From 3c423061f6dc186c200535b975cdf4a9d0488e7c Mon Sep 17 00:00:00 2001
From: Le Tan <tamlokveer@gmail.com>
Date: Wed, 22 Aug 2018 20:08:58 +0800
Subject: [PATCH] LivePreview: update live preview when using old cache

---
 src/vlivepreviewhelper.cpp | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/src/vlivepreviewhelper.cpp b/src/vlivepreviewhelper.cpp
index bdf4908a..a72bb996 100644
--- a/src/vlivepreviewhelper.cpp
+++ b/src/vlivepreviewhelper.cpp
@@ -169,9 +169,16 @@ void VLivePreviewHelper::updateCodeBlocks(TimeStamp p_timeStamp, const QVector<V
         m_codeBlocks.append(CodeBlockPreviewInfo(vcb));
         int idx = m_codeBlocks.size() - 1;
 
+        bool oldCache = false;
         auto it = m_cache.find(text);
         if (it != m_cache.end()) {
             QSharedPointer<CodeBlockImageCacheEntry> &entry = it.value();
+            // If this cache is not used at the last timestamp, we still need to
+            // update the live preview.
+            if (entry->m_ts < m_timeStamp - 1) {
+                oldCache = true;
+            }
+
             entry->m_ts = m_timeStamp;
             cached = true;
             m_codeBlocks[idx].setImageData(entry->m_imgFormat, entry->m_imgData);
@@ -193,7 +200,7 @@ void VLivePreviewHelper::updateCodeBlocks(TimeStamp p_timeStamp, const QVector<V
             && livePreview
             && vcb.m_startBlock <= cursorBlock
             && vcb.m_endBlock >= cursorBlock) {
-            if (lastIndex == idx && cached) {
+            if (lastIndex == idx && cached && !oldCache) {
                 needUpdate = false;
             }