Allow for auto-scaling of image in Gtk4

General Usage
1

In the following MWE, we can resize the window and the contained image fills out the space accordingly (while retaining the aspect ratio):

using Gtk4, GtkObservables
using Colors

win = GtkWindow("Example")
h = 100
c = canvas(h, h)
f = GtkAspectFrame(h, h, 1, false)
f[] = c.widget
push!(win, f)
img = Observable(rand(RGB, h, h))
redraw = Gtk4.draw(c, img) do cnvs, img
    copy!(cnvs, img)
end

But if I want to add more components (e.g. dropdown), and to that end I put the image in a GtkBox:

win = GtkWindow("Example")
win[] = bx = GtkBox(:v) # this will contain my image AND my dropdown
h = 100
c = canvas(h, h)
f = GtkAspectFrame(h, h, 1, false)
f[] = c.widget
push!(bx, f) # let's put that image in that container
img = Observable(rand(RGB, h, h))
redraw = Gtk4.draw(c, img) do cnvs, img
    copy!(cnvs, img)
end

This breaks. The image is static and does not expand to the resized window.

How can I get this to work?

2

The issue is that GtkDrawingArea’s properties “vexpand” and “hexpand” are false by default.

Try

widget(c).hexpand = widget(c).vexpand = true

I think most often people want the canvas to expand, so maybe we should set these properties to true by default in GtkObservable’s canvas.

3

That worked! Thanks!

we should set these properties to true by default in GtkObservable’s canvas.

In hopes of crating a PR to fix this, I tried to find where in Gtk4 or GtkObservables hexpand and vexpand are set to false but I only found instances in examples, documentations, and a player widget. Where exactly do you suggest this default should be set?

4

The properties are not currently set by the package, so they use the default settings from GTK4. I would put it in the constructor for GtkObservables. I’m trying to keep Gtk4 fairly close to GTK4 as far as defaults are concerned.