--- a/Platforms/WebAssembly/Defaults.cpp	Thu Jun 14 13:28:40 2018 +0200
+++ b/Platforms/WebAssembly/Defaults.cpp	Thu Jun 14 15:06:29 2018 +0200
@@ -5,6 +5,7 @@
 #include "Framework/Widgets/TestCairoWidget.h"
 #include <Framework/Viewport/WidgetViewport.h>
 #include <Framework/Widgets/LayerWidget.h>
+#include <algorithm>
 
 static unsigned int width_ = 0;
 static unsigned int height_ = 0;
@@ -12,13 +13,21 @@
 /**********************************/
 
 static std::auto_ptr<OrthancStone::BasicWasmApplication> application;
-static std::shared_ptr<OrthancStone::WidgetViewport> viewport_;
 static OrthancStone::ChangeObserver changeObserver_;
 static OrthancStone::StatusBar statusBar_;
 
 
 static std::list<std::shared_ptr<OrthancStone::WidgetViewport>> viewports_;
 
+std::shared_ptr<OrthancStone::WidgetViewport> FindViewportSharedPtr(ViewportHandle viewport) {
+  for (const auto& v : viewports_) {
+    if (v.get() == viewport) {
+      return v;
+    }
+    assert(false);
+  }
+}
+
 #ifdef __cplusplus
 extern "C" {
 #endif
@@ -38,8 +47,6 @@
     viewport->SetStatusBar(statusBar_);
     viewport->Register(changeObserver_);
 
-    // TODO: remove once we really want to handle multiple viewports
-    viewport_ = viewport;
     return viewport.get();
   }
 
@@ -50,7 +57,6 @@
     printf("There are now %d viewports in C++\n", viewports_.size());
   }
 
-
   void EMSCRIPTEN_KEEPALIVE CreateWasmApplication(ViewportHandle viewport) {
 
     printf("CreateWasmApplication\n");
@@ -66,7 +72,7 @@
     application->SetStartupParameter(keyc, value);
   }
 
-  void EMSCRIPTEN_KEEPALIVE StartWasmApplication() {
+  void EMSCRIPTEN_KEEPALIVE StartWasmApplication(ViewportHandle viewport) {
 
     printf("StartWasmApplication\n");
 
@@ -74,79 +80,36 @@
     boost::program_options::variables_map parameters;
     application->GetStartupParameters(parameters);
 
-    BasicWasmApplicationContext& context = dynamic_cast<BasicWasmApplicationContext&>(application->CreateApplicationContext(OrthancStone::WasmWebService::GetInstance(), viewport_));;
+    BasicWasmApplicationContext& context = dynamic_cast<BasicWasmApplicationContext&>(application->CreateApplicationContext(OrthancStone::WasmWebService::GetInstance(), FindViewportSharedPtr(viewport)));
     application->Initialize(statusBar_, parameters);
 
-    viewport_->SetSize(width_, height_);
+    viewport->SetSize(width_, height_);
     printf("StartWasmApplication - completed\n");
   }
-
-  // void EMSCRIPTEN_KEEPALIVE ViewportUpdate(const char* _instanceId) {
-  //   printf("updating viewport content, Instance = [%s]\n", instanceId.c_str());
-
-  //   layerSource->LoadFrame(instanceId, 0);
-  //   printf("frame loaded\n");
-  //   instanceWidget->UpdateContent();
-
-  //   printf("update should be done\n");
-  // }
   
-  // void EMSCRIPTEN_KEEPALIVE ViewportStart()
-  // {
-
-  //   viewport_.reset(new OrthancStone::WidgetViewport);
-  //   viewport_->SetStatusBar(statusBar_);
-  //   viewport_->Register(changeObserver_);
-  //   instanceWidget.reset(new OrthancStone::LayerWidget);
-  //   layerSource = new OrthancStone::OrthancFrameLayerSource(OrthancStone::WasmWebService::GetInstance());
-
-  //   if (!instanceId.empty())
-  //   {
-  //     layerSource->LoadFrame(instanceId, 0);
-  //   } else {
-  //     printf("No instance provided so far\n");
-  //   }
-
-  //   instanceWidget->AddLayer(layerSource);
-
-  //   {
-  //     OrthancStone::RenderStyle s;
-  //     //s.drawGrid_ = true;
-  //     s.alpha_ = 1;
-  //     s.windowing_ = OrthancStone::ImageWindowing_Bone;
-  //     instanceWidget->SetLayerStyle(0, s);
-  //   }
-
-  //   viewport_->SetCentralWidget(instanceWidget.release());
-  //   viewport_->SetSize(width_, height_);
-
-
-  // }
-
   void EMSCRIPTEN_KEEPALIVE NotifyUpdateContent()
   {
-    // TODO Only launch the JavaScript timer if "HasUpdateContent()"
-    if (viewport_.get() != NULL &&
-        viewport_->HasUpdateContent())
-    {
-      viewport_->UpdateContent();
+    for (auto viewport : viewports_) {
+      // TODO Only launch the JavaScript timer if "HasUpdateContent()"
+      if (viewport->HasUpdateContent())
+      {
+        viewport->UpdateContent();
+      }
+
     }
 
   }
   
 
-  void EMSCRIPTEN_KEEPALIVE ViewportSetSize(unsigned int width, unsigned int height)
+  void EMSCRIPTEN_KEEPALIVE ViewportSetSize(ViewportHandle viewport, unsigned int width, unsigned int height)
   {
     width_ = width;
     height_ = height;
     
-    if (viewport_.get() != NULL)
-    {
-      viewport_->SetSize(width, height);
-    }
+    viewport->SetSize(width, height);
   }
 
-  int EMSCRIPTEN_KEEPALIVE ViewportRender(OrthancStone::WidgetViewport* viewport,
+  int EMSCRIPTEN_KEEPALIVE ViewportRender(ViewportHandle viewport,
                                           unsigned int width,
                                           unsigned int height,
                                           uint8_t* data)
@@ -184,7 +147,8 @@
   }
 
 
-  void EMSCRIPTEN_KEEPALIVE ViewportMouseDown(unsigned int rawButton,
+  void EMSCRIPTEN_KEEPALIVE ViewportMouseDown(ViewportHandle viewport,
+                                              unsigned int rawButton,
                                               int x,
                                               int y,
                                               unsigned int rawModifiers)
@@ -208,20 +172,17 @@
         return;  // Unknown button
     }
 
-    if (viewport_.get() != NULL)
-    {
-      viewport_->MouseDown(button, x, y, OrthancStone::KeyboardModifiers_None /* TODO */);
-    }
+    viewport->MouseDown(button, x, y, OrthancStone::KeyboardModifiers_None /* TODO */);
   }
   
 
-  void EMSCRIPTEN_KEEPALIVE ViewportMouseWheel(int deltaY,
+  void EMSCRIPTEN_KEEPALIVE ViewportMouseWheel(ViewportHandle viewport,
+                                               int deltaY,
                                                int x,
                                                int y,
                                                int isControl)
   {
-    if (viewport_.get() != NULL &&
-        deltaY != 0)
+    if (deltaY != 0)
     {
       OrthancStone::MouseWheelDirection direction = (deltaY < 0 ?
                                                      OrthancStone::MouseWheelDirection_Up :
@@ -233,68 +194,55 @@
         modifiers = OrthancStone::KeyboardModifiers_Control;
       }
 
-      viewport_->MouseWheel(direction, x, y, modifiers);
+      viewport->MouseWheel(direction, x, y, modifiers);
     }
   }
   
 
-  void EMSCRIPTEN_KEEPALIVE ViewportMouseMove(int x,
+  void EMSCRIPTEN_KEEPALIVE ViewportMouseMove(ViewportHandle viewport,
+                                              int x,
                                               int y)
   {
-    if (viewport_.get() != NULL)
-    {
-      viewport_->MouseMove(x, y);
-    }
+    viewport->MouseMove(x, y);
   }
   
-  void EMSCRIPTEN_KEEPALIVE ViewportKeyPressed(const char* key, 
+  void EMSCRIPTEN_KEEPALIVE ViewportKeyPressed(ViewportHandle viewport,
+                                               const char* key, 
                                                bool isShiftPressed, 
                                                bool isControlPressed,
                                                bool isAltPressed)
                                                
   {
-    if (viewport_.get() != NULL)
-    {
-      OrthancStone::KeyboardModifiers modifiers = OrthancStone::KeyboardModifiers_None;
-      if (isShiftPressed) {
-        modifiers = static_cast<OrthancStone::KeyboardModifiers>(modifiers + OrthancStone::KeyboardModifiers_Shift);
-      }
-      if (isControlPressed) {
-        modifiers = static_cast<OrthancStone::KeyboardModifiers>(modifiers + OrthancStone::KeyboardModifiers_Control);
-      }
-      if (isAltPressed) {
-        modifiers = static_cast<OrthancStone::KeyboardModifiers>(modifiers + OrthancStone::KeyboardModifiers_Alt);
-      }
-      printf("key pressed : %c\n", key[0]);
-      viewport_->KeyPressed(key[0], modifiers);
+    OrthancStone::KeyboardModifiers modifiers = OrthancStone::KeyboardModifiers_None;
+    if (isShiftPressed) {
+      modifiers = static_cast<OrthancStone::KeyboardModifiers>(modifiers + OrthancStone::KeyboardModifiers_Shift);
     }
+    if (isControlPressed) {
+      modifiers = static_cast<OrthancStone::KeyboardModifiers>(modifiers + OrthancStone::KeyboardModifiers_Control);
+    }
+    if (isAltPressed) {
+      modifiers = static_cast<OrthancStone::KeyboardModifiers>(modifiers + OrthancStone::KeyboardModifiers_Alt);
+    }
+    printf("key pressed : %c\n", key[0]);
+    viewport->KeyPressed(key[0], modifiers);
   }
   
 
-  void EMSCRIPTEN_KEEPALIVE ViewportMouseUp()
+  void EMSCRIPTEN_KEEPALIVE ViewportMouseUp(ViewportHandle viewport)
   {
-    if (viewport_.get() != NULL)
-    {
-      viewport_->MouseUp();
-    }
+    viewport->MouseUp();
   }
   
 
-  void EMSCRIPTEN_KEEPALIVE ViewportMouseEnter()
+  void EMSCRIPTEN_KEEPALIVE ViewportMouseEnter(ViewportHandle viewport)
   {
-    if (viewport_.get() != NULL)
-    {
-      viewport_->MouseEnter();
-    }
+    viewport->MouseEnter();
   }
   
 
-  void EMSCRIPTEN_KEEPALIVE ViewportMouseLeave()
+  void EMSCRIPTEN_KEEPALIVE ViewportMouseLeave(ViewportHandle viewport)
   {
-    if (viewport_.get() != NULL)
-    {
-      viewport_->MouseLeave();
-    }
+    viewport->MouseLeave();
   }
 
 

--- a/Platforms/WebAssembly/Defaults.h	Thu Jun 14 13:28:40 2018 +0200
+++ b/Platforms/WebAssembly/Defaults.h	Thu Jun 14 15:06:29 2018 +0200
@@ -20,8 +20,6 @@
   
   // C++ methods accessible from JS
   extern void EMSCRIPTEN_KEEPALIVE CreateWasmApplication(ViewportHandle viewport);
-//   extern void EMSCRIPTEN_KEEPALIVE SetStartupParameter(const char* keyc, const char* value);
-//   extern void EMSCRIPTEN_KEEPALIVE StartWasmApplication();
 
 #ifdef __cplusplus
 }

--- a/Platforms/WebAssembly/wasm-application.js	Thu Jun 14 13:28:40 2018 +0200
+++ b/Platforms/WebAssembly/wasm-application.js	Thu Jun 14 15:06:29 2018 +0200
@@ -87,7 +87,7 @@
     }
   }
 
-  StartWasmApplication();
+  StartWasmApplication(viewport.GetCppViewport());
   /************************************** */
 
   UpdateContentThread();

--- a/Platforms/WebAssembly/wasm-viewport.ts	Thu Jun 14 13:28:40 2018 +0200
+++ b/Platforms/WebAssembly/wasm-viewport.ts	Thu Jun 14 15:06:29 2018 +0200
@@ -37,15 +37,19 @@
       this.htmlCanvas_ = document.getElementById(this.canvasId_) as HTMLCanvasElement;
       this.context_ = this.htmlCanvas_.getContext('2d');
 
-      this.ViewportSetSize = this.module_.cwrap('ViewportSetSize', null, [ 'number', 'number' ]);
+      this.ViewportSetSize = this.module_.cwrap('ViewportSetSize', null, [ 'any', 'number', 'number' ]);
       this.ViewportRender = this.module_.cwrap('ViewportRender', null, [ 'any', 'number', 'number', 'number' ]);
-      this.ViewportMouseDown = this.module_.cwrap('ViewportMouseDown', null, [ 'number', 'number', 'number', 'number' ]);
-      this.ViewportMouseMove = this.module_.cwrap('ViewportMouseMove', null, [ 'number', 'number' ]);
-      this.ViewportMouseUp = this.module_.cwrap('ViewportMouseUp', null, [ ]);
-      this.ViewportMouseEnter = this.module_.cwrap('ViewportMouseEnter', null, []);
-      this.ViewportMouseLeave = this.module_.cwrap('ViewportMouseLeave', null, []);
-      this.ViewportMouseWheel = this.module_.cwrap('ViewportMouseWheel', null, [ 'number', 'number', 'number', 'number' ]);
-      this.ViewportKeyPressed = this.module_.cwrap('ViewportKeyPressed', null, [ 'string', 'number', 'number' ]);
+      this.ViewportMouseDown = this.module_.cwrap('ViewportMouseDown', null, [ 'any', 'number', 'number', 'number', 'number' ]);
+      this.ViewportMouseMove = this.module_.cwrap('ViewportMouseMove', null, [ 'any', 'number', 'number' ]);
+      this.ViewportMouseUp = this.module_.cwrap('ViewportMouseUp', null, [ 'any' ]);
+      this.ViewportMouseEnter = this.module_.cwrap('ViewportMouseEnter', null, [ 'any' ]);
+      this.ViewportMouseLeave = this.module_.cwrap('ViewportMouseLeave', null, [ 'any' ]);
+      this.ViewportMouseWheel = this.module_.cwrap('ViewportMouseWheel', null, [ 'any', 'number', 'number', 'number', 'number' ]);
+      this.ViewportKeyPressed = this.module_.cwrap('ViewportKeyPressed', null, [ 'any', 'string', 'number', 'number' ]);
+    }
+
+    public GetCppViewport() : any {
+      return this.pimpl_;
     }
 
     public Redraw() {
@@ -76,12 +80,12 @@
         this.imageData_ = null;
       }
       
-      this.htmlCanvas_.width = window.innerWidth;
+      this.htmlCanvas_.width = window.innerWidth;  
       this.htmlCanvas_.height = window.innerHeight;
   
       if (this.imageData_ === null) {
         this.imageData_ = this.context_.getImageData(0, 0, this.htmlCanvas_.width, this.htmlCanvas_.height);
-        this.ViewportSetSize(this.htmlCanvas_.width, this.htmlCanvas_.height);
+        this.ViewportSetSize(this.pimpl_, this.htmlCanvas_.width, this.htmlCanvas_.height);
   
         if (this.renderingBuffer_ != null) {
           this.module_._free(this.renderingBuffer_);
@@ -100,53 +104,53 @@
       // Force the rendering of the viewport for the first time
       this.Resize();
     
+      var that : WasmViewport = this;
       // Register an event listener to call the Resize() function 
       // each time the window is resized.
-      window.addEventListener('resize', this.Resize, false);
+      window.addEventListener('resize', function(event) {
+        that.Resize();
+      }, false);
   
-      var that = this;
-    
       this.htmlCanvas_.addEventListener('contextmenu', function(event) {
         // Prevent right click on the canvas
         event.preventDefault();
       }, false);
       
       this.htmlCanvas_.addEventListener('mouseleave', function(event) {
-        that.ViewportMouseLeave();
+        that.ViewportMouseLeave(that.pimpl_);
       });
       
       this.htmlCanvas_.addEventListener('mouseenter', function(event) {
-        that.ViewportMouseEnter();
+        that.ViewportMouseEnter(that.pimpl_);
       });
     
       this.htmlCanvas_.addEventListener('mousedown', function(event) {
         var x = event.pageX - this.offsetLeft;
         var y = event.pageY - this.offsetTop;
-        that.ViewportMouseDown(event.button, x, y, 0 /* TODO */);    
+        that.ViewportMouseDown(that.pimpl_, event.button, x, y, 0 /* TODO */);    
       });
     
       this.htmlCanvas_.addEventListener('mousemove', function(event) {
         var x = event.pageX - this.offsetLeft;
         var y = event.pageY - this.offsetTop;
-        that.ViewportMouseMove(x, y);
+        that.ViewportMouseMove(that.pimpl_, x, y);
       });
     
       this.htmlCanvas_.addEventListener('mouseup', function(event) {
-        that.ViewportMouseUp();
+        that.ViewportMouseUp(that.pimpl_);
       });
     
       window.addEventListener('keydown', function(event) {
-        that.ViewportKeyPressed(event.key, event.shiftKey, event.ctrlKey, event.altKey);
+        that.ViewportKeyPressed(that.pimpl_, event.key, event.shiftKey, event.ctrlKey, event.altKey);
       });
     
       this.htmlCanvas_.addEventListener('wheel', function(event) {
         var x = event.pageX - this.offsetLeft;
         var y = event.pageY - this.offsetTop;
-        that.ViewportMouseWheel(event.deltaY, x, y, event.ctrlKey);
+        that.ViewportMouseWheel(that.pimpl_, event.deltaY, x, y, event.ctrlKey);
         event.preventDefault();
       });
 
-      var that = this;
       this.htmlCanvas_.addEventListener('touchstart', function(event) {
         that.ResetTouch();
       });
@@ -158,26 +162,28 @@
       this.htmlCanvas_.addEventListener('touchmove', function(event) {
         if (that.touchTranslation_.length == 2) {
           var t = that.GetTouchTranslation(event);
-          that.ViewportMouseMove(t[0], t[1]);
+          that.ViewportMouseMove(that.pimpl_, t[0], t[1]);
         }
         else if (that.touchZoom_.length == 3) {
           var z0 = that.touchZoom_;
           var z1 = that.GetTouchZoom(event);
-          that.ViewportMouseMove(z0[0], z0[1] - z0[2] + z1[2]);
+          that.ViewportMouseMove(that.pimpl_, z0[0], z0[1] - z0[2] + z1[2]);
         }
         else {
           // Realize the gesture event
           if (event.targetTouches.length == 1) {
             // Exactly one finger inside the canvas => Setup a translation
             that.touchTranslation_ = that.GetTouchTranslation(event);
-            that.ViewportMouseDown(1 /* middle button */,
+            that.ViewportMouseDown(that.pimpl_, 
+                                  1 /* middle button */,
                                   that.touchTranslation_[0],
                                   that.touchTranslation_[1], 0);
           } else if (event.targetTouches.length == 2) {
             // Exactly 2 fingers inside the canvas => Setup a pinch/zoom
             that.touchZoom_ = that.GetTouchZoom(event);
             var z0 = that.touchZoom_;
-            that.ViewportMouseDown(2 /* right button */,
+            that.ViewportMouseDown(that.pimpl_, 
+                                  2 /* right button */,
                                   z0[0],
                                   z0[1], 0);
           }        
@@ -188,7 +194,7 @@
   public ResetTouch() {
     if (this.touchTranslation_ ||
         this.touchZoom_) {
-      this.ViewportMouseUp();
+      this.ViewportMouseUp(this.pimpl_);
     }
 
     this.touchTranslation_ = false;