wasm: support rendering to multiple canvases

Qt (via the the qtloader.js API) now supports rendering
to multiple canvases. The application sees each canvas
as a QScreen.

Make qtloader.js support multiple canvases:

  var qtloader = QtLoader({
    canvasElements : [array-of-canvas],
    showCanvas: function() {
      // make canvas(es) visible
    },
 });

The canvases were previously created/returned by showCanvas(),
however this function is called after the Qt app has
been started and adding screens that that point is
too late. (This worked before since there was only one
screen, and no need to connect each screen instance
to specific canvas.)

Remove QWasmScreen, QWasmCompositor, and QWasmEventTranslator
singletons from QWasmIntegration. These are are now
crated per-screen and are owned by the QWasmScreen.

Task-number: QTBUG-64079
Change-Id: I24689929fd5bfb7ff0ba076f66937728fa4bc4e4
Reviewed-by: Lorn Potter <lorn.potter@gmail.com>

1 files changed, 29 insertions, 24 deletions

diff --git a/src/plugins/platforms/wasm/qwasmclipboard.cpp b/src/plugins/platforms/wasm/qwasmclipboard.cpp
index 63fea7738d..7a7b253b19 100644
--- a/src/plugins/platforms/wasm/qwasmclipboard.cpp
+++ b/src/plugins/platforms/wasm/qwasmclipboard.cpp
@@ -123,9 +123,11 @@ EMSCRIPTEN_BINDINGS(clipboard_module) {
     function("qClipboardPasteTo", &qClipboardPasteTo);
 }
 
-QWasmClipboard::QWasmClipboard() :
-    hasClipboardApi(false)
+QWasmClipboard::QWasmClipboard()
 {
+    val clipboard = val::global("navigator")["clipboard"];
+    hasClipboardApi = (!clipboard.isUndefined() && !clipboard["readText"].isUndefined());
+
     initClipboardEvents();
 }
 
@@ -177,29 +179,32 @@ void QWasmClipboard::qWasmClipboardPaste(QMimeData *mData)
 
 void QWasmClipboard::initClipboardEvents()
 {
-    val navigator = val::global("navigator");
-    val permissions = navigator["permissions"];
-    val clipboard = navigator["clipboard"];
+    if (!hasClipboardApi)
+        return;
 
-    hasClipboardApi = (!clipboard.isUndefined() && !clipboard["readText"].isUndefined());
-    if (hasClipboardApi) {
-        val readPermissionsMap = val::object();
-        readPermissionsMap.set("name", val("clipboard-read"));
-        permissions.call<val>("query", readPermissionsMap);
-
-        val writePermissionsMap = val::object();
-        writePermissionsMap.set("name", val("clipboard-write"));
-        permissions.call<val>("query", writePermissionsMap);
-
-    } else {
-        val canvas = val::module_property("canvas");
-        canvas.call<void>("addEventListener", std::string("cut"),
-                          val::module_property("qClipboardCutTo"));
-        canvas.call<void>("addEventListener", std::string("copy"),
-                          val::module_property("qClipboardCopyTo"));
-        canvas.call<void>("addEventListener", std::string("paste"),
-                          val::module_property("qClipboardPasteTo"));
-    }
+    val permissions = val::global("navigator")["permissions"];
+    val readPermissionsMap = val::object();
+    readPermissionsMap.set("name", val("clipboard-read"));
+    permissions.call<val>("query", readPermissionsMap);
+
+    val writePermissionsMap = val::object();
+    writePermissionsMap.set("name", val("clipboard-write"));
+    permissions.call<val>("query", writePermissionsMap);
+}
+
+void QWasmClipboard::installEventHandlers(const QString &canvasId)
+{
+    if (hasClipboardApi)
+        return;
+
+    // Fallback path for browsers which do not support direct clipboard access
+    val canvas = val::global(canvasId.toUtf8().constData());
+    canvas.call<void>("addEventListener", std::string("cut"),
+                      val::module_property("qClipboardCutTo"));
+    canvas.call<void>("addEventListener", std::string("copy"),
+                      val::module_property("qClipboardCopyTo"));
+    canvas.call<void>("addEventListener", std::string("paste"),
+                      val::module_property("qClipboardPasteTo"));
 }
 
 void QWasmClipboard::readTextFromClipboard()