Resizable widgets using mouse

[kabanek]

hello, I want to add possibility to resize width of widgets in layout using mouse.
I mean... to put mouse between this two widgets, drag and move left/right changing the width of widgets. How can I do that?

[nish]

read about QSplitter

[kabanek]

It looks good, but I have a problem with width of this objects. I want to have widths for example: 200px (first widget), 200px (last widget) and the rest of width to the second object. I wrote:

MainSplitter = new QSplitter(Qt::Horizontal, ui->centralWidget);
    MainSplitter->insertWidget(0, ui->projectsTab);
    MainSplitter->insertWidget(1, ui->filesTab);
    MainSplitter->insertWidget(2, ui->detailsTab);
 
    ui->projectsTab->setGeometry(0,0, 500, 100);

MainSplitter = new QSplitter(Qt::Horizontal, ui->centralWidget);
    MainSplitter->insertWidget(0, ui->projectsTab);
    MainSplitter->insertWidget(1, ui->filesTab);
    MainSplitter->insertWidget(2, ui->detailsTab);

    ui->projectsTab->setGeometry(0,0, 500, 100);

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but I get the window does not look like I want to look