[LyX/master] Factor out the generation of the code to create a preview.

[Thibaut Cuvelier]

commit 3502f5c999f7c91da83d247e1a460ef30a497aa0
Author: Thibaut Cuvelier <tcuvelier at lyx.org>
Date:   Wed Oct 13 03:01:54 2021 +0200

    Factor out the generation of the code to create a preview.
    
    This will be soon reused in InsetText to generate images for DocBook.
---
 src/insets/InsetPreview.cpp |   16 +++++++++++-----
 src/insets/InsetPreview.h   |    2 ++
 2 files changed, 13 insertions(+), 5 deletions(-)

diff --git a/src/insets/InsetPreview.cpp b/src/insets/InsetPreview.cpp
index e08fdcd..c4f1b8d 100644
--- a/src/insets/InsetPreview.cpp
+++ b/src/insets/InsetPreview.cpp
@@ -107,19 +107,25 @@ MacroNameSet gatherMacroDefinitions(const Buffer* buffer, const Inset * inset)
 }
 
 
-void InsetPreview::preparePreview(DocIterator const & pos) const
+docstring insetToLaTeXSnippet(const Buffer* buffer, const Inset * inset)
 {
 	odocstringstream str;
 	otexstream os(str);
-	OutputParams runparams(&pos.buffer()->params().encoding());
-	latex(os, runparams);
+	OutputParams runparams(&buffer->params().encoding());
+	inset->latex(os, runparams);
 
-	MacroNameSet defs = gatherMacroDefinitions(pos.buffer(), this);
+	MacroNameSet defs = gatherMacroDefinitions(buffer, inset);
 	docstring macro_preamble;
 	for (const auto& def : defs)
 		macro_preamble.append(def);
 
-	docstring const snippet = macro_preamble + str.str();
+	return macro_preamble + str.str();
+}
+
+
+void InsetPreview::preparePreview(DocIterator const & pos) const
+{
+	docstring const snippet = insetToLaTeXSnippet(pos.buffer(), this);
 	preview_->addPreview(snippet, *pos.buffer());
 }
 
diff --git a/src/insets/InsetPreview.h b/src/insets/InsetPreview.h
index 55353e7..db2a2af 100644
--- a/src/insets/InsetPreview.h
+++ b/src/insets/InsetPreview.h
@@ -90,6 +90,8 @@ protected:
 
 /// gathers the list of macro definitions used in the given inset
 MacroNameSet gatherMacroDefinitions(const Buffer* buffer, const Inset * inset);
+/// returns the LaTeX snippet to compute the preview of the given inset
+docstring insetToLaTeXSnippet(const Buffer* buffer, const Inset * inset);
 
 
 } // namespace lyx