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// Copyright (c) 2010 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include <windows.h>
#include <vector>
#include "base/basictypes.h"
namespace gfx {
class Rect;
namespace printing {
// Simple wrapper class that manage an EMF data stream and its virtual HDC.
class Emf {
class Record;
class Enumerator;
struct EnumerationContext;
// Generates a virtual HDC that will record every GDI commands and compile it
// in a EMF data stream.
// hdc is used to setup the default DPI and color settings. hdc is optional.
// rect specifies the dimensions (in .01-millimeter units) of the EMF. rect is
// optional.
bool CreateDc(HDC sibling, const RECT* rect);
// Load a EMF data stream. buffer contains EMF data.
bool CreateFromData(const void* buffer, uint32 size);
// TODO(maruel): CreateFromFile(). If ever used. Maybe users would like to
// have the ability to save web pages to an EMF file? Afterward, it is easy to
// convert to PDF or PS.
// Closes the HDC created by CreateDc() and generates the compiled EMF
// data.
bool CloseDc();
// Closes the EMF data handle when it is not needed anymore.
void CloseEmf();
// "Plays" the EMF buffer in a HDC. It is the same effect as calling the
// original GDI function that were called when recording the EMF. |rect| is in
// "logical units" and is optional. If |rect| is NULL, the natural EMF bounds
// are used.
// Note: Windows has been known to have stack buffer overflow in its GDI
// functions, whether used directly or indirectly through precompiled EMF
// data. We have to accept the risk here. Since it is used only for printing,
// it requires user intervention.
bool Playback(HDC hdc, const RECT* rect) const;
// The slow version of Playback(). It enumerates all the records and play them
// back in the HDC. The trick is that it skip over the records known to have
// issue with some printers. See Emf::Record::SafePlayback implementation for
// details.
bool SafePlayback(HDC hdc) const;
// Retrieves the bounds of the painted area by this EMF buffer. This value
// should be passed to Playback to keep the exact same size.
gfx::Rect GetBounds() const;
// Retrieves the EMF stream size.
uint32 GetDataSize() const;
// Retrieves the EMF stream.
bool GetData(void* buffer, uint32 size) const;
// Retrieves the EMF stream. It is an helper function.
bool GetData(std::vector<uint8>* buffer) const;
HENHMETAFILE emf() const {
return emf_;
HDC hdc() const {
return hdc_;
// Inserts a custom GDICOMMENT records indicating StartPage/EndPage calls
// (since StartPage and EndPage do not work in a metafile DC). Only valid
// when hdc_ is non-NULL.
bool StartPage();
bool EndPage();
// Saves the EMF data to a file as-is. It is recommended to use the .emf file
// extension but it is not enforced. This function synchronously writes to the
// file. For testing only.
bool SaveTo(const std::wstring& filename) const;
// Playbacks safely one EMF record.
static int CALLBACK SafePlaybackProc(HDC hdc,
HANDLETABLE* handle_table,
const ENHMETARECORD* record,
int objects_count,
LPARAM param);
// Compiled EMF data handle.
// Valid when generating EMF data through a virtual HDC.
HDC hdc_;
struct Emf::EnumerationContext {
HANDLETABLE* handle_table;
int objects_count;
HDC hdc;
// One EMF record. It keeps pointers to the EMF buffer held by Emf::emf_.
// The entries become invalid once Emf::CloseEmf() is called.
class Emf::Record {
// Plays the record.
bool Play() const;
// Plays the record working around quirks with SetLayout,
// SetWorldTransform and ModifyWorldTransform. See implementation for details.
bool SafePlayback(const XFORM* base_matrix) const;
// Access the underlying EMF record.
const ENHMETARECORD* record() const { return record_; }
Record(const EnumerationContext* context,
const ENHMETARECORD* record);
friend class Emf;
friend class Enumerator;
const ENHMETARECORD* record_;
const EnumerationContext* context_;
// Retrieves individual records out of a Emf buffer. The main use is to skip
// over records that are unsupported on a specific printer or to play back
// only a part of an EMF buffer.
class Emf::Enumerator {
// Iterator type used for iterating the records.
typedef std::vector<Record>::const_iterator const_iterator;
// Enumerates the records at construction time. |hdc| and |rect| are
// both optional at the same time or must both be valid.
// Warning: |emf| must be kept valid for the time this object is alive.
Enumerator(const Emf& emf, HDC hdc, const RECT* rect);
// Retrieves the first Record.
const_iterator begin() const;
// Retrieves the end of the array.
const_iterator end() const;
// Processes one EMF record and saves it in the items_ array.
static int CALLBACK EnhMetaFileProc(HDC hdc,
HANDLETABLE* handle_table,
const ENHMETARECORD* record,
int objects_count,
LPARAM param);
// The collection of every EMF records in the currently loaded EMF buffer.
// Initialized by Enumerate(). It keeps pointers to the EMF buffer held by
// Emf::emf_. The entries become invalid once Emf::CloseEmf() is called.
std::vector<Record> items_;
EnumerationContext context_;
} // namespace printing