QListWidget resize item to reproduce Windows behavior : Magical Number needed

[ChrisW67]

The magic is likely some element(s) of the style's rendering of the widgets that you are not accounting for. You may be able to work the amount of "magic" required using the QStyle::pixelMetric() function and constants
http://doc.qt.io/qt-4.8/qstyle.html#PixelMetric-enum

The flickering is probably because the automatic scrollbar is being added and removed repeatedly because the size of the contained widget is changing around the scroll area's critical size. You need to be careful that the appearance of the scroll bar, which narrows the viewport, does not trigger a shrinking of the layout that causes the viewport to grow... Circular updates.

[Alundra]

The idea is easy, simply compensate the empty space on each item to use the whole space on the width but to remove this constant, it's not so easy.
Using a little value to only have very little empty space you got bad result (flickering). The solution I give is the only one I found after lot of tests.
Maybe a padding-left needed to solve completely, but then you have big margin on the left and right of the row.
using :

m_ListWidget->setStyleSheet( "QListView{ padding-left: 10px; }" );

m_ListWidget->setStyleSheet( "QListView{ padding-left: 10px; }" );

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I have to use this value to have 0 flickering (if the scrollbar is visible or not) :

const int RightMargin = 28;

const int RightMargin = 28;

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But the margin is not the same on the left and right, I have 10px on the left but more space on the right, 28px.
For the case where no padding-left is set, I got also good visual without flickering using 18px for the RightMargin, which gives less empty space than 20px.
That works very well but it's not centered, you have 0 empty space on the left and 18px empty space on the right and no solution found to have it centered...