I am currently working on an existing Linux application called Xpad, which is a sticky notes application written in C. I try to implement transparency but I have a hard time achieving what I want. A sticky note looks like this.
I have a (toplevel) gtk_window with a gtk_textview. If the background color of the textview is set with the function gtk_widget_override_background_color() to a transparant color (GdkRGBA where alpha value is smaller than 1), the color of the gtk_window behind it, becomes more visible.
However, I don't want to see the gtk_window, but the applications behind the gtk_window, such as the browser, libreoffice, or the desktop.
If the gtk_window is set to a certain transparancy, either with gtk_widget_override_background_color() or with gtk_widget_set_opacity(), the whole widget, including the window decorations become (partially) transparent.
To make the relations between the visible objects more clear, I have created a diagram of the different parts, and marked the place where I believe the transparency issue is taking place.
Anybody have any ideas how to make the textview background transparent, without making the window decorations transparent, so I can see whatever is behind this application?