c/set-protocol/include/set_plot.h

@@ -16,7 +16,8 @@ enum set_plot_operation {
     SET_PLOT_VALUE = 3,     /* fraction,low,high,inverted -> value (not clamped) */
     SET_PLOT_DRAG = 4,      /* initial,deltaPixels,length,low,high,inverted -> clamped value */
     SET_PLOT_TICK_STEP = 5, /* range,lengthPixels -> nice step */
-    SET_PLOT_DELTA = 6      /* A,B,multiplier -> (B-A)*multiplier */
+    SET_PLOT_DELTA = 6,     /* A,B,multiplier -> (B-A)*multiplier */
+    SET_PLOT_DB_DELTA = 7   /* A,B -> 20*log10(abs(B/A)); zero is invalid */
 };
 
 /** Version of this plot ABI, independently of the transport ABI. */

c/set-protocol/ports/android/kotlin/ru/setcorp/setprotocol/trends/NativePlot.kt

@@ -30,3 +30,5 @@ data class PlotBounds(val left: Double, val right: Double, val bottom: Double, v
 
 fun plotTickStep(range: Double, pixels: Double): Double = NativePlot.call(5, range, pixels)[0]
 fun plotDelta(a: Double, b: Double, multiplier: Double = 1.0): Double = NativePlot.call(6, a, b, multiplier)[0]
+fun plotDbDelta(a: Double, b: Double): Double? =
+    runCatching { NativePlot.call(7, a, b)[0] }.getOrNull()

c/set-protocol/ports/android/kotlin/ru/setcorp/setprotocol/trends/PlotViewport.kt

@@ -1,10 +1,12 @@
 package ru.setcorp.setprotocol.trends
 
 /** Normalized top-left viewport; independent of pixels, units, toolkit and samples. */
-data class PlotViewport(val x: Double = 0.0, val y: Double = 0.0, val width: Double = 1.0, val height: Double = 1.0) {
+data class PlotViewport(val x: Double = 0.0, val y: Double = 0.0, val width: Double = 1.0, val height: Double = 1.0,
+                        val locked: Boolean = false) {
     fun transform(zoomX: Double = 1.0, zoomY: Double = 1.0, panX: Double = 0.0, panY: Double = 0.0,
                   focusX: Double = 0.5, focusY: Double = 0.5): PlotViewport {
+        if (locked) return this
         val result = NativePlot.call(0, x, y, width, height, zoomX, zoomY, panX, panY, focusX, focusY)
-        return PlotViewport(result[0], result[1], result[2], result[3])
+        return PlotViewport(result[0], result[1], result[2], result[3], locked)
     }
 }

c/set-protocol/ports/android/tests/ru/setcorp/setprotocol/trends/PlotContractTest.kt

@@ -37,4 +37,12 @@ class PlotContractTest {
         val crossed = markers.move(TrendMarker.A, 1900.0).move(TrendMarker.B, 1100.0)
         assertEquals(-800.0, plotDelta(crossed.a!!, crossed.b!!), 0.0)
     }
+
+    @Test fun lockedViewportIgnoresZoomAndPanAndDbUsesAmplitudeRatio() {
+        val locked = PlotViewport(locked = true)
+        assertEquals(locked, locked.transform(zoomX = 2.0, panY = 0.2))
+        assertEquals(20.0, plotDbDelta(1.0, 10.0)!!, 1e-10)
+        assertEquals(-20.0, plotDbDelta(10.0, 1.0)!!, 1e-10)
+        assertNull(plotDbDelta(0.0, 1.0))
+    }
 }

c/set-protocol/src/set_plot.c

@@ -11,9 +11,9 @@ static int finite_values(const double *v, size_t n) {
 uint32_t set_plot_abi_version(void) { return 1U; }
 
 size_t set_plot_eval(uint32_t op, const double *v, size_t n, double *out, size_t cap) {
-    static const size_t sizes[] = {10, 3, 4, 4, 6, 2, 3};
+    static const size_t sizes[] = {10, 3, 4, 4, 6, 2, 3, 2};
     double span, fraction;
-    if (op > SET_PLOT_DELTA || !v || !out || n != sizes[op] ||
+    if (op > SET_PLOT_DB_DELTA || !v || !out || n != sizes[op] ||
         cap < (op == SET_PLOT_TRANSFORM ? 4U : 1U)) return 0;
     if (op == SET_PLOT_TRANSFORM) {
         double w, h, fx, fy;
@@ -65,6 +65,10 @@ size_t set_plot_eval(uint32_t op, const double *v, size_t n, double *out, size_t
         break;
     }
     case SET_PLOT_DELTA: out[0] = (v[1] - v[0]) * v[2]; break;
+    case SET_PLOT_DB_DELTA:
+        if (v[0] == 0 || v[1] == 0) return 0;
+        out[0] = 20 * log10(fabs(v[1] / v[0]));
+        break;
     default: return 0;
     }
     return isfinite(out[0]) ? 1 : 0;

c/set-protocol/tests/fixtures/plot-v1.json

@@ -20,6 +20,9 @@
     {"name":"ticks","op":5,"input":[100,800],"output":[20]},
     {"name":"negative_delta","op":6,"input":[10,0,1],"output":[-10]},
     {"name":"milliseconds","op":6,"input":[0,0.01,1000],"output":[10]},
+    {"name":"db_gain","op":7,"input":[1,10],"output":[20]},
+    {"name":"db_attenuation","op":7,"input":[10,1],"output":[-20]},
+    {"name":"db_zero_reference","op":7,"input":[0,1],"output":null},
     {"name":"zero_range","op":2,"input":[1,1,1,0],"output":null},
     {"name":"zero_pixels","op":4,"input":[0,1,0,0,1,0],"output":null},
     {"name":"bad_viewport","op":0,"input":[0,0,0,1,2,1,0,0,0.5,0.5],"output":null}

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)

python/tests/test_plot.py

@@ -50,6 +50,13 @@ class PlotTests(unittest.TestCase):
             with self.assertRaises(ValueError):
                 self.core.pinch_axis(value, 10, 8)
 
+    def test_locked_viewport_and_decibel_delta(self):
+        locked = Viewport(locked=True)
+        self.assertEqual(locked, locked.transform(self.core, zoom_x=2, pan_y=.2))
+        self.assertAlmostEqual(20, self.core.db_delta(1, 10))
+        self.assertAlmostEqual(-20, self.core.db_delta(10, 1))
+        self.assertIsNone(self.core.db_delta(0, 1))
+
 
 if __name__ == "__main__":
     unittest.main()