ProgramGamer toys around in C++

ProgramGamer

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aka Mireille

ProgramGamer toys around in C++

« on: August 07, 2015, 04:13:37 AM »

So, I've been messing with C++ again lately, and I thought I'd post about my adventures in Stroustrup land. Beer!

So, for the first post, I've been toying with SDL2 and it's functions lately. I downloaded Lazy Foo's tutorial file and started extrapolating that into something. So far there are color cycling, easing functions and inverted color cube movement. Here's the code:

(also epilepsy warning I guess even though the color cycling is not that fast and the screen size is not that big)

Code:

//Using SDL and standard IO
#include <SDL.h>
#include "stdio.h"

//Screen dimension constants
const int SCREEN_WIDTH = 256;
const int SCREEN_HEIGHT = 192;

int EaseInOutQuad(double t,double b,double c,double d)
{
	//t: current time
	//b: start value
	//c: change in value
	//d: duration
	t /= d/2;
	if (t < 1) return c/2*t*t + b;
	t--;
	return -c/2 * (t*(t-2) - 1) + b;
}


int main( int argc, char* args[] )
{
	//The window we'll be rendering to
	SDL_Window* window = NULL;

	//The surface contained by the window
	SDL_Surface* screenSurface = NULL;

	//Screen buffer
	SDL_Surface* screenBuffer = NULL;

	//Initialize SDL
	if( SDL_Init( SDL_INIT_VIDEO ) < 0 )
	{
		printf( "SDL could not initialize! SDL_Error: %s\n", SDL_GetError() );
	}
	else
	{
		//Create window
		window = SDL_CreateWindow( "SDL Tutorial", SDL_WINDOWPOS_UNDEFINED, SDL_WINDOWPOS_UNDEFINED, SCREEN_WIDTH, SCREEN_HEIGHT, SDL_WINDOW_SHOWN );
		if( window == NULL )
		{
			printf( "Window could not be created! SDL_Error: %s\n", SDL_GetError() );
		}
		else
		{
			//Get window surface
			screenSurface = SDL_GetWindowSurface( window );

			//Create a surface
			screenBuffer = SDL_CreateRGBSurface(0,SCREEN_WIDTH,SCREEN_HEIGHT,32,0,0,0,0);
			if (screenBuffer == NULL)
            {
                printf( "Could not create buffer! SDL_Error: %s\n", SDL_GetError() );
            }

			//Game loop
			bool running = true;
			SDL_Event event;
			int colorRed = 255;
			int colorGreen = 255;
			int colorBlue = 255;
			int const increment = 1;
            int x = 0;
            int y = 0;
			int xSpeed = 0;
			int ySpeed = 0;
			while (running)
            {
                //Event handling
                while (SDL_PollEvent(&event))
                {
                    if (event.type == SDL_QUIT)
                    {
                        running = false;
                    }
                    else if (event.type == SDL_KEYDOWN)
                    {
                        if (event.key.keysym.scancode == SDL_SCANCODE_LEFT)
                        {
                            xSpeed = -4;
                        }
                        else if (event.key.keysym.scancode == SDL_SCANCODE_RIGHT)
                        {
                            xSpeed = 4;
                        }
                        else if (event.key.keysym.scancode == SDL_SCANCODE_UP)
                        {
                            ySpeed = -4;
                        }
                        else if (event.key.keysym.scancode == SDL_SCANCODE_DOWN)
                        {
                            ySpeed = 4;
                        }
                    }
                    else if (event.type == SDL_KEYUP)
                    {
                        if (event.key.keysym.scancode == SDL_SCANCODE_LEFT)
                        {
                            xSpeed = 0;
                        }
                        else if (event.key.keysym.scancode == SDL_SCANCODE_RIGHT)
                        {
                            xSpeed = 0;
                        }
                        else if (event.key.keysym.scancode == SDL_SCANCODE_UP)
                        {
                            ySpeed = 0;
                        }
                        else if (event.key.keysym.scancode == SDL_SCANCODE_DOWN)
                        {
                            ySpeed = 0;
                        }
                    }
                }

                //Moves the player around
                x += xSpeed;
                y += ySpeed;

                //Cycle through colors
                if (colorRed < 255 && colorGreen == 0 && colorBlue == 0)
                {
                    colorRed += increment;
                }
                else if (colorRed == 255 && colorGreen < 255 && colorBlue == 0)
                {
                    colorGreen += increment;
                }
                else if (colorRed > 0 && colorGreen == 255 && colorBlue == 0)
                {
                    colorRed -= increment;
                }
                else if (colorRed == 0 && colorGreen == 255 && colorBlue < 255)
                {
                    colorBlue += increment;
                }
                else if (colorRed == 0 && colorGreen > 0 && colorBlue == 255)
                {
                    colorGreen -= increment;
                }
                else if (colorRed < 255 && colorGreen == 0 && colorBlue == 255)
                {
                    colorRed += increment;
                }
                else if (colorRed == 255 && colorGreen == 0 && colorBlue > 0)
                {
                    colorBlue -= increment;
                }
                else if (colorRed > 0 && colorGreen == 255 && colorBlue == 255)
                {
                    colorRed -= increment;
                }

                //Draw a colored rectangle to the screen
                SDL_FillRect(screenBuffer, NULL, SDL_MapRGB(screenSurface->format,EaseInOutQuad(colorRed,0,255,255),EaseInOutQuad(colorGreen,0,255,255),EaseInOutQuad(colorBlue,0,255,255)));

                //Draw a square on top of this
                SDL_Rect rect;
                rect.x = x;
                rect.y = y;
                rect.w = 32;
                rect.h = 32;
                SDL_FillRect(screenBuffer, &rect, SDL_MapRGB(screenSurface->format,255 - EaseInOutQuad(colorRed,0,255,255),255 - EaseInOutQuad(colorGreen,0,255,255),255 - EaseInOutQuad(colorBlue,0,255,255)));

                //Blit the buffer to the screen surface
                if (SDL_BlitSurface(screenBuffer,NULL,screenSurface,NULL)!=0)
                {
                    printf( "Window could not be blit! SDL_Error: %s\n", SDL_GetError() );
                }

                //Update the surface
                SDL_UpdateWindowSurface( window );

                //Wait one frame
                SDL_Delay(17);
            }
			//Free the surface after game loop
			SDL_FreeSurface(screenBuffer);
		}
	}
	//Destroy window
	SDL_DestroyWindow( window );

	//Quit SDL subsystems
	SDL_Quit();

	return 0;
}

So yeah, I had to deal with SDL's input system, which is... great. Having to cycle through a stack of inputs is just fine and not at all tedious. I had less trouble drawing to the screen surprisingly, and was even able to make an intermediate level color cycling routine. I even ported an easing function to make it smoother, which worked wonderfully! The only issue I can find is that clicking and dragging the window pauses the program for some reason, so I'll look into that next.


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JWki

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