navigation_entry_screenshot.h | Explore in Territory

// Copyright 2023 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef CONTENT_BROWSER_RENDERER_HOST_NAVIGATION_TRANSITIONS_NAVIGATION_ENTRY_SCREENSHOT_H_
#define CONTENT_BROWSER_RENDERER_HOST_NAVIGATION_TRANSITIONS_NAVIGATION_ENTRY_SCREENSHOT_H_

#include "base/supports_user_data.h"
#include "cc/resources/ui_resource_bitmap.h"
#include "cc/resources/ui_resource_client.h"
#include "content/common/content_export.h"

class SkBitmap;

namespace content {

class NavigationEntryScreenshotCache;

// Wraps around a `cc::UIResourceBitmap`, which is used to show the user a
// preview of the previous page. This class is stored as user data on
// `NavigationEntry`.
//
// The screenshot is captured for the leaving page when the navigation is about
// to commit (see `CommitDeferringCondition`), subsequently stashed into the
// `NavigationEntry` that this screenshot is captured for. The capture is done
// in the browser process. The pixel data includes sensitive cross-origin data,
// so it must never be leaked to a renderer process.
//
// The screenshot is taken out of the `NavigationEntry` when it will be used for
// an animated transition for a gestured navigation.
//   - If the screenshot ends up being used, or deemed invalid (i.e. mismatches
//   with the current viewport size) for a preview, the caller is responsible
//   for destroying the screenshot.
//   - If the screenshot is not used for a preview but still valid (e.g. user
//   gesture cancels the animation thus no navigation, or the user initiates a
//   gesture to go back to multiple entries), the caller is responsible for
//   putting the screenshot back into the `NavigationEntryScreenshotCache`.
//
// If the user clears the navigation history, the screenshot is deleted when
// its owning `NavigationEntry` is destroyed. The screenshot is never recreated
// or cloned even when its `NavigationEntry` is cloned (tab clone) or restored
// (i.e., by restoring the last closed tab), because
// `base::SupportsUserData::Data::Clone()` is not implemented by
// `NavigationEntryScreenshot`.
class CONTENT_EXPORT NavigationEntryScreenshot
    : public cc::UIResourceClient,
      public base::SupportsUserData::Data { … };

}  // namespace content

#endif  // CONTENT_BROWSER_RENDERER_HOST_NAVIGATION_TRANSITIONS_NAVIGATION_ENTRY_SCREENSHOT_H_
chromium/content/browser/renderer_host/navigation_transitions/navigation_entry_screenshot.h
