GtkRuler is right now deprecated for the reason that it seems to be covering a too special use cases. Although there are quite a few apps using it. Some even forked the widget to make it more useful. Instead of removing it, we could also make it better.

1. Use Cases

• use with images
• use for plots as axis labels

2. Forks and other implementations

2.1. Ardour

gtk-custom-ruler.c, gtk-custom-ruler.h, gtk-custom-hruler.c, gtk-custom-hruler.h

• "show_position" property (no need for GTK_RULER_GET_CLASS(ruler)->draw_pos = NULL; hack)

• callback based GtkRulerMetric replacement

2.2. GtkDatabox

gtkdatabox_ruler.c gtkdatabox_ruler.h

• supports linear and logarithmic scales
• in the vertical orientation, the labels are rotated 90°
• it works for very small and very large value ranges

3. Things we should change

• add "show_position" property

  • either boolean or we turn it into a enum { Off, Triangle, ColorTick, ... }

    • ColorTick would be a colored line

• have something smarter for GtkRulerMetric as current API is broken:

  • GtkRulerMetric is public, but there is no API using it

  • GtkMetricType is an enum of 3 values with no way of registering own GtkRulerMetric

  • it does not cover non-linear rulers (e.g. Log), that could be solved with a callback

• open bugs

• get rid of gtk_ruler_{s,g}et_range and use a GtkAdjustment instead

  • that'd allow to sync a GtkRuler with a GtkScale and a GtkViewport (share the GtkAdjustment)

  • we could add gtk_ruler_{s,g}et_adjustment
  • ideally we'd have the same constructors like Gtk{H,V}Scale
• the rulers look not nice
  • add more padding between ticks and numbers
  • use half-color for minor ticks