From fb3b51c123bdd5a7f1ea1aba03af0b78b8147eee Mon Sep 17 00:00:00 2001
From: Miho1254 <nguyenha280876@gmail.com>
Date: Thu, 5 Mar 2026 11:19:01 +0700
Subject: [PATCH] fix: improve key buffering and state recovery to prevent
 dropped keys

---
 src/lotus-state.cpp | 43 +++++++++++++++++++++++++++++++++++++++----
 src/lotus-state.h   |  5 +++--
 2 files changed, 42 insertions(+), 6 deletions(-)

diff --git a/src/lotus-state.cpp b/src/lotus-state.cpp
index 0869507..6fa2054 100644
--- a/src/lotus-state.cpp
+++ b/src/lotus-state.cpp
@@ -559,7 +559,7 @@ namespace fcitx {
             } else {
                 std::string keyUtf8Check = Key::keySymToUTF8(currentSym);
                 if (!keyUtf8Check.empty() && buffered_keys_.size() < MAX_BUFFERED_KEYS) {
-                    buffered_keys_.push_back(currentSym);
+                    buffered_keys_.push_back({currentSym, keyEvent.rawKey().states()});
                 }
                 keyEvent.filterAndAccept();
             }
@@ -641,9 +641,21 @@ namespace fcitx {
 
         auto commitAfterReplay = UniqueCPtr<char>(EnginePullCommit(lotusEngine_.handle()));
         if (commitAfterReplay && commitAfterReplay.get()[0]) {
+            std::string commitStr = commitAfterReplay.get();
+            std::string commonPrefix, deletedPart, addedPart;
+            compareAndSplitStrings(oldPreBuffer_, commitStr, commonPrefix, deletedPart, addedPart);
+
+            if (!deletedPart.empty()) {
+                performReplacement(deletedPart, addedPart);
+            } else if (!addedPart.empty()) {
+                ic_->commitString(addedPart);
+            }
+
             history_.clear();
             ResetEngine(lotusEngine_.handle());
             oldPreBuffer_.clear();
+
+            keyEvent.filterAndAccept();
             return;
         }
 
@@ -997,13 +1009,14 @@ namespace fcitx {
         auto keys = std::move(buffered_keys_);
         buffered_keys_.clear();
         for (size_t i = 0; i < keys.size(); ++i) {
-            KeySym      sym     = keys[i];
+            KeySym      sym     = static_cast<KeySym>(keys[i].sym);
+            uint32_t    state   = keys[i].state;
             std::string keyUtf8 = Key::keySymToUTF8(sym);
             if (keyUtf8.empty()) {
                 continue;
             }
 
-            bool processed = EngineProcessKeyEvent(lotusEngine_.handle(), sym, 0);
+            bool processed = EngineProcessKeyEvent(lotusEngine_.handle(), sym, state);
 
             auto commitF = UniqueCPtr<char>(EnginePullCommit(lotusEngine_.handle()));
             if (commitF && commitF.get()[0]) {
@@ -1019,10 +1032,12 @@ namespace fcitx {
                         }
                     }
                     performReplacement(deletedPart, addedPart);
+                    history_.clear();
+                    ResetEngine(lotusEngine_.handle());
+                    oldPreBuffer_.clear();
                     return;
                 } else if (!addedPart.empty()) {
                     ic_->commitString(addedPart);
-                    oldPreBuffer_ = commitStr;
                 }
 
                 history_.clear();
@@ -1043,6 +1058,26 @@ namespace fcitx {
 
             auto commitAfterReplay = UniqueCPtr<char>(EnginePullCommit(lotusEngine_.handle()));
             if (commitAfterReplay && commitAfterReplay.get()[0]) {
+                std::string commitStr = commitAfterReplay.get();
+                std::string commonPrefix, deletedPart, addedPart;
+                compareAndSplitStrings(oldPreBuffer_, commitStr, commonPrefix, deletedPart, addedPart);
+
+                if (!deletedPart.empty()) {
+                    // Re-buffer remaining keys for next replay cycle.
+                    for (size_t j = i + 1; j < keys.size(); ++j) {
+                        if (buffered_keys_.size() < MAX_BUFFERED_KEYS) {
+                            buffered_keys_.push_back(keys[j]);
+                        }
+                    }
+                    performReplacement(deletedPart, addedPart);
+                    history_.clear();
+                    ResetEngine(lotusEngine_.handle());
+                    oldPreBuffer_.clear();
+                    return;
+                } else if (!addedPart.empty()) {
+                    ic_->commitString(addedPart);
+                }
+
                 history_.clear();
                 ResetEngine(lotusEngine_.handle());
                 oldPreBuffer_.clear();
diff --git a/src/lotus-state.h b/src/lotus-state.h
index 63c834e..6e87ecc 100644
--- a/src/lotus-state.h
+++ b/src/lotus-state.h
@@ -17,6 +17,7 @@
 
 #include "lotus.h"
 #include "emoji.h"
+#include "lotus-utils.h"
 #include <fcitx-utils/key.h>
 #include <fcitx/inputcontext.h>
 #include <fcitx/inputcontextproperty.h>
@@ -199,7 +200,7 @@ namespace fcitx {
         friend class LotusEngine;
 
       private:
-        static constexpr size_t MAX_BUFFERED_KEYS = 10;
+        static constexpr size_t MAX_BUFFERED_KEYS = 50;
 
         LotusEngine*            engine_;
         InputContext*           ic_;
@@ -213,7 +214,7 @@ namespace fcitx {
         std::string             emojiBuffer_;
         std::vector<EmojiEntry> emojiCandidates_;
         bool                    waitAck_ = false;
-        std::vector<KeySym>     buffered_keys_; ///< Keystrokes buffered during replacement
+        std::vector<KeyEntry>   buffered_keys_; ///< Keystrokes buffered during replacement
     };
 
 } // namespace fcitx