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>

mkspecs/wasm-emscripten/qmake.conf

@@ -35,6 +35,7 @@ EMCC_COMMON_LFLAGS += \
     -s USE_WEBGL2=1 \
     -s NO_EXIT_RUNTIME=0 \
     -s ERROR_ON_UNDEFINED_SYMBOLS=1 \
+    -s EXTRA_EXPORTED_RUNTIME_METHODS=[\"UTF16ToString\",\"stringToUTF16\"] \
     --bind
 
 # The -s arguments can also be used with release builds,

src/plugins/platforms/wasm/qwasmclipboard.cpp

@@ -29,6 +29,7 @@
 
 #include "qwasmclipboard.h"
 #include "qwasmwindow.h"
+#include "qwasmstring.h"
 
 #include <emscripten.h>
 #include <emscripten/html5.h>
@@ -40,22 +41,22 @@
 using namespace emscripten;
 
 // there has got to be a better way...
-static QByteArray g_clipboardArray;
-static QByteArray g_clipboardFormat;
+static QString g_clipboardText;
+static QString g_clipboardFormat;
 
 static val getClipboardData()
 {
-    return val(g_clipboardArray.constData());
+    return QWasmString::fromQString(g_clipboardText);
 }
 
 static val getClipboardFormat()
 {
-    return val(g_clipboardFormat.constData());
+    return QWasmString::fromQString(g_clipboardFormat);
 }
 
 static void pasteClipboardData(emscripten::val format, emscripten::val dataPtr)
 {
-    QString formatString = QString::fromStdString(format.as<std::string>());
+    QString formatString = QWasmString::toQString(format);
     QByteArray dataArray =  QByteArray::fromStdString(dataPtr.as<std::string>());
     QMimeData *mMimeData = new QMimeData;
     mMimeData->setData(formatString, dataArray);
@@ -102,11 +103,10 @@ static void qClipboardPasteTo(val event)
     bool hasClipboardApi = QWasmIntegration::get()->getWasmClipboard()->hasClipboardApi;
     val clipdata = hasClipboardApi ?
         val::global("Module").call<val>("qtGetClipboardData") :
-        event["clipboardData"].call<val>("getData", std::string("text"));
+        event["clipboardData"].call<val>("getData", val("text"));
 
-    const std::string data = clipdata.as<std::string>();
-    if (data.length() > 0) {
-        QString qstr = QString::fromStdString(data);
+    const QString qstr = QWasmString::toQString(clipdata);
+    if (qstr.length() > 0) {
         QMimeData *mMimeData = new QMimeData;
         mMimeData->setText(qstr);
         QWasmClipboard::qWasmClipboardPaste(mMimeData);
@@ -133,7 +133,7 @@ QWasmClipboard::QWasmClipboard()
 
 QWasmClipboard::~QWasmClipboard()
 {
-    g_clipboardArray.clear();
+    g_clipboardText.clear();
     g_clipboardFormat.clear();
 }
 
@@ -148,11 +148,11 @@ QMimeData* QWasmClipboard::mimeData(QClipboard::Mode mode)
 void QWasmClipboard::setMimeData(QMimeData* mimeData, QClipboard::Mode mode)
 {
     if (mimeData->hasText()) {
-        g_clipboardFormat = mimeData->formats().at(0).toUtf8();
-        g_clipboardArray = mimeData->text().toUtf8();
+        g_clipboardFormat = mimeData->formats().at(0);
+        g_clipboardText = mimeData->text();
     } else if (mimeData->hasHtml()) {
-        g_clipboardFormat =mimeData->formats().at(0).toUtf8();
-        g_clipboardArray = mimeData->html().toUtf8();
+        g_clipboardFormat = mimeData->formats().at(0);
+        g_clipboardText = mimeData->html();
     }
 
     QPlatformClipboard::setMimeData(mimeData, mode);
@@ -199,13 +199,13 @@ void QWasmClipboard::installEventHandlers(const QString &canvasId)
 
     // Fallback path for browsers which do not support direct clipboard access
     val document = val::global("document");
-    val canvas = document.call<val>("getElementById", val(canvasId.toUtf8().constData()));
+    val canvas = document.call<val>("getElementById", QWasmString::fromQString(canvasId));
 
-    canvas.call<void>("addEventListener", std::string("cut"),
+    canvas.call<void>("addEventListener", val("cut"),
                       val::module_property("qtClipboardCutTo"));
-    canvas.call<void>("addEventListener", std::string("copy"),
+    canvas.call<void>("addEventListener", val("copy"),
                       val::module_property("qtClipboardCopyTo"));
-    canvas.call<void>("addEventListener", std::string("paste"),
+    canvas.call<void>("addEventListener", val("paste"),
                       val::module_property("qtClipboardPasteTo"));
 }
 
@@ -226,6 +226,6 @@ void QWasmClipboard::writeTextToClipboard()
         val txt = module.call<val>("qtGetClipboardData");
         val format =  module.call<val>("qtGetClipboardFormat");
         val navigator = val::global("navigator");
-        navigator["clipboard"].call<void>("writeText", txt.as<std::string>());
+        navigator["clipboard"].call<void>("writeText", txt);
     }
 }

src/plugins/platforms/wasm/qwasmcursor.cpp

@@ -29,6 +29,7 @@
 
 #include "qwasmcursor.h"
 #include "qwasmscreen.h"
+#include "qwasmstring.h"
 
 #include <QtCore/qdebug.h>
 #include <QtGui/qwindow.h>
@@ -56,11 +57,11 @@ void QWasmCursor::changeCursor(QCursor *windowCursor, QWindow *window)
         htmlCursorName = "auto";
 
     // Set cursor on the canvas
-    QByteArray canvasId = QWasmScreen::get(screen)->canvasId().toUtf8();
+    val jsCanvasId = QWasmString::fromQString(QWasmScreen::get(screen)->canvasId());
     val document = val::global("document");
-    val canvas = document.call<val>("getElementById", val(canvasId.constData()));
+    val canvas = document.call<val>("getElementById", jsCanvasId);
     val canvasStyle = canvas["style"];
-    canvasStyle.set("cursor", emscripten::val(htmlCursorName.constData()));
+    canvasStyle.set("cursor", val(htmlCursorName.constData()));
 }
 
 QByteArray QWasmCursor::cursorShapeToHtml(Qt::CursorShape shape)

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"));
         }
     }

src/plugins/platforms/wasm/qwasmintegration.cpp

@@ -36,6 +36,7 @@
 #include "qwasmclipboard.h"
 #include "qwasmservices.h"
 #include "qwasmoffscreensurface.h"
+#include "qwasmstring.h"
 
 #include "qwasmwindow.h"
 #ifndef QT_NO_OPENGL
@@ -67,19 +68,19 @@ static void browserBeforeUnload(emscripten::val)
 
 static void addCanvasElement(emscripten::val canvas)
 {
-    QString canvasId = QString::fromStdString(canvas["id"].as<std::string>());
+    QString canvasId = QWasmString::toQString(canvas["id"]);
     QWasmIntegration::get()->addScreen(canvasId);
 }
 
 static void removeCanvasElement(emscripten::val canvas)
 {
-    QString canvasId = QString::fromStdString(canvas["id"].as<std::string>());
+    QString canvasId = QWasmString::toQString(canvas["id"]);
     QWasmIntegration::get()->removeScreen(canvasId);
 }
 
 static void resizeCanvasElement(emscripten::val canvas)
 {
-    QString canvasId = QString::fromStdString(canvas["id"].as<std::string>());
+    QString canvasId = QWasmString::toQString(canvas["id"]);
     QWasmIntegration::get()->resizeScreen(canvasId);
 }
 
@@ -115,11 +116,11 @@ QWasmIntegration::QWasmIntegration()
         int screenCount = qtCanvaseElements["length"].as<int>();
         for (int i = 0; i < screenCount; ++i) {
             emscripten::val canvas = qtCanvaseElements[i].as<emscripten::val>();
-            QString canvasId = QString::fromStdString(canvas["id"].as<std::string>());
+            QString canvasId = QWasmString::toQString(canvas["id"]);
             addScreen(canvasId);
         }
     } else if (!canvas.isUndefined()){
-        QString canvasId = QString::fromStdString(canvas["id"].as<std::string>());
+        QString canvasId = QWasmString::toQString(canvas["id"]);
         addScreen(canvasId);
     }
 

src/plugins/platforms/wasm/qwasmscreen.cpp

@@ -32,6 +32,8 @@
 #include "qwasmeventtranslator.h"
 #include "qwasmcompositor.h"
 #include "qwasmintegration.h"
+#include "qwasmstring.h"
+
 #include <emscripten/bind.h>
 #include <emscripten/val.h>
 
@@ -184,7 +186,7 @@ void QWasmScreen::updateQScreenAndCanvasRenderSize()
 
     QSizeF canvasSize = cssSize * devicePixelRatio();
     val document = val::global("document");
-    val canvas = document.call<val>("getElementById", val(canvasId.constData()));
+    val canvas = document.call<val>("getElementById", QWasmString::fromQString(m_canvasId));
 
     canvas.set("width", canvasSize.width());
     canvas.set("height", canvasSize.height());

src/plugins/platforms/wasm/qwasmservices.cpp

@@ -28,6 +28,8 @@
 ****************************************************************************/
 
 #include "qwasmservices.h"
+#include "qwasmstring.h"
+
 #include <QtCore/QUrl>
 #include <QtCore/QDebug>
 
@@ -37,8 +39,8 @@ QT_BEGIN_NAMESPACE
 
 bool QWasmServices::openUrl(const QUrl &url)
 {
-    QByteArray utf8Url = url.toString().toUtf8();
-    emscripten::val::global("window").call<void>("open", emscripten::val(utf8Url.constData()), emscripten::val("_blank"));
+    emscripten::val jsUrl = QWasmString::fromQString(url.toString());
+    emscripten::val::global("window").call<void>("open", jsUrl, emscripten::val("_blank"));
     return true;
 }
 

src/plugins/platforms/wasm/qwasmstring.cpp

@@ -0,0 +1,61 @@
+/****************************************************************************
+**
+** Copyright (C) 2020 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the plugins of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:GPL$
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see https://www.qt.io/terms-conditions. For further
+** information use the contact form at https://www.qt.io/contact-us.
+**
+** GNU General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 3 or (at your option) any later version
+** approved by the KDE Free Qt Foundation. The licenses are as published by
+** the Free Software Foundation and appearing in the file LICENSE.GPL3
+** included in the packaging of this file. Please review the following
+** information to ensure the GNU General Public License requirements will
+** be met: https://www.gnu.org/licenses/gpl-3.0.html.
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#include "qwasmstring.h"
+
+QT_BEGIN_NAMESPACE
+
+using namespace emscripten;
+
+val QWasmString::fromQString(const QString &str)
+{
+    static const val UTF16ToString(
+        val::global("Module")["UTF16ToString"]);
+
+    auto ptr = quintptr(str.utf16());
+    return UTF16ToString(val(ptr));
+}
+
+QString QWasmString::toQString(const val &v)
+{
+    QString result;
+    if (!v.isString())
+        return result;
+
+    static const val stringToUTF16(
+        val::global("Module")["stringToUTF16"]);
+    static const val length("length");
+
+    result.resize(v[length].as<int>());
+    auto ptr = quintptr(result.utf16());
+    stringToUTF16(v, val(ptr));
+    return result;
+}
+
+QT_END_NAMESPACE

src/plugins/platforms/wasm/qwasmstring.h

@@ -0,0 +1,45 @@
+/****************************************************************************
+**
+** Copyright (C) 2020 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the plugins of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:GPL$
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see https://www.qt.io/terms-conditions. For further
+** information use the contact form at https://www.qt.io/contact-us.
+**
+** GNU General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 3 or (at your option) any later version
+** approved by the KDE Free Qt Foundation. The licenses are as published by
+** the Free Software Foundation and appearing in the file LICENSE.GPL3
+** included in the packaging of this file. Please review the following
+** information to ensure the GNU General Public License requirements will
+** be met: https://www.gnu.org/licenses/gpl-3.0.html.
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#pragma once
+
+#include <qstring.h>
+
+#include <emscripten/val.h>
+
+QT_BEGIN_NAMESPACE
+
+class QWasmString
+{
+public:
+    static emscripten::val fromQString(const QString &str);
+    static QString toQString(const emscripten::val &v);
+};
+QT_END_NAMESPACE
+

src/plugins/platforms/wasm/wasm.pro

@@ -23,7 +23,8 @@ SOURCES = \
     qwasmtheme.cpp \
     qwasmclipboard.cpp \
     qwasmservices.cpp \
-    qwasmoffscreensurface.cpp
+    qwasmoffscreensurface.cpp \
+    qwasmstring.cpp
 
 HEADERS = \
     qwasmintegration.h \
@@ -39,7 +40,8 @@ HEADERS = \
     qwasmtheme.h \
     qwasmclipboard.h \
     qwasmservices.h \
-    qwasmoffscreensurface.h
+    qwasmoffscreensurface.h \
+    qwasmstring.h
 
 wasmfonts.files = \
     ../../../3rdparty/wasm/Vera.ttf \