--- a/OrthancStone/Sources/OpenGL/WebAssemblyOpenGLContext.cpp	Mon Sep 21 18:29:53 2020 +0200
+++ b/OrthancStone/Sources/OpenGL/WebAssemblyOpenGLContext.cpp	Wed Sep 23 17:25:25 2020 +0200
@@ -52,6 +52,14 @@
         EmscriptenWebGLContextAttributes attr; 
         emscripten_webgl_init_context_attributes(&attr);
 
+#if 0
+        // The next line might be necessary to print on Firefox 71
+        // using WebGL. Sometimes, if set to "false" (the default
+        // value), the canvas was rendered as a fully white or black
+        // area. UNCONFIRMED, so disabled.
+        attr.preserveDrawingBuffer = true;
+#endif
+
         context_ = emscripten_webgl_create_context(canvasSelector.c_str(), &attr);
         if (context_ == 0)
         {