One taper, one modifier law: extract param_taper, raise the stage ceiling to 10 s, and make the AHDSR schematic axis the taper itself

tests/test_param_slider.cpp

@@ -245,22 +245,35 @@ static void testKnobNeedlePointOnCircle() {
 
 static void testKnobDragUpIncreases() {
     // Up (negative dy) increases, down decreases, scaled by the drag range.
-    CHECK(approx(knobDragValue(0.5, -32, 128), 0.75));
-    CHECK(approx(knobDragValue(0.5, +32, 128), 0.25));
+    CHECK(approx(knobDragValue(0.5, -32, {}, 128), 0.75));
+    CHECK(approx(knobDragValue(0.5, +32, {}, 128), 0.25));
     // A full-range upward drag from 0 lands exactly at 1.
-    CHECK(approx(knobDragValue(0.0, -128, 128), 1.0));
+    CHECK(approx(knobDragValue(0.0, -128, {}, 128), 1.0));
     // Default sensitivity applies when the range is omitted.
     CHECK(approx(knobDragValue(0.0, -kKnobDragRangePixels), 1.0));
 }
 
 static void testKnobDragClamps() {
-    CHECK(approx(knobDragValue(0.9, -64, 128), 1.0));  // over-drag up clamps at 1
-    CHECK(approx(knobDragValue(0.1, +64, 128), 0.0));  // over-drag down clamps at 0
+    CHECK(approx(knobDragValue(0.9, -64, {}, 128), 1.0));  // over-drag up clamps at 1
+    CHECK(approx(knobDragValue(0.1, +64, {}, 128), 0.0));  // over-drag down clamps at 0
     // The start value itself is clamped before the delta applies.
-    CHECK(approx(knobDragValue(1.5, 0, 128), 1.0));
-    CHECK(approx(knobDragValue(-0.5, 0, 128), 0.0));
+    CHECK(approx(knobDragValue(1.5, 0, {}, 128), 1.0));
+    CHECK(approx(knobDragValue(-0.5, 0, {}, 128), 0.0));
     // A degenerate drag range yields the clamped start value.
-    CHECK(approx(knobDragValue(0.7, -50, 0), 0.7));
+    CHECK(approx(knobDragValue(0.7, -50, {}, 0), 0.7));
+}
+
+// Ctrl scales the drag rate; Shift+Ctrl is Shift, so the rate goes back to coarse. The snap
+// itself is not this module's — only the rate is.
+static void testCtrlScalesTheDragRateAndShiftOverridesIt() {
+    const DragModifiers fine{false, true};
+    const DragModifiers both{true, true};
+    CHECK(approx(knobDragValue(0.5, -32, fine, 128), 0.5 + 0.25 * kFineDragScale));
+    CHECK(approx(knobDragValue(0.5, -32, both, 128), 0.75));
+    CHECK(approx(knobDragValue(0.5, -32, DragModifiers{true, false}, 128), 0.75));
+    // Continuity across a transition is the CALLER's re-anchor, not this function's: at a
+    // zero delta both rates agree, which is exactly the state a re-anchor establishes.
+    CHECK(knobDragValue(0.42, 0, fine, 128) == knobDragValue(0.42, 0, {}, 128));
 }
 
 // --- controlAtPoint routing ---------------------------------------------------
@@ -321,6 +334,7 @@ int main() {
     testKnobNeedlePointOnCircle();
     testKnobDragUpIncreases();
     testKnobDragClamps();
+    testCtrlScalesTheDragRateAndShiftOverridesIt();
     testControlAtPointRoutes();
     testControlAtPointMisses();