Question

I like to use the Sleep() function in a Windows Forms project, but the Sleep() is executed before anything else. I read that i should flush using fflush(), but i don’t know what to flush. Can someone help me?

The code:

private: System::Void button1_Click(System::Object^  sender, System::EventArgs^  e) {                    

             this->label1->Visible= false;
             this->button1->Visible= false;


             r = (float)rand()/(float)RAND_MAX;                              
             r = r*100000;
             i = r;
             r = r - i;              

             String^ strR = "" + r;
             this->label2->Text = strR;


             if(r >= 0.5)
             {
                 this->pictureBox1->Visible= true;
                 this->pictureBox1->BackColor = System::Drawing::Color::Blue;                    
             }
             else
             {
                 this->pictureBox1->Visible= true;
                 this->pictureBox1->BackColor = System::Drawing::Color::Red;                                         
             }   

             Sleep(500);

         }

Answer 1

The call to Sleep() is blocking your main (UI) thread, which prevents the message pump from updating your controls.

In this case, it doesn’t appear that the call to Sleep really serves a purpose, other than blocking your UI – if you want to prevent the button from being pressed again, a better option would be to disable it, then use a timer (System::Windows::Forms::Timer) with a 500 ms interval to re-enable the button.

By using a timer, you won’t block the UI thread, which allows your controls to stay active, but you still prevent the user from pressing the button.