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https://docs.gtk.org/gtk4/visual_index.html            widgets gallery
https://forge.a-lec.org/gem-graph/gem-graph-client/src/branch/devel/Makefile
https://docs.gtk.org/gtk4/class.Widget.html#height-for-width-geometry-management
https://docs.gtk.org/gtk4/drag-and-drop.html           drag-and-drop  
https://docs.gtk.org/gtk4/class.GestureZoom.html       GtkGestureZoom  
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GTK_ORIENTATION_VERTICAL       GTK_ORIENTATION_HORIZONTAL

g_signal_connect (button, "clicked", G_CALLBACK (printf("%s\n", text)), text);
g_signal_connect_swapped (button, "clicked", G_CALLBACK (gtk_window_destroy), window);

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GtkBox       GtkGrid     GtkRevealer    GtkStack
GtkOverlay   GtkPaned    GtkExpander    GtkFixed

box = gtk_box_new (GTK_ORIENTATION_VERTICAL, 0);
gtk_widget_set_halign (box, GTK_ALIGN_FILL);
gtk_widget_set_valign (box, GTK_ALIGN_CENTER);  //  START  CENTER  END  FILL
gtk_window_set_child (GTK_WINDOW (window), box);
puis, après déclaration du bouton, gtk_box_append (GTK_BOX (box), button);

grid = gtk_grid_new ();
gtk_window_set_child (GTK_WINDOW (window), grid);
button = gtk_button_new_with_label (" I ");               n fois
gtk_grid_attach (GTK_GRID (grid), button, 0, 0, 1, 1);    n fois 

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