LOK: Impress checks a deck before a show

.uno:SlideCheck lists, for every slide and master, the font families
its text asks for, its linked files (pictures, OLE) and whether each is
missing, and the objects the kernel cannot show (unreadable pictures,
OLE objects with no data, pictures that do not decode). A missing
linked picture is listed once.

diff --git a/sd/source/ui/unoidl/unomodel.cxx b/sd/source/ui/unoidl/unomodel.cxx
index 3aa98bc..8027106 100644
--- a/sd/source/ui/unoidl/unomodel.cxx
+++ b/sd/source/ui/unoidl/unomodel.cxx
@@ -199,6 +199,11 @@
 #include <svx/ColorSets.hxx>
 #include <docmodel/theme/Theme.hxx>
 #include <svx/svdopage.hxx>
+#include <svx/svdograf.hxx>
+#include <svx/svditer.hxx>
+#include <editeng/editdata.hxx>
+#include <com/sun/star/embed/XLinkageSupport.hpp>
+#include <svtools/embedhlp.hxx>
 #include <svx/svdopath.hxx>
 #include <tools/multisel.hxx>
 #include <basegfx/matrix/b2dhommatrix.hxx>
@@ -2072,7 +2077,7 @@ bool SdXImpressDocument::supportsCommand(std::u16string_view rCommand)
     return rCommand == u"SlideDesign" || rCommand == u"SlideObjects" || rCommand == u"Chart"
            || rCommand == u"SlideNotes" || rCommand == u"SlideTransition"
            || rCommand == u"SlideAnimations" || rCommand == u"SlideMedia"
-           || rCommand == u"SlideShow";
+           || rCommand == u"SlideShow" || rCommand == u"SlideCheck";
 }
 
 namespace
@@ -2264,6 +2269,111 @@ void lcl_SlideMedia(::tools::JsonWriter& rJson, SdPage& rPage)
     }
 }
 
+/// Fonts a text object asks for, all scripts.
+void lcl_TextFonts(const SdrTextObj& rObj, std::set<OUString>& rFonts)
+{
+    for (const auto& nWhich : { EE_CHAR_FONTINFO, EE_CHAR_FONTINFO_CJK, EE_CHAR_FONTINFO_CTL })
+        rFonts.insert(rObj.GetMergedItem(nWhich).GetFamilyName());
+    for (sal_Int32 nText = 0; nText < rObj.getTextCount(); ++nText)
+    {
+        const OutlinerParaObject* pText = rObj.getText(nText)->GetOutlinerParaObject();
+        if (!pText)
+            continue;
+        const EditTextObject& rEdit = pText->GetTextObject();
+        for (sal_Int32 nPara = 0; nPara < rEdit.GetParagraphCount(); ++nPara)
+        {
+            std::vector<EECharAttrib> aAttribs;
+            rEdit.GetCharAttribs(nPara, aAttribs);
+            for (const EECharAttrib& rAttrib : aAttribs)
+                if (auto pFont = dynamic_cast<const SvxFontItem*>(rAttrib.pAttr))
+                    rFonts.insert(pFont->GetFamilyName());
+        }
+    }
+}
+
+/// Fonts asked for, linked files, objects the kernel cannot show.
+void lcl_PageCheck(::tools::JsonWriter& rJson, SdPage& rPage)
+{
+    std::set<OUString> aFonts;
+    std::vector<std::pair<OUString, bool>> aLinks;
+    std::vector<OUString> aBroken;
+    SdrObjListIter aIter(&rPage, SdrIterMode::DeepNoGroups);
+    while (aIter.IsMore())
+    {
+        SdrObject* pObj = aIter.Next();
+        if (pObj->isAnnotationObject() || pObj->IsEmptyPresObj())
+            continue;
+        if (auto pText = DynCastSdrTextObj(pObj); pText && pText->HasText())
+            lcl_TextFonts(*pText, aFonts);
+        if (auto pGraf = dynamic_cast<SdrGrafObj*>(pObj))
+        {
+            bool bThere = true;
+            if (pGraf->IsLinkedGraphic())
+            {
+                osl::DirectoryItem aItem;
+                bThere = osl::DirectoryItem::get(pGraf->GetFileName(), aItem) == osl::FileBase::E_None;
+                aLinks.emplace_back(pGraf->GetFileName(), !bThere);
+            }
+            // Loads a link; a failed decode leaves the placeholder.
+            const GraphicType eType = pGraf->GetGraphicObject(true).GetType();
+            // A missing link is said once, as a link.
+            if (bThere && (eType == GraphicType::NONE || eType == GraphicType::Default))
+                aBroken.push_back(pObj->GetName());
+        }
+        if (auto pOle = dynamic_cast<SdrOle2Obj*>(pObj))
+        {
+            uno::Reference<embed::XLinkageSupport> xLink(pOle->getEmbeddedObjectRef().GetObject(), uno::UNO_QUERY);
+            if (xLink.is() && xLink->isLink())
+            {
+                osl::DirectoryItem aItem;
+                const OUString aUrl = xLink->getLinkURL();
+                aLinks.emplace_back(aUrl, osl::DirectoryItem::get(aUrl, aItem) != osl::FileBase::E_None);
+            }
+            if (pOle->IsEmpty())
+                aBroken.push_back(pObj->GetName());
+        }
+    }
+    {
+        auto aList = rJson.startArray("fonts");
+        for (const OUString& rFont : aFonts)
+            if (!rFont.isEmpty())
+                rJson.putSimpleValue(rFont);
+    }
+    {
+        auto aList = rJson.startArray("links");
+        for (const auto& [rUrl, bMissing] : aLinks)
+        {
+            auto aOne = rJson.startStruct();
+            rJson.put("url", rUrl);
+            rJson.put("missing", bMissing);
+        }
+    }
+    auto aList = rJson.startArray("broken");
+    for (const OUString& rName : aBroken)
+        rJson.putSimpleValue(rName);
+}
+
+/// Every slide and master, checked before a show.
+void lcl_SlideCheck(::tools::JsonWriter& rJson, SdDrawDocument& rDoc)
+{
+    {
+        auto aList = rJson.startArray("slides");
+        for (sal_uInt16 i = 0; i < rDoc.GetSdPageCount(PageKind::Standard); ++i)
+        {
+            auto aOne = rJson.startStruct();
+            lcl_PageCheck(rJson, *rDoc.GetSdPage(i, PageKind::Standard));
+        }
+    }
+    auto aList = rJson.startArray("masters");
+    for (sal_uInt16 i = 0; i < rDoc.GetMasterSdPageCount(PageKind::Standard); ++i)
+    {
+        SdPage* pMaster = rDoc.GetMasterSdPage(i, PageKind::Standard);
+        auto aOne = rJson.startStruct();
+        rJson.put("name", pMaster->GetName());
+        lcl_PageCheck(rJson, *pMaster);
+    }
+}
+
 /// Each slide for a show: hidden, notes, motion, media.
 void lcl_SlideShow(::tools::JsonWriter& rJson, SdDrawDocument& rDoc)
 {
@@ -2365,6 +2475,11 @@ void SdXImpressDocument::getCommandValues(::tools::JsonWriter& rJsonWriter, std:
         lcl_SlideShow(rJsonWriter, *mpDoc);
         return;
     }
+    if (rCommand == ".uno:SlideCheck")
+    {
+        lcl_SlideCheck(rJsonWriter, *mpDoc);
+        return;
+    }
     if (rCommand == ".uno:SlideTransition" || rCommand == ".uno:SlideAnimations")
     {
         DrawViewShell* pShell = GetViewShell();