• Announcements

    • khawk

      Download the Game Design and Indie Game Marketing Freebook   07/19/17

      GameDev.net and CRC Press have teamed up to bring a free ebook of content curated from top titles published by CRC Press. The freebook, Practices of Game Design & Indie Game Marketing, includes chapters from The Art of Game Design: A Book of Lenses, A Practical Guide to Indie Game Marketing, and An Architectural Approach to Level Design. The GameDev.net FreeBook is relevant to game designers, developers, and those interested in learning more about the challenges in game development. We know game development can be a tough discipline and business, so we picked several chapters from CRC Press titles that we thought would be of interest to you, the GameDev.net audience, in your journey to design, develop, and market your next game. The free ebook is available through CRC Press by clicking here. The Curated Books The Art of Game Design: A Book of Lenses, Second Edition, by Jesse Schell Presents 100+ sets of questions, or different lenses, for viewing a game’s design, encompassing diverse fields such as psychology, architecture, music, film, software engineering, theme park design, mathematics, anthropology, and more. Written by one of the world's top game designers, this book describes the deepest and most fundamental principles of game design, demonstrating how tactics used in board, card, and athletic games also work in video games. It provides practical instruction on creating world-class games that will be played again and again. View it here. A Practical Guide to Indie Game Marketing, by Joel Dreskin Marketing is an essential but too frequently overlooked or minimized component of the release plan for indie games. A Practical Guide to Indie Game Marketing provides you with the tools needed to build visibility and sell your indie games. With special focus on those developers with small budgets and limited staff and resources, this book is packed with tangible recommendations and techniques that you can put to use immediately. As a seasoned professional of the indie game arena, author Joel Dreskin gives you insight into practical, real-world experiences of marketing numerous successful games and also provides stories of the failures. View it here. An Architectural Approach to Level Design This is one of the first books to integrate architectural and spatial design theory with the field of level design. The book presents architectural techniques and theories for level designers to use in their own work. It connects architecture and level design in different ways that address the practical elements of how designers construct space and the experiential elements of how and why humans interact with this space. Throughout the text, readers learn skills for spatial layout, evoking emotion through gamespaces, and creating better levels through architectural theory. View it here. Learn more and download the ebook by clicking here. Did you know? GameDev.net and CRC Press also recently teamed up to bring GDNet+ Members up to a 20% discount on all CRC Press books. Learn more about this and other benefits here.
Sign in to follow this  
Followers 0
PtrN

Error using a function to initialize the screen in SDL. Could use help

2 posts in this topic

Hello.  I'm new here so I apologise if this was not the right forum.  If it isn't I'd apreciate it if you could point me in the right direction.

 

So I've been following Lazyfoo's tutorials, making some modifications to mess around with the engine and ran into a bug.  I created a function to initialize everything.  I'm passing it the screen and the screen title.  For some reason it initializes correctly in the function but when I try to flip the screen the screen pointer is pointing to NULL and thus the program crashes.  I'm wondering what is causing it to do this.

 

I have found a fix and that is to change "SDL_Flip(screen);" to "SDL_Flip(SDL_GetVideoSurface());"  However I'm more curious as to why my code isn't working and how to fix it rather than finding a work around.

 

Here is the relevant code:

 

int main( int argc, char* args[] )
{
	//surfaces
	SDL_Surface *image = NULL;
	SDL_Surface *screen = NULL;

	SDL_Event event;

	bool quit = false;

	cout << "Initializing";
	//Initialize
	if( init(screen, "Press X to Quit") == false)
	{
		cout << "Failure to initialize \n";
		return 1;
	}

//...............
        if (screen == NULL)
	{
		cout << "Error: screen pointer is null \n";
		return 1;
	}
	if( SDL_Flip( screen ) == -1)
	{
		cout << "Error flipping the screen \n";
		return 1;
	}
// End of main function

bool init(SDL_Surface* screen, std::string windowTitle)
{
	//Initialize all the SDL systems
	if( SDL_Init( SDL_INIT_EVERYTHING ) == -1 )
	{
		return false;
	}

	//Set up the screen
	screen = SDL_SetVideoMode( SCREEN_WIDTH, SCREEN_HEIGHT, SCREEN_BPP, SDL_SWSURFACE );

	//If there was an error in setting up the screen
	if( screen == NULL )
	{
		return false;
	}

	//Set the window caption
	SDL_WM_SetCaption( windowTitle.c_str(), NULL);

	//If everything initialized properly
	return true;
}

 

 

 

By checking the STDOUT.txt file I see "InitializingError: screen pointer is null" which tells me that right before I call SDL_Flip and I check the pointer the function is seeing screen == NULL.

0

Share this post


Link to post
Share on other sites

You're passing the variable screen by value, so changes to it in the init function are only made to the local copy of it and not to the one in your main function. You need to pass it by reference (preferred), or by pointer.

bool init(SDL_Surface* &screen, std::string windowTitle)
{...}
0

Share this post


Link to post
Share on other sites

Thank you that worked!  I was thinking it was a pointer issue and was trying to use a double pointer but it still wasn't working.

 

Thanks a ton.

0

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!


Register a new account

Sign in

Already have an account? Sign in here.


Sign In Now
Sign in to follow this  
Followers 0