Fix Emscripten JS issues for Qt WASM builds and enhance canvas event target handling

2 files changed, 62 insertions, 7 deletions

diff --git a/xmake/rules/qt/load.lua b/xmake/rules/qt/load.lua
index 38618553f..c09294a70 100644
--- a/xmake/rules/qt/load.lua
+++ b/xmake/rules/qt/load.lua
@@ -522,17 +522,18 @@ function main(target, opt)
         target:add("shflags", "-s FETCH=1", "-s ERROR_ON_UNDEFINED_SYMBOLS=1", "-s ALLOW_MEMORY_GROWTH=1", "--bind")
         if qt_sdkver:ge("6.0") then
             -- @see https://github.com/xmake-io/xmake/issues/4137
-            target:add("ldflags", "-s MAX_WEBGL_VERSION=2", "-s WASM_BIGINT=1", "-s ASSERTIONS=0")
+            -- @see QtWasmHelpers.cmake: qt_internal_setup_wasm_target_properties
+            target:add("ldflags", "-s MAX_WEBGL_VERSION=2", "-s WASM_BIGINT=1", "-s STACK_SIZE=5MB")
             target:add("ldflags", "-sASYNCIFY_IMPORTS=qt_asyncify_suspend_js,qt_asyncify_resume_js")
             -- FS is required for qtloader.js even if we don't use preload files
             target:add("ldflags", "-s EXPORTED_RUNTIME_METHODS=UTF16ToString,stringToUTF16,JSEvents,specialHTMLTargets,FS,callMain,cwrap,ccall,setValue,getValue,UTF8ToString,stringToUTF8")
             -- @see https://github.com/emscripten-core/emscripten/issues/21844 Export main and emscripten_thread_crashed for qtloader.js
-            target:add("ldflags", "-s EXPORTED_FUNCTIONS=_main,_malloc,_free")
+            target:add("ldflags", "-s EXPORTED_FUNCTIONS=_main,_malloc,_free,__embind_initialize_bindings", {force = true})
             target:add("ldflags", "-s MODULARIZE=1", "-s EXPORT_NAME=createQtAppInstance")
-            target:add("shflags", "-s MAX_WEBGL_VERSION=2", "-s WASM_BIGINT=1", "-s ASSERTIONS=0")
+            target:add("shflags", "-s MAX_WEBGL_VERSION=2", "-s WASM_BIGINT=1", "-s STACK_SIZE=5MB")
             target:add("shflags", "-sASYNCIFY_IMPORTS=qt_asyncify_suspend_js,qt_asyncify_resume_js")
             target:add("shflags", "-s EXPORTED_RUNTIME_METHODS=UTF16ToString,stringToUTF16,JSEvents,specialHTMLTargets,FS,callMain,cwrap,ccall,setValue,getValue,UTF8ToString,stringToUTF8")
-            target:add("shflags", "-s EXPORTED_FUNCTIONS=_main,_malloc,_free")
+            target:add("shflags", "-s EXPORTED_FUNCTIONS=_main,_malloc,_free,__embind_initialize_bindings", {force = true})
             target:add("shflags", "-s MODULARIZE=1", "-s EXPORT_NAME=createQtAppInstance")
             target:set("extension", ".js")
         else
diff --git a/xmake/rules/qt/xmake.lua b/xmake/rules/qt/xmake.lua
index f8ad260f7..048f163e4 100644
--- a/xmake/rules/qt/xmake.lua
+++ b/xmake/rules/qt/xmake.lua
@@ -55,14 +55,68 @@ rule("qt._wasm_app")
                         return w .. " " .. preload
                     end)
                     io.gsub(htmlfile, "@PRELOAD@", "")
-                    -- Fix qt-app.js errors
+                    -- Fix Emscripten JS issues for Qt WASM builds
                     local jsfile = path.join(targetdir, target:basename() .. ".js")
                     if os.isfile(jsfile) then
                         -- Remove "use strict"; to avoid issues with `this` being undefined in strict mode
                         io.gsub(jsfile, "\"use strict\";", "")
                         io.gsub(jsfile, "'use strict';", "")
-                        -- Patch visualViewport access issue if present (undefined this context) 
-                        io.gsub(jsfile, "this%.visualViewport", "(typeof window !== 'undefined' ? window.visualViewport : null)")
+                        -- Patch visualViewport access issue if present (undefined this context)
+                        io.gsub(jsfile, "this%.visualViewport",
+                            "(typeof window !== 'undefined' ? window.visualViewport : null)")
+                        -- Guard all document.querySelector(target) calls with try-catch.
+                        -- Qt WASM uses "!" prefixed selectors that are not valid CSS selectors,
+                        -- and corrupted strings from SharedArrayBuffer can also cause SyntaxErrors.
+                        io.gsub(jsfile, "document%.querySelector%(target%)",
+                            "(function(){try{return document.querySelector(target)}catch(e){return null}})()")
+                        -- Replace findCanvasEventTarget with a robust version.
+                        -- Qt WASM registers canvases in Module.specialHTMLTargets with "!" prefixed
+                        -- keys (e.g. "!qtwindow1", "!qtoffscreen_xxx"). With pthreads +
+                        -- ALLOW_MEMORY_GROWTH, Emscripten's UTF8ToString may read corrupted strings
+                        -- from SharedArrayBuffer memory, causing the specialHTMLTargets lookup to fail.
+                        -- Additionally, QWasmOffscreenSurface passes an empty string when
+                        -- OffscreenCanvas is unavailable. The replacement adds a fallback that
+                        -- iterates specialHTMLTargets to find any Qt-registered canvas element.
+                        -- @see https://code.qt.io/cgit/qt/qtbase.git/tree/src/plugins/platforms/wasm/qwasmwindow.cpp
+                        -- @see https://code.qt.io/cgit/qt/qtbase.git/tree/src/plugins/platforms/wasm/qwasmoffscreensurface.cpp
+                        local content = io.readfile(jsfile)
+                        local marker = "var findCanvasEventTarget = target => {"
+                        local pos = content:find(marker, 1, true)
+                        if pos then
+                            -- Find the end of the function by counting matched braces
+                            local depth = 1
+                            local i = pos + #marker
+                            while i <= #content and depth > 0 do
+                                local c = content:sub(i, i)
+                                if c == "{" then depth = depth + 1
+                                elseif c == "}" then depth = depth - 1 end
+                                i = i + 1
+                            end
+                            if content:sub(i, i) == ";" then i = i + 1 end
+                            local new_func = "var findCanvasEventTarget = target => {\n"
+                                .. " target = maybeCStringToJsString(target);\n"
+                                .. " if (specialHTMLTargets[target]) return specialHTMLTargets[target];\n"
+                                .. " if (GL.offscreenCanvases[target]) return GL.offscreenCanvases[target];\n"
+                                .. " if (typeof target === 'string' && target.length > 0) {\n"
+                                .. "  var s = target.substr(1);\n"
+                                .. "  if (GL.offscreenCanvases[s]) return GL.offscreenCanvases[s];\n"
+                                .. " }\n"
+                                .. " if (target === 'canvas') {\n"
+                                .. "  var k = Object.keys(GL.offscreenCanvases);\n"
+                                .. "  if (k.length) return GL.offscreenCanvases[k[0]];\n"
+                                .. " }\n"
+                                .. " for (var key in specialHTMLTargets) {\n"
+                                .. "  if (typeof key === 'string' && key.charAt(0) === '!') {\n"
+                                .. "   var el = specialHTMLTargets[key];\n"
+                                .. "   if (el && (el.tagName === 'CANVAS' || (typeof OffscreenCanvas !== 'undefined' && el instanceof OffscreenCanvas))) return el;\n"
+                                .. "  }\n"
+                                .. " }\n"
+                                .. " try { return typeof document !== 'undefined' ? document.querySelector(target) : undefined; }\n"
+                                .. " catch(e) { return undefined; }\n"
+                                .. "};"
+                            content = content:sub(1, pos - 1) .. new_func .. content:sub(i)
+                            io.writefile(jsfile, content)
+                        end
                     end
                 end
                 os.vcp(path.join(pluginsdir, "platforms/qtloader.js"), targetdir)