Re: How does one overlay one image on top of another ?

[Bob Murphy <bob murphy access-company com>]

Hi Gregory,

> Step 3 (where you put the 1st GtkFixed into the GtkVBox) - You specify 
> that you "position"
> it in teh "upper left" corner. GtkVBox doesn't let you position it's 
> children, and
> GtkFixed doesn't let you position itself (only it's children). So I'm 
> wondering about your
> statement of "put it at the upper left of the GtkVBox"

I was writing that from memory, and clearly remembered it wrong. It 
should have been that I added the GtkFixed to the the GtkVBox, and then 
added the GtkImage to that so it was positioned at the upper left corner 
of the screen.

> Step 4) The 2nd GtkFixed is a child of which ? the GtkVBox, or the 1st 
> GtkFixed. It seems
> to me that the only way to position the 2nd GtkFixed, is to make it a 
> child of the 1st
> GtkFixed. Is this what you did ?

My recollection on this is wrong, too. Upon reviewing the documentation, 
I'm pretty sure I only used one GtkFixed and put both GtkImages into it 
at different positions. I may have even omitted the GtkVBox, and just 
put one GtkFixed into the window.

> Other than that, this looks pretty much like what I'm looking for. When 
> I want to move the
> embedded image, I just gtk_fixed_move the embedded image within the 1st 
> GtkFixed. In
> fact... it looks to me like I do not need the 2nd GtkImage embedded 
> inside of a GtkFixed,
> since (as near as I can tell from reading the GtkFixed documentation), 
> positioning the
> embedded image will be done by gtk_fixed_move() of the child inside the 
> top layer
> GtkFixed. Do you concur ?

I strongly suggest you experiment with this.

Here's what I hear you saying:
1. Make a window, and put some kind of container (GtkVBox/GtkHBox) in it.
2. Make a GtkFixed, put that in the container, and put the first 
GtkImage inside it.
3. Make a second GtkImage and put it in the container, too.
4. When you want, move the first GtkImage around with gtk_fixed_move().


If that's correct, I doubt it will work. The GtkFixed from step 2 and 
the GtkImage from step 3 are peers, and won't overlap. The GtkFixed will 
try to set its size to accommodate its children, and second (non-child) 
GtkImage (or any other peer widgets) will try to move out of its way.

In fact, I just reviewed the GtkFixed sources. When you do a 
gtk_fixed_move() on the child GtkImage, that triggers a size 
renegotiation, and the non-child GtkImage will keep moving out of its 
way. So you won't be able to make the two GtkImages overlap by moving 
one of them around.

So if you want overlap, you would probably do better to put both 
GtkImages inside the same GtkFixed. Then you can move them around and 
force them to overlap.

- Bob