[LyX/master] Fix crash with info inset and dialogs

[Jean-Marc Lasgouttes]

commit 17e60e2e8559e5b702189c82a5a746b9f41cd219
Author: Jean-Marc Lasgouttes <lasgouttes at lyx.org>
Date:   Mon Feb 6 21:34:08 2023 +0100

    Fix crash with info inset and dialogs
    
    See the thread
      2.4 Crash (was: Updated LaTeXConfig.lyx (bxjsclasses added))
    on lyx-devel (26/01/2023).
    
    The backtrace imply a problem like:
    1/ metrics are computed for some info inset
    2/ the info inset is regenerated (and thus the paragraph it held is now invalid)
    3/ We draw the inset and because of the new (disabled by default)
       bookmark display code, we access the id() of the invalid paragraph.
    4/ boom!
    
    To fix the issue, introduce a new boolean member that indicates when
    the Row object of the metrics should not be used. In this case, the
    draw() method returns early.
---
 src/insets/InsetInfo.cpp |    8 +++++++-
 src/insets/InsetInfo.h   |    2 ++
 2 files changed, 9 insertions(+), 1 deletions(-)

diff --git a/src/insets/InsetInfo.cpp b/src/insets/InsetInfo.cpp
index 46d656c..f2d3b93 100644
--- a/src/insets/InsetInfo.cpp
+++ b/src/insets/InsetInfo.cpp
@@ -467,7 +467,7 @@ string InsetInfoParams::infoType() const
 
 
 InsetInfo::InsetInfo(Buffer * buf, string const & info)
-	: InsetCollapsible(buf), initialized_(false)
+	: InsetCollapsible(buf), initialized_(false), dirty_(true)
 {
 	params_.type = InsetInfoParams::UNKNOWN_INFO;
 	params_.force_ltr = false;
@@ -779,15 +779,19 @@ void InsetInfo::metrics(MetricsInfo & mi, Dimension & dim) const
 {
 	const_cast<InsetInfo *>(this)->build();
 	InsetCollapsible::metrics(mi, dim);
+	dirty_ = false;
 }
 
 
 void InsetInfo::draw(PainterInfo & pi, int x, int y) const
 {
+	if (dirty_)
+		return;
 	Changer chg = changeVar(lyxrc.mark_foreign_language, false);
 	InsetCollapsible::draw(pi, x, y);
 }
 
+
 void InsetInfo::updateBuffer(ParIterator const & it, UpdateType utype, bool const deleted)
 
 {
@@ -1235,6 +1239,8 @@ void InsetInfo::build()
 	}
 	}
 
+	// indicate that metrics are not usable anymore
+	dirty_ = true;
 	// Just to do something with that string
 	LYXERR(Debug::INFO, "info inset text: " << gui);
 }
diff --git a/src/insets/InsetInfo.h b/src/insets/InsetInfo.h
index 3531b41..17d60e2 100644
--- a/src/insets/InsetInfo.h
+++ b/src/insets/InsetInfo.h
@@ -236,6 +236,8 @@ private:
 	void build();
 	///
 	bool initialized_;
+	/// true when metrics Row object should not be used
+	mutable bool dirty_;
 	///
 	InsetInfoParams params_;
 	///