Add navigation option

src/activities/reader/EpubReaderPrintedPageInputActivity.h

@@ -0,0 +1,46 @@
+#pragma once
+
+#include "MappedInputManager.h"
+#include "activities/Activity.h"
+
+// Numeric input dialog for "jump to printed page".
+// User adjusts a single integer (mirroring the printed-page label as shown in the book).
+// Up/Down change the digit under the cursor by ±1 (single) or ±10 (double-click).
+// Left/Right move the cursor between digits; Confirm returns the typed string.
+// Books with non-integer labels (roman numerals, etc.) are not addressable via this dialog;
+// the menu item is hidden if the book has no integer-parseable printed-page labels.
+class EpubReaderPrintedPageInputActivity final : public Activity {
+ public:
+  explicit EpubReaderPrintedPageInputActivity(GfxRenderer& renderer, MappedInputManager& mappedInput, int initialValue,
+                                              int minValue, int maxValue)
+      : Activity("EpubReaderPrintedPageInput", renderer, mappedInput),
+        value(initialValue),
+        minValue(minValue),
+        maxValue(maxValue) {
+    clampValue();
+    cursorDigit = 0;  // ones place
+  }
+
+  void onEnter() override;
+  void onExit() override;
+  void loop() override;
+  void render(RenderLock&&) override;
+
+ private:
+  int value = 0;
+  int minValue = 1;
+  int maxValue = 1;
+  int cursorDigit = 0;  // 0 = ones, 1 = tens, 2 = hundreds, ...
+
+  void clampValue();
+  void adjustDigit(int delta);
+  void adjustDigitTimes(int multiplier, int sign);  // delta = sign * multiplier * 10^cursorDigit
+  void moveCursor(int delta);
+  static int powTen(int exponent);
+  int digitCount() const;
+  // Highest cursor position the user can reach: one less than the digit count of maxValue.
+  // Lets the user move the cursor "past" the current value to higher digit positions that
+  // don't exist yet, so they can grow the number quickly (e.g. start at 1, move cursor left,
+  // press Up to make 11, etc.) without single-pressing dozens of times.
+  int maxCursorDigit() const;
+};