Fix max range, range cursor, and stc range control readouts

global_data.cpp

@@ -122,10 +122,15 @@ float uniform_noise_filter = 0.0f;
 // Components: Chain Home A-scope
 float uniform_radiogoniometer = 0.0f;
 
-// Maximum radar range (scope-dependent units) — keyboard o (lower) / p (higher)
-// GLSL uniform: float max_range
-// Components: Marine A-scope, PPI scopes (not Chain Home; that is fixed)
-float uniform_max_range = 1.0f;
+/*
+ * Maximum radar range in nautical miles (NOT normalized).
+ * Chain Home: fixed at CHAIN_HOME_MAX_RANGE_NM; o/p keys ignored.
+ * Others: set from the radar's step table when a radar is activated; updated by o/p.
+ * 0.0 is the placeholder before any radar is selected.
+ * GLSL uniform: float max_range
+ * Components: all scope renderers
+ */
+float uniform_max_range = 0.0f;
 
 // Range cursor position (normalized 0-1) — keyboard a (lower) / s (higher)
 // GLSL uniform: float range_cursor