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// Copyright 2020 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef CHROME_BROWSER_UI_THUMBNAILS_THUMBNAIL_SCHEDULER_IMPL_H_
#define CHROME_BROWSER_UI_THUMBNAILS_THUMBNAIL_SCHEDULER_IMPL_H_
#include <map>
#include "base/containers/linked_list.h"
#include "chrome/browser/ui/thumbnails/thumbnail_capture_driver.h"
#include "chrome/browser/ui/thumbnails/thumbnail_readiness_tracker.h"
#include "chrome/browser/ui/thumbnails/thumbnail_scheduler.h"
// A basic scheduler that given two limits, |max_total_captures| and
// |max_low_priority_captures|, ensures the following:
//
// - At most |max_total_captures| tabs capture simultaneously, and
// - At most |max_low_priority_captures| tabs with low priority
// capture simultaneously.
//
// Tabs are only rescheduled in response to tab state changes.
class ThumbnailSchedulerImpl : public ThumbnailScheduler {
public:
static constexpr int kMaxTotalCaptures = 10;
static constexpr int kMaxLowPriorityCaptures = 5;
explicit ThumbnailSchedulerImpl(
int max_total_captures = kMaxTotalCaptures,
int max_low_priority_captures = kMaxLowPriorityCaptures);
~ThumbnailSchedulerImpl() override;
// ThumbnailScheduler:
void AddTab(TabCapturer* tab) override;
void RemoveTab(TabCapturer* tab) override;
void SetTabCapturePriority(TabCapturer* tab,
TabCapturePriority priority) override;
private:
// Contains all state that can influence scheduling decisions for a
// tab.
struct TabSchedulingData;
// Stored in scheduling data structures.
struct TabNode;
// Runs scheduling after a change in |tab_node|'s scheduling data.
// |old_data| is |tab_node|'s state before the change. Called after a
// state change in any tab.
void Schedule(TabNode* tab_node, const TabSchedulingData& old_data);
TabNode* GetTabNode(TabCapturer* tab);
const int max_total_captures_;
const int max_low_priority_captures_;
// Maps TabCapturer, the interface for a tab in the public API, to
// TabNode, our internal representation of a tab. Each node is also in
// at most one of the lists below, or none.
std::map<TabCapturer*, TabNode> tabs_;
// Queue of tabs that want to capture but haven't been scheduled yet.
// One for each priority.
base::LinkedList<TabNode> hi_prio_waiting_;
base::LinkedList<TabNode> lo_prio_waiting_;
// List of currently capturing tabs for each priority.
base::LinkedList<TabNode> hi_prio_capturing_;
base::LinkedList<TabNode> lo_prio_capturing_;
// Number of tabs in each capture list (since base::LinkedList doesn't
// track its size).
int hi_prio_capture_count_ = 0;
int lo_prio_capture_count_ = 0;
};
#endif // CHROME_BROWSER_UI_THUMBNAILS_THUMBNAIL_SCHEDULER_IMPL_H_
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