loop: crossfade the Gate sustain seam, and unshadow the loop handles that made loop points look gone

src/shell/instrument/editor_paint_waveform.cpp

@@ -98,6 +98,17 @@ void ReaSamplerEditor::paintWaveform(LICE_IBitmap* bmp, const Rect& band) {
                           static_cast<float>(kLoopSpanFillAlpha), 0);
         }
     }
+    // The crossfade region, at half the loop span's weight so the two read as nested rather
+    // than as a second loop. Drawn before the marker bars so the bars stay on top.
+    if (m.hasLoop && m.crossfade > 0) {
+        const int fx = frameToX(overlay, frames, m.loopStart - m.crossfade);
+        const int lx = frameToX(overlay, frames, m.loopStart);
+        if (lx > fx) {
+            LICE_FillRect(bmp, fx, overlayRect.y, lx - fx, overlayRect.height,
+                          toLice(roleColor(kRoleLoopMarker)),
+                          static_cast<float>(kLoopSpanFillAlpha) * 0.5f, 0);
+        }
+    }
     const std::int64_t markerFrames[3] = {m.start, m.loopStart, m.loopEnd};
     const Role markerRoles[3] = {kRoleStartMarker, kRoleLoopMarker, kRoleLoopMarker};
     for (int i = 0; i < 3; ++i) {
@@ -107,6 +118,15 @@ void ReaSamplerEditor::paintWaveform(LICE_IBitmap* bmp, const Rect& band) {
         LICE_FillRect(bmp, mx - 1, overlayRect.y, 2, overlayRect.height,
                       toLice(roleColor(markerRoles[i])), alpha, 0);
     }
+    // The crossfade's grab tab. Only offered with a loop set, matching the hit-test, and it
+    // is the whole affordance for a zero-length fade — nothing else marks where it sits.
+    if (m.hasLoop) {
+        const Rect tab = markerHandleRect(overlay, frames, m.loopStart - m.crossfade);
+        if (!tab.empty()) {
+            LICE_FillRect(bmp, tab.x, tab.y, tab.width, tab.height,
+                          toLice(roleColor(kRoleLoopMarker)), 1.0f, 0);
+        }
+    }
 
     paintEnvelopeOverlay(bmp, overlay, frames);
 }