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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.
#include "content/browser/renderer_host/navigation_transitions/navigation_entry_screenshot_cache.h"
#include "base/memory/ptr_util.h"
#include "content/browser/renderer_host/navigation_controller_impl.h"
#include "content/browser/renderer_host/navigation_transitions/navigation_entry_screenshot.h"
#include "content/browser/renderer_host/navigation_transitions/navigation_entry_screenshot_manager.h"
#include "content/public/browser/browser_thread.h"
#include "content/public/browser/navigation_entry.h"
#include "content/public/common/content_features.h"
namespace content {
namespace {
std::unique_ptr<NavigationEntryScreenshot> RemoveScreenshotFromEntry(
NavigationEntry* entry) {
CHECK(entry);
std::unique_ptr<base::SupportsUserData::Data> data =
entry->TakeUserData(NavigationEntryScreenshot::kUserDataKey);
CHECK(data);
auto* screenshot = static_cast<NavigationEntryScreenshot*>(data.release());
CHECK(screenshot->is_cached());
screenshot->set_cache(nullptr);
return base::WrapUnique(screenshot);
}
} // namespace
bool AreBackForwardTransitionsEnabled() {
// TODO(https://crbug.com/1414164): We might want to disable this feature on
// low-end devices.
return base::FeatureList::IsEnabled(features::kBackForwardTransitions);
}
NavigationEntryScreenshotCache::NavigationEntryScreenshotCache(
base::SafeRef<NavigationEntryScreenshotManager> manager,
NavigationControllerImpl* nav_controller)
: manager_(manager), nav_controller_(nav_controller) {
DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
CHECK(AreBackForwardTransitionsEnabled());
}
NavigationEntryScreenshotCache::~NavigationEntryScreenshotCache() {
DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
Purge();
}
void NavigationEntryScreenshotCache::SetScreenshot(
NavigationEntry* entry,
std::unique_ptr<NavigationEntryScreenshot> screenshot) {
DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
// We must be caching screenshot for a valid entry.
CHECK(entry);
// A navigation entry without a screenshot will be removed from the cache
// first (thus not tracked). Impossible to overwrite for a cached entry.
CHECK(!entry->GetUserData(NavigationEntryScreenshot::kUserDataKey));
CHECK(cached_screenshots_.find(entry->GetUniqueID()) ==
cached_screenshots_.end());
CHECK(!screenshot->is_cached());
screenshot->set_cache(this);
const size_t size = screenshot->SizeInBytes();
entry->SetUserData(NavigationEntryScreenshot::kUserDataKey,
std::move(screenshot));
cached_screenshots_.insert(entry->GetUniqueID());
manager_->OnScreenshotCached(this, size);
if (new_screenshot_cached_callback_) {
std::move(new_screenshot_cached_callback_).Run(entry->GetUniqueID());
}
}
std::unique_ptr<NavigationEntryScreenshot>
NavigationEntryScreenshotCache::RemoveScreenshot(
NavigationEntry* navigation_entry) {
DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
CHECK(navigation_entry);
const int navigation_entry_id = navigation_entry->GetUniqueID();
auto it = cached_screenshots_.find(navigation_entry_id);
// `CHECK_NE` is not compatible with `base::flat_set`.
CHECK(it != cached_screenshots_.end());
// Remove the tracked nav entry id and the entry and update the metadata.
cached_screenshots_.erase(it);
auto screenshot = RemoveScreenshotFromEntry(navigation_entry);
manager_->OnScreenshotRemoved(this, screenshot->SizeInBytes());
return screenshot;
}
void NavigationEntryScreenshotCache::OnNavigationEntryGone(
int navigation_entry_id,
size_t size) {
DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
auto it = cached_screenshots_.find(navigation_entry_id);
CHECK(it != cached_screenshots_.end());
cached_screenshots_.erase(it);
manager_->OnScreenshotRemoved(this, size);
}
void NavigationEntryScreenshotCache::EvictScreenshotsUntilUnderBudgetOrEmpty() {
DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
CHECK(!IsEmpty());
CHECK_GT(manager_->GetCurrentCacheSize(), manager_->GetMaxCacheSize());
const int current_index = nav_controller_->GetCurrentEntryIndex();
const int current_entry_id =
nav_controller_->GetEntryAtIndex(current_index)->GetUniqueID();
// It's impossible to have a screenshot for the current entry.
CHECK(!cached_screenshots_.contains(current_entry_id));
// Impossible to have just one entry (the current entry).
CHECK_GT(nav_controller_->GetEntryCount(), 1);
int distance_to_leftmost = current_index;
int distance_to_rightmost =
nav_controller_->GetEntryCount() - current_index - 1;
// The eviction strategy is to priotrize keeping the screenshots for the
// navigation entries that are closer to the "current entry" (last committed).
// This strategy assumes the user is equally likely to go back/forward. This
// is not true for Android where native OS gesture navigation only takes the
// user back (even right-edge swipe).
//
// TODO(crbug.com/1415332): Iterate on the eviction strategy based on metrics
// when this launches.
//
// Ex: [3, 4&, 5*, 6&, 7, 8&], where "*" means the last committed entry and
// "&" means an entry with a screenshot. In this case `distance_to_leftmost` =
// 2 and `distance_to_rightmost` = 3. The eviction order will be: entry8,
// entry6 and entry4.
//
while (manager_->GetCurrentCacheSize() > manager_->GetMaxCacheSize() &&
!IsEmpty()) {
int candidate_nav_entry_id = -1;
CHECK(distance_to_leftmost > 0 || distance_to_rightmost > 0);
if (distance_to_leftmost > distance_to_rightmost) {
candidate_nav_entry_id =
nav_controller_->GetEntryAtIndex(current_index - distance_to_leftmost)
->GetUniqueID();
--distance_to_leftmost;
} else {
candidate_nav_entry_id =
nav_controller_
->GetEntryAtIndex(current_index + distance_to_rightmost)
->GetUniqueID();
--distance_to_rightmost;
}
// Check whether this candidate entry has a screenshot to remove, or
// continue to move closer to the current entry.
auto* candidate_entry =
nav_controller_->GetEntryWithUniqueID(candidate_nav_entry_id);
CHECK(candidate_entry);
if (auto it = cached_screenshots_.find(candidate_nav_entry_id);
it != cached_screenshots_.end()) {
std::unique_ptr<NavigationEntryScreenshot> evicted_screenshot =
RemoveScreenshotFromEntry(candidate_entry);
cached_screenshots_.erase(it);
CHECK_LE(evicted_screenshot->SizeInBytes(),
manager_->GetCurrentCacheSize());
manager_->OnScreenshotRemoved(this, evicted_screenshot->SizeInBytes());
}
}
}
void NavigationEntryScreenshotCache::Purge() {
DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
auto it = cached_screenshots_.begin();
while (!IsEmpty()) {
auto* evicted_entry = nav_controller_->GetEntryWithUniqueID(*it);
CHECK(evicted_entry);
auto purged = RemoveScreenshotFromEntry(evicted_entry);
cached_screenshots_.erase(it);
CHECK_LE(purged->SizeInBytes(), manager_->GetCurrentCacheSize());
manager_->OnScreenshotRemoved(this, purged->SizeInBytes());
it = cached_screenshots_.begin();
}
}
bool NavigationEntryScreenshotCache::IsEmpty() const {
return cached_screenshots_.empty();
}
void NavigationEntryScreenshotCache::SetNewScreenshotCachedCallbackForTesting(
NewScreenshotCachedCallbackForTesting callback) {
CHECK(!new_screenshot_cached_callback_);
new_screenshot_cached_callback_ = std::move(callback);
}
} // namespace content
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