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use enhanced metafiles for wxMSW print preview: this is as accurate as previous code, but much faster (fixes #9970)

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git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@60844 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775
This commit is contained in:
Václav Slavík 2009-05-31 19:15:07 +00:00
parent cc3445715d
commit a5c1223d2f
2 changed files with 27 additions and 291 deletions
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15
include/wx/msw/printwin.h
View File

@ -44,8 +44,6 @@ private:
// wxPrintout.
// ---------------------------------------------------------------------------
#define wxUSE_HIGH_QUALITY_PREVIEW (wxUSE_IMAGE && wxUSE_WXDIB)
class WXDLLIMPEXP_CORE wxWindowsPrintPreview : public wxPrintPreviewBase
{
public:
@ -60,22 +58,9 @@ public:
virtual bool Print(bool interactive);
virtual void DetermineScaling();
#if wxUSE_HIGH_QUALITY_PREVIEW
protected:
bool RenderPageIntoBitmapHQ(wxBitmap& bmp, int pageNum);
virtual bool RenderPageIntoBitmap(wxBitmap& bmp, int pageNum);
private:
bool RenderPageFragment(float scaleX, float scaleY,
int *nextFinalLine,
wxPrinterDC& printer,
wxMemoryDC& finalDC,
const wxRect& rect,
int pageNum);
bool m_hqPreviewFailed;
#endif // wxUSE_HIGH_QUALITY_PREVIEW
DECLARE_DYNAMIC_CLASS_NO_COPY(wxWindowsPrintPreview)
};

303
src/msw/printwin.cpp
View File

@ -49,6 +49,7 @@
#include "wx/msw/printdlg.h"
#include "wx/msw/private.h"
#include "wx/msw/dcprint.h"
#include "wx/msw/enhmeta.h"
#include <stdlib.h>
@ -335,9 +336,6 @@ wxWindowsPrintPreview::wxWindowsPrintPreview(wxPrintout *printout,
wxPrintDialogData *data)
: wxPrintPreviewBase(printout, printoutForPrinting, data)
{
#if wxUSE_HIGH_QUALITY_PREVIEW
m_hqPreviewFailed = false;
#endif
DetermineScaling();
}
@ -346,9 +344,6 @@ wxWindowsPrintPreview::wxWindowsPrintPreview(wxPrintout *printout,
wxPrintData *data)
: wxPrintPreviewBase(printout, printoutForPrinting, data)
{
#if wxUSE_HIGH_QUALITY_PREVIEW
m_hqPreviewFailed = false;
#endif
DetermineScaling();
}
@ -429,296 +424,52 @@ void wxWindowsPrintPreview::DetermineScaling()
m_previewScaleY = float(logPPIScreenY) / logPPIPrinterY;
}
#if wxUSE_HIGH_QUALITY_PREVIEW
// The preview, as implemented in wxPrintPreviewBase (and as used prior to wx3)
// is inexact: it uses screen DC, which has much lower resolution and has
// other properties different from printer DC, so the preview is not quite
// right.
//
// To make matters worse, if the application depends heavily on GetTextExtent()
// or does text layout itself, the output in preview and on paper can be very
// different. In particular, wxHtmlEasyPrinting is affected and the preview
// can be easily off by several pages.
//
// To fix this, we attempt to render the preview into high-resolution bitmap
// using DC with same resolution etc. as the printer DC. This takes lot of
// memory, so the code is more complicated than it could be, but the results
// are much better.
//
// Finally, this code is specific to wxMSW, because it doesn't make sense to
// bother with it on other platforms. Both OSX and modern GNOME/GTK+
// environments have builtin accurate preview (that applications should use
// instead) and the differences between screen and printer DC in wxGTK are so
// large than this trick doesn't help at all.
namespace
bool wxWindowsPrintPreview::RenderPageIntoBitmap(wxBitmap& bmp, int pageNum)
{
// If there's not enough memory, we need to render the preview in parts.
// Unfortunately we cannot simply use wxMemoryDC, because it reports its size
// as bitmap's size, and we need to use smaller bitmap while still reporting
// original ("correct") DC size, because printing code frequently uses
// GetSize() to determine scaling factor. This DC class handles this.
class PageFragmentDCImpl : public wxMemoryDCImpl
{
public:
PageFragmentDCImpl(wxMemoryDC *owner, wxDC *printer,
const wxPoint& offset,
const wxSize& fullSize)
: wxMemoryDCImpl(owner, printer),
m_offset(offset),
m_fullSize(fullSize)
{
SetDeviceOrigin(0, 0);
}
virtual void SetDeviceOrigin(wxCoord x, wxCoord y)
{
wxMemoryDCImpl::SetDeviceOrigin(x - m_offset.x, y - m_offset.y);
}
virtual void DoGetDeviceOrigin(wxCoord *x, wxCoord *y) const
{
wxMemoryDCImpl::DoGetDeviceOrigin(x, y);
if ( x ) *x += m_offset.x;
if ( x ) *y += m_offset.y;
}
virtual void DoGetSize(int *width, int *height) const
{
if ( width )
*width = m_fullSize.x;
if ( height )
*height = m_fullSize.y;
}
private:
wxPoint m_offset;
wxSize m_fullSize;
};
class PageFragmentDC : public wxDC
{
public:
PageFragmentDC(wxDC* printer, wxBitmap& bmp,
const wxPoint& offset,
const wxSize& fullSize)
: wxDC(new PageFragmentDCImpl((wxMemoryDC*)this, printer, offset, fullSize))
{
static_cast<PageFragmentDCImpl*>(m_pimpl)->DoSelect(bmp);
}
};
// estimate how big chunks we can render, given available RAM
long ComputeFragmentSize(long printerDepth,
long width,
long height)
{
// Compute the amount of memory needed to generate the preview.
// Memory requirements of RenderPageFragment() are as follows:
// The preview, as implemented in wxPrintPreviewBase (and as used prior to
// wx3) is inexact: it uses screen DC, which has much lower resolution and
// has other properties different from printer DC, so the preview is not
// quite right.
//
// (memory DC - always)
// width * height * printerDepth/8
// (wxImage + wxDIB instance)
// width * height * (3 + 4)
// (this could be reduced to *3 if using wxGraphicsContext)
// To make matters worse, if the application depends heavily on
// GetTextExtent() or does text layout itself, the output in preview and on
// paper can be very different. In particular, wxHtmlEasyPrinting is
// affected and the preview can be easily off by several pages.
//
// So, given amount of memory M, we can render at most
//
// height = M / (width * (printerDepth/8 + F))
//
// where F is 3 or 7 depending on whether wxGraphicsContext is used or not
wxMemorySize memAvail = wxGetFreeMemory();
if ( memAvail == -1 )
{
// we don't know; 10meg shouldn't be a problem hopefully
memAvail = 10000000;
}
else
{
// limit ourselves to half of available RAM to have a margin for other
// apps, for our rendering code, and for miscalculations
memAvail /= 2;
}
const float perPixel = float(printerDepth)/8 + (3 + 4);
const long perLine = long(width * perPixel);
const long maxstep = (memAvail / perLine).GetValue();
const long step = wxMin(height, maxstep);
wxLogTrace("printing",
"using %liMB of RAM (%li lines) for preview, %li %lipx fragments",
long((memAvail >> 20).GetValue()),
maxstep,
(height+step-1) / step,
step);
return step;
}
} // anonymous namespace
// To fix this, we render the preview into high-resolution enhanced
// metafile with properties identical to the printer DC. This guarantees
// metrics correctness while still being fast.
bool wxWindowsPrintPreview::RenderPageFragment(float scaleX, float scaleY,
int *nextFinalLine,
wxPrinterDC& printer,
wxMemoryDC& finalDC,
const wxRect& rect,
int pageNum)
{
// compute 'rect' equivalent in the small final bitmap:
const wxRect smallRect(wxPoint(0, *nextFinalLine),
wxPoint(int(rect.GetRight() * scaleX),
int(rect.GetBottom() * scaleY)));
wxLogTrace("printing",
"rendering fragment of page %i: [%i,%i,%i,%i] scaled down to [%i,%i,%i,%i]",
pageNum,
rect.x, rect.y, rect.GetRight(), rect.GetBottom(),
smallRect.x, smallRect.y, smallRect.GetRight(), smallRect.GetBottom()
);
// create DC and bitmap compatible with printer DC:
wxBitmap large(rect.width, rect.height, printer);
if ( !large.IsOk() )
return false;
// render part of the page into it:
{
PageFragmentDC memoryDC(&printer, large,
rect.GetPosition(),
wxSize(m_pageWidth, m_pageHeight));
if ( !memoryDC.IsOk() )
return false;
memoryDC.Clear();
if ( !RenderPageIntoDC(memoryDC, pageNum) )
return false;
} // release bitmap from memoryDC
// now scale the rendered part down and blit it into final output:
wxImage img;
{
wxDIB dib(large);
if ( !dib.IsOk() )
return false;
large = wxNullBitmap; // free memory a.s.a.p.
img = dib.ConvertToImage();
} // free the DIB now that it's no longer needed, too
if ( !img.IsOk() )
return false;
img.Rescale(smallRect.width, smallRect.height, wxIMAGE_QUALITY_HIGH);
if ( !img.IsOk() )
return false;
wxBitmap bmp(img);
if ( !bmp.IsOk() )
return false;
img = wxNullImage;
finalDC.DrawBitmap(bmp, smallRect.x, smallRect.y);
if ( bmp.IsOk() )
{
*nextFinalLine += smallRect.height;
return true;
}
return false;
}
bool wxWindowsPrintPreview::RenderPageIntoBitmapHQ(wxBitmap& bmp, int pageNum)
{
wxLogTrace("printing", "rendering HQ preview of page %i", pageNum);
// print the preview into a metafile:
wxPrinterDC printerDC(m_printDialogData.GetPrintData());
if ( !printerDC.IsOk() )
wxEnhMetaFileDC metaDC(printerDC,
wxEmptyString,
printerDC.GetSize().x, printerDC.GetSize().y);
if ( !RenderPageIntoDC(metaDC, pageNum) )
return false;
// compute scale factor
const float scaleX = float(bmp.GetWidth()) / float(m_pageWidth);
const float scaleY = float(bmp.GetHeight()) / float(m_pageHeight);
wxEnhMetaFile *metafile = metaDC.Close();
if ( !metafile )
return false;
// now render the metafile:
wxMemoryDC bmpDC;
bmpDC.SelectObject(bmp);
bmpDC.Clear();
const int initialStep = ComputeFragmentSize(printerDC.GetDepth(),
m_pageWidth, m_pageHeight);
wxRect outRect(0, 0, bmp.GetWidth(), bmp.GetHeight());
metafile->Play(&bmpDC, &outRect);
wxRect todo(0, 0, m_pageWidth, initialStep); // rect to render
int nextFinalLine = 0; // first not-yet-rendered output line
while ( todo.y < m_pageHeight )
{
todo.SetBottom(wxMin(todo.GetBottom(), m_pageHeight - 1));
delete metafile;
if ( !RenderPageFragment(scaleX, scaleY,
&nextFinalLine,
printerDC,
bmpDC,
todo,
pageNum) )
{
if ( todo.height < 20 )
{
// something is very wrong if we can't render even at this
// slow space, let's bail out and fall back to low quality
// preview
wxLogTrace("printing",
"it seems that HQ preview doesn't work at all");
return false;
}
// it's possible our memory calculation was off, or conditions
// changed, or there's not enough _bitmap_ resources; try if using
// smaller bitmap would help:
todo.height /= 2;
wxLogTrace("printing",
"preview of fragment failed, reducing height to %ipx",
todo.height);
continue; // retry at the same position again
}
// move to the next segment
todo.Offset(0, todo.height);
}
// TODO: we should keep the metafile and reuse it when changing zoom level
return true;
}
bool wxWindowsPrintPreview::RenderPageIntoBitmap(wxBitmap& bmp, int pageNum)
{
// try high quality rendering first:
if ( !m_hqPreviewFailed )
{
if ( RenderPageIntoBitmapHQ(bmp, pageNum) )
{
return true;
}
else
{
wxLogTrace("printing",
"high-quality preview failed, falling back to normal");
m_hqPreviewFailed = true; // don't bother re-trying
}
}
// if it fails, use the generic method that is less resource intensive,
// but inexact
return wxPrintPreviewBase::RenderPageIntoBitmap(bmp, pageNum);
}
#endif // wxUSE_HIGH_QUALITY_PREVIEW
/****************************************************************************