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// 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_MANAGER_H_
#define CONTENT_BROWSER_RENDERER_HOST_NAVIGATION_TRANSITIONS_NAVIGATION_ENTRY_SCREENSHOT_MANAGER_H_
#include "base/containers/lru_cache.h"
#include "base/gtest_prod_util.h"
#include "base/memory/memory_pressure_listener.h"
#include "base/memory/safe_ref.h"
#include "content/common/content_export.h"
namespace content {
class NavigationEntryScreenshotCacheEvictor;
// This class manages the metadata for all `NavigationEntryScreenshot`s captured
// for the backward and forward navigation entries per `FrameTree`. The
// screenshots are used to present users with previews of the previous pages
// when the users initiate back/forward-navigations. This class is owned by a
// `BrowserContext`. All primary `FrameTree`s sharing the same `BrowserContext`
// share the same manager. The manager should only be accessed by the
// `NavigationEntryScreenshotCache` and tests.
class CONTENT_EXPORT NavigationEntryScreenshotManager {
public:
NavigationEntryScreenshotManager();
NavigationEntryScreenshotManager(const NavigationEntryScreenshotManager&) =
delete;
NavigationEntryScreenshotManager& operator=(
const NavigationEntryScreenshotManager&) = delete;
~NavigationEntryScreenshotManager();
// Called when a screenshot is stashed into a `NavigationEntry`, or when a
// screenshot is removed from the entry (for preview, or during the
// destruction of the entry).
void OnScreenshotCached(NavigationEntryScreenshotCacheEvictor* cache,
size_t size);
void OnScreenshotRemoved(NavigationEntryScreenshotCacheEvictor* cache,
size_t size);
// Called when a cache's owning `NavigationController` becomes visible. This
// cache is the the most recently used cache.
void OnCacheBecameVisible(NavigationEntryScreenshotCacheEvictor* cache);
bool IsEmpty() const;
size_t GetCurrentCacheSize() const { return current_cache_size_in_bytes_; }
size_t GetMaxCacheSize() const { return max_cache_size_in_bytes_; }
// Allow tests to customize memory budget.
void SetMemoryBudgetForTesting(size_t size) {
max_cache_size_in_bytes_ = size;
}
base::SafeRef<NavigationEntryScreenshotManager> GetSafeRef() const {
return weak_factory_.GetSafeRef();
}
private:
// Called when the first screenshot is cached into `cache`, and when the last
// screenshot is removed from `cache`.
void Register(NavigationEntryScreenshotCacheEvictor* cache);
void Unregister(NavigationEntryScreenshotCacheEvictor* cache);
// Called at the end of `OnScreenshotCached`.
void EvictIfOutOfMemoryBudget();
// Used by `listener_`. When the system memory is under critical pressure, all
// screenshots under this `Profile` are purged.
void OnMemoryPressure(
base::MemoryPressureListener::MemoryPressureLevel memory_pressure_level);
FRIEND_TEST_ALL_PREFIXES(NavigationEntryScreenshotCacheTest,
OnMemoryPressureCritical);
size_t max_cache_size_in_bytes_;
size_t current_cache_size_in_bytes_ = 0U;
// The `listener_` monitors the system memory pressure, and calls
// `NavigationEntryScreenshotManager::OnMemoryPressure` when the system
// memory pressure level changes.
std::unique_ptr<base::MemoryPressureListener> listener_;
// The most recently used cache is stored at the front of the
// `base::LRUCacheSet`. A limited interface to the tab's cache is used so that
// this BrowserContext-wide manager does not have access to details like URLs
// or pixels within each tab.
base::LRUCacheSet<NavigationEntryScreenshotCacheEvictor*> managed_caches_;
SEQUENCE_CHECKER(sequence_checker_);
base::WeakPtrFactory<NavigationEntryScreenshotManager> weak_factory_{this};
};
} // namespace content
#endif // CONTENT_BROWSER_RENDERER_HOST_NAVIGATION_TRANSITIONS_NAVIGATION_ENTRY_SCREENSHOT_MANAGER_H_
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