wasm: fix redundant string conversions between wasm and JavaScript

Avoid redundant conversions from UTF16 to UTF8 to UTF16 with
help of new class QWasmString static methods:
+ QWasmString::fromQString to convert QString to js string
using js Module.UTF16ToString
+ QWasmString::toQString to convert js string to QString
using js Module.stringToUTF16

Fixed document.getElementById calls for cavasId with unicode characters.

Change-Id: I3fc55bfeb6aeda75fa3acd85d22cea667b542f38
Reviewed-by: Morten Johan Sørvig <morten.sorvig@qt.io>
Reviewed-by: Lorn Potter <lorn.potter@gmail.com>

1 files changed, 4 insertions, 2 deletions

diff --git a/src/plugins/platforms/wasm/qwasmeventtranslator.cpp b/src/plugins/platforms/wasm/qwasmeventtranslator.cpp
index 8b7d00082f..1ccac87afa 100644
--- a/src/plugins/platforms/wasm/qwasmeventtranslator.cpp
+++ b/src/plugins/platforms/wasm/qwasmeventtranslator.cpp
@@ -32,6 +32,7 @@
 #include "qwasmcompositor.h"
 #include "qwasmintegration.h"
 #include "qwasmclipboard.h"
+#include "qwasmstring.h"
 
 #include <QtGui/qevent.h>
 #include <qpa/qwindowsysteminterface.h>
@@ -355,9 +356,10 @@ void QWasmEventTranslator::initEventHandlers()
 
         if (emscripten::val::global("window")["safari"].isUndefined()) {
             val document = val::global("document");
-            val canvas = document.call<val>("getElementById", val(canvasId));
+            val jsCanvasId = QWasmString::fromQString(screen()->canvasId());
+            val canvas = document.call<val>("getElementById", jsCanvasId);
             canvas.call<void>("addEventListener",
-                              std::string("wheel"),
+                              val("wheel"),
                               val::module_property("qtMouseWheelEvent"));
         }
     }