[okular] [Bug 353300] Text search does not work in Arabic

[Saladin Shaban]

https://bugs.kde.org/show_bug.cgi?id=353300

Saladin Shaban <salshaaban at gmail.com> changed:

           What    |Removed                     |Added
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                 CC|                            |salshaaban at gmail.com

--- Comment #4 from Saladin Shaban <salshaaban at gmail.com> ---
I have been investigating this with ChatGPT's help:
https://chat.openai.com/share/69484c6f-d974-4047-8d52-c92d6ea0ebf9

There seem to be two issues affecting Arabic and, apparently, other RTL
languages as well.

One of them is in TextDocumentUtils::calculateBoundingRect(), where the final
if statement is incorrectly triggered for all Arabic text, causing all
characters to be substituted with newlines.

Trying to work around the issue with this patch, the TinyTextEntity's are
created with the correct characters and the correct bounding rectangles, as far
as I can see. But the search still seems to expect the TinyTextEntity's in left
to right order. I can only find Arabic words if I type them backwards in the
Find bar.


diff --git a/core/textdocumentgenerator_p.h b/core/textdocumentgenerator_p.h
index fb1a5e395..bf17e2e52 100644
--- a/core/textdocumentgenerator_p.h
+++ b/core/textdocumentgenerator_p.h
@@ -44,19 +44,23 @@ static void calculateBoundingRect(QTextDocument *document,
int startPosition, in
     const QTextLine startLine = startLayout->lineForTextPosition(startPos);
     const QTextLine endLine = endLayout->lineForTextPosition(endPos);

-    const double x = startBoundingRect.x() + startLine.cursorToX(startPos);
+    double x = startBoundingRect.x() + startLine.cursorToX(startPos);
     const double y = startBoundingRect.y() + startLine.y();
-    const double r = endBoundingRect.x() + endLine.cursorToX(endPos);
+    double r = endBoundingRect.x() + endLine.cursorToX(endPos);
     const double b = endBoundingRect.y() + endLine.y() + endLine.height();

     const int offset = qRound(y) % qRound(pageSize.height());

-    if (x > r) { // line break, so return a pseudo character on the start line
+    if (startLine.y() != endLine.y()) { // line break, so return a pseudo
character on the start line
         rect = QRectF(x / pageSize.width(), offset / pageSize.height(), 3 /
pageSize.width(), startLine.height() / pageSize.height());
         page = -1;
         return;
     }

+    const auto direction = document->characterAt(startPosition).direction();
+    if (direction == QChar::DirAL || direction == QChar::DirR)
+        std::swap(x, r);
+
     page = qRound(y) / qRound(pageSize.height());
     rect = QRectF(x / pageSize.width(), offset / pageSize.height(), (r - x) /
pageSize.width(), (b - y) / pageSize.height());
 }

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