Mouse events on a cairo context

Question

I'm developing an application with C++ and GTK3 but I'm stucked. I've created a visual application with glade which has three columns and one of them, the middle one, is a DrawingArea. In that DrawingArea I want to draw some circles at the point I want to after pressing a button and have different mouse events on that circles (like drag and drop, double click, right click...). I've made the first thing (draw a circle after pressing a button) following the official documentation, but the problem is that I don't know how to do the mouse events, but I thought about it and I have some different solutions (I don't know if they are the bests solutions or maybe there are better):

1. I think the best way is to create a signal to the cairomm context, but I didn't see anything to do that. Maybe the way would be to create a cairo surface or something like that.

2. Every time I click to create a circle, I would have to create a gtk widget in which I can handle mouse events. The problem here is that the widget needs to have circular shape and need to be drawable. Is it possible to create a circular DrawingArea? It could be the best. I saw the way to create custom widgets here.

3. Use goocanvasmm. The problem here is that goocanvasmm has a little documentation (I'm sorry I can not post more than two links because of my reputation) and I think this is not the best solution, I prefer to use cairomm.

This application was written in C using GTK2, and the circles were drawn using gnomecanvas, adding signals in an easy way to each circle; and now I'm moving this application to C++ and GTK3 to renew it.

I'm very new to GTK (and graphical interfaces in general), but I looked for solutions for hours and I don't know what is the best way in order to continue my work.

Thank you for your help :)

Answer 1

It's best to use a canvas library for this such as GooCanvas. Doing it with cairo alone would require you to listen to mouse events on the whole drawing area, and keep track of where the circles were in order to decide which circle the mouse event belongs to - exactly the problem which the canvas library has already solved for you.

If you are having trouble with goocanvasmm documentation, a look at the documentation for GooCanvas' C API combined with knowledge of how the C API translates into C++ will usually suffice. Although the GooCanvasmm documentation seems fairly extensive to me.