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, 34 insertions, 22 deletions

diff --git a/src/plugins/platforms/wasm/qwasmintegration.cpp b/src/plugins/platforms/wasm/qwasmintegration.cpp
index f45048ffa4..1964cefdad 100644
--- a/src/plugins/platforms/wasm/qwasmintegration.cpp
+++ b/src/plugins/platforms/wasm/qwasmintegration.cpp
@@ -70,36 +70,35 @@ QWasmIntegration *QWasmIntegration::s_instance;
 
 QWasmIntegration::QWasmIntegration()
     : m_fontDb(nullptr),
-      m_compositor(new QWasmCompositor),
-      m_screen(new QWasmScreen(m_compositor)),
       m_eventDispatcher(nullptr),
       m_clipboard(new QWasmClipboard)
 {
-
-    globalHtml5Integration = this;
     s_instance = this;
 
-    emscripten::val defaultCanvasId = emscripten::val::global("canvas");
-    canvasIds.append(QString::fromStdString(defaultCanvasId["id"].as<std::string>()));
-    m_screen->setCanvas(canvasIds.at(0));
-
-    globalHtml5Integration = this;
-
-    screen()->updateQScreenAndCanvasRenderSize(m_screen->m_canvasId);
-    screenAdded(m_screen);
-
-    m_eventTranslator = new QWasmEventTranslator;
+    // We expect that qtloader.js has populated Module.qtCanvasElements with one or more canvases.
+    // Also check Module.canvas, which may be set if the emscripen or a custom loader is used.
+    emscripten::val qtCanvaseElements = val::module_property("qtCanvasElements");
+    emscripten::val canvas = val::module_property("canvas");
+
+    if (!qtCanvaseElements.isUndefined()) {
+        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>());
+            addScreen(canvasId);
+        }
+    } else if (!canvas.isUndefined()){
+        QString canvasId = QString::fromStdString(canvas["id"].as<std::string>());
+        addScreen(canvasId);
+    }
 
     emscripten::val::global("window").set("onbeforeunload", val::module_property("browserBeforeUnload"));
-
 }
 
 QWasmIntegration::~QWasmIntegration()
 {
-    delete m_compositor;
-    destroyScreen(m_screen);
     delete m_fontDb;
-    delete m_eventTranslator;
+    qDeleteAll(m_screens);
     s_instance = nullptr;
 }
 
@@ -124,13 +123,15 @@ bool QWasmIntegration::hasCapability(QPlatformIntegration::Capability cap) const
 
 QPlatformWindow *QWasmIntegration::createPlatformWindow(QWindow *window) const
 {
-    return new QWasmWindow(window, m_compositor, m_backingStores.value(window));
+    QWasmCompositor *compositor = QWasmScreen::get(window->screen())->compositor();
+    return new QWasmWindow(window, compositor, m_backingStores.value(window));
 }
 
 QPlatformBackingStore *QWasmIntegration::createPlatformBackingStore(QWindow *window) const
 {
 #ifndef QT_NO_OPENGL
-    QWasmBackingStore *backingStore = new QWasmBackingStore(m_compositor, window);
+    QWasmCompositor *compositor = QWasmScreen::get(window->screen())->compositor();
+    QWasmBackingStore *backingStore = new QWasmBackingStore(compositor, window);
     m_backingStores.insert(window, backingStore);
     return backingStore;
 #else
@@ -177,9 +178,20 @@ QPlatformTheme *QWasmIntegration::createPlatformTheme(const QString &name) const
 
 QPlatformClipboard* QWasmIntegration::clipboard() const
 {
-    if (!m_clipboard)
-        m_clipboard = new QWasmClipboard;
     return m_clipboard;
 }
 
+QVector<QWasmScreen *> QWasmIntegration::screens()
+{
+    return m_screens;
+}
+
+void QWasmIntegration::addScreen(const QString &canvasId)
+{
+    QWasmScreen *screen = new QWasmScreen(canvasId);
+    m_clipboard->installEventHandlers(canvasId);
+    m_screens.append(screen);
+    screenAdded(screen);
+}
+
 QT_END_NAMESPACE