视频播放器开发日志-paint event 不响应的解决办法

场景：
点击按钮，隐藏界面上的控件，然后在paint 里面输出提示信息。
如题

代码如下：

   private void cbxCoverSub_CheckedChanged(object sender, EventArgs e)
        {
    
    
            bool bShow = !cbxCoverSub.Checked;
            showSubtitle(bShow);
            showNotice();
        }

两个函数的代码如下：

        private void showSubtitle(bool bShow)
        {
    
    
             txtBackSubtitle.Visible = bShow;
             txtTopSubtitle.Visible = bShow;
        }

这段代码用于更新提示信息

        private void showNotice()
        {
    
    
            string str = "You can move and adjust this bar with mouse to cover the hard subtitle.";
            Graphics g = this.CreateGraphics();//
            Pen p = new Pen(Color.Blue, 2);//定义了一个蓝色,宽度为的画笔
            SolidBrush brsh = new SolidBrush(m_mouseMvBkClr);
            // clear the background 
            g.FillRectangle(brsh, this.ClientRectangle);

            // measure the length of the string in pixel 
            StringFormat format = new StringFormat();
            format.Alignment = StringAlignment.Center;
            format.LineAlignment = StringAlignment.Center;
            Size size = TextRenderer.MeasureText(str, this.Font);

            Rectangle rect = new Rectangle((this.Width - pnlRight.Width) / 2 - size.Width / 2, (this.Height - size.Height) / 2, size.Width, size.Height);
            TextRenderer.DrawText(g, str, this.Font, rect, Color.Yellow, m_mouseMvBkClr);
            //draw a border for this form
            g.DrawRectangle(p, this.ClientRectangle);
        }

paint 事件中：

    private void showSubForm_Paint(object sender, PaintEventArgs e)
        {
    
    
            //draw a border that the user can see the border of this form
            if (cbxCoverSub.Checked){
    
    
                showNotice();
            }
            //g.DrawEllipse(p, 10, 10, 100, 100);//在画板上画椭圆,起始坐标为(10,10),外接矩形的宽为,高为

        }

一切看似乎完美，然而，期待的画面没有出现，必须手动刷新才得到期待的结果：

尝试 Refreash,无效；
后来深度怀疑是visible 属性引发了一个貌似滞后的消息，即这个隐藏行为发生在paint之后，因此，paint感觉好像没有执行。弄了个timer测试了一些，发现可以得到预想界面。但是这样显然不是正解，忽然想到，控件的显示和隐藏函数应该是阻塞方式，于是将代码改了一下，即

   private void showSubtitle(bool bShow)
        {
    
    
            //pay attention of the following code
            // it seems that Visible = true will trigger the system to send a  a message and it will take effect after the paint event
            // that makes the codes in paint event run before the control response to this message.
            if (bShow)
            {
    
    
                //txtBackSubtitle.Visible = bShow;
                //txtTopSubtitle.Visible = bShow;
                txtBackSubtitle.Show();
                txtTopSubtitle.Show();
            }
            else
            {
    
    
                txtBackSubtitle.Hide();
                txtTopSubtitle.Hide();

            }
            this.Refresh();
        }

马拉孙于2021-01-24
海淀泛五道口地区