Re: gtkmm-list Digest, Vol 195, Issue 6

[Ian Martin <ianmartin0071 gmail com>]

Hi,

It sounds like you're confusing "there is no programmatic limit on the size of the scrollable area" with an infinitely scrollable area.  The easy solution is to simply make the window maybe 10x as big as you'll ever need, but even then somebody somewhere will find the limit sooner or later.  I'd suggest you might have more durability if you start with an arbitrary sized window, and then use a signal handler to increase it whenever the adjustment reaches one or other end of its range. 

ian

On Mon, Aug 24, 2020 at 12:00 AM <gtkmm-list-request gnome org> wrote:

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Today's Topics:

   1. Help on Gtk::Layout and Gtk::ScrolledWindow (josephenry)


----------------------------------------------------------------------

Message: 1
Date: Sat, 22 Aug 2020 13:53:03 +0000
From: josephenry <josephenry protonmail com>
To: "gtkmm-list gnome org" <gtkmm-list gnome org>
Subject: Help on Gtk::Layout and Gtk::ScrolledWindow
Message-ID:
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Hi,

I am learning Gtk+ with gtkmm and my goal is to create a node based interface for visual programming. I started a thread on the Gnome discourse : [https://discourse.gnome.org/t/project-guidance-node-based-ui/](https://discourse.gnome.org/t/project-guidance-node-based-ui/4019)

Basically what I want is to have my custom node widgets on a "canvas" so I can be able to move them by dragging them. If anyone knows Blender's node editor, it should also be possible to pan with middle mouse button and also zoom.

The Gtk::Layout component seems the right one when it comes to put nodes at specific location on the interface. I also want to draw a custom grid so this so the documentation seems adapted :

Infinite scrollable area containing child widgets and/or custom drawing.

Now the "infinite scrollable area" concept interest me because I want to be able to move on the node tree. The documentation says that I can just put the layout into a Gtk::ScrolledWindow and it supports scrolling natively.

I am struggling to understand how it works with the Gtk::Adjustments, do I need to create them when I instantiate a Gtk::ScrolledWindow? Or are they are controlled by the Gtk::Layout child?

This is a small example to make it work (compile it with g++ gtk_layout.cpp -o gtk_layout `pkg-config gtkmm-3.0 --cflags --libs`):

#include

<

gtkmm.h

>

int

main

(

int

argc

,

char

*

argv

[])

{

auto

app

=

Gtk

::

Application

::

create

(

argc

,

argv

,

"

org.gtkmm.example

"

)

;

Gtk

::

Window window

;

Gtk

::

ScrolledWindow scrolled_window

(

Gtk

::

Adjustment

::

create

(

0

,

0

,

5000

),

Gtk

::

Adjustment

::

create

(

0

,

0

,

5000

))

;

Gtk

::

Layout layout

;

Gtk

::

Button button

(

"

Hello World!

"

)

;

layout

.

put

(

button

,

100

,

100

)

;

scrolled_window

.

set_policy

(

Gtk

::

POLICY_ALWAYS

,

Gtk

::

POLICY_ALWAYS

)

;

scrolled_window

.

add

(

layout

)

;

window

.

add

(

scrolled_window

)

;

window

.

show_all

()

;

return

app

->

run

(

window

)

;

}

How can I get an infinite scrollable area?

Thanks in advance

Joseph
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