QTimer Slot - time delta varies depending on Slot-Method content

Flaming Moe

Hello there,

I´m making a quick and dirty Neo-Pixel sim where I have a QHLayout on the Widget, placew some widgets in in the Layout as representing the pixels.
Then there is a method, which translates the lower 24bit of a uint32_t to RGB values for creating a stylesheet which is passed with indivisual color values to the widgets in the layout.

Currently I just use a rainbow effect based on the approach of deviding a 256 step color circle in 3 segments (like the Arduin-Project does it, which is the later destination hardware for created effects):
This is ony a "getting started" effect. So a "rainbow gradient is not what I´m loking for.
For the fading effect I use a QTimer timeout slot "void Widget::SltTimerEl()"```
code_text

What I observe is, depending how many HLayouts with thier corresponding widgets I treat in the Slot the time delta´s kind of scale with the amount of HLayouts.
I measured that with retrieving by QTime.msec and calculating the differences.

Does the repainting of the widgets take so long, that it blocks the slot?

What would be a more clever way to do this?

#include "widget.h"
#include "ui_widget.h"
#include <QDebug>

Widget::Widget(QWidget *parent) :
    QWidget(parent),
    ui(new Ui::Widget)
{
    ui->setupUi(this);
   pixel* p = new pixel;
    p ->SetColor(4198520);
    //ui->horizontalLayout->addWidget(p);
    for(uint32_t i=0; i<10; i++)
    {
        QWidget* w = new QWidget;
        ui->horizontalLayout->addWidget(w);
        pixelList.append(w);
    }


    for(uint32_t i=0; i<50; i++)
    {
        QWidget* w = new QWidget;
        ui->horizontalLayout_2->addWidget(w);
        pixelList2.append(w);
    }


    for(uint32_t i=0; i<100; i++)
    {
        QWidget* w = new QWidget;
        ui->horizontalLayout_3->addWidget(w);
        pixelList3.append(w);
    }

    //connect(ui->pushButton, SIGNAL(clicked()), this, SLOT(SltShow()));
    connect(&timer, SIGNAL(timeout()), this, SLOT(SltTimerEl()));

    timer.setInterval(20);
    timer.start();
    time.start();
}

Widget::~Widget()
{
    delete ui;
}

void Widget::SltShow()
{
    SltTimerEl();
}

void Widget::SetColor(QWidget* w, uint32_t col)
{
    QString stSheet;
    unsigned int red, green, blue;
    red = (col & 16711680) >> 16;
    green = (col & 65280) >> 8;
    blue = col & 255;
    //qDebug() << "  red: " << red<< "  green: " << green<< "  blue: " << blue;
    stSheet.append("background-color: rgb(");
    stSheet.append(QString::number(red));
    stSheet.append(',');
    stSheet.append(QString::number(green));
    stSheet.append(',');
    stSheet.append(QString::number(blue));
    stSheet.append(");");
    w->setStyleSheet(stSheet);

    //qDebug() << stSheet;
}

void Widget::Rainbow()
{

}

void Widget::SltTimerEl()
{
    static uint32_t j = 0;
    static uint32_t k = 0;
    static uint32_t l = 0;

    static int sameCntr = 0, lastRes = 0, curRes;
    static uint32_t oldTime, newTime, timeDiff;

    newTime = time.msec();
    time.start();
    if(newTime >= oldTime)
    {
        timeDiff = newTime-oldTime;
    }
    else
    {
        timeDiff = 999-oldTime + newTime;
    }
    qDebug() << " newTime " << newTime << " timeDiff " << timeDiff;
    oldTime = newTime;

if(ui->pushButton->isDown())
{
    for(uint32_t i=0; i< pixelList.length(); i++)
      {
          SetColor(pixelList.at(i), Wheel(((i * 256 / (pixelList.length()))//+ j) & 255));
                                           + (j * 256 / (100)) )& 255));
          curRes = (j * 256 / (100));
          if(curRes != lastRes)
          {
              newTime = time.msec();
              time.start();
              if(newTime >= oldTime)
              {
                  timeDiff = newTime-oldTime;
              }
              else
              {
                  timeDiff = 999-oldTime + newTime;
              }
              //qDebug() << sameCntr << "  " << lastRes << " newTime " << newTime << " timeDiff " << timeDiff;
              sameCntr = 0;
          }
          else
          {
             sameCntr++;
          }
          lastRes = curRes;

                                          //+(j * 256 / (pixelList.length())) & 255));
          pixelList.at(i)->repaint();
       }
/**/
    for(uint32_t i=0; i< pixelList2.length(); i++)
      {
          SetColor(pixelList2.at(i), Wheel(((i * 256 / (pixelList2.length()))//+ j) & 255));
                                           + (k * 256 / (100)) )& 255));
                                          //+(j * 256 / (pixelList.length())) & 255));
          pixelList2.at(i)->repaint();
       }


    for(uint32_t i=0; i< pixelList3.length(); i++)
      {
          SetColor(pixelList3.at(i), Wheel(((i * 256 / (pixelList3.length()))//+ j) & 255));
                                           + (l * 256 / (100)) )& 255));
                                          //+(j * 256 / (pixelList.length())) & 255));
          pixelList3.at(i)->repaint();
       }

    j++;
    if(j >= 100) j = 0;

    k++;
    if(k >= 100) k = 0;

    l++;
    if(l >= 100) l = 0;
}
}

uint32_t Widget::Wheel(uint32_t WheelPos)
{
    uint32_t r, g, b, ret;
  if(WheelPos < 85)
  {
      r = WheelPos * 3;
      g = 255 - WheelPos * 3;
      b = 0;

     return ret = (r<<16) + (g<<8) +b;
  }
  else if(WheelPos < 170)
  {
      WheelPos -= 85;
      b = WheelPos * 3;
      r = 255 - WheelPos * 3;
      g = 0;

        return ret = (r<<16) + (g<<8) +b;
    }
    else
    {
      WheelPos -= 170;
      g = WheelPos * 3;
      b = 255 - WheelPos * 3;
      r = 0;

        return ret = (r<<16) + (g<<8) +b;
    }
}

Christian Ehrlicher

Can you please format your post so that it's readable?
20 ms is a very short time, it's the minimum time for normal windows timers so yes, the timeout can vary. Doing such stuff with stylesheets is also not the best way - override QWidget::paintEvent() and paint the background there.

Flaming Moe

yes... Saw the unformatted code - tryed to edit, but there it is displayed formated.
Perhaps I have to try a different browser or control-signs

JonB

@Flaming-Moe
Put a line with just ``` above your code and the same line again below your code.

Outside of this, where your

What I observe is,

paragraphs are, do not allow lines to start with 4 or more spaces, which I believe is what you have now.

Christian Ehrlicher

@Flaming-Moe I fixed your first post.