Provide visual progress feedback during indexing

lib/Epub/Epub/parsers/ChapterHtmlSlimParser.h

@@ -26,7 +26,7 @@ class ChapterHtmlSlimParser {
   const std::string& filepath;
   GfxRenderer& renderer;
   std::function<void(std::unique_ptr<Page>)> completePageFn;
-  std::function<void()> popupFn;  // Popup callback
+  std::function<void(int)> progressFn;  // Progress callback (0-100)
   int depth = 0;
   int skipUntilDepth = INT_MAX;
   int boldUntilDepth = INT_MAX;
@@ -102,7 +102,8 @@ class ChapterHtmlSlimParser {
                                  const std::function<void(std::unique_ptr<Page>)>& completePageFn,
                                  const bool embeddedStyle, const std::string& contentBase,
                                  const std::string& imageBasePath, const uint8_t imageRendering = 0,
-                                 const std::function<void()>& popupFn = nullptr, const CssParser* cssParser = nullptr)
+                                 const std::function<void(int)>& progressFn = nullptr,
+                                 const CssParser* cssParser = nullptr)
 
       : epub(epub),
         filepath(filepath),
@@ -115,7 +116,7 @@ class ChapterHtmlSlimParser {
         viewportHeight(viewportHeight),
         hyphenationEnabled(hyphenationEnabled),
         completePageFn(completePageFn),
-        popupFn(popupFn),
+        progressFn(progressFn),
         cssParser(cssParser),
         embeddedStyle(embeddedStyle),
         imageRendering(imageRendering),