From cc4f9fe53d1469f7629765163eec518ca3a40def Mon Sep 17 00:00:00 2001
From: Forrest Li <forrest.li@kitware.com>
Date: Tue, 27 Feb 2018 16:35:00 -0500
Subject: [PATCH 1/3] fix(Layout2D): Show/hide slider based on active source

---
 Sources/layouts/Layout2D.js | 18 ++++++++++++------
 1 file changed, 12 insertions(+), 6 deletions(-)

diff --git a/Sources/layouts/Layout2D.js b/Sources/layouts/Layout2D.js
index f8a1d811..e0d2a3d5 100644
--- a/Sources/layouts/Layout2D.js
+++ b/Sources/layouts/Layout2D.js
@@ -13,6 +13,10 @@ export default class Layout2D extends React.Component {
   constructor(props) {
     super(props);
 
+    this.state = {
+      sliceSliderVisible: false,
+    };
+
     // Setup vtk.js objects
     this.activeRepresentation = null;
     this.view = props.proxyManager.createProxy('Views', props.viewType);
@@ -42,11 +46,11 @@ export default class Layout2D extends React.Component {
       this.props.proxyManager.onActiveSourceChange(this.onActiveSourceChange),
       this.props.proxyManager.onActiveViewChange(this.flush),
     ];
-
-    this.onActiveSourceChange();
   }
 
   componentDidMount() {
+    this.onActiveSourceChange();
+
     this.view.setContainer(this.container);
     this.slider.setContainer(this.sliderContainer);
 
@@ -121,6 +125,11 @@ export default class Layout2D extends React.Component {
       });
     }
     this.updateSlider();
+
+    // update slider visibility based on current active source/representation
+    this.setState({
+      sliceSliderVisible: newRep && newRep.getSlice,
+    });
   }
 
   updateSlider() {
@@ -222,10 +231,7 @@ export default class Layout2D extends React.Component {
             className={style.sideBar}
             style={{
               background: COLOR_BY_AXIS[this.view.getAxis()],
-              visibility:
-                this.activeRepresentation && this.activeRepresentation.getSlice
-                  ? 'visible'
-                  : 'hidden',
+              visibility: this.state.sliceSliderVisible ? 'visible' : 'hidden',
             }}
             ref={(c) => {
               this.sliderContainer = c;

From da47702ff06e95ef23ce636e76edb566bc428713 Mon Sep 17 00:00:00 2001
From: Forrest Li <forrest.li@kitware.com>
Date: Tue, 27 Feb 2018 16:36:55 -0500
Subject: [PATCH 2/3] fix(Layout2D): Remove duplicate onActiveSourceChange call

---
 Sources/layouts/Layout2D.js | 1 -
 1 file changed, 1 deletion(-)

diff --git a/Sources/layouts/Layout2D.js b/Sources/layouts/Layout2D.js
index e0d2a3d5..255328ae 100644
--- a/Sources/layouts/Layout2D.js
+++ b/Sources/layouts/Layout2D.js
@@ -156,7 +156,6 @@ export default class Layout2D extends React.Component {
         reps[i].setSlicingMode('XYZ'[state.axis]);
       }
     }
-    this.onActiveSourceChange();
     this.props.proxyManager.modified();
     this.view.resetCamera();
     this.view.renderLater();

From 8000044cd6650e078a10f19698eb6770c7616324 Mon Sep 17 00:00:00 2001
From: Forrest Li <forrest.li@kitware.com>
Date: Tue, 27 Feb 2018 16:56:46 -0500
Subject: [PATCH 3/3] fix(Layout2D): Update corner annotations when no active
 source exists

Explicitly set the active representation to newRep even when newRep is
undefined/null. This allows other logic to tell if there even is an
active representation.
---
 Sources/layouts/Layout2D.js | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/Sources/layouts/Layout2D.js b/Sources/layouts/Layout2D.js
index 255328ae..991806cc 100644
--- a/Sources/layouts/Layout2D.js
+++ b/Sources/layouts/Layout2D.js
@@ -98,7 +98,6 @@ export default class Layout2D extends React.Component {
       this.repSubscription = null;
     }
     if (newRep) {
-      this.activeRepresentation = newRep;
       this.repSubscription = newRep.onModified(() => {
         if (this.activeRepresentation && this.activeRepresentation.getSlice) {
           this.slider.setValue(Number(this.activeRepresentation.getSlice()));
@@ -118,12 +117,20 @@ export default class Layout2D extends React.Component {
       });
     }
 
+    this.activeRepresentation = newRep;
+
     if (this.activeRepresentation && this.activeRepresentation.getColorWindow) {
       this.view.updateCornerAnnotation({
         colorWindow: Math.round(this.activeRepresentation.getColorWindow()),
         colorLevel: Math.round(this.activeRepresentation.getColorLevel()),
       });
+    } else {
+      this.view.updateCornerAnnotation({
+        colorWindow: '(none)',
+        colorLevel: '(none)',
+      });
     }
+
     this.updateSlider();
 
     // update slider visibility based on current active source/representation
@@ -144,6 +151,10 @@ export default class Layout2D extends React.Component {
       this.view.updateCornerAnnotation({
         slice: Number(this.activeRepresentation.getSlice()).toFixed(2),
       });
+    } else {
+      this.view.updateCornerAnnotation({
+        slice: '(none)',
+      });
     }
   }