Compile/link the code with $ gcc test1.c -o test1 `pkg-config --cflags --libs gtk+-3.0` and run $ ./test1
I have tried to use GtkAlignment to set the paddings with gtk_alignment_set_padding(GTK_ALIGNMENT(alignment0), 10, 10, 0, 0); but this then makes the other widgets in hbox0 thicker/fatter. Eg. the [Button 1] is fatter than the [Button 2].
This GtkAlignment trick used to work in GTK 2.
The screenshot shows also the actual target application. I want to make the level indicator (GtkProgressBar) in the audio-recorder much smaller.
Notice: I have no plans to use gtk-builder or glade.