RmlUi/Samples/luainvaders/src/DecoratorStarfield.cpp

/*
 * This source file is part of RmlUi, the HTML/CSS Interface Middleware
 *
 * For the latest information, see http://github.com/mikke89/RmlUi
 *
 * Copyright (c) 2008-2010 CodePoint Ltd, Shift Technology Ltd
 * Copyright (c) 2019 The RmlUi Team, and contributors
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 * 
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
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 */

#include "DecoratorStarfield.h"
#include <RmlUi/Core/Math.h>
#include <RmlUi/Core/Element.h>
#include <Shell.h>
#include <ShellOpenGL.h>
#include "GameDetails.h"

float last_update_time = 0.0f;

DecoratorStarfield::~DecoratorStarfield()
{
}

bool DecoratorStarfield::Initialise(int _num_layers, const Rml::Core::Colourb& _top_colour, const Rml::Core::Colourb& _bottom_colour, float _top_speed, float _bottom_speed, int _top_density, int _bottom_density)
{
	num_layers = _num_layers;
	top_colour = _top_colour;
	bottom_colour = _bottom_colour;
	top_speed = _top_speed;
	bottom_speed = _bottom_speed;
	top_density = _top_density;
	bottom_density = _bottom_density;

	return true;
}

/// Called on a decorator to generate any required per-element data for a newly decorated element.
Rml::Core::DecoratorDataHandle DecoratorStarfield::GenerateElementData(Rml::Core::Element* element) const
{
	StarField* star_field = new StarField();

	star_field->star_layers.resize(num_layers);

	for (int i = 0; i < num_layers; i++)
	{
		float layer_depth = i / (float)num_layers;

		int density = Rml::Core::Math::RealToInteger((top_density * layer_depth) + (bottom_density * (1.0f - layer_depth)));
		star_field->star_layers[i].stars.resize(density);

		Rml::Core::Colourb colour = (top_colour * layer_depth) + (bottom_colour * (1.0f - layer_depth));
		star_field->star_layers[i].colour = colour;

		float speed = (top_speed * layer_depth) + (bottom_speed * (1.0f - layer_depth));
		star_field->star_layers[i].speed = speed;

		star_field->dimensions = element->GetBox().GetSize(Rml::Core::Box::PADDING);

		if (star_field->dimensions.x > 0)
		{
			for (int j = 0; j < density; j++)
			{
				star_field->star_layers[i].stars[j].x = (float) Rml::Core::Math::RandomReal(star_field->dimensions.x);
				star_field->star_layers[i].stars[j].y = (float) Rml::Core::Math::RandomReal(star_field->dimensions.y);
			}
		}

		star_field->last_update = Shell::GetElapsedTime();
	}

	return (Rml::Core::DecoratorDataHandle)star_field;
}

// Called to release element data generated by this decorator.
void DecoratorStarfield::ReleaseElementData(Rml::Core::DecoratorDataHandle element_data) const
{
	delete (StarField*)element_data;
}

// Called to render the decorator on an element.
void DecoratorStarfield::RenderElement(Rml::Core::Element* RMLUI_UNUSED_PARAMETER(element), Rml::Core::DecoratorDataHandle element_data) const
{
	RMLUI_UNUSED(element);

	StarField* star_field = (StarField*)element_data;
	star_field->Update();

	glDisable(GL_TEXTURE_2D);
	glPointSize(2);
	glBegin(GL_POINTS);

	for (size_t i = 0; i < star_field->star_layers.size(); i++)
	{
		glColor4ubv(star_field->star_layers[i].colour);
		
		for (size_t j = 0; j < star_field->star_layers[i].stars.size(); j++)
		{
			glVertex2f(star_field->star_layers[i].stars[j].x, star_field->star_layers[i].stars[j].y);
		}
	}

	glEnd();

	glColor4ub(255, 255, 255, 255);
}

void DecoratorStarfield::StarField::Update()
{
	double time = Shell::GetElapsedTime();
	float delta_time = float(time - last_update);
	last_update = time;

	if (!GameDetails::GetPaused())
	{
		for (size_t i = 0; i < star_layers.size(); i++)
		{
			float movement = star_layers[i].speed * delta_time;

			for (size_t j = 0; j < star_layers[i].stars.size(); j++)
			{
				star_layers[i].stars[j].y += movement;
				if (star_layers[i].stars[j].y > dimensions.y)
				{
					star_layers[i].stars[j].y = 0;
					star_layers[i].stars[j].x = Rml::Core::Math::RandomReal(dimensions.x);
				}
			}
		}
	}
}