CEF Forum

Strange behavior of the CefBrowserHost::SendKeyEvent method.

Hello.

After updating the cef framework from version 3865 to version 4103.
When a character input event is generated using the method CefBrowserHost::SendKeyEvent.
Instead of letters (a,b,c), numbers appear in the input field.

cefsimple, lubuntu linux 19 OS x64.

The code below displays '123123123' in the Google input field instead of the 'abcabcabc'.

Code: Select all

void SimpleHandler::OnLoadingStateChange(CefRefPtr<CefBrowser> browser,
                                         bool isLoading,
                                         bool canGoBack,
                                         bool canGoForward) {
    LOG(INFO) << "SimpleApp::OnLoadingStateChange";
    LOG(INFO) << isLoading;

    if (false == isLoading) {
        CefKeyEvent keyEvent;
        char16 chr = 'a';
        char16 chr2 = 'b';
        char16 chr3 = 'c';

        keyEvent.type = KEYEVENT_CHAR;
        keyEvent.modifiers = 0;
        keyEvent.unmodified_character = chr;
        keyEvent.is_system_key = false;
        keyEvent.focus_on_editable_field = true;
        CefRefPtr<CefBrowserHost> browserHost = browser->GetHost();

        for (int i = 0; i < 9; ++i) {
            if (0 == (i % 3)) {
                keyEvent.character = chr;
                int lKeyCode = static_cast<int>(keyEvent.character);
                keyEvent.windows_key_code = lKeyCode;
                keyEvent.native_key_code = lKeyCode;
            }
            else if (1 == (i % 3)) {
                keyEvent.character = chr2;
                int lKeyCode = static_cast<int>(keyEvent.character);
                keyEvent.windows_key_code = lKeyCode;
                keyEvent.native_key_code = lKeyCode;
            }
            else if (2 == (i % 3)) {
                keyEvent.character = chr3;
                int lKeyCode = static_cast<int>(keyEvent.character);
                keyEvent.windows_key_code = lKeyCode;
                keyEvent.native_key_code = lKeyCode;
            }
            browserHost->SendKeyEvent(keyEvent);
        }
    }
}

You can hook up to key events using CefKeyboardHandler in a windowed application and compare events. Note that SendKeyEvent is for off-screen rendering, any other usage I guess is undefined.

Just to give some more background information about this, we have a demo in the CEF4Delphi project that uses SendKeyEvent in a windowed browser with CEF 83.4.2.

I just tested this feature again in Windows 7 and it works correctly.

Hook up with CefKeyboardHandler::OnPreKeyEvent and CefKeyboardHandler::OnKeyEvent shows that strange character code conversions are occurring.


Code fragment from cefsimple.

Code: Select all

void SimpleHandler::OnLoadingStateChange(CefRefPtr<CefBrowser> browser,
                                         bool isLoading,
                                         bool canGoBack,
                                         bool canGoForward) {
    if (false == isLoading) {
        LOG(INFO) << "SimpleApp::OnLoadingStateChange";

        CefKeyEvent keyEvent;
        char16 chr = 'a';
        char16 chr2 = 'b';
        char16 chr3 = 'z';

        keyEvent.type = KEYEVENT_CHAR;
        keyEvent.modifiers = 0;
        keyEvent.unmodified_character = chr;
        keyEvent.is_system_key = false;
        keyEvent.focus_on_editable_field = true;
        CefRefPtr<CefBrowserHost> browserHost = browser->GetHost();

        LOG(INFO) << "keyEvent.type " << KEYEVENT_CHAR;
        LOG(INFO) << "keyEvent.modifiers " << keyEvent.modifiers;
        LOG(INFO) << "keyEvent.unmodified_character " << keyEvent.unmodified_character;
        LOG(INFO) << "keyEvent.is_system_key " << keyEvent.is_system_key;
        LOG(INFO) << "keyEvent.focus_on_editable_field " << keyEvent.focus_on_editable_field;

        for (int i = 0; i < 9; ++i) {
            if (0 == (i % 3)) {
                keyEvent.character = chr;
                int lKeyCode = static_cast<int>(keyEvent.character);
                keyEvent.windows_key_code = lKeyCode;
                keyEvent.native_key_code = lKeyCode;

                LOG(INFO) << "keyEvent.character " << keyEvent.character;
                LOG(INFO) << "char(keyEvent.character) " << static_cast<char>(keyEvent.character);
                LOG(INFO) << "keyEvent.windows_key_code " << keyEvent.windows_key_code;
                LOG(INFO) << "keyEvent.native_key_code " << keyEvent.native_key_code;
            }
            else if (1 == (i % 3)) {
                keyEvent.character = chr2;
                int lKeyCode = static_cast<int>(keyEvent.character);
                keyEvent.windows_key_code = lKeyCode;
                keyEvent.native_key_code = lKeyCode;

                LOG(INFO) << "keyEvent.character " << keyEvent.character;
                LOG(INFO) << "char(keyEvent.character) " << static_cast<char>(keyEvent.character);
                LOG(INFO) << "keyEvent.windows_key_code " << keyEvent.windows_key_code;
                LOG(INFO) << "keyEvent.native_key_code " << keyEvent.native_key_code;
            }
            else if (2 == (i % 3)) {
                keyEvent.character = chr3;
                int lKeyCode = static_cast<int>(keyEvent.character);
                keyEvent.windows_key_code = lKeyCode;
                keyEvent.native_key_code = lKeyCode;

                LOG(INFO) << "keyEvent.character " << keyEvent.character;
                LOG(INFO) << "char(keyEvent.character) " << static_cast<char>(keyEvent.character);
                LOG(INFO) << "keyEvent.windows_key_code " << keyEvent.windows_key_code;
                LOG(INFO) << "keyEvent.native_key_code " << keyEvent.native_key_code;
            }
            browserHost->SendKeyEvent(keyEvent);
        }
    }
}
//------------------

bool SimpleHandler::OnPreKeyEvent(CefRefPtr<CefBrowser> browser,
                                      const CefKeyEvent& event,
                                      CefEventHandle os_event,
                                      bool* is_keyboard_shortcut) {
    CEF_REQUIRE_UI_THREAD();
    LOG(INFO) << "SimpleHandler::OnPreKeyEvent";

    LOG(INFO) << "CefKeyEvent";
    LOG(INFO) << "type " << event.type;
    LOG(INFO) << "character " << event.character;
    LOG(INFO) << "char(character) " << static_cast<char>(event.character);
    LOG(INFO) << "modifiers " << event.modifiers;
    LOG(INFO) << "is_system_key " << event.is_system_key;
    LOG(INFO) << "native_key_code " << event.native_key_code;
    LOG(INFO) << "windows_key_code " << event.windows_key_code;
    LOG(INFO) << "unmodified_character " << event.unmodified_character;
    LOG(INFO) << "focus_on_editable_field " << event.focus_on_editable_field;

    bool result {false};
    return result;
}
//------------------

bool SimpleHandler::OnKeyEvent(CefRefPtr<CefBrowser> browser,
                                   const CefKeyEvent& event,
                                   CefEventHandle os_event) {
    CEF_REQUIRE_UI_THREAD();
    LOG(INFO) << "SimpleHandler::OnKeyEvent";

    LOG(INFO) << "CefKeyEvent";
    LOG(INFO) << "type " << event.type;
    LOG(INFO) << "character " << event.character;
    LOG(INFO) << "char(character) " << static_cast<char>(event.character);
    LOG(INFO) << "modifiers " << event.modifiers;
    LOG(INFO) << "is_system_key " << event.is_system_key;
    LOG(INFO) << "native_key_code " << event.native_key_code;
    LOG(INFO) << "windows_key_code " << event.windows_key_code;
    LOG(INFO) << "unmodified_character " << event.unmodified_character;
    LOG(INFO) << "focus_on_editable_field " << event.focus_on_editable_field;

    bool result {false};
    return result;
}
//------------------


The background is CEF 83.4.0+gfd6631b+chromium-83.0.4103.106, Lubuntu linux 19.10 x64, I don’t know what features of the system can affect anymore.

I think I’ll have to use javascript events generation for the keyboard.

Good day.
I decided to work around this strange problem by using the javascript property document.activeElement.value to fill in the selected text fields on the web page.

For example.

Code: Select all

CefString code {document.activeElement.value += "string1"};
browser->GetMainFrame()->ExecuteJavaScript(code,CefString(),0);


Used windowless (off-screen) rendering mode. Problem solved.