From efe1da95268d4ebb5c73088f53938b78d2b7ffa7 Mon Sep 17 00:00:00 2001
From: Dave Allie <dave@daveallie.com>
Date: Mon, 8 Dec 2025 19:44:19 +1100
Subject: [PATCH] Re-use existing buffer and write to whole screen for 'partial
 update'

---
 lib/EpdRenderer/EpdRenderer.cpp  | 11 ++++++++---
 lib/EpdRenderer/EpdRenderer.h    |  3 ++-
 open-x4-sdk                      |  2 +-
 src/screens/EpubReaderScreen.cpp |  4 +++-
 4 files changed, 14 insertions(+), 6 deletions(-)

diff --git a/lib/EpdRenderer/EpdRenderer.cpp b/lib/EpdRenderer/EpdRenderer.cpp
index b8a001d..f3eca77 100644
--- a/lib/EpdRenderer/EpdRenderer.cpp
+++ b/lib/EpdRenderer/EpdRenderer.cpp
@@ -216,9 +216,12 @@ void EpdRenderer::flushDisplay(const EInkDisplay::RefreshMode refreshMode) const
 }
 
 // TODO: Support partial window update
-void EpdRenderer::flushArea(const int x, const int y, const int width, const int height) const {
-  einkDisplay.displayBuffer();
-}
+// void EpdRenderer::flushArea(const int x, const int y, const int width, const int height) const {
+//   const int rotatedX = y;
+//   const int rotatedY = EInkDisplay::DISPLAY_HEIGHT - 1 - x;
+//
+//   einkDisplay.displayBuffer(EInkDisplay::FAST_REFRESH, rotatedX, rotatedY, height, width);
+// }
 
 int EpdRenderer::getPageWidth() const { return EInkDisplay::DISPLAY_HEIGHT - marginLeft - marginRight; }
 
@@ -230,6 +233,8 @@ int EpdRenderer::getLineHeight() const {
   return regularFontRenderer->fontFamily->getData(REGULAR)->advanceY * lineCompression;
 }
 
+void EpdRenderer::swapBuffers() const { einkDisplay.swapBuffers(); }
+
 void EpdRenderer::copyGrayscaleLsbBuffers() const { einkDisplay.copyGrayscaleLsbBuffers(einkDisplay.getFrameBuffer()); }
 
 void EpdRenderer::copyGrayscaleMsbBuffers() const { einkDisplay.copyGrayscaleMsbBuffers(einkDisplay.getFrameBuffer()); }
diff --git a/lib/EpdRenderer/EpdRenderer.h b/lib/EpdRenderer/EpdRenderer.h
index 75c1abd..a9e76d3 100644
--- a/lib/EpdRenderer/EpdRenderer.h
+++ b/lib/EpdRenderer/EpdRenderer.h
@@ -33,6 +33,7 @@ class EpdRenderer {
   void drawImage(const uint8_t bitmap[], int x, int y, int width, int height) const;
   void drawImageNoMargin(const uint8_t bitmap[], int x, int y, int width, int height) const;
 
+  void swapBuffers() const;
   void copyGrayscaleLsbBuffers() const;
   void copyGrayscaleMsbBuffers() const;
   void displayGrayBuffer() const;
@@ -41,7 +42,7 @@ class EpdRenderer {
   void invertScreen() const;
 
   void flushDisplay(EInkDisplay::RefreshMode refreshMode = EInkDisplay::FAST_REFRESH) const;
-  void flushArea(int x, int y, int width, int height) const;
+  // void flushArea(int x, int y, int width, int height) const;
 
   int getPageWidth() const;
   int getPageHeight() const;
diff --git a/open-x4-sdk b/open-x4-sdk
index fe963b3..a126d4b 160000
--- a/open-x4-sdk
+++ b/open-x4-sdk
@@ -1 +1 @@
-Subproject commit fe963b32821dec7fb22abbfa22daa8fc67f286d1
+Subproject commit a126d4b0bf66cd2895d11748774f7ec2c366cc4c
diff --git a/src/screens/EpubReaderScreen.cpp b/src/screens/EpubReaderScreen.cpp
index 448a054..3201a0d 100644
--- a/src/screens/EpubReaderScreen.cpp
+++ b/src/screens/EpubReaderScreen.cpp
@@ -160,10 +160,12 @@ void EpubReaderScreen::renderScreen() {
         constexpr int y = 50;
         const int w = textWidth + margin * 2;
         const int h = renderer.getLineHeight() + margin * 2;
+        renderer.swapBuffers();
         renderer.fillRect(x, y, w, h, 0);
         renderer.drawText(x + margin, y + margin, "Indexing...");
         renderer.drawRect(x + 5, y + 5, w - 10, h - 10);
-        renderer.flushArea(x, y, w, h);
+        renderer.flushDisplay(EInkDisplay::HALF_REFRESH);
+        pagesUntilFullRefresh = 0;
       }
 
       section->setupCacheDir();