feat(plot): lock axes and calculate marker levels in dB

python/protocan/plot.py

@@ -61,6 +61,12 @@ class PlotMath:
     def delta(self, a: float, b: float, multiplier: float = 1) -> float:
         return self.call(6, a, b, multiplier)[0]
 
+    def db_delta(self, a: float, b: float) -> Optional[float]:
+        try:
+            return self.call(7, a, b)[0]
+        except ValueError:
+            return None
+
 
 @dataclass(frozen=True)
 class Viewport:
@@ -68,12 +74,15 @@ class Viewport:
     y: float = 0.0
     width: float = 1.0
     height: float = 1.0
+    locked: bool = False
 
     def transform(self, core: PlotMath, zoom_x: float = 1, zoom_y: float = 1,
                   pan_x: float = 0, pan_y: float = 0,
                   focus_x: float = 0.5, focus_y: float = 0.5) -> "Viewport":
+        if self.locked:
+            return self
         return Viewport(*core.call(0, self.x, self.y, self.width, self.height,
-            zoom_x, zoom_y, pan_x, pan_y, focus_x, focus_y))
+            zoom_x, zoom_y, pan_x, pan_y, focus_x, focus_y), locked=self.locked)
 
 
 @dataclass(frozen=True)