Add X3 fast LUT option

lib/GfxRenderer/GfxRenderer.h

@@ -230,6 +230,11 @@ class GfxRenderer {
   void writeGrayscalePlaneStrip(bool lsbPlane, const uint8_t* scratch, int yStart, int numRows) const;
   bool supportsStripGrayscale() const;
 
+  // X3-only: trade AA visual fidelity for ~2.2 s faster page-flip wall clock.
+  // No effect on X4 (its single grayscale LUT already runs at ~500 ms).
+  void setFastGrayscaleLut(bool fast) const { display.setFastGrayscaleLut(fast); }
+  bool getFastGrayscaleLut() const { return display.getFastGrayscaleLut(); }
+
   // Tiled grayscale strip target. While active, drawPixel(), clearScreen(),
   // fillPhysicalHSpanByte() and renderGlyphFast2Bit() operate on `scratch`
   // (panelWidthBytes * stripRows bytes, holding physical rows

lib/I18n/translations/english.yaml

@@ -97,6 +97,7 @@ STR_SLEEP_COVER_MODE: "Sleep Screen Cover Mode"
 STR_HIDE_BATTERY: "Hide Battery %"
 STR_EXTRA_SPACING: "Extra Paragraph Spacing"
 STR_TEXT_AA: "Text Anti-Aliasing"
+STR_FAST_AA: "Fast AA (X3 only)"
 STR_TEXT_DARKNESS: "Text Darkness"
 STR_EXTRA_DARK: "Extra Dark"
 STR_MAX_DARK: "Maximum"

lib/hal/HalDisplay.cpp

@@ -104,6 +104,10 @@ void HalDisplay::writeGrayscalePlaneStrip(bool lsbPlane, const uint8_t* rows, ui
 
 bool HalDisplay::supportsStripGrayscale() const { return einkDisplay.supportsStripGrayscale(); }
 
+void HalDisplay::setFastGrayscaleLut(bool fast) { einkDisplay.setFastGrayscaleLut(fast); }
+
+bool HalDisplay::getFastGrayscaleLut() const { return einkDisplay.getFastGrayscaleLut(); }
+
 uint16_t HalDisplay::getDisplayWidth() const { return einkDisplay.getDisplayWidth(); }
 
 uint16_t HalDisplay::getDisplayHeight() const { return einkDisplay.getDisplayHeight(); }

lib/hal/HalDisplay.h

@@ -61,6 +61,12 @@ class HalDisplay {
   void writeGrayscalePlaneStrip(bool lsbPlane, const uint8_t* rows, uint16_t yStart, uint16_t numRows);
   bool supportsStripGrayscale() const;
 
+  // X3-only knob: pick between the OEM 53-frame grayscale LUT (default, slow
+  // and accurate) and the 7-frame community LUT (fast, slightly darker
+  // mid-tones). No effect on X4. See EInkDisplay::setFastGrayscaleLut.
+  void setFastGrayscaleLut(bool fast);
+  bool getFastGrayscaleLut() const;
+
   // Runtime geometry passthrough
   uint16_t getDisplayWidth() const;
   uint16_t getDisplayHeight() const;

src/CrossPointSettings.h

@@ -223,6 +223,11 @@ class CrossPointSettings {
   // Text rendering settings
   uint8_t extraParagraphSpacing = 1;
   uint8_t textAntiAliasing = 1;
+  // X3-only: when on, the AA refresh uses the 7-frame community grayscale LUT
+  // (~130 ms panel time) instead of the OEM 53-frame LUT (~2.4 s). Mid-tones
+  // run slightly darker than X4. Matches what papyrix-reader has shipped since
+  // 2025-11. Default off preserves OEM-fidelity grays. No effect on X4.
+  uint8_t fastAntiAliasing = 0;
   // Text darkness (0 = normal, 1 = dark, 2 = extra dark). Default 1 preserves
   // historical AA rendering (both grayscale shades drawn in the MSB pass).
   uint8_t textDarkness = DARKNESS_DARK;

src/SettingsList.h

@@ -111,6 +111,14 @@ inline const std::vector<SettingInfo> list = {
     SettingInfo::Toggle(StrId::STR_TEXT_AA, &CrossPointSettings::textAntiAliasing, "textAntiAliasing",
                         StrId::STR_CAT_READER)
         .withSubmenu(StrId::STR_MENU_READER_FONT),
+    // X3-only fast AA LUT toggle. Swaps the 53-frame OEM grayscale waveform
+    // (~2.4 s panel time, X4-accurate grays) for the 7-frame community LUT
+    // (~130 ms, mid-tones slightly darker). See open-x4-sdk
+    // EInkDisplay::setFastGrayscaleLut for trade-offs.
+    SettingInfo::Toggle(StrId::STR_FAST_AA, &CrossPointSettings::fastAntiAliasing, "fastAntiAliasing",
+                        StrId::STR_CAT_READER)
+        .withSubmenu(StrId::STR_MENU_READER_FONT)
+        .withDeviceTarget(SettingDeviceTarget::X3),
     SettingInfo::Enum(StrId::STR_TEXT_DARKNESS, &CrossPointSettings::textDarkness,
                       {StrId::STR_NORMAL, StrId::STR_DARK, StrId::STR_EXTRA_DARK, StrId::STR_MAX_DARK}, "textDarkness",
                       StrId::STR_CAT_READER)

src/activities/reader/EpubReaderActivity.cpp

@@ -174,9 +174,15 @@ bool computePageDynamicYBand(const Page& page, const GfxRenderer& renderer, cons
 // renderCharImpl culls out-of-band glyphs before bitmap decode so the cost
 // stays close to one render. Only renderTextOnly() is called here, matching the
 // legacy AA pass — images and HRs do not participate in grayscale.
-bool runTiledGrayscalePass(GfxRenderer& renderer, Page& page, int fontId, int marginLeft, int contentTop) {
+bool runTiledGrayscalePass(GfxRenderer& renderer, Page& page, int fontId, int marginLeft, int contentTop, bool fastAA) {
   if (!renderer.supportsStripGrayscale()) return false;
 
+  // Push the SETTINGS toggle into the SDK before the AA refresh. No-op on X4;
+  // on X3 picks between OEM _gc (slow/accurate) and community _grayscale
+  // (fast/darker mid-tones). Re-applied per render so a settings change takes
+  // effect on the next page flip without rebooting.
+  renderer.setFastGrayscaleLut(fastAA);
+
   // Strip height trades scratch size for the number of re-renders. Each render
   // pays layout + glyph-cull overhead even when bitmap decode is skipped, so
   // fewer/bigger bands win as long as the scratch fits. 240 rows × ~100 bytes
@@ -2157,7 +2163,8 @@ void EpubReaderActivity::renderContents(std::unique_ptr<Page> page, const int or
   if (aaEnabledForThisRender) {
     logReaderMemSnapshot("tiled_gray_begin");
     const auto tTiledBegin = millis();
-    grayscaleDone = runTiledGrayscalePass(renderer, *page, getEffectiveReaderFontId(), orientedMarginLeft, contentTop);
+    grayscaleDone = runTiledGrayscalePass(renderer, *page, getEffectiveReaderFontId(), orientedMarginLeft, contentTop,
+                                          SETTINGS.fastAntiAliasing);
     if (grayscaleDone) {
       tiledGrayMs = millis() - tTiledBegin;
       fcm->logStats("tiled_gray");
@@ -2219,6 +2226,9 @@ void EpubReaderActivity::renderContents(std::unique_ptr<Page> page, const int or
     // grayscale rendering
     // TODO: Only do this if font supports it
     if (aaEnabledForThisRender && bwBufferStored) {
+      // Push fast-AA toggle into the SDK before the AA refresh (X3 only; no-op
+      // on X4). Mirrors what runTiledGrayscalePass() does.
+      renderer.setFastGrayscaleLut(SETTINGS.fastAntiAliasing);
       logReaderMemSnapshot("gray_lsb_begin");
       renderer.clearScreen(0x00);
       renderer.setRenderMode(GfxRenderer::GRAYSCALE_LSB);
@@ -2341,7 +2351,8 @@ void EpubReaderActivity::displayPreRenderedPage(const Page& page, const int orie
   const bool aaConfigured = SETTINGS.textAntiAliasing && !antiAliasingSuspendedLowMemory;
   if (aaConfigured) {
     Page& pageRef = const_cast<Page&>(page);
-    if (runTiledGrayscalePass(renderer, pageRef, getEffectiveReaderFontId(), orientedMarginLeft, contentTop)) {
+    if (runTiledGrayscalePass(renderer, pageRef, getEffectiveReaderFontId(), orientedMarginLeft, contentTop,
+                              SETTINGS.fastAntiAliasing)) {
       return;
     }
 
@@ -2360,6 +2371,7 @@ void EpubReaderActivity::displayPreRenderedPage(const Page& page, const int orie
       const int snapshotTop = contentTop + bandTop;
       const int snapshotHeight = std::max(0, bandBottom - bandTop);
       if (renderer.storeBwBufferRect(contentLeft, snapshotTop, contentRight - contentLeft, snapshotHeight)) {
+        renderer.setFastGrayscaleLut(SETTINGS.fastAntiAliasing);
         renderer.clearScreen(0x00);
         renderer.setRenderMode(GfxRenderer::GRAYSCALE_LSB);
         page.renderTextOnly(renderer, getEffectiveReaderFontId(), orientedMarginLeft, contentTop);