Add QTextListFormat::start: html and markdown ordered list index offset

This is useful for a lot of applications that render text coming from
sources which already support arbitrarily numbered lists (like chat
applications for example). Application-side workarounds usually have
significant overhead; and this feature has been requested multiple times.

It should be possible to both read and write HTML with the <ol start="x">
attribute, and read and write Markdown with arbitrary numbers for the
first item in a list.

[ChangeLog][QtGui] QTextList now supports specifying a start index using
the new QTextList::{setStart, start} functions. The HTML start attribute
on ordered lists in rich text documents is now parsed and used when
rendering a text list. Non-negative indices in markdown lists are now
also parsed and written properly. This allows starting a list with a
different number than 1.

Fixes: QTBUG-30407
Fixes: QTBUG-65384
Task-number: QTBUG-107562
Change-Id: Ib35b9378d9134ffedaa2d92f728b0984793aa7c1
Reviewed-by: Shawn Rutledge <shawn.rutledge@qt.io>

1 files changed, 3 insertions, 1 deletions

diff --git a/src/gui/text/qtextmarkdownwriter.cpp b/src/gui/text/qtextmarkdownwriter.cpp
index f535ff8aa8..5fb67ccc67 100644
--- a/src/gui/text/qtextmarkdownwriter.cpp
+++ b/src/gui/text/qtextmarkdownwriter.cpp
@@ -344,7 +344,9 @@ int QTextMarkdownWriter::writeBlock(const QTextBlock &block, bool wrap, bool ign
     if (block.textList()) { // it's a list-item
         auto fmt = block.textList()->format();
         const int listLevel = fmt.indent();
-        const int number = block.textList()->itemNumber(block) + 1;
+        // Negative numbers don't start a list in Markdown, so ignore them.
+        const int start = fmt.start() >= 0 ? fmt.start() : 1;
+        const int number = block.textList()->itemNumber(block) + start;
         QByteArray bullet = " ";
         bool numeric = false;
         switch (fmt.style()) {