Better quality previews in print dialog.

Make a fixed size bitmap of the current document for preview in
print dialog. The bitmap is scaled when the dialog is resized, which
is faster and better quality as it uses "BEST" scaling method for
resizing the bitmap.

Change-Id: I3be0bec30a7f2cd594c56d23fe2b39221aff807c

2 files changed, 57 insertions, 52 deletions

diff --git a/vcl/inc/printdlg.hxx b/vcl/inc/printdlg.hxx
index d57218ebd2bb..296d5b89edea 100644
--- a/vcl/inc/printdlg.hxx
+++ b/vcl/inc/printdlg.hxx
@@ -45,16 +45,21 @@ namespace vcl
     public:
         class PrintPreviewWindow : public Window
         {
+            static const sal_Int32 PREVIEW_BITMAP_WIDTH;
+
             GDIMetaFile         maMtf;
             Size                maOrigSize;
             Size                maPreviewSize;
             VirtualDevice       maPageVDev;
+            Bitmap              maPreviewBitmap;
             rtl::OUString       maReplacementString;
             rtl::OUString       maToolTipString;
             bool                mbGreyscale;
             FixedLine           maHorzDim;
             FixedLine           maVertDim;
 
+            void preparePreviewBitmap();
+
         public:
             PrintPreviewWindow( Window* pParent );
             virtual ~PrintPreviewWindow();
diff --git a/vcl/source/window/printdlg.cxx b/vcl/source/window/printdlg.cxx
index 7562a16880a5..bfceb7e7b168 100644
--- a/vcl/source/window/printdlg.cxx
+++ b/vcl/source/window/printdlg.cxx
@@ -84,6 +84,8 @@ PrintDialog::PrintPreviewWindow::~PrintPreviewWindow()
 {
 }
 
+const sal_Int32 PrintDialog::PrintPreviewWindow::PREVIEW_BITMAP_WIDTH = 1600;
+
 void PrintDialog::PrintPreviewWindow::DataChanged( const DataChangedEvent& i_rDCEvt )
 {
     // react on settings changed
@@ -133,13 +135,11 @@ void PrintDialog::PrintPreviewWindow::Resize()
     // quality of the preview, e.g. when its height approaches the number of text lines
     // find a good scaling factor
     Size aPreviewMMSize( maPageVDev.PixelToLogic( aScaledSize, MapMode( MAP_100TH_MM ) ) );
-    double fZoom = double(maOrigSize.Height())/double(aPreviewMMSize.Height());
-    while( fZoom > 10 )
-    {
-        aScaledSize.Width() *= 2;
-        aScaledSize.Height() *= 2;
-        fZoom /= 2.0;
-    }
+
+    double aAspectRatio = aScaledSize.Height() / (double) aScaledSize.Width();
+
+    aScaledSize.Width()  = PREVIEW_BITMAP_WIDTH;
+    aScaledSize.Height() = PREVIEW_BITMAP_WIDTH * aAspectRatio;
 
     maPageVDev.SetOutputSizePixel( aScaledSize, sal_False );
 
@@ -175,47 +175,9 @@ void PrintDialog::PrintPreviewWindow::Paint( const Rectangle& )
     }
     else
     {
-        GDIMetaFile aMtf( maMtf );
-
-        const Size aVDevSize( maPageVDev.GetOutputSizePixel() );
-        const Size aLogicSize( maPageVDev.PixelToLogic( aVDevSize, MapMode( MAP_100TH_MM ) ) );
-        Size aOrigSize( maOrigSize );
-        if( aOrigSize.Width() < 1 )
-            aOrigSize.Width() = aLogicSize.Width();
-        if( aOrigSize.Height() < 1 )
-            aOrigSize.Height() = aLogicSize.Height();
-        double fScale = double(aLogicSize.Width())/double(aOrigSize.Width());
-
-
-        maPageVDev.Erase();
-        maPageVDev.Push();
-        maPageVDev.SetMapMode( MAP_100TH_MM );
-        sal_uLong nOldDrawMode = maPageVDev.GetDrawMode();
-        if( mbGreyscale )
-            maPageVDev.SetDrawMode( maPageVDev.GetDrawMode() |
-                                    ( DRAWMODE_GRAYLINE | DRAWMODE_GRAYFILL | DRAWMODE_GRAYTEXT |
-                                      DRAWMODE_GRAYBITMAP | DRAWMODE_GRAYGRADIENT ) );
-        aMtf.WindStart();
-        aMtf.Scale( fScale, fScale );
-        aMtf.WindStart();
-
-        const sal_uInt16 nOriginalAA(maPageVDev.GetAntialiasing());
-        maPageVDev.SetAntialiasing(nOriginalAA | ANTIALIASING_ENABLE_B2DDRAW);
-
-        aMtf.Play( &maPageVDev, Point( 0, 0 ), aLogicSize );
-        maPageVDev.Pop();
-
-        maPageVDev.SetAntialiasing(nOriginalAA);
-
-        SetMapMode( MAP_PIXEL );
-        maPageVDev.SetMapMode( MAP_PIXEL );
-
-        // use lanzcos scaling
-        Bitmap aContent(maPageVDev.GetBitmap(Point(0, 0), aVDevSize));
-        aContent.Scale(maPreviewSize, BMP_SCALE_BEST);
-        DrawBitmap(aOffset, aContent);
-
-        maPageVDev.SetDrawMode( nOldDrawMode );
+        Bitmap aPreviewBitmap(maPreviewBitmap);
+        aPreviewBitmap.Scale(maPreviewSize, BMP_SCALE_BEST);
+        DrawBitmap(aOffset, aPreviewBitmap);
     }
 
     Rectangle aFrameRect( aOffset + Point( -1, -1 ),
@@ -236,10 +198,6 @@ void PrintDialog::PrintPreviewWindow::Command( const CommandEvent& rEvt )
                 pDlg->previewForward();
             else if( pWheelData->GetDelta() < 0 )
                 pDlg->previewBackward();
-            /*
-            else
-                huh ?
-            */
         }
     }
 }
@@ -291,9 +249,51 @@ void PrintDialog::PrintPreviewWindow::setPreview( const GDIMetaFile& i_rNewPrevi
     maVertDim.SetText( aBuf.makeStringAndClear() );
 
     Resize();
+    preparePreviewBitmap();
     Invalidate();
 }
 
+void PrintDialog::PrintPreviewWindow::preparePreviewBitmap()
+{
+    GDIMetaFile aMtf( maMtf );
+
+    Size aVDevSize( maPageVDev.GetOutputSizePixel() );
+    const Size aLogicSize( maPageVDev.PixelToLogic( aVDevSize, MapMode( MAP_100TH_MM ) ) );
+    Size aOrigSize( maOrigSize );
+    if( aOrigSize.Width() < 1 )
+        aOrigSize.Width() = aLogicSize.Width();
+    if( aOrigSize.Height() < 1 )
+        aOrigSize.Height() = aLogicSize.Height();
+    double fScale = double(aLogicSize.Width())/double(aOrigSize.Width());
+
+
+    maPageVDev.Erase();
+    maPageVDev.Push();
+    maPageVDev.SetMapMode( MAP_100TH_MM );
+    sal_uLong nOldDrawMode = maPageVDev.GetDrawMode();
+    if( mbGreyscale )
+        maPageVDev.SetDrawMode( maPageVDev.GetDrawMode() |
+                                ( DRAWMODE_GRAYLINE | DRAWMODE_GRAYFILL | DRAWMODE_GRAYTEXT |
+                                  DRAWMODE_GRAYBITMAP | DRAWMODE_GRAYGRADIENT ) );
+    aMtf.WindStart();
+    aMtf.Scale( fScale, fScale );
+    aMtf.WindStart();
+
+    const sal_uInt16 nOriginalAA(maPageVDev.GetAntialiasing());
+    maPageVDev.SetAntialiasing(nOriginalAA | ANTIALIASING_ENABLE_B2DDRAW);
+    aMtf.Play( &maPageVDev, Point( 0, 0 ), aLogicSize );
+    maPageVDev.SetAntialiasing(nOriginalAA);
+
+    maPageVDev.Pop();
+
+    SetMapMode( MAP_PIXEL );
+    maPageVDev.SetMapMode( MAP_PIXEL );
+
+    maPreviewBitmap = Bitmap(maPageVDev.GetBitmap(Point(0, 0), aVDevSize));
+
+    maPageVDev.SetDrawMode( nOldDrawMode );
+}
+
 PrintDialog::ShowNupOrderWindow::ShowNupOrderWindow( Window* i_pParent )
     : Window( i_pParent, WB_NOBORDER )
     , mnOrderMode( 0 )