lib_ui/ui/click_handler.h

// This file is part of Desktop App Toolkit,
// a set of libraries for developing nice desktop applications.
//
// For license and copyright information please follow this link:
// https://github.com/desktop-app/legal/blob/master/LEGAL
//
#pragma once

#include "base/basic_types.h"
#include "base/flat_map.h"

#include <QtCore/QVariant>

class ClickHandler;
using ClickHandlerPtr = std::shared_ptr<ClickHandler>;

struct ClickContext {
	Qt::MouseButton button = Qt::LeftButton;
	QVariant other;
};

class ClickHandlerHost {
protected:
	virtual void clickHandlerActiveChanged(const ClickHandlerPtr &action, bool active) {
	}
	virtual void clickHandlerPressedChanged(const ClickHandlerPtr &action, bool pressed) {
	}
	virtual ~ClickHandlerHost() = 0;
	friend class ClickHandler;

};

enum class EntityType : uchar;
class ClickHandler {
public:
	virtual ~ClickHandler() {
	}

	virtual void onClick(ClickContext context) const = 0;

	// Some sort of `id`, for text links contains urls.
	virtual QString url() const {
		return QString();
	}

	// What text to show in a tooltip when mouse is over that click handler as a link in Text.
	virtual QString tooltip() const {
		return QString();
	}

	// What to drop in the input fields when dragging that click handler as a link from Text.
	virtual QString dragText() const {
		return QString();
	}

	// Copy to clipboard support.
	virtual QString copyToClipboardText() const {
		return QString();
	}
	virtual QString copyToClipboardContextItemText() const {
		return QString();
	}

	// Entities in text support.
	struct TextEntity {
		EntityType type = EntityType();
		QString data;
	};
	virtual TextEntity getTextEntity() const;

	void setProperty(int id, QVariant value);
	[[nodiscard]] const QVariant &property(int id) const;

	// This method should be called on mouse over a click handler.
	// It returns true if the active handler was changed or false otherwise.
	static bool setActive(const ClickHandlerPtr &p, ClickHandlerHost *host = nullptr);

	// This method should be called when mouse leaves the host.
	// It returns true if the active handler was changed or false otherwise.
	static bool clearActive(ClickHandlerHost *host = nullptr);

	// This method should be called on mouse press event.
	static void pressed();

	// This method should be called on mouse release event.
	// The activated click handler (if any) is returned.
	static ClickHandlerPtr unpressed();

	static ClickHandlerPtr getActive();
	static ClickHandlerPtr getPressed();

	static bool showAsActive(const ClickHandlerPtr &p);
	static bool showAsPressed(const ClickHandlerPtr &p);
	static void hostDestroyed(ClickHandlerHost *host);

private:
	static ClickHandlerHost *_activeHost;
	static ClickHandlerHost *_pressedHost;

	base::flat_map<int, QVariant> _properties;

};

class LeftButtonClickHandler : public ClickHandler {
public:
	void onClick(ClickContext context) const override final {
		if (context.button == Qt::LeftButton) {
			onClickImpl();
		}
	}

protected:
	virtual void onClickImpl() const = 0;

};

class GenericClickHandler : public ClickHandler {
public:
	GenericClickHandler(Fn<void()> handler)
	: _handler([handler = std::move(handler)](ClickContext) { handler(); }) {
	}
	GenericClickHandler(Fn<void(ClickContext)> handler)
	: _handler(std::move(handler)) {
	}
	void onClick(ClickContext context) const override {
		if (_handler) {
			_handler(context);
		}
	}

private:
	Fn<void(ClickContext)> _handler;

};

class LambdaClickHandler : public GenericClickHandler {
public:
	using GenericClickHandler::GenericClickHandler;

	void onClick(ClickContext context) const override final {
		if (context.button == Qt::LeftButton) {
			GenericClickHandler::onClick(std::move(context));
		}
	}

};

void ActivateClickHandler(
	not_null<QWidget*> guard,
	ClickHandlerPtr handler,
	ClickContext context);
void ActivateClickHandler(
	not_null<QWidget*> guard,
	ClickHandlerPtr handler,
	Qt::MouseButton button);