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 /* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */

 /* 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 mozilla_layers_APZCCallbackHelper_h

 #define mozilla_layers_APZCCallbackHelper_h

 #include "FrameMetrics.h"

 #include "nsIContent.h"

 #include "nsIDocument.h"

 #include "nsIDOMWindowUtils.h"

 namespace mozilla {

 namespace layers {

 /* This class contains some helper methods that facilitate implementing the

    GeckoContentController callback interface required by the AsyncPanZoomController.

    Since different platforms need to implement this interface in similar-but-

    not-quite-the-same ways, this utility class provides some helpful methods

    to hold code that can be shared across the different platform implementations.

  */

 class APZCCallbackHelper

 {

     typedef mozilla::layers::FrameMetrics FrameMetrics;

     typedef mozilla::layers::ScrollableLayerGuid ScrollableLayerGuid;

 public:

     /* Checks to see if the pres shell that the given FrameMetrics object refers

        to is still the valid pres shell for the DOMWindowUtils. This can help

        guard against apply stale updates (updates meant for a pres shell that has

        since been torn down and replaced). */

     static bool HasValidPresShellId(nsIDOMWindowUtils* aUtils,

                                     const FrameMetrics& aMetrics);

     /* Applies the scroll and zoom parameters from the given FrameMetrics object to

        the root frame corresponding to the given DOMWindowUtils. If tiled thebes

        layers are enabled, this will align the displayport to tile boundaries.

        Setting the scroll position can cause some small adjustments to be made

        to the actual scroll position. aMetrics' display port and scroll position

        will be updated with any modifications made. */

     static void UpdateRootFrame(nsIDOMWindowUtils* aUtils,

                                 FrameMetrics& aMetrics);

     /* Applies the scroll parameters from the given FrameMetrics object to the subframe

        corresponding to the given content object. If tiled thebes

        layers are enabled, this will align the displayport to tile boundaries.

        Setting the scroll position can cause some small adjustments to be made

        to the actual scroll position. aMetrics' display port and scroll position

        will be updated with any modifications made. */

     static void UpdateSubFrame(nsIContent* aContent,

                                FrameMetrics& aMetrics);

     /* Get the DOMWindowUtils for the window corresponding to the given document. */

     static already_AddRefed<nsIDOMWindowUtils> GetDOMWindowUtils(const nsIDocument* aDoc);

     /* Get the DOMWindowUtils for the window corresponding to the givent content

        element. This might be an iframe inside the tab, for instance. */

     static already_AddRefed<nsIDOMWindowUtils> GetDOMWindowUtils(const nsIContent* aContent);

     /* Get the presShellId and view ID for the given content element, if they can be

        found. Returns false if the values could not be found, true if they could. */

     static bool GetScrollIdentifiers(const nsIContent* aContent,

                                      uint32_t* aPresShellIdOut,

                                      FrameMetrics::ViewID* aViewIdOut);

     /* Tell layout that we received the scroll offset update for the given view ID, so

        that it accepts future scroll offset updates from APZ. */

     static void AcknowledgeScrollUpdate(const FrameMetrics::ViewID& aScrollId,

                                         const uint32_t& aScrollGeneration);

     /* Save an "input transform" property on the content element corresponding to

        the scrollable content. This is needed because in some cases when the APZ code

        sends a paint request via the GeckoContentController interface, we don't always

        apply the scroll offset that was requested. Since the APZ code doesn't know

        that we didn't apply it, it will transform inputs assuming that we had applied

        it, and so we need to apply a fixup to the input to account for the fact that

        we didn't.

        The |aApzcMetrics| argument are the metrics that the APZ sent us, and the

        |aActualMetrics| argument are the metrics representing the gecko state after we

        applied some or all of the APZ metrics. */

     static void UpdateCallbackTransform(const FrameMetrics& aApzcMetrics,

                                         const FrameMetrics& aActualMetrics);

     /* Apply an "input transform" to the given |aInput| and return the transformed value.

        The input transform applied is the one for the content element corresponding to

        |aGuid|; this is populated in a previous call to UpdateCallbackTransform. See that

        method's documentations for details. */

     static CSSPoint ApplyCallbackTransform(const CSSPoint& aInput,

                                            const ScrollableLayerGuid& aGuid);

     /* Same as above, but operates on nsIntPoint that are assumed to be in LayoutDevice

        pixel space. Requires an additonal |aScale| parameter to convert between CSS and

        LayoutDevice space. */

     static nsIntPoint ApplyCallbackTransform(const nsIntPoint& aPoint,

                                              const ScrollableLayerGuid& aGuid,

                                              const CSSToLayoutDeviceScale& aScale);

 };

 }

 }

 #endif /* mozilla_layers_APZCCallbackHelper_h */