Рисование - почему не закрашиваются квадраты?

//---------------------------------------------------------------------------
#include <vcl.h>
#pragma hdrstop
 
#include "Unit1.h"
#include "stdio.h"
#include "stdlib.h"
#include "windows.h"
#include "ctime.h"
#include <process.h>
//---------------------------------------------------------------------------
#pragma package(smart_init)
#pragma resource "*.dfm"
TForm1 *Form1;
int x1,y1,x,y,i;
RECT rect={0};
HANDLE han2;
char str[5];
int  colorIndex;
struct Painting
{int radius;};
Painting paint;
 
DWORD WINAPI ris (LPVOID pvParam)
{
Painting p = *( Painting*) pvParam;
int r = p.radius;
for(i=0;i<7;i++)
{ srand(time(NULL));
rect=Application->MainForm->ClientRect;
const W=(rect.right)+(rect.left);
const H=(rect.bottom)+(rect.top);
x=rand()%W;
y=rand()%H;
x1=x-r;
y1=y-r;
Form1->Canvas->Rectangle(x,y,x1,y1);
Sleep(1000);}
return (0); }
 
 
void riskv( int radius, int colorIndex)
{
x = random(x1);
y = random(y1);
if(colorIndex ==0)Form1->Canvas->Brush->Color = clBlack;
if(colorIndex ==1)Form1->Canvas->Brush->Color = clRed;
if(colorIndex ==2)Form1->Canvas->Brush->Color = clGreen;
Form1->Canvas->Rectangle(x,y,x1 - 2*radius,y1 - 2*radius);
Sleep(1000);
i++;
}
 
 
 
//---------------------------------------------------------------------------
__fastcall TForm1::TForm1(TComponent* Owner)
        : TForm(Owner)
{
}
//---------------------------------------------------------------------------
 
void __fastcall TForm1::Button1Click(TObject *Sender)
{ srand(time(NULL));
paint.radius = StrToInt(Form1->Edit1->Text.c_str());
x = x1-2*paint.radius;
y = y1-2*paint.radius;
i=0;
DWORD dw;
han2 = CreateThread(NULL,0, ris ,(void*)&paint,0,&dw);
}
//---------------------------------------------------------------------------
void __fastcall TForm1::Button2Click(TObject *Sender)
{
Close();
}