wasm: Support non-canvas container elements

Support specifying that Qt should use a div element
as the root container, in which case canvas management
is moved to Qt C++ code.

This enables us to take ownership of the canvas and its
configuration. In addition, it allows creating child
elements for the Qt container (canvas element children
have a special role are as fallback elements displayed
in case the browser can’t show the canvas)

Remove support for reading Module.canvas, which was
deprecated in Qt 5.

Add support for reading Module.qtContainerElements,
which can be either a canvas element (legacy) or a
div element (preferred).

Deprecate qtCanvasElements and print warning on usage.

Change QWasmScreen to accept either a canvas or any
html element. In the latter case, create the canvas
and configure it as required by Qt.

Change-Id: I57df8fb5772b2bfbba081af3f572b8b0e7d51897
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@qt.io>

1 files changed, 3 insertions, 3 deletions

diff --git a/src/plugins/platforms/wasm/qtloader.js b/src/plugins/platforms/wasm/qtloader.js
index 08bf0ed421..4f5bfcc2d8 100644
--- a/src/plugins/platforms/wasm/qtloader.js
+++ b/src/plugins/platforms/wasm/qtloader.js
@@ -142,7 +142,7 @@ function QtLoader(config)
 
     // Qt properties. These are propagated to the Emscripten module after
     // it has been created.
-    self.qtCanvasElements = undefined;
+    self.qtContainerElements = undefined;
     self.qtFontDpi = 96;
 
     function webAssemblySupported() {
@@ -431,13 +431,13 @@ function QtLoader(config)
                 module.ENV[key.toUpperCase()] = value;
             }
             // Propagate Qt module properties
-            module.qtCanvasElements = self.qtCanvasElements;
+            module.qtContainerElements = self.qtContainerElements;
             module.qtFontDpi = self.qtFontDpi;
         });
 
         self.moduleConfig.mainScriptUrlOrBlob = new Blob([emscriptenModuleSource], {type: 'text/javascript'});
 
-        self.qtCanvasElements = config.canvasElements;
+        self.qtContainerElements = config.canvasElements;
 
         config.restart = function() {