The C# Column

The Timezone application - II

In the last article we had declared the location class containing data members to hold hours, minutes, city name and x-y coordinates of the city on the map, and then populated the array in the Form1 class.

Now comes the real part.

private void Form1_MouseMove ( object sender, MouseEventArgs e )

{
    // Previous code
    int i = search ( new Point ( e.X, e.Y ) ) ;
    Rectangle m_rect = new Rectangle( ) ;
     if ( i != -1 )
     {
           m_rect = this.ClientRectangle ;
           Point dpt = new Point ( 0, 0 ) ;
           if ( e.X + 150 < m_rect.Width )
           dpt.X = e.X + 5 ;
       else
            dpt.X = e.X - 155 ;
          if ( e.Y + 20 < m_rect.Height )
            dpt.Y = e.Y + 5 ;
      else
         dpt.Y = e.Y - 20 ;
         string str = calculate ( i ) ;
         l.Left = dpt.X ;
         l.Top = dpt.Y ;
         l.Size = new Size ( 150, 20 ) ;
         l.Text = str ;
         l.Visible = true ;
     }
     else
         l.Visible = false ;
}

We have called the search( ) method that returns the index of the array element whose coordinates match with the coordinates of the current mouse position. We have then calculated the suitable place where the label of size 150 x 20 can be displayed. The left-top position is stored in the dpt object. Next we have called the calculate( ) method. This method customises the string containing information of the city and returns the same.

Once we have the information, what remains is to display this information on the label. We must first create the label. For this, add the following code in the Load event handler.

l = new Label( ) ;
l.Visible = false ;
Controls.Add ( l ) ;

The following statements specify the position, size and text of the label. The label is invisible initially. We have to make it visible using the Visible property.

l.Left = dpt.X ;
l.Top = dpt.Y ;
l.Size = new Size ( 150, 20 ) ;
l.Text = str ;
l.Visible = true ;

If the mouse is positioned at some obscure place in the world whose entry is not present in the array the search( ) method returns a value -1. In such a case the label is hidden by setting the Visible property to false.

Let’s now look at the two helper functions, search( ) and calculate( ). They are given below.

int search ( Point p )

{
   Rectangle r = new Rectangle ( p.X , p.Y , 5, 5 ) ;
   Point pt ;
   for ( int i = 0 ; i < loc.Length ; i++ )
   {
       pt = new Point ( loc [ i ].x, loc [ i ].y ) ;
       if ( r.Contains ( pt ) )
       return i ;
    }
    return -1 ;
}

To this method we have passed the current mouse position. We have run a for loop to see whether coordinates of any city fall within the specified area. If they do, we have returned the index of the element.

This index is then passed to the calculate( ) method.

string calculate ( int i )
{
   int m_hour = loc [ i ].hours ;
   int m_minute = loc [ i ].minutes ;
   DateTime t = DateTime.Now ;
   t = t.AddHours ( m_hour ) ;
   t = t.AddMinutes ( m_minute ) ;
   string week_day = t.DayOfWeek.ToString( ) ;
   string str = week_day + “ “ + t.Hour + “:” +
   t.Minute + “ “ + loc [ i ].city ;
   return str ;
}

In this method, we have read the hour and minutes of the specified array element. Remember that these hour and minute values specify the time with respect to the Indian Standard Time. We have added this time to the current time to get the exact time at the city. Lastly, we have obtained the day of week and constructed the string with all the information we have. This string is returned back to the MouseMove event handler.

Run the program and move the mouse on the form. You will get the pop-ups as shown in the following snap shot.

Yashavant Kanetkar, one of the first Express Computer columnists, is an established software expert, speaker and author with several best-sellers to his credit, including titles like “Let Us C” and the “Fundas” series. Contact him at kanetkar@dcubesoft.com