Eeschema: SCH_SHEET_LIST improvements.

* Derive SCH_SHEET_LIST from std::vector rather than using internal array
  management.  Change all internal code to use iterators or array operator
  in loops.
* Allow creation of empty SCH_SHEET_LIST for external population for plotting
  and printing.
* Clean up print an plot code to take advantage of new SCH_SHEET_LIST behavior.
* Make BuildSheetList() public so list can be populated after creation.
* Update all instances of SCH_SHEET_LIST with the appropriate SCH_SHEET
  object on initialization.
* Create const and non-const version of SCH_SHEET_PATH::GetSheet().

eeschema/plot_schematic_PDF.cpp

@@ -41,7 +41,6 @@
 void DIALOG_PLOT_SCHEMATIC::createPDFFile( bool aPlotAll, bool aPlotFrameRef )
 {
     SCH_SCREEN*     screen = m_parent->GetScreen();
-    SCH_SHEET_PATH* sheetpath;
     SCH_SHEET_PATH  oldsheetpath = m_parent->GetCurrentSheet();     // sheetpath is saved here
 
     /* When printing all pages, the printed page is not the current page.  In
@@ -51,9 +50,12 @@ void DIALOG_PLOT_SCHEMATIC::createPDFFile( bool aPlotAll, bool aPlotFrameRef )
      * between many sheets and component references depend on the actual sheet
      * path used
      */
-    SCH_SHEET_LIST SheetList( NULL );
+    SCH_SHEET_LIST sheetList;
 
-    sheetpath = SheetList.GetFirst();
+    if( aPlotAll )
+        sheetList.BuildSheetList( g_RootSheet );
+    else
+        sheetList.push_back( m_parent->GetCurrentSheet() );
 
     // Allocate the plotter and set the job level parameter
     PDF_PLOTTER* plotter = new PDF_PLOTTER();
@@ -65,26 +67,14 @@ void DIALOG_PLOT_SCHEMATIC::createPDFFile( bool aPlotAll, bool aPlotFrameRef )
     wxFileName plotFileName;
     REPORTER& reporter = m_MessagesBox->Reporter();
 
-    // First page handling is different
-    bool first_page = true;
-
-    do
+    for( unsigned i = 0; i < sheetList.size(); i++ )
     {
-        // Step over the schematic hierarchy
-        if( aPlotAll )
-        {
-            wxCHECK_RET( sheetpath != NULL, wxT( "Attempt to plot undefined sheet path." ) );
+        m_parent->SetCurrentSheet( sheetList[i] );
+        m_parent->GetCurrentSheet().UpdateAllScreenReferences();
+        m_parent->SetSheetNumberAndCount();
+        screen = m_parent->GetCurrentSheet().LastScreen();
 
-            SCH_SHEET_PATH list = *sheetpath;
-
-            m_parent->SetCurrentSheet( list );
-            m_parent->GetCurrentSheet().UpdateAllScreenReferences();
-            m_parent->SetSheetNumberAndCount();
-            screen = m_parent->GetCurrentSheet().LastScreen();
-            sheetpath = SheetList.GetNext();
-        }
-
-        if( first_page )
+        if( i == 0 )
         {
 
             try
@@ -107,8 +97,6 @@ void DIALOG_PLOT_SCHEMATIC::createPDFFile( bool aPlotAll, bool aPlotFrameRef )
                 SetLocaleTo_C_standard();
                 setupPlotPagePDF( plotter, screen );
                 plotter->StartPlot();
-                first_page = false;
-
             }
             catch( const IO_ERROR& e )
             {
@@ -131,7 +119,7 @@ void DIALOG_PLOT_SCHEMATIC::createPDFFile( bool aPlotAll, bool aPlotFrameRef )
         }
 
         plotOneSheetPDF( plotter, screen, aPlotFrameRef );
-    } while( aPlotAll && sheetpath );
+    }
 
     // Everything done, close the plot and restore the environment
     msg.Printf( _( "Plot: '%s' OK.\n" ), GetChars( plotFileName.GetFullPath() ) );