Wrong scroll direction on Linux with OSR enabled. about java-cef HOT 2 OPEN

Scroll direction is usually an OS configuration option. I'm not sure how that is read/represented in Java.

from java-cef.

I have a proposal for a somewhat hacky solution

This is the code in X11Window class responsible for making the mouse event.

if (xev.get_type() == XConstants.ButtonPress) {
    MouseWheelEvent mwe = new MouseWheelEvent((Component)getEventSource(),MouseEvent.MOUSE_WHEEL, jWhen,
       modifiers,
       x, y,
       xbe.get_x_root(),
       xbe.get_y_root(),
       1,false,MouseWheelEvent.WHEEL_UNIT_SCROLL,
       3,button==4 ?  -1 : 1);
    postEventToEventQueue(mwe);
}

So when scrolling down normally the button passed is 5 and delta is positive, X11Window does keep track of lastButton so in the native code we could fetch that and just reverse this behavior on linux

Made a POC that works, its just working in the case for natural scrolling, we would have to do the opposite of getWheelRotation() to calculate the delta properly

jclass xWindow = env->FindClass("sun/awt/X11/XWindow");
jfieldID lastButtonId = env->GetStaticFieldID(xWindow, "lastButton", "J");
jlong button = env->GetStaticLongField(xWindow, lastButtonId);
 
// Would check against getWheelRotation 
if (button == 5L) { 
   delta = -3;
} else {
   delta = 3;
}

from java-cef.