feat: add RTL support in epub and txt readers (#1700)

Co-authored-by: Zach Nelson <zach@zdnelson.com>

src/activities/reader/TxtReaderActivity.cpp

@@ -1,5 +1,6 @@
 #include "TxtReaderActivity.h"
 
+#include <BidiUtils.h>
 #include <FontCacheManager.h>
 #include <GfxRenderer.h>
 #include <HalStorage.h>
@@ -358,20 +359,25 @@ void TxtReaderActivity::renderPage() {
     for (const auto& line : currentPageLines) {
       if (!line.empty()) {
         int x = cachedOrientedMarginLeft;
+        const bool lineIsRtl = BidiUtils::startsWithRtl(line.c_str(), BidiUtils::RTL_PARAGRAPH_PROBE_DEPTH);
+        uint8_t effectiveAlignment = cachedParagraphAlignment;
+        if (lineIsRtl && (effectiveAlignment == CrossPointSettings::LEFT_ALIGN ||
+                          effectiveAlignment == CrossPointSettings::JUSTIFIED)) {
+          effectiveAlignment = CrossPointSettings::RIGHT_ALIGN;
+        }
+        const int textWidth = renderer.getTextAdvanceX(cachedFontId, line.c_str(), EpdFontFamily::REGULAR);
 
         // Apply text alignment
-        switch (cachedParagraphAlignment) {
+        switch (effectiveAlignment) {
           case CrossPointSettings::LEFT_ALIGN:
           default:
             // x already set to left margin
             break;
           case CrossPointSettings::CENTER_ALIGN: {
-            int textWidth = renderer.getTextAdvanceX(cachedFontId, line.c_str(), EpdFontFamily::REGULAR);
             x = cachedOrientedMarginLeft + (contentWidth - textWidth) / 2;
             break;
           }
           case CrossPointSettings::RIGHT_ALIGN: {
-            int textWidth = renderer.getTextAdvanceX(cachedFontId, line.c_str(), EpdFontFamily::REGULAR);
             x = cachedOrientedMarginLeft + contentWidth - textWidth;
             break;
           }