From 95eafaecd15811e1738ab9c7d821cf85e6fb9506 Mon Sep 17 00:00:00 2001
From: jpirnay <jens@pirnay.com>
Date: Mon, 4 May 2026 15:41:10 +0200
Subject: [PATCH] Smarter cache eviction

---
 lib/EpdFont/FontDecompressor.cpp     | 38 ++++++++++++++++++++++------
 lib/EpdFont/FontDecompressor.h       |  2 +-
 lib/GfxRenderer/FontCacheManager.cpp |  7 +++--
 3 files changed, 36 insertions(+), 11 deletions(-)

diff --git a/lib/EpdFont/FontDecompressor.cpp b/lib/EpdFont/FontDecompressor.cpp
index e95883ab..1b347673 100644
--- a/lib/EpdFont/FontDecompressor.cpp
+++ b/lib/EpdFont/FontDecompressor.cpp
@@ -219,13 +219,6 @@ int32_t FontDecompressor::findGlyphIndex(const EpdFontData* fontData, uint32_t c
 int FontDecompressor::prewarmCache(const EpdFontData* fontData, const char* utf8Text) {
   if (!fontData || !fontData->groups || !utf8Text) return 0;
 
-  // Allocate the next available slot (caller must call freePageBuffer/clearCache to reset)
-  if (pageSlotCount >= MAX_PAGE_SLOTS) {
-    LOG_ERR("FDC", "All %u page buffer slots full, cannot prewarm fontData=%p", MAX_PAGE_SLOTS, (void*)fontData);
-    return -1;
-  }
-  PageSlot& slot = pageSlots[pageSlotCount];
-
   // Step 1: Collect unique glyph indices needed for this page
   uint32_t neededGlyphs[MAX_PAGE_GLYPHS];
   uint16_t glyphCount = 0;
@@ -239,7 +232,29 @@ int FontDecompressor::prewarmCache(const EpdFontData* fontData, const char* utf8
     int32_t glyphIdx = findGlyphIndex(fontData, cp);
     if (glyphIdx < 0) continue;
 
-    // Deduplicate
+    // Deduplicate against already prewarmed slots
+    bool alreadyCached = false;
+    for (uint8_t s = 0; s < pageSlotCount; s++) {
+      if (pageSlots[s].fontData != fontData || pageSlots[s].glyphCount == 0) continue;
+      int left = 0, right = pageSlots[s].glyphCount - 1;
+      while (left <= right) {
+        int mid = left + (right - left) / 2;
+        if (pageSlots[s].glyphs[mid].glyphIndex == static_cast<uint32_t>(glyphIdx)) {
+          if (pageSlots[s].glyphs[mid].bufferOffset != UINT32_MAX) {
+            alreadyCached = true;
+          }
+          break;
+        }
+        if (pageSlots[s].glyphs[mid].glyphIndex < static_cast<uint32_t>(glyphIdx))
+          left = mid + 1;
+        else
+          right = mid - 1;
+      }
+      if (alreadyCached) break;
+    }
+    if (alreadyCached) continue;
+
+    // Deduplicate within the current page pass
     bool found = false;
     for (uint16_t i = 0; i < glyphCount; i++) {
       if (neededGlyphs[i] == static_cast<uint32_t>(glyphIdx)) {
@@ -297,6 +312,13 @@ int FontDecompressor::prewarmCache(const EpdFontData* fontData, const char* utf8
 
   if (glyphCount == 0) return 0;
 
+  // Allocate the next available slot
+  if (pageSlotCount >= MAX_PAGE_SLOTS) {
+    LOG_ERR("FDC", "All %u page buffer slots full, cannot prewarm fontData=%p", MAX_PAGE_SLOTS, (void*)fontData);
+    return -1;
+  }
+  PageSlot& slot = pageSlots[pageSlotCount];
+
   // Step 2: Compute total buffer size and collect unique groups
   uint32_t totalBytes = 0;
   uint16_t neededGroups[128];
diff --git a/lib/EpdFont/FontDecompressor.h b/lib/EpdFont/FontDecompressor.h
index afb9c61c..8f574dba 100644
--- a/lib/EpdFont/FontDecompressor.h
+++ b/lib/EpdFont/FontDecompressor.h
@@ -7,7 +7,7 @@
 class FontDecompressor {
  public:
   static constexpr uint16_t MAX_PAGE_GLYPHS = 512;
-  static constexpr uint8_t MAX_PAGE_SLOTS = 8;  // Provide enough slots for heavily stylized HTML pages
+  static constexpr uint8_t MAX_PAGE_SLOTS = 4;  // One per font style (R/B/I/BI)
 
   FontDecompressor() = default;
   ~FontDecompressor();
diff --git a/lib/GfxRenderer/FontCacheManager.cpp b/lib/GfxRenderer/FontCacheManager.cpp
index 36620f2e..ff13fb8d 100644
--- a/lib/GfxRenderer/FontCacheManager.cpp
+++ b/lib/GfxRenderer/FontCacheManager.cpp
@@ -24,8 +24,6 @@ void FontCacheManager::clearCache() {
 }
 
 void FontCacheManager::prewarmCache(int fontId, const char* utf8Text, uint8_t styleMask) {
-  clearCache();
-
   // SD card font prewarm path: prewarm all requested styles in one call
   auto sdIt = sdCardFonts_.find(fontId);
   if (sdIt != sdCardFonts_.end()) {
@@ -52,6 +50,11 @@ void FontCacheManager::prewarmCache(int fontId, const char* utf8Text, uint8_t st
     const EpdFontData* data = fontMap_.at(fontId).getData(style);
     if (!data || !data->groups) continue;
     int missed = fontDecompressor_->prewarmCache(data, utf8Text);
+    if (missed < 0) {
+      LOG_DBG("FCM", "prewarmCache: Cache slots full! Clearing and retrying slot allocation.");
+      clearCache();
+      missed = fontDecompressor_->prewarmCache(data, utf8Text);
+    }
     if (missed > 0) {
       LOG_DBG("FCM", "prewarmCache: %d glyph(s) not cached for style %d", missed, i);
     }