41 replies to this topic

[Assassin7257]

So I'm making a lottery game, I got the three slots and all. But all I have left, is how to set a certain amount of credit, say 1500 and decrease everytime the user clicks "insert credit". How would I decrease it ?

[TheUnbeliever]

We need way more information (like language and libraries used) if you want detailed help, but this is basically going to be a case of

- having a 'money' variable stored in an appropriate scope
- when the user clicks the button, decrement this value then update the display

[Assassin7257]

I'm using SDL, and C++, would I use an interger and how would I output it.

[RulerOfNothing]

One way is to convert the integer to a string (using the itoa or sprintf functions) then using the SDL_ttf library to write the resulting string to the screen.

[boogyman19946]

I take it you're making a graphical user interface. Rather to us an integer or a float depends on if you're going to allow someone to insert fractions of a credit. If you allow only 1 credit at a time, which seems to be most sensible, us an integer. Once you detect that the player clicked insert credit, credits = credits - X (X being number of credits inserted) or credits-- to decrease by one.

As to converting the number, in C++ you can use std::stringstream like so

std::stringstream ss;
ss << credits;
std::string creditString = ss.str(); // returns string representation of credits.

[Assassin7257]

|error: cannot convert 'std::basic_string<char, std::char_traits<char>, std::allocator<char> >' to 'SDL_Surface*' for argument '3' to 'void apply_surface(int, int, SDL_Surface*, SDL_Surface*, SDL_Rect*)'| I did what you said but all I keep getting this error, How would I show it on the screen ?

[RulerOfNothing]

As I said, input the string to the SDL_ttf library (it has a function called TTF_WriteText or something like that which takes a character string and produces a SDL_Surface with the string in graphical form). If you are using stringstream, you need to transform the std::string into a char*, which should be possible using a function called c_str() (or something like that)

[boogyman19946]

That's because apply_surface is expecting a pointer to an SDL_Surface struct and you're trying to pass it an std::string object. The streamstring only converts the integer into a string. As RulerOfNothing said, you can then use the SDL_ttf library to convert the string into a struct that you can feed to apply_surface.

[Assassin7257]

Could I get an example ?

[RulerOfNothing]

well, you could use the following:

std::stringstream ss;
ss << credits;
std::string creditString = ss.str();
SDL_Surface* output = TTF_RenderText_Solid(font, ss.c_str(), color);

which will allow you to blit the output surface to the screen, provided that you have already called TTF_Init() somewhere and loaded a font into the font variable. Also color is a SDL_Color.

[Assassin7257]

std::stringstream ss;
ss << score;
std::string creditString = ss.c_str();

SDL_Surface* output = TTF_RenderText_Solid(font, ss.c_str(), color);

apply_surface( 0, 150, output, screen );



//apply surfaces
apply_surface( 0, 0, background, screen );

Here is the chunck of code I have and I still dont get it

[Assassin7257]

'struct std::stringstream' has no member named 'c_str'| is says that

[BCullis]

1) Get used to reading references for the language or library you're using: like this for example. There is no c_str() but there IS a str() function, which is what you're looking for. That reference even has example code.

2) In your TTF_RenderText_Solid call, use creditString, not another call to the str() function, otherwise why bother with the variable at all? More obvious EDIT: use creditString.c_str(). My previous suggestion was made while unfamiliar with the TTF function's argument list.

EDIT: RulerOfNothing, did your example code mean to use the c_str() call on the string object, not the stream? as in:

SDL_Surface* output = TTF_RenderText_Solid(font, creditString.c_str(), color);

That may be where the confusion is coming from, as Assassin here is just copy-pasting from your example.

[Assassin7257]

Now it says this cannot convert 'std::string' to 'const char*' for argument '2' to 'SDL_Surface* TTF_RenderText_Solid(TTF_Font*, const char*, SDL_Color)

[Assassin7257]

//The header

#include"SDL/SDL.h"

#include"SDL/SDL_image.h"

#include"SDL/SDL_ttf.h"

#include<string>

#include<sstream>





//Screen Attributes

const int SCREEN_WIDTH = 640;

const int SCREEN_HEIGHT = 480;

const int SCREEN_BPP = 32;



//Surface

SDL_Surface* background = NULL;

SDL_Surface* message = NULL;

SDL_Surface* screen = NULL;



//Event Structure

SDL_Event event;



//int score

int score = 9990;



//The fonts thats going to be used

TTF_Font *font = NULL;



//The colour of the font

SDL_Color textColor = { 255, 255, 255 };



SDL_Surface* load_image( std::string filename )

{

	//Temporary hold image

	SDL_Surface* loadedImage = NULL;



	//Optimized IMage

	SDL_Surface* optimizedImage = NULL;



	//Load image

	loadedImage = IMG_Load( filename.c_str() );



	if ( loadedImage != NULL )

	{

		//Optimize Image now

		optimizedImage = SDL_DisplayFormat ( loadedImage );



		//Free surface

		SDL_FreeSurface ( loadedImage );



		//if optimized with no errors

		if ( optimizedImage != NULL )

		{

			//Set colour key

			SDL_SetColorKey ( optimizedImage, SDL_SRCCOLORKEY, SDL_MapRGB ( optimizedImage->format, 0, 0xFF,0xFF) );



		}

	}



	//if no errors

	return optimizedImage;

}



bool init()

{

	if ( SDL_Init( SDL_INIT_EVERYTHING) == -1)

	{

		return false;

	}



	//set up screen

	screen = SDL_SetVideoMode ( SCREEN_WIDTH, SCREEN_HEIGHT, SCREEN_BPP, SDL_SWSURFACE );



	//if there was no errors

	if ( screen == NULL )

	{

		return false;

	}



	//Initilize TTF_Init()

	if ( TTF_Init () == -1)

	{

		return false;

	}



	//set window caption

	SDL_WM_SetCaption( "Rendering Text", NULL );



	//if there was no errors

	return true;

}



void apply_surface( int x, int y, SDL_Surface* source, SDL_Surface* destination, SDL_Rect* clip = NULL )

{

	//Offset

	SDL_Rect offset;



	//assigning offset

	offset.x = x;

	offset.y = y;



	//BlitSurface

	SDL_BlitSurface( source, clip, destination, &offset);

}



bool load_files()

{

	//load image

	background = load_image ( "background.png" );



	if ( background == NULL )

	{

		return false;

	}



	font = TTF_OpenFont( "lazy.ttf", 28);



	if ( font == NULL )

	{

		return false;

	}



	//if no errors at all

	return true;

}



void cleanup()

{

	//Free up surface

	SDL_FreeSurface ( background );

	SDL_FreeSurface ( message );



	//Close the font being use

	TTF_CloseFont ( font );



	//Quit font

	TTF_Quit();



	//SDL Quit

	SDL_Quit();

}



int main ( int argc, char* args [] )

{

	//event quit

	bool quit = false;



	if ( init() == false )

	{

		return 1;

	}



	if ( load_files() == false)

	{

		return 1;

	}



	std::stringstream ss;

	ss << score;

	std::string creditString = ss.str();



	SDL_Surface* output = TTF_RenderText_Solid(font, creditString, textColor);

	SDL_BlitSurface( creditString, NULL, screen, NULL);











	//apply surfaces

	apply_surface( 0, 0, background, screen );



	//Update screen

	if ( SDL_Flip (screen) == -1 )

	{

		return 1;

	}



	//while quit is false

	while ( quit == false)

	{

		//while there event to handle

		while ( SDL_PollEvent ( &event ))

		{

			//if the user hasn't quit

			if ( event.type == SDL_QUIT )

			{

				//if the user hasnt Xed

				quit = true;

			}

		}

	}



	//end program

	cleanup();



	return 0;

}

[Assassin7257]

Idk what i'm doing wrong

[RulerOfNothing]

BCullis you are right in that I meant creditString.c_str() not ss.c_str(). Sorry about that Assassin7257.

[BCullis]

Assassin, read my edit. Here's your problem line:

SDL_Surface* output = TTF_RenderText_Solid(font, creditString, textColor);

Which should read:

SDL_Surface* output = TTF_RenderText_Solid(font, creditString.c_str(), textColor);

because the TTF_RenderText_Solid method expects argument 2 to be a c-style string (a pointer) and not a std::string. Thankfully, std::string has a method that converts from string to c-style string. Hooray documentation and reference!

[Assassin7257]

I change it to creditstring.c_str and it still not showing on the screen

[Assassin7257]

i blit the surface too