gtk DrawingArea expand inside Fixed

Question

I currently load a DrawingArea widget inside a Frame - and it always expands to fill the frame. I can then set the configure event on the DrawingArea to allocate a pixmap of the same size as the window, draw on it, then draw the pixmap to the DrawingArea (using draw_drawable).

However, now I want to overlay invisible widgets ontop of the DrawingArea - in order to create tooltip events for parts of the image displayed. So I tried to put the DrawingArea inside a Fixed instead - but now it does not expand to fill the window. I can give the DrawingArea an explicit size request - however I would really like it to expand to fill whatever space allocation it's parent window has been given. I have tried setting the size request to -1, but that does not help any.

Any suggestions?

Answer 1

Came up with a solution that sort of works:

• Create a Fixed.
• Create a DrawingArea and add it to Fixed.
• Connect Fixed to 'size_allocate' signal, and in the signal handler, get the Fixed allocation (width and height), then get the DrawingArea to make a size_request of the current allocation.

It appears to do what I want, however I noticed now that two "size_allocate" signals are sent to fixed - one when the window is resized, and another presumably when the DrawingArea requests a new size allocation. To avoid doing a lot of extra unnecessary work in the second signal, I just return if the previous height/width match the new allocation. But I would rather do away with the second signal if possible.

I tried blocking/unblocking the size_allocate signal before/after the DrawingArea size_request to no avail (maybe because I am already inside the size_allocation handler).

Anyone know of a cleaner way to deal with this?

Answer 2

It sounds like you're jumping through a lot of hoops to avoid just implementing a custom widget. It might be worth your time to just learn to do that; override size request/allocate to get the size you want, override expose_event to draw your image, and override motion_notify_event or whatever other event handlers to handle mouse position and clicks.