Autorefresh after image pages to get rid of ghosting artifacts (#116)

src/CrossPointSettings.h

@@ -237,6 +237,8 @@ class CrossPointSettings {
   uint8_t sleepTimeout = SLEEP_10_MIN;
   // E-ink refresh frequency (default 15 pages)
   uint8_t refreshFrequency = REFRESH_15;
+  // Perform a half refresh on the page immediately following an EPUB page that displayed images.
+  uint8_t halfRefreshAfterImagePage = 1;
   uint8_t hyphenationEnabled = 0;
 
   // Reader screen margin settings

src/SettingsList.h

@@ -72,6 +72,9 @@ inline const std::vector<SettingInfo> list = {
         {StrId::STR_PAGES_1, StrId::STR_PAGES_5, StrId::STR_PAGES_10, StrId::STR_PAGES_15, StrId::STR_PAGES_30},
         "refreshFrequency", StrId::STR_CAT_DISPLAY)
         .withSubcategory(StrId::STR_MENU_DISP_REFRESH),
+    SettingInfo::Toggle(StrId::STR_REFRESH_AFTER_IMAGE_PAGES, &CrossPointSettings::halfRefreshAfterImagePage,
+                        "halfRefreshAfterImagePage", StrId::STR_CAT_DISPLAY)
+        .withSubcategory(StrId::STR_MENU_DISP_REFRESH),
     SettingInfo::Toggle(StrId::STR_SUNLIGHT_FADING_FIX, &CrossPointSettings::fadingFix, "fadingFix",
                         StrId::STR_CAT_DISPLAY),
     SettingInfo::Enum(StrId::STR_UI_THEME, &CrossPointSettings::uiTheme,

src/activities/reader/EpubReaderActivity.cpp

@@ -1145,6 +1145,8 @@ void EpubReaderActivity::renderContents(std::unique_ptr<Page> page, const int or
 
   // Force special handling for pages with images when anti-aliasing is on
   bool imagePageWithAA = page->hasImages() && SETTINGS.textAntiAliasing;
+  bool forceHalfRefreshThisPage = pendingHalfRefreshAfterImagePage && SETTINGS.halfRefreshAfterImagePage;
+  pendingHalfRefreshAfterImagePage = false;
 
   logReaderMemSnapshot("before_bw_render");
   page->render(renderer, SETTINGS.getReaderFontId(), orientedMarginLeft, orientedMarginTop);
@@ -1172,6 +1174,12 @@ void EpubReaderActivity::renderContents(std::unique_ptr<Page> page, const int or
       renderer.displayBuffer(HalDisplay::HALF_REFRESH);
     }
     // Double FAST_REFRESH handles ghosting for image pages; don't count toward full refresh cadence
+    if (forceHalfRefreshThisPage) {
+      pagesUntilFullRefresh = SETTINGS.getRefreshFrequency();
+    }
+  } else if (forceHalfRefreshThisPage) {
+    renderer.displayBuffer(HalDisplay::HALF_REFRESH);
+    pagesUntilFullRefresh = SETTINGS.getRefreshFrequency();
   } else {
     ReaderUtils::displayWithRefreshCycle(renderer, pagesUntilFullRefresh);
   }
@@ -1183,6 +1191,10 @@ void EpubReaderActivity::renderContents(std::unique_ptr<Page> page, const int or
   const auto tBwStore = millis();
   logReaderMemSnapshot("bw_store_end");
 
+  if (page->hasImages() && SETTINGS.imageRendering != CrossPointSettings::IMAGES_SUPPRESS) {
+    pendingHalfRefreshAfterImagePage = true;
+  }
+
   // grayscale rendering
   // TODO: Only do this if font supports it
   if (SETTINGS.textAntiAliasing) {

src/activities/reader/EpubReaderActivity.h

@@ -37,6 +37,7 @@ class EpubReaderActivity final : public Activity {
   int cachedChapterTotalPageCount = 0;
   unsigned long lastPageTurnTime = 0UL;
   unsigned long pageTurnDuration = 0UL;
+  bool pendingHalfRefreshAfterImagePage = false;
   // Signals that the next render should reposition within the newly loaded section
   // based on a cross-book percentage jump.
   bool pendingPercentJump = false;