--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/Framework/Viewport/WebAssemblyCairoViewport.cpp	Mon Dec 09 17:46:33 2019 +0100
@@ -0,0 +1,133 @@
+/**
+ * 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 "WebAssemblyCairoViewport.h"
+
+#include "../Scene2D/CairoCompositor.h"
+
+#include <Core/Images/Image.h>
+
+namespace OrthancStone
+{
+  void WebAssemblyCairoViewport::GetCanvasSize(unsigned int& width,
+                                               unsigned int& height)
+  {
+    double w, h;
+    emscripten_get_element_css_size(GetFullCanvasId().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)
+    {
+      width = static_cast<unsigned int>(boost::math::iround(w));
+      height = static_cast<unsigned int>(boost::math::iround(h));
+    }
+    else
+    {
+      width = 0;
+      height = 0;
+    }
+  }
+
+
+  void WebAssemblyCairoViewport::Paint(ICompositor& compositor,
+                                       ViewportController& controller)
+  {
+    compositor.Refresh(controller.GetScene());
+
+    // Create a temporary memory buffer for the canvas in JavaScript
+    Orthanc::ImageAccessor cairo;
+    dynamic_cast<CairoCompositor&>(compositor).GetCanvas().GetReadOnlyAccessor(cairo);
+
+    const unsigned int width = cairo.GetWidth();
+    const unsigned int height = cairo.GetHeight();
+
+    if (javascript_.get() == NULL ||
+        javascript_->GetWidth() != width ||
+        javascript_->GetHeight() != height)
+    {
+      javascript_.reset(new Orthanc::Image(Orthanc::PixelFormat_RGBA32, width, height,
+                                           true /* force minimal pitch */));
+    }
+      
+    // Convert from BGRA32 memory layout (only color mode supported
+    // by Cairo, which corresponds to CAIRO_FORMAT_ARGB32) to RGBA32
+    // (as expected by HTML5 canvas). This simply amounts to
+    // swapping the B and R channels. Alpha channel is also set to
+    // full opacity (255).
+    uint8_t* q = reinterpret_cast<uint8_t*>(javascript_->GetBuffer());
+    for (unsigned int y = 0; y < height; y++)
+    {
+      const uint8_t* p = reinterpret_cast<const uint8_t*>(cairo.GetConstRow(y));
+      for (unsigned int x = 0; x < width; x++)
+      {
+        q[0] = p[2];  // R
+        q[1] = p[1];  // G
+        q[2] = p[0];  // B
+        q[3] = 255;   // A
+
+        p += 4;
+        q += 4;
+      }
+    }
+
+    // Execute JavaScript commands to blit the image buffer onto the
+    // 2D drawing context of the HTML5 canvas
+    EM_ASM({
+        const data = new Uint8ClampedArray(Module.HEAP8.buffer, $1, 4 * $2 * $3);
+        const img = new ImageData(data, $2, $3);
+        const ctx = document.getElementById(UTF8ToString($0)).getContext('2d');
+        ctx.putImageData(img, 0, 0);
+      },
+      GetShortCanvasId().c_str(), // $0
+      javascript_->GetBuffer(),   // $1
+      javascript_->GetWidth(),    // $2
+      javascript_->GetHeight());  // $3
+  }
+    
+
+  void WebAssemblyCairoViewport::UpdateSize(ICompositor& compositor)
+  {
+    unsigned int width, height;
+    GetCanvasSize(width, height);
+    emscripten_set_canvas_element_size(GetFullCanvasId().c_str(), width, height);
+
+    dynamic_cast<CairoCompositor&>(compositor).UpdateSize(width, height);
+  }
+
+
+  WebAssemblyCairoViewport::WebAssemblyCairoViewport(const std::string& canvasId) :
+    WebAssemblyViewport(canvasId, NULL)
+  {
+    unsigned int width, height;
+    GetCanvasSize(width, height);
+    emscripten_set_canvas_element_size(GetFullCanvasId().c_str(), width, height);
+    AcquireCompositor(new CairoCompositor(width, height));
+  }
+}