[img-editor] Refined eraser brush algorithm.

Telegram/SourceFiles/editor/editor.style

@@ -110,6 +110,7 @@ photoEditorMarkerSizeMultiplier: 2.5;
 photoEditorArrowHeadLengthFactor: 2.5;
 photoEditorArrowHeadMinDistanceFactor: 1.5;
 photoEditorArrowHeadAngleDegrees: 26;
+photoEditorEraserPreviewOpacity: 0.25;
 
 photoEditorBrushSizeControlLeftSkip: 0px;
 photoEditorBrushSizeControlHeight: 280px;

Telegram/SourceFiles/editor/editor_paint.cpp

@@ -68,7 +68,10 @@ Paint::Paint(
 	_view->setVerticalScrollBarPolicy(Qt::ScrollBarAlwaysOff);
 	_view->setHorizontalScrollBarPolicy(Qt::ScrollBarAlwaysOff);
 	_view->setFrameStyle(int(QFrame::NoFrame) | QFrame::Plain);
+	_view->setBackgroundBrush(Qt::transparent);
+	_view->setAttribute(Qt::WA_TranslucentBackground, true);
 	_viewport->setAutoFillBackground(false);
+	_viewport->setAttribute(Qt::WA_TranslucentBackground, true);
 	_viewport->installEventFilter(this);
 
 	// Undo / Redo.

Telegram/SourceFiles/editor/scene/scene.cpp

@@ -19,6 +19,81 @@ namespace {
 
 using ItemPtr = std::shared_ptr<NumberedItem>;
 
+class ItemEraser final : public NumberedItem {
+public:
+	struct Target {
+		std::shared_ptr<ItemLine> item;
+		QPixmap before;
+	};
+
+	ItemEraser(
+		QPixmap mask,
+		QPointF maskPos,
+		std::vector<Target> targets)
+	: _mask(std::move(mask))
+	, _maskPos(maskPos)
+	, _targets(std::move(targets)) {
+	}
+
+	void apply() {
+		for (const auto &target : _targets) {
+			target.item->applyEraser(_mask, _maskPos);
+		}
+	}
+
+	void revert() {
+		for (const auto &target : _targets) {
+			target.item->setPixmap(target.before);
+		}
+	}
+
+	QRectF boundingRect() const override {
+		return QRectF();
+	}
+
+	void paint(
+			QPainter *,
+			const QStyleOptionGraphicsItem *,
+			QWidget *) override {
+	}
+
+	bool hasState(SaveState state) const override {
+		const auto &saved = (state == SaveState::Keep) ? _keeped : _saved;
+		return saved.saved;
+	}
+
+	void save(SaveState state) override {
+		auto &saved = (state == SaveState::Keep) ? _keeped : _saved;
+		saved = {
+			.saved = true,
+			.status = status(),
+		};
+	}
+
+	void restore(SaveState state) override {
+		if (!hasState(state)) {
+			return;
+		}
+		const auto &saved = (state == SaveState::Keep) ? _keeped : _saved;
+		setStatus(saved.status);
+		if (saved.status == Status::Normal) {
+			apply();
+		} else if (saved.status == Status::Undid) {
+			revert();
+		}
+	}
+
+private:
+	QPixmap _mask;
+	QPointF _maskPos;
+	std::vector<Target> _targets;
+
+	struct {
+		bool saved = false;
+		NumberedItem::Status status;
+	} _saved, _keeped;
+};
+
 bool SkipMouseEvent(not_null<QGraphicsSceneMouseEvent*> event) {
 	return event->isAccepted() || (event->button() == Qt::RightButton);
 }
@@ -34,9 +109,54 @@ Scene::Scene(const QRectF &rect)
 
 	_canvas->grabContentRequests(
 	) | rpl::on_next([=](ItemCanvas::Content &&content) {
+		if (content.clear) {
+			auto mask = std::move(content.pixmap);
+			if (mask.isNull()) {
+				return;
+			}
+			const auto maskPos = content.position;
+			const auto maskSize = mask.size()
+				/ float64(mask.devicePixelRatio());
+			const auto maskRect = QRectF(maskPos, maskSize);
+			auto targets = std::vector<ItemEraser::Target>();
+			const auto hits = QGraphicsScene::items(
+				maskRect,
+				Qt::IntersectsItemBoundingRect,
+				Qt::DescendingOrder);
+			for (auto *raw : hits) {
+				const auto it = _itemsByPointer.find(raw);
+				if (it == end(_itemsByPointer)) {
+					continue;
+				}
+				const auto &item = it->second;
+				if (!item->isNormalStatus()) {
+					continue;
+				}
+				const auto line = std::dynamic_pointer_cast<ItemLine>(item);
+				if (!line) {
+					continue;
+				}
+				auto before = line->pixmap();
+				if (!line->applyEraser(mask, maskPos)) {
+					continue;
+				}
+				targets.push_back({
+					.item = line,
+					.before = std::move(before),
+				});
+			}
+			if (!targets.empty()) {
+				const auto eraser = std::make_shared<ItemEraser>(
+					std::move(mask),
+					maskPos,
+					std::move(targets));
+				addItem(eraser);
+				_canvas->setZValue(++_lastLineZ);
+			}
+			return;
+		}
 		const auto item = std::make_shared<ItemLine>(
-			std::move(content.pixmap),
-			content.clear);
+			std::move(content.pixmap));
 		item->setPos(content.position);
 		addItem(item);
 		_canvas->setZValue(++_lastLineZ);
@@ -53,7 +173,9 @@ void Scene::addItem(ItemPtr item) {
 	}
 	item->setNumber(_itemNumber++);
 	QGraphicsScene::addItem(item.get());
+	const auto raw = item.get();
 	_items.push_back(std::move(item));
+	_itemsByPointer.emplace(raw, _items.back());
 	_addsItem.fire({});
 }
 
@@ -147,6 +269,9 @@ void Scene::performUndo() {
 
 	const auto it = ranges::find_if(filtered, &NumberedItem::isNormalStatus);
 	if (it != filtered.end()) {
+		if (const auto eraser = dynamic_cast<ItemEraser*>(it->get())) {
+			eraser->revert();
+		}
 		(*it)->setStatus(NumberedItem::Status::Undid);
 	}
 }
@@ -156,6 +281,9 @@ void Scene::performRedo() {
 
 	const auto it = ranges::find_if(filtered, &NumberedItem::isUndidStatus);
 	if (it != filtered.end()) {
+		if (const auto eraser = dynamic_cast<ItemEraser*>(it->get())) {
+			eraser->apply();
+		}
 		(*it)->setStatus(NumberedItem::Status::Normal);
 	}
 }
@@ -173,6 +301,10 @@ void Scene::removeIf(Fn<bool(const ItemPtr &)> proj) {
 		}
 	}
 	_items = std::move(copy);
+	_itemsByPointer.clear();
+	for (const auto &item : _items) {
+		_itemsByPointer.emplace(item.get(), item);
+	}
 }
 
 void Scene::clearRedoList() {

Telegram/SourceFiles/editor/scene/scene.h

@@ -65,6 +65,7 @@ private:
 	const std::shared_ptr<float64> _lastZ;
 
 	std::vector<ItemPtr> _items;
+	std::unordered_map<QGraphicsItem*, ItemPtr> _itemsByPointer;
 
 	float64 _lastLineZ = 0.;
 	int _itemNumber = 0;

Telegram/SourceFiles/editor/scene/scene_item_canvas.cpp

@@ -382,7 +382,7 @@ void ItemCanvas::paint(
 	p->fillRect(_rectToUpdate, Qt::transparent);
 	if (_brushData.tool == Brush::Tool::Eraser) {
 		p->save();
-		p->setCompositionMode(QPainter::CompositionMode_Clear);
+		p->setOpacity(st::photoEditorEraserPreviewOpacity);
 		p->drawPixmap(0, 0, _pixmap);
 		p->restore();
 	} else {

Telegram/SourceFiles/editor/scene/scene_item_line.cpp

@@ -8,13 +8,13 @@ https://github.com/telegramdesktop/tdesktop/blob/master/LEGAL
 #include "editor/scene/scene_item_line.h"
 
 #include <QGraphicsScene>
+#include <QtGui/QPainter>
 
 namespace Editor {
 
-ItemLine::ItemLine(QPixmap &&pixmap, bool clear)
+ItemLine::ItemLine(QPixmap &&pixmap)
 : _pixmap(std::move(pixmap))
-, _rect(QPointF(), _pixmap.size() / float64(style::DevicePixelRatio()))
-, _clear(clear) {
+, _rect(QPointF(), _pixmap.size() / float64(style::DevicePixelRatio())) {
 }
 
 QRectF ItemLine::boundingRect() const {
@@ -25,16 +25,39 @@ void ItemLine::paint(
 		QPainter *p,
 		const QStyleOptionGraphicsItem *,
 		QWidget *) {
-	if (_clear) {
-		p->save();
-		p->setCompositionMode(QPainter::CompositionMode_Clear);
-		p->drawPixmap(0, 0, _pixmap);
-		p->restore();
-		return;
-	}
 	p->drawPixmap(0, 0, _pixmap);
 }
 
+const QPixmap &ItemLine::pixmap() const {
+	return _pixmap;
+}
+
+void ItemLine::setPixmap(QPixmap pixmap) {
+	_pixmap = std::move(pixmap);
+	update();
+}
+
+bool ItemLine::applyEraser(const QPixmap &mask, const QPointF &maskPos) {
+	if (mask.isNull()) {
+		return false;
+	}
+	const auto maskSize = mask.size() / float64(mask.devicePixelRatio());
+	const auto localTopLeft = maskPos - pos();
+	const auto localRect = QRectF(localTopLeft, maskSize);
+	if (!localRect.intersects(_rect)) {
+		return false;
+	}
+	auto image = _pixmap.toImage().convertToFormat(
+		QImage::Format_ARGB32_Premultiplied);
+	auto p = QPainter(&image);
+	p.setCompositionMode(QPainter::CompositionMode_DestinationOut);
+	p.drawPixmap(localTopLeft, mask);
+	p.end();
+	_pixmap = QPixmap::fromImage(std::move(image));
+	update();
+	return true;
+}
+
 bool ItemLine::collidesWithItem(
 		const QGraphicsItem *,
 		Qt::ItemSelectionMode) const {

Telegram/SourceFiles/editor/scene/scene_item_line.h

@@ -13,12 +13,15 @@ namespace Editor {
 
 class ItemLine : public NumberedItem {
 public:
-	ItemLine(QPixmap &&pixmap, bool clear = false);
+	ItemLine(QPixmap &&pixmap);
 	QRectF boundingRect() const override;
 	void paint(
 		QPainter *p,
 		const QStyleOptionGraphicsItem *option,
 		QWidget *widget) override;
+	[[nodiscard]] const QPixmap &pixmap() const;
+	void setPixmap(QPixmap pixmap);
+	bool applyEraser(const QPixmap &mask, const QPointF &maskPos);
 
 	bool hasState(SaveState state) const override;
 	void save(SaveState state) override;
@@ -31,9 +34,8 @@ protected:
 		const QPainterPath &,
 		Qt::ItemSelectionMode) const override;
 private:
-	const QPixmap _pixmap;
+	QPixmap _pixmap;
 	const QRectF _rect;
-	const bool _clear = false;
 
 	struct {
 		bool saved = false;