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

src/shell/instrument/editor_input_waveform.cpp

@@ -35,9 +35,8 @@ bool ReaSamplerEditor::mouseDownWaveform(const FaceLayout& fl, int x, int y) {
 
     const DeckEnableState gates = deckEnableState();
     const bool splineLive = overlayIsSpline() && overlayEnvEnabled(overlayEnv_, gates);
-    const SplineGesture gesture = (GetKeyState(VK_CONTROL) & 0x8000) != 0
-                                      ? SplineGesture::kControlLeft
-                                      : SplineGesture::kLeft;
+    const SplineGesture gesture =
+        dragModifiers().ctrl ? SplineGesture::kControlLeft : SplineGesture::kLeft;
 
     // The staged envelope's draggable node and the drawn contour's node are mutually exclusive
     // (overlayEnvInert flips the staged one inert exactly when its envelope is in Spline mode),
@@ -107,6 +106,7 @@ bool ReaSamplerEditor::mouseDownWaveform(const FaceLayout& fl, int x, int y) {
                 envNode_ = envNodeHit.node;
                 dragStartX_ = x;
                 dragStartY_ = y;
+                dragMods_ = dragModifiers();
                 dragStartEnv_ = env;
                 dragSampleFrames_ = frames;
                 dragStartParams_ = params_;
@@ -213,9 +213,20 @@ void ReaSamplerEditor::dragWaveform(const FaceLayout& fl, int x, int y) {
         const double rate = liveSampleRate();
         if (frames <= 0 || rate <= 0.0) return;
         const double totalSeconds = static_cast<double>(frames) / rate;
-        const StageEnvelope edited = resolveNodeDrag(dragStartEnv_, envNode_, overlay,
-                                                     totalSeconds, envClampBounds(), dx,
-                                                     y - dragStartY_);
+        const DragModifiers mods = dragModifiers();
+        if (mods != dragMods_) {
+            // Re-anchor (see dragMods_): the node's CURRENT params and the cursor's current
+            // position become the origin, so the flip changes only the rate. Re-packing the
+            // grab envelope is what makes that true for the delta this resolver measures.
+            dragStartEnv_ =
+                packEnvelope(overlayEnv_, params_.play, frames, params_.startPoint.value_or(0));
+            dragStartX_ = x;
+            dragStartY_ = y;
+            dragMods_ = mods;
+        }
+        const StageEnvelope edited =
+            resolveNodeDrag(dragStartEnv_, envNode_, overlay, totalSeconds, envClampBounds(),
+                            x - dragStartX_, y - dragStartY_, mods);
         unpackEnvelope(overlayEnv_, edited, params_.play);
         if (dragCommitsLive(DragKind::kEnvNode)) commitLive();
         invalidate();  // live feedback; commit on WM_LBUTTONUP