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Re: Touchscreen on raspberry: problem with events [message #48635 is a reply to message #48625]

Thu, 10 August 2017 16:22

Giorgio
Messages: 218
Registered: August 2015

Experienced Member

Ok, I found the problem and a verrrrrrrrrrrrrrrry nasty solution.

This is the cycle of gtk events and Switch methods with a real mouse:

GDK_BUTTON_PRESS
GDK_PROPERTY_NOTIFY
Switch::MouseMove: pushindex: 3 value: 002
Switch::LeftDown: pushindex: 3 value: 002
GDK_EXPOSE
GDK_BUTTON_RELEASE
Switch::LeftUp (before the outer if cycle): pushindex: 3 value: 002
Switch::LeftUp (inside the outer if cycle): pushindex: 3 value: 002
Switch::LeftUp (inside the inner if cycle): pushindex: 3 v: 005 value: 002
Switch::LeftUp: pushindex: -1 value: 005

And this is the cycle with the touch screen:

GDK_BUTTON_PRESS
GDK_PROPERTY_NOTIFY
Switch::MouseMove: pushindex: 3 value: 002
GDK_EXPOSE
Switch::MouseMove: pushindex: 3 value: 002
Switch::LeftDown: pushindex: 3 value: 002
GDK_EXPOSE
GDK_MOTION_NOTIFY
GDK_BUTTON_RELEASE
Switch::MouseMove: pushindex: -1 value: 002
GDK_EXPOSE
Switch::LeftUp (before the outer if cycle): pushindex: -1 value: 002
Switch::LeftUp: pushindex: -1 value: 002

With the real mouse the LeftUp method is called immediately after the LeftDown; with the touch screen there is a MouseMove method in between. This MouseMove method set pushindex to -1. Now let's go where the variable "value" (the variable containing the value of the selected case) is set: inside the LeftUp method.

This is the relevant code:

	if(pushindex >= 0 && pushindex < cs.GetCount()) {
		RefreshCase(GetIndex());
		const Value& v = cs[pushindex].value;
		if(v != value) {
			value = v;
			UpdateAction();
		}
		RefreshCase(pushindex);
	}

As you can see, the value is set only if pushindex >=0, but the MouseMove method has set it to -1.

Let's see what the MouseMove method does:

	int i = GetIndex(p);
	int a = -1;
	if(keyflags & K_MOUSELEFT)
		a = i;
	if(pushindex != a) {
		RefreshCase(pushindex);
		RefreshCase(a);
		pushindex = a;
	}

Honestly I don't understand what that code actually does; I tried to comment out the whole method and the application crashes, so I modified it as follows:

	int i = GetIndex(p);
//	int a = -1;
	int a = pushindex;
	if(keyflags & K_MOUSELEFT)
		a = i;
	if(pushindex != a) {
		RefreshCase(pushindex);
		RefreshCase(a);
		pushindex = a;
	}

With this modification the Switch control works also with the touch screen and the application does not crash. Of course that code is there for some reason, so I am not so comfortable with my modification. I will try to reach out the person who wrote Switch.cpp to see how we can work out things in a way that the touch screen is supported. Thanks a lot Klugier for the support.
Regards,
Gio

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