wasm: improve qstdweb::EventCallback

We are storing a copy of the this pointer in the constructor,
and later deference it to access EventCallback object
memebers. This makes the class noncopyable: delete
the copy constructor to make sure it isn’t.

Also change the callback API to propagate the event
to the event callback.

Change-Id: Ida4bb192b3e905b260ebeec30293aad71b7d8c49
Reviewed-by: Lorn Potter <lorn.potter@gmail.com>

3 files changed, 30 insertions, 15 deletions

diff --git a/src/corelib/platform/wasm/qstdweb.cpp b/src/corelib/platform/wasm/qstdweb.cpp
index 2bbf57953b..e58447db1a 100644
--- a/src/corelib/platform/wasm/qstdweb.cpp
+++ b/src/corelib/platform/wasm/qstdweb.cpp
@@ -151,7 +151,7 @@ void File::stream(uint32_t offset, uint32_t length, char *buffer, const std::fun
             return;
         }
         char *nextChunkBuffer = chunkBuffer + result.byteLength();
-        fileReader->onLoad([=]() { (*chunkCompleted)(nextChunkBegin, nextChunkBuffer); });
+        fileReader->onLoad([=](emscripten::val) { (*chunkCompleted)(nextChunkBegin, nextChunkBuffer); });
         qstdweb::Blob blob = fileHandle.slice(nextChunkBegin, nextChunkEnd);
         fileReader->readAsArrayBuffer(blob);
     };
@@ -203,17 +203,17 @@ void FileReader::readAsArrayBuffer(const Blob &blob) const
     m_fileReader.call<void>("readAsArrayBuffer", blob.m_blob);
 }
 
-void FileReader::onLoad(const std::function<void ()> &onLoad)
+void FileReader::onLoad(const std::function<void(emscripten::val)> &onLoad)
 {
     m_onLoad.reset(new EventCallback(m_fileReader, "load", onLoad));
 }
 
-void FileReader::onError(const std::function<void ()> &onError)
+void FileReader::onError(const std::function<void(emscripten::val)> &onError)
 {
     m_onError.reset(new EventCallback(m_fileReader, "error", onError));
 }
 
-void FileReader::onAbort(const std::function<void ()> &onAbort)
+void FileReader::onAbort(const std::function<void(emscripten::val)> &onAbort)
 {
     m_onAbort.reset(new EventCallback(m_fileReader, "abort", onAbort));
 }
@@ -305,11 +305,19 @@ emscripten::val Uint8Array::constructor_()
 
 // Registers a callback function for a named event on the given element. The event
 // name must be the name as returned by the Event.type property: e.g. "load", "error".
-EventCallback::EventCallback(emscripten::val element, const std::string &name, const std::function<void ()> &fn)
-:m_fn(fn)
+EventCallback::~EventCallback()
 {
-    element.set(contextPropertyName(name).c_str(), emscripten::val(intptr_t(this)));
-    element.set((std::string("on") + name).c_str(), emscripten::val::module_property("qtStdWebEventCallbackActivate"));
+    m_element.set(contextPropertyName(m_eventName).c_str(), emscripten::val::undefined());
+    m_element.set((std::string("on") + m_eventName).c_str(), emscripten::val::undefined());
+}
+
+EventCallback::EventCallback(emscripten::val element, const std::string &name, const std::function<void(emscripten::val)> &fn)
+    :m_element(element)
+    ,m_eventName(name)
+    ,m_fn(fn)
+{
+    m_element.set(contextPropertyName(m_eventName).c_str(), emscripten::val(intptr_t(this)));
+    m_element.set((std::string("on") + m_eventName).c_str(), emscripten::val::module_property("qtStdWebEventCallbackActivate"));
 }
 
 void EventCallback::activate(emscripten::val event)
@@ -317,7 +325,7 @@ void EventCallback::activate(emscripten::val event)
     emscripten::val target = event["target"];
     std::string eventName = event["type"].as<std::string>();
     EventCallback *that = reinterpret_cast<EventCallback *>(target[contextPropertyName(eventName).c_str()].as<intptr_t>());
-    that->m_fn();
+    that->m_fn(event);
 }
 
 std::string EventCallback::contextPropertyName(const std::string &eventName)
diff --git a/src/corelib/platform/wasm/qstdweb_p.h b/src/corelib/platform/wasm/qstdweb_p.h
index 9d5e2418ec..cd3f029860 100644
--- a/src/corelib/platform/wasm/qstdweb_p.h
+++ b/src/corelib/platform/wasm/qstdweb_p.h
@@ -129,9 +129,9 @@ namespace qstdweb {
         ArrayBuffer result() const;
         void readAsArrayBuffer(const Blob &blob) const;
 
-        void onLoad(const std::function<void ()> &onLoad);
-        void onError(const std::function<void ()> &onError);
-        void onAbort(const std::function<void ()> &onAbort);
+        void onLoad(const std::function<void(emscripten::val)> &onLoad);
+        void onError(const std::function<void(emscripten::val)> &onError);
+        void onAbort(const std::function<void(emscripten::val)> &onAbort);
 
     private:
         emscripten::val m_fileReader = emscripten::val::global("FileReader").new_();
@@ -166,11 +166,18 @@ namespace qstdweb {
     class EventCallback
     {
     public:
-        EventCallback(emscripten::val element, const std::string &name, const std::function<void ()> &fn);
+        EventCallback() = default;
+        ~EventCallback();
+        EventCallback(EventCallback const&) = delete;
+        EventCallback& operator=(EventCallback const&) = delete;
+        EventCallback(emscripten::val element, const std::string &name,
+                      const std::function<void(emscripten::val)> &fn);
         static void activate(emscripten::val event);
     private:
         static std::string contextPropertyName(const std::string &eventName);
-        std::function<void ()> m_fn;
+        emscripten::val m_element = emscripten::val::undefined();
+        std::string m_eventName;
+        std::function<void(emscripten::val)> m_fn;
     };
 }
 
diff --git a/src/gui/platform/wasm/qwasmlocalfileaccess.cpp b/src/gui/platform/wasm/qwasmlocalfileaccess.cpp
index 76e9c6c519..cd1c26c72e 100644
--- a/src/gui/platform/wasm/qwasmlocalfileaccess.cpp
+++ b/src/gui/platform/wasm/qwasmlocalfileaccess.cpp
@@ -96,7 +96,7 @@ void openFileDialog(const std::string &accept, FileSelectMode fileSelectMode,
 
     // Note: there is no event in case the user cancels the file dialog.
     static std::unique_ptr<qstdweb::EventCallback> changeEvent;
-    auto callback = [=]() { filesSelected(qstdweb::FileList(input["files"])); };
+    auto callback = [=](emscripten::val) { filesSelected(qstdweb::FileList(input["files"])); };
     changeEvent.reset(new qstdweb::EventCallback(input, "change", callback));
 
     // Activate file input