Wasm: enable thread support

configure.json: Make the “thread” feature be allowed
for wasm but disabled by default.

Change qmake.conf and wasm.prf to enable Emscripten
pthreads mode:
- Add USE_PTHREADS=1 linker flag
- Add PTHREAD_POOL_SIZE linker flag with a default pool size (4).
- Add TOTAL_MEMORY linker flag to set available memory (1GB)

It is possible to override options such as PTHREAD_POOL_SIZE
from the application .pro file using QMAKE_WASM_PTHREAD_POOL_SIZE
To change TOTAL_MEMORY, use QMAKE_WASM_TOTAL_MEMORY

Make qtloader.js work in pthreads mode:
- The Module.instantiateWasm callback must provide the module
  in addition to the instance to Emscripten.
- Set Module.mainScriptUrlOrBlob so that the pthreads web workers
  can access the main script

Task-number: QTBUG-64625
Change-Id: I1ab5a559ec97c27c5fc24500ba5f863bcd275141
Reviewed-by: Morten Johan Sørvig <morten.sorvig@qt.io>
Reviewed-by: Lorn Potter <lorn.potter@gmail.com>

1 files changed, 5 insertions, 3 deletions

diff --git a/src/plugins/platforms/wasm/qtloader.js b/src/plugins/platforms/wasm/qtloader.js
index 37a5308034..84694c7b9f 100644
--- a/src/plugins/platforms/wasm/qtloader.js
+++ b/src/plugins/platforms/wasm/qtloader.js
@@ -312,13 +312,13 @@ function QtLoader(config)
         // and is ready to be instantiated. Define the instantiateWasm callback which
         // emscripten will call to create the instance.
         Module.instantiateWasm = function(imports, successCallback) {
-            return WebAssembly.instantiate(wasmModule, imports).then(function(instance) {
-                successCallback(instance);
-                return instance;
+            WebAssembly.instantiate(wasmModule, imports).then(function(instance) {
+                successCallback(instance, wasmModule);
             }, function(error) {
                 self.error = error;
                 setStatus("Error");
             });
+            return {};
         };
 
         Module.locateFile = Module.locateFile || function(filename) {
@@ -382,6 +382,8 @@ function QtLoader(config)
             }
         });
 
+        Module.mainScriptUrlOrBlob = new Blob([emscriptenModuleSource], {type: 'text/javascript'});
+
         config.restart = function() {
 
             // Restart by reloading the page. This will wipe all state which means