feat: Slim dictionary (#2583)

Co-authored-by: Ryan Hitchman <hitchmanr@gmail.com>
Co-authored-by: Kurtis Grant <kurtis.b.grant@gmail.com>
Co-authored-by: kemonine <kemonine@kemonine.info>
Co-authored-by: DustinHu <hu.dustin@gmail.com>
Co-authored-by: Justin Mitchell <justin@jmitch.com>

src/activities/reader/DictionaryWordSelectActivity.h

@@ -0,0 +1,84 @@
+#pragma once
+
+#include <Epub/Page.h>
+#include <I18n.h>
+
+#include <memory>
+#include <vector>
+
+#include "activities/Activity.h"
+#include "util/Dictionary.h"
+
+// Button-driven word selection over the current reader page: Left/Right step
+// through words in reading order, Up/Down jump rows, Confirm looks the word up
+// and opens DictionaryDefinitionActivity, Back returns to the reader.
+class DictionaryWordSelectActivity final : public Activity {
+ public:
+  explicit DictionaryWordSelectActivity(GfxRenderer& renderer, MappedInputManager& mappedInput,
+                                        std::unique_ptr<Page> page, int marginLeft, int marginTop)
+      : Activity("DictionaryWordSelect", renderer, mappedInput),
+        page(std::move(page)),
+        marginLeft(marginLeft),
+        marginTop(marginTop) {}
+
+  void onEnter() override;
+  void loop() override;
+  void render(RenderLock&&) override;
+
+ private:
+  // Screen box of one selectable word. `text` points into the owned Page's
+  // TextBlock arena (NUL-terminated), valid for this activity's lifetime.
+  struct WordBox {
+    int16_t x;
+    int16_t y;
+    int16_t width;
+    uint16_t row;
+    const char* text;
+    EpdFontFamily::Style style;
+  };
+
+  enum class Popup : uint8_t { None, Busy, NotFound, Error };
+
+  void extractWords();
+  int closestInRow(uint16_t row, int centerX) const;
+  void moveVertical(int direction);
+  void performLookup();
+  bool drawHighlightWithSnapshot();
+  void drawHints() const;
+
+  std::unique_ptr<Page> page;
+  const int marginLeft;
+  const int marginTop;
+  int fontId = 0;
+  int lineHeight = 0;
+
+  std::vector<WordBox> words;
+  int selected = 0;
+  uint16_t rowCount = 0;
+
+  Dictionary dict;
+  bool dictOpenAttempted = false;
+  bool dictOpenOk = false;
+
+  Popup popup = Popup::None;
+  StrId popupMsg = StrId::STR_DICT_NOT_FOUND;
+  unsigned long popupTime = 0;
+
+  // Differential highlight repaint: the pixels under the current highlight
+  // box, so a cursor move restores them and repaints only the two affected
+  // boxes instead of re-running the full two-pass page render (which also
+  // reloads every SD-font glyph on the page). snapshotIdx is the word whose
+  // under-pixels are saved; -1 means the framebuffer no longer holds a clean
+  // page (popup drawn, sub-activity shown) and the next render must be full.
+  static constexpr size_t SNAPSHOT_CAPACITY = 4096;
+  std::unique_ptr<uint8_t[]> snapshot;
+  int16_t snapshotX = 0;
+  int16_t snapshotY = 0;
+  int16_t snapshotW = 0;
+  int16_t snapshotH = 0;
+  int snapshotIdx = -1;
+
+  // The activity is entered while Confirm is still held (long-press trigger):
+  // ignore the stale release until a fresh press is seen.
+  bool confirmPressSeen = false;
+};