--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/Framework/OpenGL/WebAssemblyOpenGLContext.cpp	Thu May 02 13:27:41 2019 +0200
@@ -0,0 +1,168 @@
+/**
+ * Stone of Orthanc
+ * Copyright (C) 2012-2016 Sebastien Jodogne, Medical Physics
+ * Department, University Hospital of Liege, Belgium
+ * Copyright (C) 2017-2019 Osimis S.A., Belgium
+ *
+ * This program is free software: you can redistribute it and/or
+ * modify it under the terms of the GNU Affero General Public License
+ * as published by the Free Software Foundation, either version 3 of
+ * the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Affero General Public License for more details.
+ * 
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ **/
+
+
+#include "WebAssemblyOpenGLContext.h"
+
+#if ORTHANC_ENABLE_WASM == 1
+
+#include <Core/OrthancException.h>
+
+#include <emscripten/html5.h>
+#include <boost/math/special_functions/round.hpp>
+
+namespace OrthancStone
+{
+  namespace OpenGL
+  {
+    class WebAssemblyOpenGLContext::PImpl
+    {
+    private:
+      std::string                      canvas_;
+      EMSCRIPTEN_WEBGL_CONTEXT_HANDLE  context_;
+      unsigned int                     canvasWidth_;
+      unsigned int                     canvasHeight_;
+
+    public:
+      PImpl(const std::string& canvas) :
+        canvas_(canvas)
+      {
+        // Context configuration
+        EmscriptenWebGLContextAttributes attr; 
+        emscripten_webgl_init_context_attributes(&attr);
+
+        context_ = emscripten_webgl_create_context(canvas.c_str(), &attr);
+        if (context_ < 0)
+        {
+          throw Orthanc::OrthancException(Orthanc::ErrorCode_InternalError,
+                                          "Cannot create an OpenGL context for canvas: " + canvas);
+        }
+
+        UpdateSize();
+      }
+
+      ~PImpl()
+      {
+        emscripten_webgl_destroy_context(context_);
+      }
+
+      void MakeCurrent()
+      {
+        if (emscripten_webgl_make_context_current(context_) != EMSCRIPTEN_RESULT_SUCCESS)
+        {
+          throw Orthanc::OrthancException(Orthanc::ErrorCode_InternalError,
+                                          "Cannot set the OpenGL context");
+        }
+      }
+
+      void SwapBuffer() 
+      {
+        /**
+         * "Rendered WebGL content is implicitly presented (displayed to
+         * the user) on the canvas when the event handler that renders with
+         * WebGL returns back to the browser event loop."
+         * https://emscripten.org/docs/api_reference/html5.h.html#webgl-context
+         *
+         * Could call "emscripten_webgl_commit_frame()" if
+         * "explicitSwapControl" option were set to "true".
+         **/
+      }
+
+      unsigned int GetCanvasWidth() const
+      {
+        return canvasWidth_;
+      }
+
+      unsigned int GetCanvasHeight() const
+      {
+        return canvasHeight_;
+      }
+
+      void UpdateSize()
+      {
+        double w, h;
+        emscripten_get_element_css_size(canvas_.c_str(), &w, &h);
+
+        /**
+         * Emscripten has the function emscripten_get_element_css_size()
+         * to query the width and height of a named HTML element. I'm
+         * calling this first to get the initial size of the canvas DOM
+         * element, and then call emscripten_set_canvas_size() to
+         * initialize the framebuffer size of the canvas to the same
+         * size as its DOM element.
+         * https://floooh.github.io/2017/02/22/emsc-html.html
+         **/
+
+        if (w <= 0 ||
+            h <= 0)
+        {
+          canvasWidth_ = 0;
+          canvasHeight_ = 0;
+        }
+        else
+        {
+          canvasWidth_ = static_cast<unsigned int>(boost::math::iround(w));
+          canvasHeight_ = static_cast<unsigned int>(boost::math::iround(h));
+        }
+    
+        emscripten_set_canvas_element_size(canvas_.c_str(), canvasWidth_, canvasHeight_);
+      }
+    };
+
+
+    WebAssemblyOpenGLContext::WebAssemblyOpenGLContext(const std::string& canvas) :
+      pimpl_(new PImpl(canvas))
+    {
+    }
+
+    void WebAssemblyOpenGLContext::MakeCurrent()
+    {
+      assert(pimpl_.get() != NULL);
+      pimpl_->MakeCurrent();
+    }
+
+
+    void WebAssemblyOpenGLContext::SwapBuffer() 
+    {
+      assert(pimpl_.get() != NULL);
+      pimpl_->SwapBuffer();
+    }
+
+    unsigned int WebAssemblyOpenGLContext::GetCanvasWidth() const
+    {
+      assert(pimpl_.get() != NULL);
+      return pimpl_->GetCanvasWidth();
+    }
+
+    unsigned int WebAssemblyOpenGLContext::GetCanvasHeight() const
+    {
+      assert(pimpl_.get() != NULL);
+      return pimpl_->GetCanvasHeight();
+    }
+
+    void WebAssemblyOpenGLContext::UpdateSize()
+    {
+      assert(pimpl_.get() != NULL);
+      pimpl_->UpdateSize();
+    }
+  }
+}
+
+#endif