Widget is not so smooth when resizing?

[MorrisLiang]

I'm not sure if I can fully expain what is this question,but please read on.

Here,I'm creating a frameless window.

MyWindow::MyWindow(QWidget *parent) :
    QMainWindow(parent)
{
    ui.setupUi(this);
    setWindowFlags(Qt::FramelessWindowHint);
    setAttribute(Qt::WA_TranslucentBackground);
    setAttribute(Qt::WA_NoMousePropagation);
    resizeHandle = new ResizeHandle(this);
    resizeHandle->setCursor(Qt::SizeVerCursor);
    ...
    connect(resizeHandle, SIGNAL(sizeChanged(QPoint&)), this, SLOT(rearrange(QPoint&)));
}

MyWindow::MyWindow(QWidget *parent) :
    QMainWindow(parent)
{
    ui.setupUi(this);
    setWindowFlags(Qt::FramelessWindowHint);
    setAttribute(Qt::WA_TranslucentBackground);
    setAttribute(Qt::WA_NoMousePropagation);
    resizeHandle = new ResizeHandle(this);
    resizeHandle->setCursor(Qt::SizeVerCursor);
    ...
    connect(resizeHandle, SIGNAL(sizeChanged(QPoint&)), this, SLOT(rearrange(QPoint&)));
}

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At the bottom,there's the resizeHandle.When I press on it,I can drag it.Then it will emit sizeChanged(QPoint&) signal,indicating how much I drag(usually 1 to 3 pixel per SIGNAL).Then I resize MyWindow in rearrange(QPoint&):

void MyWindow::rearrange(QPoint& newSize)
{
    int newH = newSize.ry();
 
    resize(this->width(), this->height() + newH);
    QFrame* footer = ui.footerFrame;
    footer->setGeometry(footer->x(), footer->y() + newH, footer->width(), footer->height());
    ....
}

void MyWindow::rearrange(QPoint& newSize)
{
    int newH = newSize.ry();

    resize(this->width(), this->height() + newH);
    QFrame* footer = ui.footerFrame;
    footer->setGeometry(footer->x(), footer->y() + newH, footer->width(), footer->height());
    ....
}

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Here is what it looks like when I resizing:

Seems like a glitch.It's not always this dramatic,but it appears even when I'm dragging slowly.Anyway,it's all about the effect.
Maybe I'm missing something when I implement such kind of function.Should I use so-called double-buffer or something,and how?

[squidge]

Have you tried this in release mode instead of debug? I'm noticed a few things are a bit jerky in debug mode, probably because of the unoptimised code and lots more validation.

[MorrisLiang]

Ok,I will try that.

This problem is gone when I build release.
Thanks~