Use native candidate actions and harden frontend resource loading

tests/testm3uicandidatemenu.cpp

@@ -0,0 +1,63 @@
+#include <memory>
+#include <vector>
+
+#include "fcitx-utils/log.h"
+#include "fcitx/candidatelist.h"
+#include "../src/candidatemenu.h"
+
+using namespace fcitx;
+using namespace fcitx::m3ui;
+
+namespace {
+
+class EngineActions : public ActionableCandidateList {
+public:
+    explicit EngineActions(bool available) : available_(available) {}
+    bool hasAction(const CandidateWord &) const override { return available_; }
+    std::vector<CandidateAction>
+    candidateActions(const CandidateWord &) const override {
+        CandidateAction action;
+        action.setId(-42); // IDs must not be interpreted by the UI.
+        action.setText("Engine action");
+        CandidateAction separator;
+        separator.setSeparator(true);
+        return {separator, action};
+    }
+    void triggerAction(const CandidateWord &, int) override {}
+
+private:
+    bool available_;
+};
+
+} // namespace
+
+int main() {
+    CommonCandidateList list;
+    list.setPageSize(5);
+    list.append<DisplayOnlyCandidateWord>(Text("候选词"));
+    list.append<DisplayOnlyCandidateWord>(Text("保留的词"));
+
+    // Never invent a blocking action when ranking operations are unavailable.
+    auto menu = candidateMenu(list, list.candidate(0));
+    FCITX_ASSERT(menu.actions.empty());
+
+    // An engine can have an action interface but no actions for this word.
+    list.setActionableImpl(std::make_unique<EngineActions>(false));
+    menu = candidateMenu(list, list.candidate(0));
+    FCITX_ASSERT(menu.actions.empty());
+
+    // Keep engine actions and IDs intact; omit separators, never append blocking.
+    list.setActionableImpl(std::make_unique<EngineActions>(true));
+    menu = candidateMenu(list, list.candidate(0));
+    FCITX_ASSERT(menu.actions.size() == 1);
+    FCITX_ASSERT(menu.actions[0].id() == -42);
+    FCITX_ASSERT(menu.actions[0].text() == "Engine action");
+    FCITX_ASSERT(list.size() == 2);
+    FCITX_ASSERT(list.candidate(0).text().toString() == "候选词");
+
+    // Do not offer an ineffective block action for a read-only list.
+    DisplayOnlyCandidateList readOnly;
+    readOnly.setContent(std::vector<std::string>{"只读"});
+    menu = candidateMenu(readOnly, readOnly.candidate(0));
+    FCITX_ASSERT(menu.actions.empty());
+}