QTextDocument: table border scaling broken for print

QTextDocument has no concept of units. So values given for margins, paddings or border width have to be provided in pixels. Internally QTextDocument uses qt_defaultDpi and the QPaintDevice's dpi metrics to calculate a scale factor (see internal QTextDocumentLayout::scaleToDevice method).

So in order to apply e.g. metric values, one has to calculate a pixel value based on qt_defaultDpi (which is more or less a private function, so you must use QGuiApplication::primaryScreen()->logicalDotsPerInchX() to get that value).

But while metrics like cellPadding are correctly scaled, some values in QTextFrameFormat are not:

• [top|left|right|bottom]Margin
• padding
• border

The attached example program tries to set the 'border' value. Attached are the results for on-screen rendering and printing.

A patch to fix this is being worked on.