GUIManager.h

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/* Copyright (C) 2022 Wildfire Games.
 * This file is part of 0 A.D.
 *
 * 0 A.D. is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 2 of the License, or
 * (at your option) any later version.
 *
 * 0 A.D. is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with 0 A.D.  If not, see <http://www.gnu.org/licenses/>.
 */

#ifndef INCLUDED_GUIMANAGER
#define INCLUDED_GUIMANAGER

#include "lib/file/vfs/vfs_path.h"
#include "lib/input.h"
#include "ps/CStr.h"
#include "ps/TemplateLoader.h"
#include "scriptinterface/StructuredClone.h"

#include <deque>
#include <string>
#include <unordered_set>

class CCanvas2D;
class CGUI;

/**
 * External interface to the GUI system.
 *
 * The GUI consists of a set of pages. Each page is constructed from a
 * series of XML files, and is independent from any other page.
 * Only one page is active at a time. All events and render requests etc
 * will go to the active page. This lets the GUI switch between pre-game menu
 * and in-game UI.
 */
class CGUIManager
{
    NONCOPYABLE(CGUIManager);
public:
    CGUIManager();
    ~CGUIManager();

    std::shared_ptr<ScriptInterface> GetScriptInterface()
    {
        return m_ScriptInterface;
    }
    std::shared_ptr<ScriptContext> GetContext() { return m_ScriptContext; }
    std::shared_ptr<CGUI> GetActiveGUI() { return top(); }

    /**
     * Returns the number of currently open GUI pages.
     */
    size_t GetPageCount() const;

    /**
     * Load a new GUI page and make it active. All current pages will be destroyed.
     */
    void SwitchPage(const CStrW& name, const ScriptInterface* srcScriptInterface, JS::HandleValue initData);

    /**
     * Load a new GUI page and make it active. All current pages will be retained,
     * and will still be drawn and receive tick events, but will not receive
     * user inputs.
     * If given, the callbackHandler function will be executed once this page is closed.
     */
    void PushPage(const CStrW& pageName, Script::StructuredClone initData, JS::HandleValue callbackFunc);

    /**
     * Unload the currently active GUI page, and make the previous page active.
     * (There must be at least two pages when you call this.)
     */
    void PopPage(Script::StructuredClone args);

    /**
     * Called when a file has been modified, to hotload changes.
     */
    Status ReloadChangedFile(const VfsPath& path);

    /**
     * Called when we should reload all pages (e.g. translation hotloading update).
     */
    Status ReloadAllPages();

    /**
     * Pass input events to the currently active GUI page.
     */
    InReaction HandleEvent(const SDL_Event_* ev);

    /**
     * See CGUI::SendEventToAll; applies to the currently active page.
     */
    void SendEventToAll(const CStr& eventName) const;
    void SendEventToAll(const CStr& eventName, JS::HandleValueArray paramData) const;

    /**
     * See CGUI::TickObjects; applies to @em all loaded pages.
     */
    void TickObjects();

    /**
     * See CGUI::Draw; applies to @em all loaded pages.
     */
    void Draw(CCanvas2D& canvas) const;

    /**
     * See CGUI::UpdateResolution; applies to @em all loaded pages.
     */
    void UpdateResolution();

    /**
     * Check if a template with this name exists
     */
    bool TemplateExists(const std::string& templateName) const;

    /**
     * Retrieve the requested template, used for displaying faction specificities.
     */
    const CParamNode& GetTemplate(const std::string& templateName);

    /**
     * Display progress / description in loading screen.
     */
    void DisplayLoadProgress(int percent, const wchar_t* pending_task);

private:
    struct SGUIPage
    {
        // COPYABLE, because event handlers may invalidate page stack iterators by open or close pages,
        // and event handlers need to be called for the entire stack.

        /**
         * Initializes the data that will be used to create the CGUI page one or multiple times (hotloading).
         */
        SGUIPage(const CStrW& pageName, const Script::StructuredClone initData);

        /**
         * Create the CGUI with it's own ScriptInterface. Deletes the previous CGUI if it existed.
         */
        void LoadPage(std::shared_ptr<ScriptContext> scriptContext);

        /**
         * Sets the callback handler when a new page is opened that will be performed when the page is closed.
         */
        void SetCallbackFunction(ScriptInterface& scriptInterface, JS::HandleValue callbackFunc);

        /**
         * Execute the stored callback function with the given arguments.
         */
        void PerformCallbackFunction(Script::StructuredClone args);

        CStrW m_Name;
        std::unordered_set<VfsPath> inputs; // for hotloading
        Script::StructuredClone initData; // data to be passed to the init() function
        std::shared_ptr<CGUI> gui; // the actual GUI page

        /**
         * Function executed by this parent GUI page when the child GUI page it pushed is popped.
         * Notice that storing it in the SGUIPage instead of CGUI means that it will survive the hotloading CGUI reset.
         */
        std::shared_ptr<JS::PersistentRootedValue> callbackFunction;
    };

    std::shared_ptr<CGUI> top() const;

    std::shared_ptr<ScriptContext> m_ScriptContext;
    std::shared_ptr<ScriptInterface> m_ScriptInterface;

    /**
     * The page stack must not move pointers on push/pop, or pushing a page in a page's init method
     * may crash (as the pusher page will suddenly have moved, and the stack will be confused).
     * Therefore use std::deque over std::vector.
     */
    using PageStackType = std::deque<SGUIPage>;
    PageStackType m_PageStack;

    CTemplateLoader m_TemplateLoader;
};

extern CGUIManager* g_GUI;

extern InReaction gui_handler(const SDL_Event_* ev);

#endif // INCLUDED_GUIMANAGER