Qt: add naive lazy loading to screenshot manager

rpcs3/rpcs3qt/screenshot_manager_dialog.cpp

@@ -8,47 +8,49 @@
 #include <QDirIterator>
 #include <QListWidget>
 #include <QScreen>
+#include <QScrollBar>
 #include <QVBoxLayout>
+#include <QtConcurrent>
 
 screenshot_manager_dialog::screenshot_manager_dialog(QWidget* parent) : QDialog(parent)
 {
 	setWindowTitle(tr("Screenshots"));
 
+	m_icon_size = QSize(160, 90);
+
 	m_grid = new QListWidget(this);
 	m_grid->setViewMode(QListWidget::IconMode);
 	m_grid->setMovement(QListWidget::Static);
 	m_grid->setResizeMode(QListWidget::Adjust);
-	m_grid->setIconSize(QSize(160, 90));
-	m_grid->setGridSize(m_grid->iconSize() + QSize(10, 10));
+	m_grid->setIconSize(m_icon_size);
+	m_grid->setGridSize(m_icon_size + QSize(10, 10));
 
 	const std::string screen_path = fs::get_config_dir() + "screenshots/";
 	const QStringList filter{ QStringLiteral("*.png") };
 	QDirIterator dir_iter(QString::fromStdString(screen_path), filter, QDir::Files | QDir::NoDotAndDotDot, QDirIterator::Subdirectories);
 
+	QPixmap placeholder(m_icon_size);
+	placeholder.fill(Qt::gray);
+	m_placeholder = QIcon(placeholder);
+
 	while (dir_iter.hasNext())
 	{
 		const QString filepath = dir_iter.next();
 
 		QListWidgetItem* item = new QListWidgetItem;
-		item->setData(Qt::UserRole, filepath);
-		item->setIcon(QIcon(filepath));
+		item->setData(item_role::source, filepath);
+		item->setData(item_role::loaded, false);
+		item->setIcon(m_placeholder);
 		item->setToolTip(filepath);
 
 		m_grid->addItem(item);
 	}
 
-	connect(m_grid, &QListWidget::itemDoubleClicked, [this](QListWidgetItem* item)
-	{
-		if (!item)
-		{
-			return;
-		}
+	m_icon_loader = new QFutureWatcher<thumbnail>(this);
+	connect(m_icon_loader, &QFutureWatcher<QIcon>::resultReadyAt, this, &screenshot_manager_dialog::update_icon);
 
-		const QString filepath = item->data(Qt::UserRole).toString();
-
-		screenshot_preview* preview = new screenshot_preview(filepath);
-		preview->show();
-	});
+	connect(m_grid, &QListWidget::itemDoubleClicked, this, &screenshot_manager_dialog::show_preview);
+	connect(m_grid->verticalScrollBar(), &QScrollBar::valueChanged, this, &screenshot_manager_dialog::update_icons);
 
 	QVBoxLayout* layout = new QVBoxLayout;
 	layout->setContentsMargins(0, 0, 0, 0);
@@ -57,3 +59,89 @@ screenshot_manager_dialog::screenshot_manager_dialog(QWidget* parent) : QDialog(
 
 	resize(QGuiApplication::primaryScreen()->availableSize() * 3 / 5);
 }
+
+screenshot_manager_dialog::~screenshot_manager_dialog()
+{
+	m_icon_loader->cancel();
+	m_icon_loader->waitForFinished();
+}
+
+void screenshot_manager_dialog::show_preview(QListWidgetItem* item)
+{
+	if (!item)
+	{
+		return;
+	}
+
+	const QString filepath = item->data(Qt::UserRole).toString();
+
+	screenshot_preview* preview = new screenshot_preview(filepath);
+	preview->show();
+}
+
+void screenshot_manager_dialog::update_icon(int index)
+{
+	const thumbnail tn = m_icon_loader->resultAt(index);
+
+	if (QListWidgetItem* item = m_grid->item(tn.index))
+	{
+		item->setIcon(tn.icon);
+		item->setData(item_role::loaded, true);
+	}
+}
+
+void screenshot_manager_dialog::update_icons(int value)
+{
+	const QRect visible_rect = rect();
+
+	QList<thumbnail> thumbnails_to_load;
+
+	const bool forward = value >= m_scrollbar_value;
+	m_scrollbar_value  = value;
+
+	const int first = forward ? 0 : (m_grid->count() - 1);
+	const int last  = forward ? (m_grid->count() - 1) : 0;
+
+	for (int i = first; forward ? i <= last : i >= last; forward ? ++i : --i)
+	{
+		if (QListWidgetItem* item = m_grid->item(i))
+		{
+			const bool is_loaded  = item->data(item_role::loaded).toBool();
+			const bool is_visible = visible_rect.intersects(m_grid->visualItemRect(item));
+
+			if (is_visible)
+			{
+				if (!is_loaded)
+				{
+					thumbnails_to_load.push_back({ QIcon(), item->data(item_role::source).toString() , i });
+				}
+			}
+			else if (is_loaded)
+			{
+				item->setIcon(m_placeholder);
+				item->setData(item_role::loaded, false);
+			}
+		}
+	}
+
+	if (m_icon_loader->isRunning())
+	{
+		m_icon_loader->cancel();
+		m_icon_loader->waitForFinished();
+	}
+
+	std::function<thumbnail(thumbnail)> load = [icon_size = m_icon_size](thumbnail tn) -> thumbnail
+	{
+		QPixmap pixmap(tn.path);
+		tn.icon = QIcon(pixmap.scaled(icon_size, Qt::IgnoreAspectRatio, Qt::SmoothTransformation));
+		return tn;
+	};
+
+	m_icon_loader->setFuture(QtConcurrent::mapped(thumbnails_to_load, load));
+}
+
+void screenshot_manager_dialog::resizeEvent(QResizeEvent* event)
+{
+	QDialog::resizeEvent(event);
+	update_icons(m_scrollbar_value);
+}

rpcs3/rpcs3qt/screenshot_manager_dialog.h

@@ -1,8 +1,12 @@
 #pragma once
 
 #include <QDialog>
+#include <QFutureWatcher>
+#include <QIcon>
+#include <QSize>
 
 class QListWidget;
+class QListWidgetItem;
 
 class screenshot_manager_dialog : public QDialog
 {
@@ -10,7 +14,40 @@ class screenshot_manager_dialog : public QDialog
 
 public:
 	screenshot_manager_dialog(QWidget* parent = nullptr);
+	~screenshot_manager_dialog();
+
+protected:
+	void resizeEvent(QResizeEvent* event) override;
+
+private Q_SLOTS:
+	void update_icon(int index);
+
+Q_SIGNALS:
+	void signal_icon_change(int index, const QString& path);
 
 private:
+	void show_preview(QListWidgetItem* item);
+	void update_icons(int value);
+
+	enum item_role
+	{
+		source = Qt::UserRole,
+		loaded = Qt::UserRole + 1,
+	};
+
+	struct thumbnail
+	{
+		QIcon icon;
+		QString path;
+		int index = 0;
+	};
+
 	QListWidget* m_grid = nullptr;
+
+	QFutureWatcher<thumbnail>* m_icon_loader;
+
+	QSize m_icon_size;
+	QIcon m_placeholder;
+
+	int m_scrollbar_value = 0;
 };