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Re: Multi-touch Gestures




Not an expert but thought I might be able to provide a comment or two.

1> I think pan is more for handling swiping (e.g. changing pages in evince). Maybe you're more interested in https://developer.gnome.org/gtk3/stable/GtkGestureDrag.html ?
3> If you use GestureDrag you can use https://developer.gnome.org/gtk3/stable/GtkGestureDrag.html#gtk-gesture-drag-get-offset
2> https://developer.gnome.org/gtk3/stable/GtkGesture.html#gtk-gesture-get-bounding-box-center
3> Can't you check in a function attached to the "sequence-state-changed" signal if GtkEventSequenceState is GTK_EVENT_SEQUENCE_NONE? Because "

By default, all sequences start out in the GTK_EVENT_SEQUENCE_NONE state, sequences in this state trigger the gesture event handler, but event propagation will continue unstopped by gestures."

(not sure if this is actually the case.)


On Mon, Jun 19, 2017 at 4:54 AM, Prashant Kumar <prashantkn94@xxxxxxxxx> wrote:
Hi everyone,

I am a GSoC student participating this year from wxWidgets. The aim of my project is to implement an API for 3 multi-touch gestures (pan, zoom and rotate) for 3 major platforms (windows, linux and macOS). Understanding the features provided by windows and macOS wasn't hard at all (even though I was not familiar with Win32 and Cocoa). On gtk+, I find it difficult to understand the gesture API
So, my question is where do I need to look to implement an API for the above mentioned gestures in gtk+ ?
I looked at the "gestures and event handling guide" by gtk but that didn't help me much. Also, there are few questions that I want to ask someone who is familiar with gestures in gtk+ and willing to help me.

1> There is something called the expected pan gesture direction that we have to set before receiving the pan gesture. Now, what if we want to receive it for all 4 directions ?
3> Is it possible to know the position of pan gesture i.e. position of the finger in action ?
2> Is it possible to get the center of the zoom gesture ?
3> After we receive some gesture , Is it possible to know if it a starting of the gesture ?

I would really feel relieved if anyone provides me any help. Thank you in advance.
- prashant


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