multithreading - 替换为Thread.Suspend-恢复而不影响性能

Question

我正在制作具有过渡-缩放-平移-效果的幻灯片，其性能对于平滑渲染至关重要。这是一个我要移植到Delphi 10.3的旧项目，有一个线程可以在运行渲染到屏幕的同时从jpgeg-images的文件流中加载下一张幻灯片。在我的旧代码中，线程一直在运行，被挂起并根据需要恢复。这是现在不推荐使用的旧代码的流程:

procedure TSlideshow.Create;
begin
  MakeNextThread:=TMakenextThread.Create(true);
  MakeNextThread.FreeOnTerminate:=false;
end;

procedure TSlideshow.Render(previous, next: integer);
begin
  //Check if thread has loaded next, if not make it here

  //Send off the thread to make next+1
  //The next block takes less than 0.1 ms on average !!!
  If next+1 < count then
  begin
    //Fill fields of MakeNextThread with data to load next+1
    MakeNextThread.Resume;
  end;

  //Render to screen
end;

procedure TMakeNextThread.Execute;
begin
  while not terminated do
  begin
    //Load bitmap from jpeg-stream
    sleep(1)
    //Prepare alpha-channel for transition
    done:=true;
    suspend;
  end;
end;

我试图避免使用暂停和恢复，但是结果是 Not Acceptable ，因为它会导致幻灯片在过渡之前明显暂停。

procedure TSlideshow.Render(previous, next: integer);
begin
  //Check if thread has loaded next, if not make it here

  //Send off the thread to make next+1
  //The next block takes more than 40 ms on average !!!
  If next+1 < count then
  begin
    MakeNextThread.terminate;
    MakeNextThread.free;
    MakeNextThread:=TMakeNextThread.Create(true);
    MakeNextThread.FreeOnTerminate:=false;
    //Fill fields of MakeNextThread with data to load next+1
    MakeNextThread.Start;
  end;

  //Render to screen
end;

procedure TMakeNextThread.Execute;
begin
  //Load bitmap from jpeg-stream
  sleep(1)
  //Prepare alpha-channel for transition
    done:=true;
end;

有没有办法在不损失性能的情况下做到这一点？首先使用暂停恢复有什么危险呢？

Answer 1

您不需要每次都创建一个新线程。只需在TEvent内使用TMakeNextThread对象即可。让Execute()运行一个调用TEvent.WaitFor()的循环，然后您可以在想要“唤醒”线程时调用TEvent.SetEvent()，而在想要“暂停”线程时可以调用TEvent.ResetEvent()。当事件被信号通知且Terminated为False时，循环即可完成其工作。