为什么学了一个学期的c语言，感觉一直都是在用代码去做一些简单的数学题，没有什么实际用途？ 第1页

       #include "PainterEngine_Application.h"  PX_Application App;  px_void PX_ApplicationOnButtonClear(PX_Object *pObject,PX_Object_Event e,px_void *ptr) {  PX_Application *pApp=(PX_Application *)ptr;  pApp->status=PX_APPLICATION_STATUS_STOP;  pApp->pt_count=0;  pApp->t=0;  }  px_void PX_ApplicationOnButtonPlay(PX_Object *pObject,PX_Object_Event e,px_void *ptr) {  PX_Application *pApp=(PX_Application *)ptr;  if (pApp->pt_count<2)  {   return;  }  pApp->status=PX_APPLICATION_STATUS_PLAYING;  pApp->t=0;  }   px_void PX_ApplicationDrawBezierCurve(px_surface *rendersurface,px_point pt[],px_int pt_count,px_float t,px_int linewidth,px_color clr) {  px_int i;   if (pt_count<=0)  {   return;  }   if (pt_count==1)  {   if(rendersurface)    PX_GeoDrawPenCircle(rendersurface,pt[0].x,pt[0].y,5,clr);   return;  }   if (linewidth<1)  {   linewidth=1;  }   //draw path  if(rendersurface)  {   for (i=0;i<pt_count-1;i++)   {    PX_GeoDrawCircle(rendersurface,(px_int)pt[i].x,(px_int)pt[i].y,8,1,clr);    PX_GeoDrawLine(rendersurface,(px_int)pt[i].x,(px_int)pt[i].y,(px_int)pt[i+1].x,(px_int)pt[i+1].y,linewidth,clr);   }   PX_GeoDrawCircle(rendersurface,(px_int)pt[i].x,(px_int)pt[i].y,5,1,clr);  }     //update path  for (i=0;i<pt_count-1;i++)  {   px_point vector_unit=PX_PointUnit(PX_PointSub(pt[i+1],pt[i]));   px_float distance=PX_PointMod(PX_PointSub(pt[i+1],pt[i]));    pt[i]=PX_PointAdd(pt[i],PX_PointMul(vector_unit,distance*t));  }    PX_ApplicationDrawBezierCurve(rendersurface,pt,pt_count-1,t,linewidth-1,PX_COLOR(96,PX_randEx(pt_count)%255,PX_randEx(pt_count+1)%255,PX_randEx(pt_count+2)%255)); }   px_bool PX_ApplicationInitialize(PX_Application *pApp,px_int screen_width,px_int screen_height) {  PX_ApplicationInitializeDefault(&pApp->runtime, screen_width, screen_height);  pApp->ui_root=PX_ObjectCreate(&pApp->runtime.mp_ui,0,0,0,0,0,0,0);  pApp->btn_play=PX_Object_PushButtonCreate(&pApp->runtime.mp_ui,pApp->ui_root,0,0,64,24,"Play",PX_NULL,PX_COLOR(255,0,64,255));  pApp->btn_clear=PX_Object_PushButtonCreate(&pApp->runtime.mp_ui,pApp->ui_root,0,0,64,24,"Clear",PX_NULL,PX_COLOR(255,0,64,255));  pApp->pt_count=0;  pApp->status=PX_APPLICATION_STATUS_STOP;  pApp->t=0;    PX_ObjectRegisterEvent(pApp->btn_clear,PX_OBJECT_EVENT_EXECUTE,PX_ApplicationOnButtonClear,pApp);  PX_ObjectRegisterEvent(pApp->btn_play,PX_OBJECT_EVENT_EXECUTE,PX_ApplicationOnButtonPlay,pApp);  return PX_TRUE; }  px_void PX_ApplicationUpdate(PX_Application *pApp,px_dword elpased) {  px_float x=(px_float)pApp->runtime.RenderSurface.width;   if (pApp->status==PX_APPLICATION_STATUS_PLAYING)  {   pApp->t+=elpased/5000.0f;   if (pApp->t>1)   {    pApp->t=1;   }  }   pApp->btn_clear->x=x-pApp->btn_clear->Width;  x-=pApp->btn_clear->Width;    pApp->btn_play->x=x-pApp->btn_play->Width;  x-=pApp->btn_play->Width;     PX_ObjectUpdate(pApp->ui_root,elpased); }  px_void PX_ApplicationRender(PX_Application *pApp,px_dword elpased) {  px_int i;  px_char content[16];    px_surface *pRenderSurface=&pApp->runtime.RenderSurface;  PX_RuntimeRenderClear(&pApp->runtime,PX_COLOR(255,255,255,255));     //points texts  for (i=0;i<pApp->pt_count;i++)  {   PX_sprintf1(content,sizeof(content),"P%1",PX_STRINGFORMAT_INT(i));   PX_FontDrawText(pRenderSurface,(px_int)pApp->pt[i].x,(px_int)pApp->pt[i].y-8,PX_FONT_ALIGN_MIDBOTTOM,content,PX_COLOR(255,0,0,192));  }    switch(pApp->status)  {  case PX_APPLICATION_STATUS_STOP:   {    for (i=0;i<pApp->pt_count-1;i++)    {     PX_GeoDrawCircle(pRenderSurface,(px_int)pApp->pt[i].x,(px_int)pApp->pt[i].y,5,1,PX_COLOR(255,0,0,192));     PX_GeoDrawLine(pRenderSurface,(px_int)pApp->pt[i].x,(px_int)pApp->pt[i].y,(px_int)pApp->pt[i+1].x,(px_int)pApp->pt[i+1].y,6,PX_COLOR(255,0,0,192));    }    if(pApp->pt_count)     PX_GeoDrawSolidCircle(pRenderSurface,(px_int)pApp->pt[i].x,(px_int)pApp->pt[i].y,5,PX_COLOR(255,0,0,192));   }   break;  case PX_APPLICATION_STATUS_PLAYING:   {    px_point path[201];    px_point pt[PX_APPLICATION_MAX_POINT];    px_int pathCount=(px_int)(pApp->t/0.005f);     PX_memcpy(pt,pApp->pt,sizeof(px_point)*pApp->pt_count);    PX_ApplicationDrawBezierCurve(pRenderSurface,pt,pApp->pt_count,pApp->t,6,PX_COLOR(128,0,0,192));     path[0]=pApp->pt[0];    for (i=1;i<=pathCount;i++)    {     PX_memcpy(pt,pApp->pt,sizeof(px_point)*pApp->pt_count);     PX_ApplicationDrawBezierCurve(PX_NULL,pt,pApp->pt_count,i*0.005f,1,PX_COLOR(0,0,0,0));     path[i]=pt[0];    }    PX_GeoDrawPath(pRenderSurface,path,pathCount+1,8,PX_COLOR(128,255,0,0));     //last pt    PX_GeoDrawPenCircle(pRenderSurface,path[pathCount].x,path[pathCount].y,8,PX_COLOR(255,255,0,0));     //t    {     px_char t[8];     PX_sprintf1(t,sizeof(t),"t=%1.2",PX_STRINGFORMAT_FLOAT(pApp->t));     PX_FontDrawText(pRenderSurface,path[pathCount].x,path[pathCount].y-10,PX_FONT_ALIGN_MIDBOTTOM,t,PX_COLOR(255,255,0,0));    }    }   break;  }   PX_ObjectRender(pRenderSurface,pApp->ui_root,elpased); }  px_void PX_ApplicationPostEvent(PX_Application *pApp,PX_Object_Event e) {  PX_ApplicationEventDefault(&pApp->runtime, e);   if (e.Event==PX_OBJECT_EVENT_CURSORDOWN)  {   if (PX_Object_Event_GetCursorY(e)<24)   {    PX_ObjectPostEvent(pApp->ui_root,e);   }   else   {    if (pApp->status==PX_APPLICATION_STATUS_STOP&&pApp->pt_count<PX_COUNTOF(pApp->pt))    {     pApp->pt[pApp->pt_count].x=PX_Object_Event_GetCursorX(e);     pApp->pt[pApp->pt_count].y=PX_Object_Event_GetCursorY(e);     pApp->pt[pApp->pt_count].z=0;     pApp->pt_count++;    }   }  }  else  {   PX_ObjectPostEvent(pApp->ui_root,e);  }  }