feat: Add option to switch behavior for "back to browser / home" in Reader activity (#2366)

## Summary

It would be nice to switch back to the file list from an Reader activity
via a short back button press. This change adds an Reader option to
switch the default behavior, so a short back button press in the Reader
activity can now go back to the file list, and a long press on back goes
back to the home view. This does a fair bit of refactoring, introducing
a new constant for the ms limit.

* **What changes are included?**

- Changes to the translation
- Additional global Reader option 
- Refactoring of the back button behavior in the Reader activity

lib/I18n/translations/english.yaml

@@ -343,6 +343,7 @@ STR_EMBEDDED_STYLE: "Embedded Style"
 STR_FOCUS_READING: "Focus Reading"
 STR_OPDS_SERVER_URL: "OPDS Server URL"
 STR_PWR_BTN_FOOTNOTE_BACK: "Quick-return from footnotes"
+STR_BACK_SHORT_TO_FILE_BROWSER: "Short Back to File Browser"
 STR_SET_SLEEP_COVER: "Set Cover"
 STR_FOOTNOTES: "Footnotes"
 STR_NO_FOOTNOTES: "No footnotes on this page"

lib/I18n/translations/german.yaml

@@ -315,6 +315,7 @@ STR_BOOK_S_STYLE: "Buch-Stil"
 STR_EMBEDDED_STYLE: "Eingebetteter Stil"
 STR_FOCUS_READING: "Fokus-Lesen"
 STR_OPDS_SERVER_URL: "OPDS-Server-URL"
+STR_BACK_SHORT_TO_FILE_BROWSER: "Kurz zurück drücken zum Datei-Browser"
 STR_SET_SLEEP_COVER: "Wähle Cover"
 STR_SCREENSHOT_BUTTON: "Screenshot aufnehmen"
 STR_FOOTNOTES: "Fußnoten"

src/CrossPointSettings.h

@@ -271,6 +271,8 @@ class CrossPointSettings {
   uint8_t removeReadBooksFromRecents = 0;
   // Move epub to /Read/ folder on SD card when finished (0 = disabled, 1 = enabled)
   uint8_t moveFinishedToReadFolder = 0;
+  // Short press Back goes to file browser instead of home (0 = disabled, 1 = enabled)
+  uint8_t backShortToFileBrowser = 0;
   // Image rendering mode in EPUB reader
   uint8_t imageRendering = IMAGES_DISPLAY;
   // Tilt-based page turning (X3 only — requires QMI8658 IMU)

src/SettingsList.h

@@ -181,6 +181,8 @@ inline std::vector<SettingInfo> getSettingsList(const SdCardFontRegistry* regist
             "shortPwrBtn", StrId::STR_CAT_CONTROLS),
         SettingInfo::Toggle(StrId::STR_PWR_BTN_FOOTNOTE_BACK, &CrossPointSettings::pwrBtnFootnoteBack,
                             "pwrBtnFootnoteBack", StrId::STR_CAT_CONTROLS),
+        SettingInfo::Toggle(StrId::STR_BACK_SHORT_TO_FILE_BROWSER, &CrossPointSettings::backShortToFileBrowser,
+                            "backShortToFileBrowser", StrId::STR_CAT_CONTROLS),
 
         // --- System ---
         SettingInfo::Value(

src/activities/reader/EpubReaderActivity.cpp

@@ -448,20 +448,15 @@ void EpubReaderActivity::loop() {
     }
   }
 
-  // Long press BACK (1s+) goes to file selection
-  if (mappedInput.isPressed(MappedInputManager::Button::Back) && mappedInput.getHeldTime() >= ReaderUtils::GO_HOME_MS) {
-    activityManager.goToFileBrowser(epub ? epub->getPath() : "");
+  // Short press Back restores position when viewing a footnote (takes priority over navigation)
+  if (footnoteDepth > 0 && mappedInput.wasReleased(MappedInputManager::Button::Back) &&
+      mappedInput.getHeldTime() < ReaderUtils::GO_BACK_OR_HOME_MS) {
+    restoreSavedPosition();
     return;
   }
 
-  // Short press BACK goes directly to home (or restores position if viewing footnote)
-  if (mappedInput.wasReleased(MappedInputManager::Button::Back) &&
-      mappedInput.getHeldTime() < ReaderUtils::GO_HOME_MS) {
-    if (footnoteDepth > 0) {
-      restoreSavedPosition();
-      return;
-    }
-    onGoHome();
+  if (ReaderUtils::handleBackNavigation(mappedInput, activityManager, epub ? epub->getPath().c_str() : "",
+                                        {this, [](void* ctx) { static_cast<EpubReaderActivity*>(ctx)->onGoHome(); }})) {
     return;
   }
 

src/activities/reader/ReaderUtils.h

@@ -6,10 +6,12 @@
 #include <Logging.h>
 
 #include "MappedInputManager.h"
+#include "activities/ActivityManager.h"
 
 namespace ReaderUtils {
 
 constexpr unsigned long GO_HOME_MS = 1000;
+constexpr unsigned long GO_BACK_OR_HOME_MS = GO_HOME_MS;
 constexpr unsigned long SKIP_HOLD_MS = 700;
 constexpr unsigned long BOOKMARK_HOLD_MS = 400;
 constexpr unsigned long BOOKMARK_MESSAGE_DURATION_MS = 2500;
@@ -96,4 +98,37 @@ void renderAntiAliased(GfxRenderer& renderer, RenderFn&& renderFn) {
   renderer.restoreBwBuffer();
 }
 
+struct BackNavCallback {
+  void* ctx;
+  void (*fn)(void*);
+};
+
+// Returns true if the back button was consumed (caller should return).
+// Long press (>= GO_BACK_OR_HOME_MS):
+// - default: go to file browser
+// - with backShortToFileBrowser: go home
+// Short press (< GO_BACK_OR_HOME_MS):
+// - default: go home
+// - with backShortToFileBrowser: go to file browser.
+inline bool handleBackNavigation(const MappedInputManager& mappedInput, ActivityManager& activityManager,
+                                 const char* filePath, BackNavCallback goHome) {
+  if (mappedInput.isPressed(MappedInputManager::Button::Back) && mappedInput.getHeldTime() >= GO_BACK_OR_HOME_MS) {
+    if (SETTINGS.backShortToFileBrowser) {
+      goHome.fn(goHome.ctx);
+    } else {
+      activityManager.goToFileBrowser(filePath);
+    }
+    return true;
+  }
+  if (mappedInput.wasReleased(MappedInputManager::Button::Back) && mappedInput.getHeldTime() < GO_BACK_OR_HOME_MS) {
+    if (SETTINGS.backShortToFileBrowser) {
+      activityManager.goToFileBrowser(filePath);
+    } else {
+      goHome.fn(goHome.ctx);
+    }
+    return true;
+  }
+  return false;
+}
+
 }  // namespace ReaderUtils

src/activities/reader/TxtReaderActivity.cpp

@@ -60,16 +60,8 @@ void TxtReaderActivity::onExit() {
 }
 
 void TxtReaderActivity::loop() {
-  // Long press BACK (1s+) goes to file selection
-  if (mappedInput.isPressed(MappedInputManager::Button::Back) && mappedInput.getHeldTime() >= ReaderUtils::GO_HOME_MS) {
-    activityManager.goToFileBrowser(txt ? txt->getPath() : "");
-    return;
-  }
-
-  // Short press BACK goes directly to home
-  if (mappedInput.wasReleased(MappedInputManager::Button::Back) &&
-      mappedInput.getHeldTime() < ReaderUtils::GO_HOME_MS) {
-    onGoHome();
+  if (ReaderUtils::handleBackNavigation(mappedInput, activityManager, txt ? txt->getPath().c_str() : "",
+                                        {this, [](void* ctx) { static_cast<TxtReaderActivity*>(ctx)->onGoHome(); }})) {
     return;
   }
 

src/activities/reader/XtcReaderActivity.cpp

@@ -101,16 +101,8 @@ void XtcReaderActivity::loop() {
     openChapterSelection();
   }
 
-  // Long press BACK (1s+) goes to file selection
-  if (mappedInput.isPressed(MappedInputManager::Button::Back) && mappedInput.getHeldTime() >= ReaderUtils::GO_HOME_MS) {
-    activityManager.goToFileBrowser(xtc ? xtc->getPath() : "");
-    return;
-  }
-
-  // Short press BACK goes directly to home
-  if (mappedInput.wasReleased(MappedInputManager::Button::Back) &&
-      mappedInput.getHeldTime() < ReaderUtils::GO_HOME_MS) {
-    onGoHome();
+  if (ReaderUtils::handleBackNavigation(mappedInput, activityManager, xtc ? xtc->getPath().c_str() : "",
+                                        {this, [](void* ctx) { static_cast<XtcReaderActivity*>(ctx)->onGoHome(); }})) {
     return;
   }