Basic menu idea?

Basic menu idea?

Tquila

Member #13,741

November 2011

I've been looking around for this, but havn't quite found anything.

My own idea is something like making some text (Like "Play") and then detect if the mouse is on it and then begin game loop from there (or draw another screen if it's High Scores or whatever). This just seems a bit weird seeing you would do some "collision" detection with the mouse and the text. Is there some simple "normal best-practice go-to" way to do this? Please note I write in C (forced) so classes is not an option (albeit I hardly can see how in this case).

Edit: (totally OT) how would you scroll in a game enviroment? If you have a screen say 640x480, but a game board of 2560x1920, how would you make that scroll?

My (again I'm so good at pseudocoding this >.<) idea is that you do either of:

1: Center fix your character, and use X / Y coords to determain where on the board you are. But how would you do the actual scrolling? But how would you go about it in the code?

2: Have your character moving as per normal, and switch view when you read the end of the screen, so you kind a do it in spikes (I kind a like this idea).

Thanks for all the help I'm receiving in here btw, it's awesome. Hopefully I can chip back some day

Edgar Reynaldo

Major Reynaldo

May 2007

Question #1 :
Make a button object :

#SelectExpand
  1typedef struct Button {
  2   int x,y,w,h;
  3   const char* text;
  4};
  5
  6Button* MakeButton(int x , int y , int w , int h , const char* text) {
  7   Button* b = (Button*)malloc(sizeof(Button));
  8   if (!b) {return 0;}
  9   b->x = x;
 10   b->y = y;
 11   b->w = w;
 12   b->h = h;
 13   b->text = strdup(text);
 14   return b;
 15}
 16
 17void DestroyButton(Button* b) {free(b->text);}
 18
 19int ButtonClicked(Button* b , int mousex , int mousey) {
 20   // check if button contains mousex and mousey
 21}
 22
 23void Display(Button* b , BITMAP* dest) {
 24   // draw button text centered on the button
 25}

Question #2 :
Use an x and y variable to track the position of a camera. Set the camera position based on what you want to show (like your character). Draw everything at x - camerax and y - cameray.

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Tquila

Member #13,741

November 2011

Thanks bud,

1 question though. Where do I specify the range of what you draw?

Edgar Reynaldo

Major Reynaldo

May 2007

The range of what? Do you mean the area where you draw the text, or the button? That is based on the x,y,w,h members of the Button struct.

Tquila

Member #13,741

November 2011

Ah yeah, I can see that would seem cryptic. Got the button stuff (I think), but was thinking of what you draw on the screen.

Where do I specify I want to draw the interval between x = 200 and x = 840 and y = 500 and y = 980. Where do I set what is visible on the screen?

Edgar Reynaldo

Major Reynaldo

May 2007

Make a simple camera object :

#SelectExpand
  1typedef struct Rectangle {
  2   int x,y,w,h,brx,bry;
  3};
  4
  5Rectangle MakeRectangle(int x , int y , int w , int h) {
  6   Rectangle r;
  7   r.x = x;
  8   r.y = y;
  9   r.w = w;
 10   r.h = h;
 11   r.brx = x + w - 1;
 12   r.bry = y + h - 1;
 13   return r;
 14}
 15
 16typedef struct Camera {
 17   Rectangle viewdest;
 18   Rectangle viewsrc;
 19};
 20
 21void SetCameraPos(Camera* cam , int x , int y) {
 22   if (x < cam->viewsrc.x) {x = cam->viewsrc.x;}
 23   if (y < cam->viewsrc.y) {y = cam->viewsrc.y;}
 24   if (x > cam->viewsrc.brx + 1 - cam->viewdest.w) {
 25      x = cam->viewsrc.brx + 1 - cam->viewdest.w;
 26   }
 27   if (y > cam->viewsrc.bry + 1 - cam->viewdest.h) {
 28      y = cam->viewsrc.bry + 1 - cam->viewdest.h);
 29   }
 30   cam->x = x;
 31   cam->y = y;
 32}
 33
 34void SetCameraDestination(Camera* cam , Rectangle dest) {
 35   if (dest.w > cam->viewsrc.w) {dest.w = cam->viewsrc.w;}
 36   if (dest.h > cam->viewsrc.h) {dest.h = cam->viewsrc.h;}
 37   SetCameraPos(cam , dest.x , dest.y);
 38}
 39
 40Camera MakeCamera(Rectangle dest , Rectangle src) {
 41   Camera cam;
 42   cam.viewsrc = src;
 43   SetCameraDestination(&cam , dest);
 44   return cam;
 45}

And then to use it, you would call MakeCamera and SetCameraPos when necessary :

Camera cam = MakeCamera(MakeRectangle(0,0,640,480) , MakeRectangle(0,0,background->w,background->h));

//...

// When the player moves, reset the camera :
SetCameraPos(&cam , player->x + player->w/2 - SCREEN_W/2 , player->y + player->h/2 - SCREEN_H/2);// centers the camera on the center of the player

Or to use your example :

SetCameraPos(&cam , 200 , 500);
// OR
SetCameraDestination(&cam , Rectangle(200,500,640,480));

Gabriel Campos

Member #12,034

June 2010

Getting aboard this topic...

Edgar said this function

Buttom *MakeButtom(...)
I could not understand why to use a pointer here...
Can you help me to understand???

Why using Pointer Functions??

Audric

Member #907

January 2001

Gabriel Campos said:

Getting aboard this topic...Edgar said this function Button *MakeButton(...)
I could not understand why to use a pointer here...
Can you help me to understand???Why using Pointer Functions??

The space may be misleading, it's identical to Button* MakeButton(...) or (I think) (Button *) MakeButton(...).
It's a function that returns a pointer to a Button, ie. the address of the newly-created Button in memory.

It's the same pattern as load_bitmap(). Very classic in C.

DanielH

Member #934

January 2001

Might want to fix your malloc and free functions Edgar. You malloc a button*, but free a char* (that wasn't malloc'ed).

Pointers are useful. It's a matter of both style and necessity.

Here is an example of 3 identical buttons

#SelectExpand
  1const char *text = "Hello World!";
  2
  3// dynamic button
  4Button* button1
  5
  6// static button
  7Button button2;
  8
  9// static button
 10Button button3 = { 10, 10, 200, 200, text };
 11
 12void makeTheButtons()
 13{
 14    button1 = MakeButton( 10, 10, 200, 200, text );
 15    if ( !button1 )
 16    {
 17        //oops
 18        return;
 19    }
 20
 21    button2.x = 10;
 22    button2.y = 10;
 23    button2.w = 200;
 24    button2.h = 200;
 25    button2.text = text;
 26}
 27
 28void freeMem()
 29{
 30    if ( button1 )
 31    {
 32        free( button1 );
 33    }
 34
 35    // nothing to do for button2 or button3
 36}

YouTube Coding Channel

Edgar Reynaldo

Major Reynaldo

May 2007

DanielH said:

Might want to fix your malloc and free functions Edgar. You malloc a button*, but free a char* (that wasn't malloc'ed).

The only thing I forgot was to free the Button* itself. The free(b->text); is to free the string that was created with strdup.

Gabriel Campos said:

Getting aboard this topic...

Edgar said this functionButtom *MakeButtom(...)
I could not understand why to use a pointer here...

Can you help me to understand???Why using Pointer Functions??

He said he was using C, not C++, and a Button stores a newly allocated const char* string, hence the Create/Destroy functions.

Gabriel Campos

Member #12,034

June 2010

So, to answer once and for all (to my sanity to), what is the diference to use a object pointer from a normal object?

// whats the better?
cButtom Buttom;
// or this
cButtom *Buttom;

Edgar Reynaldo

Major Reynaldo

May 2007

An object lives on the stack and will be destroyed when it goes out of scope, when the function it is declared in exits. A pointer has to be created/allocated by you and lives on the heap. It won't be destroyed until you do it yourself. It depends on what you want to do with it, that's all. Pointers are used in C because objects often have dynamic memory that they allocate, and give you 'create' functions that save you from having to allocate it all manually.

Audric

Member #907

January 2001

Both forms have their uses...

some_function_or_block(void)
{
   cButtom Buttom;

   // some code that uses Buttom
   Buttom.DoStuff();

   // end of scope
}

"behind the scenes", the above behaves like:

some_function_or_block(void)
{
   cButtom *Buttom;
   Buttom = new Buttom(); // <-- allocate in memory and call constructor

   // some code that uses Buttom
   Buttom->DoStuff(); // it's a shorthand for (*Buttom).DoStuff();

   // end of scope
   free(Buttom); <-- call destructor then deallocate from memory
}

The memory place will be different (stack instead of heap), but it doesn't make much more difference. You can run out of stack more easily than out of heap, but it's still not a frequent problem. Only with recursive functions and/or classes that contain lots of static data, like large arrays.