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, 50 insertions, 19 deletions

diff --git a/src/plugins/platforms/wasm/qwasmscreen.cpp b/src/plugins/platforms/wasm/qwasmscreen.cpp
index fb14803ff8..a26cafa900 100644
--- a/src/plugins/platforms/wasm/qwasmscreen.cpp
+++ b/src/plugins/platforms/wasm/qwasmscreen.cpp
@@ -29,8 +29,10 @@
 
 #include "qwasmscreen.h"
 #include "qwasmwindow.h"
+#include "qwasmeventtranslator.h"
 #include "qwasmcompositor.h"
 #include <emscripten/bind.h>
+#include <emscripten/val.h>
 
 #include <QtEglSupport/private/qeglconvenience_p.h>
 #ifndef QT_NO_OPENGL
@@ -44,12 +46,13 @@
 
 QT_BEGIN_NAMESPACE
 
-QWasmScreen::QWasmScreen(QWasmCompositor *compositor)
-    : m_compositor(compositor)
-    , m_depth(32)
-    , m_format(QImage::Format_RGB32)
+QWasmScreen::QWasmScreen(const QString &canvasId)
+    : m_canvasId(canvasId)
+
 {
-    m_compositor->setScreen(this);
+    m_compositor = new QWasmCompositor(this);
+    m_eventTranslator = new QWasmEventTranslator(this);
+    updateQScreenAndCanvasRenderSize();
 }
 
 QWasmScreen::~QWasmScreen()
@@ -57,6 +60,31 @@ QWasmScreen::~QWasmScreen()
 
 }
 
+QWasmScreen *QWasmScreen::get(QPlatformScreen *screen)
+{
+    return static_cast<QWasmScreen *>(screen);
+}
+
+QWasmScreen *QWasmScreen::get(QScreen *screen)
+{
+    return get(screen->handle());
+}
+
+QWasmCompositor *QWasmScreen::compositor()
+{
+    return m_compositor;
+}
+
+QWasmEventTranslator *QWasmScreen::eventTranslator()
+{
+    return m_eventTranslator;
+}
+
+QString QWasmScreen::canvasId() const
+{
+    return m_canvasId;
+}
+
 QRect QWasmScreen::geometry() const
 {
     return m_geometry;
@@ -82,6 +110,11 @@ qreal QWasmScreen::devicePixelRatio() const
     return qreal(htmlWindowDpr);
 }
 
+QString QWasmScreen::name() const
+{
+    return m_canvasId;
+}
+
 QPlatformCursor *QWasmScreen::cursor() const
 {
     return const_cast<QWasmCursor *>(&m_cursor);
@@ -114,14 +147,7 @@ void QWasmScreen::setGeometry(const QRect &rect)
     resizeMaximizedWindows();
 }
 
-static void set_canvas_size(double width, double height, const char *canvasId)
-{
-    emscripten::val canvas = emscripten::val::global(canvasId);
-    canvas.set("width", width);
-    canvas.set("height", height);
-}
-
-void QWasmScreen::updateQScreenAndCanvasRenderSize(const QString &canvasId)
+void QWasmScreen::updateQScreenAndCanvasRenderSize()
 {
     // The HTML canvas has two sizes: the CSS size and the canvas render size.
     // The CSS size is determined according to standard CSS rules, while the
@@ -130,17 +156,22 @@ void QWasmScreen::updateQScreenAndCanvasRenderSize(const QString &canvasId)
     // Setting the render size to a value larger than the CSS size enables high-dpi
     // rendering.
 
+    QByteArray canvasId = m_canvasId.toUtf8();
     double css_width;
     double css_height;
-    emscripten_get_element_css_size(canvasId.toLocal8Bit().constData(), &css_width, &css_height);
+    emscripten_get_element_css_size(canvasId.constData(), &css_width, &css_height);
     QSizeF cssSize(css_width, css_height);
 
-    QWasmScreen *screen = QWasmIntegration::get()->screen();
-    QSizeF canvasSize = cssSize * screen->devicePixelRatio();
+    QSizeF canvasSize = cssSize * devicePixelRatio();
+    emscripten::val canvas = emscripten::val::global(canvasId.constData());
+    canvas.set("width", canvasSize.width());
+    canvas.set("height", canvasSize.height());
+
+    emscripten::val rect = canvas.call<emscripten::val>("getBoundingClientRect");
+    QPoint position(rect["left"].as<int>(), rect["top"].as<int>());
 
-    set_canvas_size(canvasSize.width(), canvasSize.height(), canvasId.toLocal8Bit().constData());
-    screen->setGeometry(QRect(QPoint(0, 0), cssSize.toSize()));
-    QWasmIntegration::get()->compositor()->redrawWindowContent();
+    setGeometry(QRect(position, cssSize.toSize()));
+    m_compositor->redrawWindowContent();
 }
 
 QT_END_NAMESPACE