procedure TfrmOCGList.LoadUseage;
var
vPageObjects: PdfPageObjectsCollection;
vPageObject: PdfPageObject;
iPageObj: integer;
vMC: PdfMarkedContentCollection;
vOCGName: string;
vGroup: PdfOCGroup;
vDict: PdfTypeDictionary;
vType: PageObjectTypes;
vOC: PdfMarkedContent;
vDictType: IndirectObjectTypes;
vItem: PdfTypeBase;
vName, vLastName, vMarkName:string;
vCount, vMarkCount: integer;
vMCID: integer;
vMarkLen, vMarkIdx: integer;
vbuffer: TBytes;
vMarkType: IndirectObjectType;

procedure addToSnap(AObj: PdfPageObject);
begin
with FDocArray[FDocIdx].SnapArray do
begin
setlength(SnapArray, length(SnapArray) + 1);
SnapArray[length(SnapArray) - 1] := AObj;
end;
end;

begin
if not FDocArray[FDocIdx].IsVector then
exit;
with FDocArray[FDocIdx].SnapArray do
begin
setlength(SnapArray, 0);
IsValid := False;
end;
vPageObjects := FPage.PageObjects;
vCount := vPageObjects.Count;
for iPageObj := vCount - 1 Downto 0 do
begin
vPageObject := vPageObjects.Item[iPageObj];
if assigned(vMC) then
FreeAndNil(vMC);
vMC := vPageObject.MarkedContent;
if assigned(vMC) then
begin
if vMC.Count > 0 then
begin
vOC := vMC.Item[0];
if assigned(vOC) then
begin
vDict := PdfTypeDictionary(vOC.Parameters);
if vDict.ObjectType = IndirectObjectTypes.Reference then
begin
vGroup := PDFOCGroup(PdfTypeIndirect(vDict).Direct);
vOCGName := vGroup.Name;
end
else if vDict.ObjectType = IndirectObjectTypes.Dictionary then
begin
if vDict.ContainsKey('Name') then
begin
vName := PdfTypeString(vDict.Item['Name']).ANSIStringNet;
if vName <> vLastName then
with FDocArray[FDocIdx].OCGUseage do
begin
SetEntry(FPageIdx, vName, True, True);
vLastName := vName;
end;
end;
end;
end;
end;
end;
if vPageObject.ObjectType = PageObjectTypes.PDFPage_PATH then
if PDFium.FPDFOCG_CheckObjectVisible(FDocArray[FDocIdx].Document.Handle,
OCGEvent.View, vPageObject.Handle) then
addToSnap(vPageObject);
end;
with FDocArray[FDocIdx].SnapArray do
IsValid := True;
end;