Hi all, I'm looking for someone who knows the inner workings of QIcon and the icon engines.
In our application, we almost exclusively use SVG icons, and we use a single SVG file for each icon (no @2x versions) that we try to design to work reasonably well at all sizes, since we do not have the resources to make custom variations for each target size. We put these SVG icons into an XDG icon theme, that we ship inside the application resources (.qrc) in the expected XDG layout and with an icon theme index file. We can then use QIcon::fromTheme("our-app-some-icon") to reference an icon (either through the .ui file or in code). The problem we've run into is that when the application is launched in a mixed-DPI setup, for example a retina Mac laptop with an external lower-DPI monitor, the icons appear too large and get cropped. In effect, it seems to always use the DPI of the primary screen (the built-in retina screen) when calculating the size of the pixmaps it generates for the icons. To work around this, we've had to put in special code in all of our widgets that use icons. The code reacts to screen change events (or changes to the underlying QWindow in some cases), and in that code, go through each and every one of our icons and do this monkey dance: auto pixmap = someButton->icon().pixmap(someButton->iconSize()); pixmap.setDevicePixelRatio(window()->windowHandle()->screen()->devicePixelRatio()); someButton->setIcon(QIcon(pixmap)); So essentially taking the pixmap out of the icon, set its DPR to that of the current screen, and then set that pixmap back on the icon. This "works", the icons now look correct on both the retina screen and the external one, and adjust themselves when the application is moved back and forth, or when the external monitor is activated/deactivated. But surely this kludge should not be necessary? We've provided Qt with an SVG, so it should be able to work out on its own that the screen has changed, and regenerate an appropriate pixmap in response to that? Some more details: - We are running with the Qt::AA_UseHighDpiPixmaps application attribute turned on. I'm not sure this is relevant for this issue though, because AFAIK that attribute is only about picking 2x versions of icons (we have a couple of those, where we have PNGs with 2x versions). - We are not running with Qt's built-in scaling activated, but relying on the Mac platform scaling (I'm not even sure Qt's built-in scaling is applicable on Mac). The application runs with NSHighResolutionCapable set to True in its Info.plist (which I also think is the default nowadays). - I have not investigated yet whether this problem also occurs on a mixed-DPI Linux setup, with Qt's high-dpi scaling activated. Nor have I checked if it happens on Windows using it's artificial "screen scaling" (we do not use Qt's built-in scaling on Windows either, trying to follow the advise in the docs to avoid that for new applications). So for now this is only about Mac retina + external monitor. Any advise on this would be highly appreciated, because the code required to re-trigger pixmap generation on screen changes is a real kludge all over our code base, and often it happens that we add buttons et.c. with icons, but forget to update this machinery. I'm not at the office at the moment, but can provide a little test program that mimics what we're doing on Monday. Thanks in advance, Elvis _______________________________________________ Development mailing list Development@qt-project.org https://lists.qt-project.org/listinfo/development