C/C++ Programming Help Thread

[lukespalding]

Calling functions with infinite loops inside other infinite loops in functions is an EXTREMELY bad idea. You eventual run out of stack memory and crash the game. In addition, it becomes nigh on impossible to exit cleanly in a sensible way.

Use a state machine:

(C code below)

#define MAIN_MENU 0
#define MAIN_GAME 1

int main()
{
	int currentState = MAIN_MENU;
	int gameInProgress = 1;
	
	while( gameInProgress )
	{
		switch( currentState )
		{
		case MAIN_MENU:
			{
				if( /* player selects to play game * / )
				{
					currentState = MAIN_GAME;
				}
			} break;
		case MAIN_GAME:
			{
			
			} break;
		default: break;
		}
	}
	
	return 0;		
}

Thanks for the heads up on that mistake then also that examplecode is really a good idea.
Thanks for the nudge to better coding!:Jump:
Luke

[yaustar]

Technically, I should have used enums instead of #defines, but that is easy enough to change.

[SilverSpring]

Couldn't you use an enum instead of the preprocessor there?

int main()
{
  enum state { MAIN_MENU, MAIN_GAME };
  state currentState = MAIN_MENU;
  return 0;
}

You still need to add enum in your variable declartions:

enum state { MAIN_MENU, MAIN_GAME };

int main()
{
  enum state currentState = MAIN_MENU;
  return 0;
}

Otherwise:

typedef enum _state
{ 
    MAIN_MENU, 
    MAIN_GAME, 

} state;

int main()
{
    state currentState1 = MAIN_MENU;

    // or if you prefer to make it more explicit 
    // so people know it's an enumerated type
    // like what you do with typedef'd structs
    // struct _mystruct var instead of mystruct var
    // to make it unambiguous
    enum _state currentState2 = MAIN_MENU;
    return 0;
}

For state machines, enum's are most definitely preferred.

[PSProgramer]

I'm still learning C++, and I was wondering what is the best lib to use for 2D graphics???

[Raphael]

There is no "best" in programming. It always just depends on what you need exactly.

[PSProgramer]

ok sorry. thanks for the info.

[lukespalding]

I'm still learning C++, and I was wondering what is the best lib to use for 2D graphics???

Im looking for a good 2d lib so if you get you hands on one then gimmie a bell id loveto have a look. thxz

[Slasher]

oslib

[slicer4ever]

wat slasher said

[Mr305]

I need a simplest example of how to blit an image using oslib. Any help?

[Anti-QuickJay]

int main() {
    oslInit(0);
    oslInitGfx(OSL_PF_8888,1);
    OSL_IMAGE * background = oslLoadImageFile("Background.png",OSL_IN_RAM,OSL_PF_8888);
    while (!osl_quit){
          oslStartDrawing();
          background->x = 0;
          background->y = 0;
          oslDrawImage(background);
          oslEndDrawing();
          oslSyncFrame();
    }
    oslEndGfx();
    oslWaitVSync();
    oslQuit();
    return 0;
}

That should work, its not tested.
You might want to look into the samples and see how they put images on screen.

[SG57]

Removed unneeded things, made it compilable, swizzle it for speed, unload resources for good practice and typically background images don't have an alpha channel so I changed the pixel format:

#include <oslib/oslib.h>

PSP_MODULE_INFO("oslib", 0, 1, 1);
PSP_MAIN_THREAD_ATTR(THREAD_ATTR_USER | THREAD_ATTR_VFPU);

int main()
{
  oslInit(0);
  oslInitGfx(OSL_PF_8888,1);
  
  OSL_IMAGE *background = oslLoadImageFilePNG("Background.png", OSL_IN_RAM | OSL_SWIZZLED, OSL_PF_5650);
  
  while (!osl_quit){
        oslStartDrawing();
        
        oslDrawImage(background);
        
        oslEndDrawing();
        oslSyncFrame();
  }
  
  if (background != NULL)
    oslDeleteImage(background);
  
  oslEndGfx();
  oslQuit();
  
  return 0;
}

[kostakis]

Hi, I recently started C programming, and I have a question. What code should I use to make the psp execute code only once when I press a button?

[PSProgramer]

ok, really great place that helped me learn. psp-programming.com

@SG57 - where are you telling the image the x and y of the screen that you are puting the image on???? or is that not included on this code cause it's a background?? if so then how would you define the x and y for a non-background image?? thanx.

[SG57]

PSProgrammer - the OSL_IMAGE structure contains everything about the image (x, y, scale, rotation angle, offsets, image data, etc.). By default, when loading an image it's x and y values are initialized to 0. You could also use a different function that takes your own x and y values as arguments ignoring it's own members.

[PSProgramer]

I'm really unfamiliar with oslib, and I'm still learning C++, but what would I need to put in the function to give me my own x and y variables???

[SafariAl]

PSPProgramer, as SG57 said for example:

OSL_IMAGE *myImage;

myImage now has x and y variables, along with the other variables mentioned by SG57. To use them you'd say for example:

myImage->x = 20;
myImage->y = 50;

which would set the image's x to 20 and y to 50. Hope that made sense.

[yaustar]

Do you know how to write a function that takes two parameters?

[SG57]

Totally off topic post (since it's a learning experience for PSProgrammer so I won't post anything) but hey there yaustar :) I haven't talked directly to you in forever

Think i can still occasionally PM you some C++ questions? I'd really like that

[yaustar]

Totally off topic post (since it's a learning experience for PSProgrammer so I won't post anything) but hey there yaustar :) I haven't talked directly to you in forever

Think i can still occasionally PM you some C++ questions? I'd really like that

Sure, or you can post on Homebrew Illuminati where there is less 'noise'.

[Mr305]

Removed unneeded things, made it compilable, swizzle it for speed, unload resources for good practice and typically background images don't have an alpha channel so I changed the pixel format:

#include <oslib/oslib.h>

PSP_MODULE_INFO("oslib", 0, 1, 1);
PSP_MAIN_THREAD_ATTR(THREAD_ATTR_USER | THREAD_ATTR_VFPU);

int main()
{
  oslInit(0);
  oslInitGfx(OSL_PF_8888,1);
  
  OSL_IMAGE *background = oslLoadImageFilePNG("Background.png", OSL_IN_RAM | OSL_SWIZZLED, OSL_PF_5650);
  
  while (!osl_quit){
        oslStartDrawing();
        
        oslDrawImage(background);
        
        oslEndDrawing();
        oslSyncFrame();
  }
  
  if (background != NULL)
    oslDeleteImage(background);
  
  oslEndGfx();
  oslQuit();
  
  return 0;
}

Is there LoadimageMemory for loading PNGs?

[SG57]

Yes, there are two methods actually. The file type doesn't matter but in this case i'll use PNG

One uses temporary file data:

//Binary data representing a PNG file
const int test_data[] = {...};
//The size of the above array data
const int test_data_size = ???;
//Set data for the temporary file
oslSetTempFileData(test_data, test_data_size, &VF_MEMORY);
//Load a PNG file using the temporary file (oslGetTempFileName to get its name)
OSL_IMAGE* image = oslLoadImageFilePNG(oslGetTempFileName(), OSL_IN_RAM | OSL_SWIZZLED, OSL_PF_5650);

and the other a virtual file system:

//Binary data representing a PNG file
const int test_png[] = {...};

//Each entry consists of a name, a pointer to the data, the size of the data, and a file type.
OSL_VIRTUALFILENAME ram_files[1] =
{
        {"ram:/test.png", (void*)test_png, sizeof(test_png), &VF_MEMORY}
};

//Add these files to the list
oslAddVirtualFileList(ram_files, oslNumberof(ram_files));

//We can now open them as if they were real files...
OSL_IMAGE *img = oslLoadImageFilePNG("ram:/test.png", OSL_IN_RAM | OSL_SWIZZLED, OSL_PF_5650);

[Mr305]

Yes, there are two methods actually. The file type doesn't matter but in this case i'll use PNG

One uses temporary file data:

//Binary data representing a PNG file
const int test_data[] = {...};
//The size of the above array data
const int test_data_size = ???;
//Set data for the temporary file
oslSetTempFileData(test_data, test_data_size, &VF_MEMORY);
//Load a PNG file using the temporary file (oslGetTempFileName to get its name)
OSL_IMAGE* image = oslLoadImageFilePNG(oslGetTempFileName(), OSL_IN_RAM | OSL_SWIZZLED, OSL_PF_5650);

and the other a virtual file system:

//Binary data representing a PNG file
const int test_png[] = {...};

//Each entry consists of a name, a pointer to the data, the size of the data, and a file type.
OSL_VIRTUALFILENAME ram_files[1] =
{
        {"ram:/test.png", (void*)test_png, sizeof(test_png), &VF_MEMORY}
};

//Add these files to the list
oslAddVirtualFileList(ram_files, oslNumberof(ram_files));

//We can now open them as if they were real files...
OSL_IMAGE *img = oslLoadImageFilePNG("ram:/test.png", OSL_IN_RAM | OSL_SWIZZLED, OSL_PF_5650);

Thanks a lot SG! :)

[PSProgramer]

yeah thank you for the help.

[Khatharr]

PSProgrammer - What you have there is a pointer to a struct. If you look up 'struct' on google you can find thousands of tutorials explaining their declaration and use. When you have just a 'normal' struct you can refer to its members by 'name_of_struct.name_of_m ember' whereas if you have a pointer to a struct, as is the case here then you can use 'name_of_struct->name_of_member' rather than '(*name_of_struct).name_o f_member'. Looks much nicer.

Structs are an invaluable asset in C/C++ programming. Good luck, mate. :)

[NoEffex]

Hi, I recently started C programming, and I have a question. What code should I use to make the psp execute code only once when I press a button?

(how I do it is)You would grab a variable, and have it when no buttons are pressed set to 0. Then, under your code to exec...ahh..screw it...here's a sample:

if(pad.Buttons & PSP_CTRL_CROSS)
{
if(!buttonBool0)
{
//CODE RIGHT IN HERE
}
buttonBool0=1;
}
else buttonBool0=0;

That should work, just make sure to declare it. There are probably simpler methods, but, this isn't one of them.

[kostakis]

Thanks, I will test it after my virtualbox problem is solved. It's been three days I cannot access my source code from it and compile it :Argh:

[Raphael]

Or alternatively, in case you have a lot of different button presses you want to handle and not have a variable for each button:

int lastButtons = 0;

while(isrunning)
{
   sceCtrlReadData(&pad);
   int pressed = ~lastButtons & pad.Buttons; // only buttons that have been pressed down this frame
   int released = lastButtons & ~pad.Buttons; // in case you want to react on the buttons being released rather than pushed
   if(pressed & PSP_CTRL_CROSS)
   {
       ... code that will only be executed the instant the button gets pushed down
   }
   lastButtons = pad.Buttons;
}

[PSProgramer]

Hey thanks for al the help Khatharr and SG57, I got alot more done. Also I find now that I quite like OSLib

[Mr305]

Donot we need to do oslSwapBuffer after enddrawing syncframe like flipscreen()?