The basic setup

In this user guide you will find basic information of how to interact with the engine's API in your C++ application. This user guide is meant to be for other developers, not users who just want to use the engine.

If you are looking for these kind of guides please refer to the Tutorials page of this documentation.

Creating your first demo application

In this section you will learn what is needed to run a minimal example and get a black window up and running.

The Main class

The engine has a Application class, that is used to control the engine. It holds the main game loop, handles all events and is responsible for updating all attached layers and the client application. In order to attach your client application to this main class, you have to implement a custom class that extends from the application class and implements all virtual functions like this:

YourApp.h

#include <HighLo.h>

class YourApp : public highlo::HLApplication
{
public:

    // This constructor is used to start the engine without any custom startup settings.
    // If you choose to use this version of the constructor,
    // the engine will start with it's default startup settings.
    YourApp()
        : highlo::HLApplication()
    {
    }

    // This constructor is used to provide custom startup settings for the engine.
    // If you choose to use this version of the custructor,
    // the engine will start with your startup settings.
    YourApp(const highlo::ApplicationSettings &settings)
        : highlo::HLApplication(settings)
    {
    }

    // called once when the engine gets initialized, your custom initialization code goes into this function
    void OnInitialize() override;

    // called once a frame, your custom per-frame code goes into this function
    void OnUpdate(highlo::Timestep timestep) override;

    // called once when the user closed the application,
    // your custom exit code goes here
    // (this should be used to free any existing pointers that were allocated on the heap before)
    void OnShutdown() override;

    // called whenever a event occurred in the application,
    // to see a list of possible events please refer to the events section.
    void OnEvent(highlo::Event &e) override;

    // called once a frame, after the OnUpdate method. Your UI code should go into this function.
    void OnUIRender(highlo::Timestep timestep) override;

    // called whenever the main window gets resized by the user,
    // providing the new width and the height of the resized window.
    void OnResize(uint32 width, uint32 height) override;
};

The Main file

After implementing your custom application class you will need a entry point for your application. Keep in mind that you do not need a standard main function, instead you will have to implement the CreateApp function that is provided by the engine.

Your main file could look like this:

Main.cpp

#include "YourApp.h"

highlo::HLApplication *highlo::CreateApp(int argc, char **argv)
{
    return new YourApp();
}

If you wish to modify some of the initial startup settings you can provide them into your demo application as well.

Main.cpp

#include "YourApp.h"

highlo::HLApplication *highlo::CreateApp(int argc, char **argv)
{
    highlo::ApplicationSettings settings;
    settings.Headless = false;                  // Determines whether to show a rendering window or not; false means show the window.
    settings.WindowTitle = "Your App Title";    // Determines the window title
    settings.WindowWidth = 1280;                // Determines the width of the shown window
    settings.WindowHeight = 720;                // Determines the height of the shown window
    return new YourApp(settings);
}

If you do not wish to implement the command line arguments yourself, we have implemented a Helper class that does handle them for you.

This example shows the usage of the command line helper class:

Main.cpp

#include "YourApp.h"

highlo::HLApplication *highlo::CreateApp(int argc, char **argv)
{
    highlo::utils::CommandLineHelper cmdHelper(argc, argv);
    return new YourApp(cmdHelper.GetAppSettings());
}