Qt 5.11, eglfs touch problem with dual-monitor setup

[pocokman]

I have a Qt-based program (using eglfs platform), and 2 monitors, one LVDS and the other one is connected by HDMI. The LVDS monitor is a touch screen. The screen of HDMI is placed to the right of the LVDS screen, both of them have resolution of 1024x768. If I touch on the LVDS on the position of (X;Y), the system thinks I have touched on (X*2;Y). I have tried this command:

xinput set-prop "eGalax Inc. eGalaxTouch EXC3000-5207-45.00.00" --type=float "Coordinate Transformation Matrix" 0.5 0 0 0 1 0 0 0 1

This works if the software is not Qt-based (like an xterm window), but my Qt software is still wrong. What is the problem, how can I fix it?