu
+   * in the native menu bar. Since the integer is 1, it is the second submeu
+   * in the native menu bar. Within that, the first item (index 0) is a
+   * submenu, and we want to activate the 5th item within that submenu.
+   */
+  virtual nsresult ActivateNativeMenuItemAt(const nsAString& indexString) = 0;
+
+  /**
+   * This is used for native menu system testing.
+   *
+   * Updates a native menu at the position specified by the index string.
+   * The index string is a string of positive integers separated by the "|"
+   * (pipe) character.
+   *
+   * Example: 1|0|4
+   * In this string, the first integer represents the top-level submenu
+   * in the native menu bar. Since the integer is 1, it is the second submeu
+   * in the native menu bar. Within that, the first item (index 0) is a
+   * submenu, and we want to update submenu at index 4 within that submenu.
+   *
+   * If this is called with an empty string it forces a full reload of the
+   * menu system.
+   */
+  virtual nsresult ForceUpdateNativeMenuAt(const nsAString& indexString) = 0;
+
+  /**
+   * This is used for testing macOS service menu code.
+   *
+   * @param aResult - the current text selection. Is empty if no selection.
+   * @return nsresult - whether or not aResult was assigned the selected text.
+   */
+  [[nodiscard]] virtual nsresult GetSelectionAsPlaintext(nsAString& aResult) {
+    return NS_ERROR_NOT_IMPLEMENTED;
+  }
+
+  /**
+   * Notify IME of the specified notification.
+   *
+   * @return If the notification is mouse button event and it's consumed by
+   *         IME, this returns NS_SUCCESS_EVENT_CONSUMED.
+   */
+  virtual nsresult NotifyIME(const IMENotification& aIMENotification) = 0;
+
+  /**
+   * MaybeDispatchInitialFocusEvent will dispatch a focus event after creation
+   * of the widget, in the event that we were not able to observe and respond to
+   * the initial focus event. This is necessary for the early skeleton UI
+   * window, which is displayed and receives its initial focus event before we
+   * can actually respond to it.
+   */
+  virtual void MaybeDispatchInitialFocusEvent() {}
+
+  /*
+   * Notifies the input context changes.
+   */
+  virtual void SetInputContext(const InputContext& aContext,
+                               const InputContextAction& aAction) = 0;
+
+  /*
+   * Get current input context.
+   */
+  virtual InputContext GetInputContext() = 0;
+
+  /**
+   * Get native IME context.  This is different from GetNativeData() with
+   * NS_RAW_NATIVE_IME_CONTEXT, the result is unique even if in a remote
+   * process.
+   */
+  virtual NativeIMEContext GetNativeIMEContext() = 0;
+
+  /*
+   * Given a WidgetKeyboardEvent, this method synthesizes a corresponding
+   * native (OS-level) event for it. This method allows tests to simulate
+   * keystrokes that trigger native key bindings (which require a native
+   * event).
+   */
+  [[nodiscard]] virtual nsresult AttachNativeKeyEvent(
+      mozilla::WidgetKeyboardEvent& aEvent) = 0;
+
+  /**
+   * Retrieve edit commands when the key combination of aEvent is used
+   * in platform native applications.
+   */
+  MOZ_CAN_RUN_SCRIPT virtual bool GetEditCommands(
+      mozilla::NativeKeyBindingsType aType,
+      const mozilla::WidgetKeyboardEvent& aEvent,
+      nsTArray<mozilla::CommandInt>& aCommands);
+
+  /*
+   * Retrieves a reference to notification requests of IME.  Note that the
+   * reference is valid while the nsIWidget instance is alive.  So, if you
+   * need to store the reference for a long time, you need to grab the widget
+   * instance too.
+   */
+  const IMENotificationRequests& IMENotificationRequestsRef();
+
+  /*
+   * Call this method when a dialog is opened which has a default button.
+   * The button's rectangle should be supplied in aButtonRect.
+   */
+  [[nodiscard]] virtual nsresult OnDefaultButtonLoaded(
+      const LayoutDeviceIntRect& aButtonRect) = 0;
+
+  /**
+   * Return true if this process shouldn't use platform widgets, and
+   * so should use PuppetWidgets instead.  If this returns true, the
+   * result of creating and using a platform widget is undefined,
+   * and likely to end in crashes or other buggy behavior.
+   */
+  static bool UsePuppetWidgets() { return XRE_IsContentProcess(); }
+
+  static already_AddRefed<nsIWidget> CreateTopLevelWindow();
+
+  static already_AddRefed<nsIWidget> CreateChildWindow();
+
+  /**
+   * Allocate and return a "puppet widget" that doesn't directly
+   * correlate to a platform widget; platform events and data must
+   * be fed to it.  Currently used in content processes.  NULL is
+   * returned if puppet widgets aren't supported in this build
+   * config, on this platform, or for this process type.
+   *
+   * This function is called "Create" to match CreateInstance().
+   * The returned widget must still be nsIWidget::Create()d.
+   */
+  static already_AddRefed<nsIWidget> CreatePuppetWidget(
+      BrowserChild* aBrowserChild);
+
+  static already_AddRefed<nsIWidget> CreateHeadlessWidget();
+
+  /**
+   * Reparent this widget's native widget.
+   * @param aNewParent the native widget of aNewParent is the new native
+   *                   parent widget
+   */
+  virtual void ReparentNativeWidget(nsIWidget* aNewParent) = 0;
+
+  /**
+   * Return true if widget has it's own GL context
+   */
+  virtual bool HasGLContext() { return false; }
+
+  /**
+   * Returns true to indicate that this widget paints an opaque background
+   * that we want to be visible under the page, so layout should not force
+   * a default background.
+   */
+  virtual bool WidgetPaintsBackground() { return false; }
+
+  virtual bool NeedsPaint() { return IsVisible() && !GetBounds().IsEmpty(); }
+
+  /**
+   * Get the natural bounds of this widget.  This method is only
+   * meaningful for widgets for which Gecko implements screen
+   * rotation natively.  When this is the case, GetBounds() returns
+   * the widget bounds taking rotation into account, and
+   * GetNaturalBounds() returns the bounds *not* taking rotation
+   * into account.
+   *
+   * No code outside of the composition pipeline should know or care
+   * about this.  If you're not an agent of the compositor, you
+   * probably shouldn't call this method.
+   */
+  virtual LayoutDeviceIntRect GetNaturalBounds() { return GetBounds(); }
+
+  /**
+   * Set size constraints on the window size such that it is never less than
+   * the specified minimum size and never larger than the specified maximum
+   * size. The size constraints are sizes of the outer rectangle including
+   * the window frame and title bar. Use 0 for an unconstrained minimum size
+   * and NS_MAXSIZE for an unconstrained maximum size. Note that this method
+   * does not necessarily change the size of a window to conform to this size,
+   * thus Resize should be called afterwards.
+   *
+   * @param aConstraints: the size constraints in device pixels
+   */
+  virtual void SetSizeConstraints(const SizeConstraints& aConstraints) = 0;
+
+  /**
+   * Return the size constraints currently observed by the widget.
+   *
+   * @return the constraints in device pixels
+   */
+  virtual const SizeConstraints GetSizeConstraints() = 0;
+
+  /**
+   * Apply the current size constraints to the given size.
+   *
+   * @param aWidth width to constrain
+   * @param aHeight height to constrain
+   */
+  virtual void ConstrainSize(int32_t* aWidth, int32_t* aHeight) = 0;
+
+  /**
+   * If this is owned by a BrowserChild, return that.  Otherwise return
+   * null.
+   */
+  virtual BrowserChild* GetOwningBrowserChild() { return nullptr; }
+
+  /**
+   * If this isn't directly compositing to its window surface,
+   * return the compositor which is doing that on our behalf.
+   */
+  virtual CompositorBridgeChild* GetRemoteRenderer() { return nullptr; }
+
+  /**
+   * Clear WebRender resources
+   */
+  virtual void ClearCachedWebrenderResources() {}
+
+  /**
+   * Clear WebRender animation resources
+   */
+  virtual void ClearWebrenderAnimationResources() {}
+
+  /**
+   * Request fast snapshot at RenderCompositor of WebRender.
+   * Since readback of Windows DirectComposition is very slow.
+   */
+  virtual bool SetNeedFastSnaphot() { return false; }
+
+  /**
+   * If this widget has its own vsync dispatcher, return it, otherwise return
+   * nullptr. An example of such a local vsync dispatcher would be Wayland frame
+   * callbacks.
+   */
+  virtual RefPtr<mozilla::VsyncDispatcher> GetVsyncDispatcher();
+
+  /**
+   * Returns true if the widget requires synchronous repaints on resize,
+   * false otherwise.
+   */
+  virtual bool SynchronouslyRepaintOnResize() { return true; }
+
+  /**
+   * Some platforms (only cocoa right now) round widget coordinates to the
+   * nearest even pixels (see bug 892994), this function allows us to
+   * determine how widget coordinates will be rounded.
+   */
+  virtual int32_t RoundsWidgetCoordinatesTo() { return 1; }
+
+  virtual void UpdateZoomConstraints(
+      const uint32_t& aPresShellId, const ScrollableLayerGuid::ViewID& aViewId,
+      const mozilla::Maybe<ZoomConstraints>& aConstraints){};
+
+  /**
+   * GetTextEventDispatcher() returns TextEventDispatcher belonging to the
+   * widget.  Note that this never returns nullptr.
+   */
+  virtual TextEventDispatcher* GetTextEventDispatcher() = 0;
+
+  /**
+   * GetNativeTextEventDispatcherListener() returns a
+   * TextEventDispatcherListener instance which is used when the widget
+   * instance handles native IME and/or keyboard events.
+   */
+  virtual TextEventDispatcherListener*
+  GetNativeTextEventDispatcherListener() = 0;
+
+  virtual void ZoomToRect(const uint32_t& aPresShellId,
+                          const ScrollableLayerGuid::ViewID& aViewId,
+                          const CSSRect& aRect, const uint32_t& aFlags) = 0;
+
+  /**
+   * LookUpDictionary shows the dictionary for the word around current point.
+   *
+   * @param aText            the word to look up dictiorary.
+   * @param aFontRangeArray  text decoration of aText
+   * @param aIsVertical      true if the word is vertical layout
+   * @param aPoint           top-left point of aText
+   */
+  virtual void LookUpDictionary(
+      const nsAString& aText,
+      const nsTArray<mozilla::FontRange>& aFontRangeArray,
+      const bool aIsVertical, const LayoutDeviceIntPoint& aPoint) {}
+
+  virtual void RequestFxrOutput() {
+    MOZ_ASSERT(false, "This function should only execute in Windows");
+  }
+
+#if defined(MOZ_WIDGET_ANDROID)
+  /**
+   * RecvToolbarAnimatorMessageFromCompositor receive message from compositor
+   * thread.
+   *
+   * @param aMessage message being sent to Android UI thread.
+   */
+  virtual void RecvToolbarAnimatorMessageFromCompositor(int32_t aMessage) = 0;
+
+  /**
+   * UpdateRootFrameMetrics steady state frame metrics send from compositor
+   * thread
+   *
+   * @param aScrollOffset  page scroll offset value in screen pixels.
+   * @param aZoom          current page zoom.
+   */
+  virtual void UpdateRootFrameMetrics(const ScreenPoint& aScrollOffset,
+                                      const CSSToScreenScale& aZoom) = 0;
+
+  /**
+   * RecvScreenPixels Buffer containing the pixel from the frame buffer. Used
+   * for android robocop tests.
+   *
+   * @param aMem  shared memory containing the frame buffer pixels.
+   * @param aSize size of the buffer in screen pixels.
+   */
+  virtual void RecvScreenPixels(mozilla::ipc::Shmem&& aMem,
+                                const ScreenIntSize& aSize,
+                                bool aNeedsYFlip) = 0;
+
+  virtual void UpdateDynamicToolbarMaxHeight(mozilla::ScreenIntCoord aHeight) {}
+  virtual mozilla::ScreenIntCoord GetDynamicToolbarMaxHeight() const {
+    return 0;
+  }
+#endif
+
+  static already_AddRefed<nsIBidiKeyboard> CreateBidiKeyboard();
+
+  /**
+   * Like GetDefaultScale, but taking into account only the system settings
+   * and ignoring Gecko preferences.
+   */
+  virtual double GetDefaultScaleInternal() { return 1.0; }
+
+  using WindowButtonType = mozilla::WindowButtonType;
+
+  /**
+   * Layout uses this to alert the widget to the client rect representing
+   * the window maximize button.  An empty rect indicates there is no
+   * maximize button (for example, in fullscreen).  This is only implemented
+   * on Windows.
+   */
+  virtual void SetWindowButtonRect(WindowButtonType aButtonType,
+                                   const LayoutDeviceIntRect& aClientRect) {}
+
+#ifdef DEBUG
+  virtual nsresult SetHiDPIMode(bool aHiDPI) {
+    return NS_ERROR_NOT_IMPLEMENTED;
+  }
+  virtual nsresult RestoreHiDPIMode() { return NS_ERROR_NOT_IMPLEMENTED; }
+#endif
+
+ protected:
+  // keep the list of children.  We also keep track of our siblings.
+  // The ownership model is as follows: parent holds a strong ref to
+  // the first element of the list, and each element holds a strong
+  // ref to the next element in the list.  The prevsibling and
+  // lastchild pointers are weak, which is fine as long as they are
+  // maintained properly.
+  nsCOMPtr<nsIWidget> mFirstChild;
+  nsIWidget* MOZ_NON_OWNING_REF mLastChild;
+  nsCOMPtr<nsIWidget> mNextSibling;
+  nsIWidget* MOZ_NON_OWNING_REF mPrevSibling;
+  // When Destroy() is called, the sub class should set this true.
+  bool mOnDestroyCalled;
+  WindowType mWindowType;
+  int32_t mZIndex;
+};
+
+NS_DEFINE_STATIC_IID_ACCESSOR(nsIWidget, NS_IWIDGET_IID)
+
+#endif  // nsIWidget_h__