//////////////////////////////////////////////
//?Double?buffered?resizeable?2D?GL?windowing?environment?using?GLUT
//////////////////////////////////////////////

#include?
#include?
#include?
#include?
//
//globale?variables
//
const?int?milliseconds_per_frame?=?500;
float?posX?posY;
float?posXA[100];
float?posYA[100];
int?sizeA[100];
float?angleA[100];
int?cnt=0;
int?size=1;
int?angle=0;
int?filled?=?1;
int?animation=1;

int?windowWidth=700;
int?windowHeight=600;
//
//?Forward?declarations
//
void?DrawScene（）;
void?DrawSnow（）;
void?DrawEdge（）;
void?FillEdge（）;
//
//?Initialisation?functions
//
static?void?DrawInit（）
{
????//?OpenGL?one-time?initialisation
????glClearColor（0.65F?0.65F0.9F?1.0F）;
????cnt=0;
}

//
//?Callbacks
//
void?Timer（int?id）
{
for（int?i=0;?i{
????angleA[i]+=（0.1+5/sizeA[i]）;
????posXA[i]+=0.25;
????posYA[i]-=0.5;
????if（posXA[i]>（windowWidth+50））
????{
?????posXA[i]-=windowWidth;
????}
????if（posYA[i]<-50）
????{
??????posYA[i]+=windowHeight;
????}

}
glutPostRedisplay（）;
}

void?DisplayFunc（）
{
????glShadeModel（GL_SMOOTH）;
????glClearColor（0.65F?0.65F0.9F?1.0F）;
????glClear（GL_COLOR_BUFFER_BIT）;
????if（animation）
??????glutTimerFunc（milliseconds_per_frameTimer1）;
????glMatrixMode（GL_MODELVIEW）;
????glLoadIdentity（）;
????DrawScene（）;
????glutSwapBuffers（）;
}

void?PainSnow（int?btn?int?state?int?x?int?y）
{
if（btn==GLUT_LEFT_BUTTON?&&?state==GLUT_DOWN）
{
????size?=?rand（）%5+1;
????angle?=?rand（）%30;
????posX=x;
????posY?=?windowHeight-y;
????posXA[cnt]=posX;
????posYA[cnt]=posY;
????sizeA[cnt]=size;
????angleA[cnt]=angle;
????cnt++;
}
}

void?KeyboardFunc（unsigned?char?key?int?x?int?y）
{
????switch（key）
????{
????????case?‘a‘?:
????????case?‘A‘?:
????????{
??????????if（animation==0）
??????????{
????????????animation=1;
??????????}else{
????????????animation=0;
??????????}
????????}
????????case?‘x‘?:
????????case?（‘X‘）:
????????{
??????????cnt=0;
??????????DrawInit（）;
??????????break;
????????}
????????case?‘f‘:
????????case?‘F‘:
????????{
??????????if（filled==1）
??????????{
????????????filled=0;
??????????}
???????????else
??????????{
???????????filled=1;
??????????}
??????????break;
????????}
????????case?27:?//?escape?key?pressed
????????{
????????????exit（0）;
????????????break;
????????}
????}
}


void?ReshapeFunc（?int?x?int?y?）
{
????//?Orthographic?view?fills?the?window
????glMatrixMode（GL_PROJECTION）;
????glLoadIdentity（）;
????gluOrtho2D（?0.0?x?0.0?y?）;
????glViewport（?0?0?x?y?）;
????windowWidth=x;
????windowHeight=y;
}

void?IdleFunc（）
{
????glutPostRedisplay（）;
}

void?FillEdge（）
{
??????glColor3f（0.70f?0.70f?1.0f）;
??????glBegin（GL_POLYGON）;
?????????glVertex2f（0.0f?30.0f）;
????????????glVertex2f（0.0f?00.0f）;
?????????glVertex2f（260.0f?00.0f）;
?????????glVertex2f（250.0f?30.0f）;