wasm: store and pass canvases as emscripten::val

Store and pass canvases as emscripten::val instead of
a QString containing the element id.

This simplifies code which interacts with the canvas
using the emscripten::val API, by removing the need to
look up with getElementById.

The Emscripten C event API does not accept emscripten::val,
and using the element id is still needed here.

emscripten::val does not provide a hash key suitable
for use with QHash, but does provide an equality-compare
in the form of val::equals(). Change the canvas->screen
mapping code to use a QVector instead of a QHash.

Change-Id: I1dbdbbc8fb06bb869031f1500e83ae2d64780a7f
Reviewed-by: Lorn Potter <lorn.potter@gmail.com>

1 files changed, 1 insertions, 3 deletions

diff --git a/src/plugins/platforms/wasm/qwasmeventtranslator.cpp b/src/plugins/platforms/wasm/qwasmeventtranslator.cpp
index 62ada796db..3e6043b083 100644
--- a/src/plugins/platforms/wasm/qwasmeventtranslator.cpp
+++ b/src/plugins/platforms/wasm/qwasmeventtranslator.cpp
@@ -354,9 +354,7 @@ void QWasmEventTranslator::initEventHandlers()
         g_useNaturalScrolling = false; // make this !default on macOS
 
         if (emscripten::val::global("window")["safari"].isUndefined()) {
-            val document = val::global("document");
-            val jsCanvasId = QWasmString::fromQString(screen()->canvasId());
-            val canvas = document.call<val>("getElementById", jsCanvasId);
+            val canvas = screen()->canvas();
             canvas.call<void>("addEventListener",
                               val("wheel"),
                               val::module_property("qtMouseWheelEvent"));