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Use single buffer mode for EInkDisplay (#34)

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## Summary

* Frees up 48kB of statically allocated RAM in exchange for 48kB just
when grayscale rendering is needed

## Additional Context

* Upstream changes:
https://github.com/open-x4-epaper/community-sdk/pull/7
This commit is contained in:
Dave Allie
2025-12-17 00:17:49 +11:00
committed by GitHub
parent 5d68c8b305
commit c287aa03a4
5 changed files with 67 additions and 21 deletions
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27
src/screens/EpubReaderScreen.cpp
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@@ -31,7 +31,6 @@ void EpubReaderScreen::onEnter() {
epub->setupCacheDir();
// TODO: Move this to a state object
if (SD.exists((epub->getCachePath() + "/progress.bin").c_str())) {
File f = SD.open((epub->getCachePath() + "/progress.bin").c_str());
uint8_t data[4];
@@ -210,20 +209,20 @@ void EpubReaderScreen::renderScreen() {
Serial.printf("[%lu] [ERS] Cache not found, building...\n", millis());
{
renderer.grayscaleRevert();
const int textWidth = renderer.getTextWidth(READER_FONT_ID, "Indexing...");
constexpr int margin = 20;
const int x = (GfxRenderer::getScreenWidth() - textWidth - margin * 2) / 2;
constexpr int y = 50;
const int w = textWidth + margin * 2;
const int h = renderer.getLineHeight(READER_FONT_ID) + margin * 2;
renderer.grayscaleRevert();
uint8_t* fb1 = renderer.getFrameBuffer();
renderer.swapBuffers();
memcpy(fb1, renderer.getFrameBuffer(), EInkDisplay::BUFFER_SIZE);
renderer.fillRect(x, y, w, h, 0);
// Round all coordinates to 8 pixel boundaries
const int x = ((GfxRenderer::getScreenWidth() - textWidth - margin * 2) / 2 + 7) / 8 * 8;
constexpr int y = 56;
const int w = (textWidth + margin * 2 + 7) / 8 * 8;
const int h = (renderer.getLineHeight(READER_FONT_ID) + margin * 2 + 7) / 8 * 8;
renderer.fillRect(x, y, w, h, false);
renderer.drawText(READER_FONT_ID, x + margin, y + margin, "Indexing...");
renderer.drawRect(x + 5, y + 5, w - 10, h - 10);
renderer.displayBuffer();
// EXPERIMENTAL: Still suffers from ghosting
renderer.displayWindow(x, y, w, h);
pagesUntilFullRefresh = 0;
}
@@ -297,6 +296,9 @@ void EpubReaderScreen::renderContents(std::unique_ptr<Page> page) {
pagesUntilFullRefresh--;
}
// Save bw buffer to reset buffer state after grayscale data sync
renderer.storeBwBuffer();
// grayscale rendering
// TODO: Only do this if font supports it
{
@@ -315,6 +317,9 @@ void EpubReaderScreen::renderContents(std::unique_ptr<Page> page) {
renderer.displayGrayBuffer();
renderer.setRenderMode(GfxRenderer::BW);
}
// restore the bw data
renderer.restoreBwBuffer();
}
void EpubReaderScreen::renderStatusBar() const {