Change GTK Label position in window - C - c

Question

I am currently coding in C for linux and I need a GUI, so I took the GTK library to do so . I now have a window with a label (to begin with) but I don't know how to move it (in (x,y) coordinates, not in zPosition) to put it at the top of the window.
Here is my GTK code in main()
//Label
pLabel=gtk_label_new(NULL);
sUtf8 = g_locale_to_utf8("<span font_desc=\"Times New Roman italic 12\" foreground=\"#0000FF\">Neural Network - XOR Example</span>\n"
,-1, NULL, NULL, NULL);
gtk_label_set_markup(GTK_LABEL(pLabel), sUtf8);
g_free(sUtf8);
gtk_label_set_justify(GTK_LABEL(pLabel), GTK_JUSTIFY_CENTER);
//Window
gtk_window_set_position(GTK_WINDOW(pWindow), GTK_WIN_POS_CENTER);
gtk_window_set_title(GTK_WINDOW(pWindow), "Neural Network");
gtk_window_set_default_size(GTK_WINDOW(pWindow), 900, 600);
gtk_container_add(GTK_CONTAINER(pWindow), pLabel);
g_signal_connect(G_OBJECT(pWindow), "destroy", G_CALLBACK(OnDestroy), NULL);
gtk_widget_show_all(pWindow);
gtk_main();
Has anybody an idea on how to move it ?
Thank you!
Here is what I got:
(source: hostingpics.net)

Answer 1

carl gave you part of the answer.
As to why you see what you have, there are two parts:
First, GtkLabel has an archaic alignment mechanism it inherits from the deprecated GtkMisc class. See GtkMisc's documentation for details: the xalign and yalign properties control the position of the text within the label's allocation, and it's set to centered by default. But remember that they are deprecated, so there's usually better alternatives.
Second, you can only have one control in a GtkWindow. This control gets allocated the entire space of the window.
Put these two facts together and you should see why you have what you have.
So what is correct instead?
You have to use a container, such as GtkBox or GtkGrid, to get more than one widget into a GtkWindow. Each widget carries with it four special properties: hexpand, halign, vexpand, and valign which control the position and size of each member of the container. These are properties of the widgets themselves.
hexpand and vexpand determine whether or not the container allocates whatever space is left over to this control in the X and Y directions, respectively. If multiple widgets have expand set, the space is divided evenly.
halign and valign determine the position of a widget in its allocation. GTK_ALIGN_START, GTK_ALIGN_CENTER, and GTK_ALIGN_END put the widget at the start, middle, and end of the given alignment side, respectively. GTK_ALIGN_FILL fills the widget to fit the allocation.
This page has more information.
If you're trying to do exact positioning of controls, you should first investigate if GtkGrid and GtkBox (applied recursively) provide what you want. An important thing about the default internal centering of GtkLabels is that a GtkLabel in a GtkGrid will already be vertically aligned to its neighbor's text; just set halign to start or end to get the label left-aligned or right-aligned (and set valign to start if its neighbor is something big like a table). There are also functions that provide margins and padding to make the UI look nice.
If you absolutely must position things yourself, however, keep everything in mind.