xrandr subpixel order is ignored on X11

I don't have hardcoded subpixel order neither in fontconfig or xresources.
All KDE4 apps, Gimp, Inkscape, Chromium and LibreOffice detect subpixel order correctly.
However, Qt5 apps (for example, Transmission-Qt) use grayscale antialiasing, unless I explicitly specify subpixel order with fontconfig. Note that Transmission-Qt uses Qt Widgets, not Qt Quick.

In Qt4 there was a call to XRenderQuerySubpixelOrder in src/gui/kernel/qapplication_x11.cpp. I can't find any similar calls in Qt 5 (except src/3rdparty/xcb).

This causes these problems:

• I have to manually specify subpixel order, while it can be autodetected
• Possibly wrong subpixel order on rotated screen (can't test right now)
• I can't specify subpixel order using fontconfig for two displays with different subpixel order