311917 2026-04-10 01:38:25 -0700 [WPE][Qt6] WPEQtView emits a premature focus change that crashes input method plugins on mouse click 2026-04-10 01:51:44 -0700 1 1 1 Unclassified WebKit WPE WebKit WebKit Nightly Build Unspecified Linux NEW P2 Critical --- 1 aiswarya.kandoth webkit-unassigned bugs-noreply oldest_to_newest 2198728 0 478992 aiswarya.kandoth 2026-04-10 01:38:25 -0700 Created attachment 478992 Complete backtrace while using a virtual keyboard with the Qt6 API. WPEQtView::mousePressEvent() calls forceActiveFocus() unconditionally before checking whether m_webView is initialized. This causes Qt to emit a focusObjectChanged signal with the not yet ready web view as the new focus object. Input method plugin that receive this signal via QInputMethod::setFocusObject() may then attempt to inspect or cast the focus object and crash because of the uninitialized state. Steps to reproduce: 1. Run the example minibrowser with the Qt6 API. 2. Add a Qt input method plugin (eg: virtual keyboard) with appropriate changes in QML (addition of InputPanel component in QML will be necessary). 3. Click on the view using a mouse before the web view is fully initialized. 4. Application crashes with a segmentation fault. Relevant backtrace: #8 WPEQtView::mousePressEvent(QMouseEvent*) () from .../qt6/qml/org/wpewebkit/qtwpe/libqtwpe.so #7 QQuickItem::forceActiveFocus(Qt::FocusReason) () #6 QQuickItem::setFocus(bool, Qt::FocusReason) () #5 QQuickDeliveryAgentPrivate::setFocusInScope(...) #4 QWindow::focusObjectChanged(QObject*) ← focus change emitted for uninitialized view → input method plugin crashes here The complete backtrace produced when using a fork of cutekeyboard (https://github.com/amarula/cutekeyboard/tree/main) with an application using the Qt6 API is attached. Note that the crash can be prevented inside an input method plugin itself using appropriate cast that tolerates unexpected object types, with qobject_cast in the case of cutekeyboard for example. However, the correct fix is not to emit the focus change prematurely. 2198731 1 aiswarya.kandoth 2026-04-10 01:51:44 -0700 Proposed fix : https://github.com/WebKit/WebKit/pull/62429 478992 2026-04-10 01:38:25 -0700 2026-04-10 01:38:25 -0700 Complete backtrace while using a virtual keyboard with the Qt6 API. backtrace-crash-on-mouse-press-libqtwpe.txt text/plain 1709 aiswarya.kandoth VGhyZWFkIDEgIm1pbmlicm93c2VyIiByZWNlaXZlZCBzaWduYWwgU0lHU0VHViwgU2VnbWVudGF0 aW9uIGZhdWx0LgogIDB4YjA1YmE2ZjggaW4gX19keW5hbWljX2Nhc3QgKCkKICAgICBmcm9tIC91 c3IvbGliL2xpYnN0ZGMrKy5zby42CiAgKGdkYikgYnQgZnVsbAogICMwICAweGIwNWJhNmY4IGlu IF9fZHluYW1pY19jYXN0ICgpCiAgICAgZnJvbSAvdXNyL2xpYi9saWJzdGRjKysuc28uNgogIE5v IHN5bWJvbCB0YWJsZSBpbmZvIGF2YWlsYWJsZS4KICAjMSAgMHhhYmFkYWVjOCBpbiBWaXJ0dWFs S2V5Ym9hcmRJbnB1dENvbnRleHQ6OnNldEZvY3VzT2JqZWN0KFFPYmplY3QqKSAoKQogICAgIGZy b20gL3Vzci9saWIvcXQ2L3BsdWdpbnMvcGxhdGZvcm1pbnB1dGNvbnRleHRzL2xpYmtleWJvYXJk cGx1Z2luLnNvCiAgTm8gc3ltYm9sIHRhYmxlIGluZm8gYXZhaWxhYmxlLgogICMyICAweGI1YzUx MzQwIGluIFFHdWlBcHBsaWNhdGlvblByaXZhdGU6Ol9xX3VwZGF0ZUZvY3VzT2JqZWN0KFFPYmpl Y3QqKSAoKQogICAgIGZyb20gL3Vzci9saWIvbGliUXQ2R3VpLnNvLjYKICBObyBzeW1ib2wgdGFi bGUgaW5mbyBhdmFpbGFibGUuCiAgIzMgIDB4YjU2YWJmZWMgaW4gdm9pZCBkb0FjdGl2YXRlPGZh bHNlPihRT2JqZWN0KiwgaW50LCB2b2lkKiopICgpCiAgICAgZnJvbSAvdXNyL2xpYi9saWJRdDZD b3JlLnNvLjYKICBObyBzeW1ib2wgdGFibGUgaW5mbyBhdmFpbGFibGUuCiAgIzQgIDB4YjVjYzk1 ODQgaW4gUVdpbmRvdzo6Zm9jdXNPYmplY3RDaGFuZ2VkKFFPYmplY3QqKSAoKQogICAgIGZyb20g L3Vzci9saWIvbGliUXQ2R3VpLnNvLjYKICBObyBzeW1ib2wgdGFibGUgaW5mbyBhdmFpbGFibGUu CiAgIzUgIDB4YjZjM2E1ZWMgaW4gUVF1aWNrRGVsaXZlcnlBZ2VudFByaXZhdGU6OnNldEZvY3Vz SW5TY29wZShRUXVpY2tJdGVtKiwgUVF1aWNrSXRlbSosIFF0OjpGb2N1c1JlYXNvbiwgUUZsYWdz PFFRdWlja0RlbGl2ZXJ5QWdlbnRQcml2YXRlOjpGb2N1c09wdGlvbj4pICgpCiAgICAgZnJvbSAv dXNyL2xpYi9saWJRdDZRdWljay5zby42CiAgTm8gc3ltYm9sIHRhYmxlIGluZm8gYXZhaWxhYmxl LgogICM2ICAweGI2YTViZWYwIGluIFFRdWlja0l0ZW06OnNldEZvY3VzKGJvb2wsIFF0OjpGb2N1 c1JlYXNvbikgKCkKICAgICBmcm9tIC91c3IvbGliL2xpYlF0NlF1aWNrLnNvLjYKICBObyBzeW1i b2wgdGFibGUgaW5mbyBhdmFpbGFibGUuCiAgIzcgIDB4YjZhNWMzOTQgaW4gUVF1aWNrSXRlbTo6 Zm9yY2VBY3RpdmVGb2N1cyhRdDo6Rm9jdXNSZWFzb24pICgpCiAgICAgZnJvbSAvdXNyL2xpYi9s aWJRdDZRdWljay5zby42CiAgTm8gc3ltYm9sIHRhYmxlIGluZm8gYXZhaWxhYmxlLgogICM4ICAw eGFjNWNlMDQ0IGluIFdQRVF0Vmlldzo6bW91c2VQcmVzc0V2ZW50KFFNb3VzZUV2ZW50KikgKCkK ICAgICBmcm9tIC91c3IvbGliL3F0Ni9xbWwvb3JnL3dwZXdlYmtpdC9xdHdwZS9saWJxdHdwZS5z bwogIE5vIHN5bWJvbCB0YWJsZSBpbmZvIGF2YWlsYWJsZS4KICAjOSAgMHhiNmE1YzY4YyBpbiBR UXVpY2tJdGVtUHJpdmF0ZTo6ZGVsaXZlclBvaW50ZXJFdmVudChRRXZlbnQqKSAoKQogICAgIGZy b20gL3Vzci9saWIvbGliUXQ2UXVpY2suc28uNgogIE5vIHN5bWJvbCB0YWJsZSBpbmZvIGF2YWls YWJsZS4KICAjMTAgMHhiNmE2NDhiOCBpbiBRUXVpY2tJdGVtOjpldmVudChRRXZlbnQqKSAoKQo=