Cairo, minimal linewidth?

[MarioBlunk]

Following the discussion at

Why type gdouble used instead of integer with Gdk_Event_Button?

I’m new to all this GTK stuff. The documentation in Gdk.EventButton says that x and y are coordinates of the pointer relative to the window. If I output the coordinates on the terminal I get floating point numbers. As far as I understand, this is about pixels. So why is the type gdouble used for the coordinates instead of integer ?

I have a question related to the minimal linewidth that can be used when drawing
a line with cairo. The linewidth is defined in logical pixels (gdouble). What happens if I set a linewidth of 0.5 ? Will the line be drawn on the screen with a width of half a device pixel ? Surely not. So it seems a linewidth below 1.0 is useless. Please help, thanks a lot.

[ebassi (Emmanuele Bassi)]

Cairo surfaces created by GTK set the device scaling to match the same scaling factor of the widget; if you create your own surfaces then you’ll need to do the same.

@MarioBlunk

What happens if I set a linewidth of 0.5 ?

See the Cairo frequently asked questions.

If you have Cairo-specific questions, feel free to ask them on the project’s mailing list.