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How to avoid adding excess 1 pixel spacing by Qt Designer

I'm working on application for embedded and we have 256x64 grayscale screen. Qt 5.3 perfectly renders on that screen with -platform linuxfb option. Obviously, we save every pixel of space, so I faced with trouble: Qt Designer adds excess 1 pixel spacing for every layout element deeper in hierarchy. So they accumulate for the most deep widgets. More precisely, for some reason child element of layout components gets coordinates (1,1) relative to parent. So, it's true for every widget except for root widget. Picture below demonstrates accumulated spacings (thin and thick red lines), and (1,1) coordinates of the very first child widget.

screenshot

I believe it's Qt behavior itself, not just Qt Designer issue (not tested yet). But I can't work further even if it's shown in Designer only: I need to have pixel-exact view while designing. Of course, every spacing and margin of every component in form set to 0. Manual coordinates assigning (from code) eliminates the problem of course, but I need to generate code by uic.

So, my question is: how to avoid such spacings? Fixing Qt core sources can be (hard) option too, since anyway we recompile Qt for the project.

Mirror post on Qt forums

Thanks. Ilia.

Solution

  • If you select Form > View Code, you can see that the geometry is not actually used for widgets which are inside a layout. So the numbers you see in the Property Editor are purely informational and have no relevance to the eventual code that is generated from the ui file (which is why they are greyed out).

    The one pixel offset is there because Qt Designer needs space to draw the red boxes around layouts. They have to be be represented somehow, so I don't see how this can be avoided given the way Qt Designer currently works. If you want a more accurate reprentation of the final results, I suppose you will have to show a preview.

    There is a facility in Settings > Preferences > Embedded Design that allows you to specify device profiles (which determine things like style, font, and screen resolution). This will add a new entry to the Preview In menu, which should allow you to refine the accuracy of the previews even further.