使用QPainter渲染SVG文件

Question

我有一组SVG文件，希望在QWidget中用作图标。在我的QWidget paintEvent函数中，我有以下内容：

void Tool::paintEvent(QPaintEvent *e) {
    QImage icon = QImage(32, 32, QImage::Format_ARGB32);
    QSvgRenderer *ren = new QSvgRenderer(QString(m_part_dir.c_str()) + "\\drawing.svg");
    QPainter painter(&icon);
    ren->render(&painter);
}

我看了很多关于如何做这件事的建议，这种方法一直被提出。然而，当我运行这段代码时，它会抛出一个异常，在这一行：

ren->render(&painter);

这个中断停在一个名为dbgrptt.c的文件中：

_CRTIMP void __cdecl _CrtDbgBreak(
    void
    )
{
    __debugbreak();
}

调用栈看起来像这样：

msvcr110d.dll!_CrtDbgBreak() Line 87    C
msvcr110d.dll!_VCrtDbgReportW(int nRptType=2, void * returnAddress=0x0f8a7553, const wchar_t * szFile=0x0f793148, int nLine=52, const wchar_t * szModule=0x00000000, const wchar_t * szFormat=0x0f77127c, char * arglist=0x0029e954) Line 506   C
msvcr110d.dll!_CrtDbgReportWV(int nRptType=2, void * returnAddress=0x0f8a7553, const wchar_t * szFile=0x0f793148, int nLine=52, const wchar_t * szModule=0x00000000, const wchar_t * szFormat=0x0f77127c, char * arglist=0x0029e954) Line 262   C++
msvcr110d.dll!_CrtDbgReportW(int nRptType=2, const wchar_t * szFile=0x0f793148, int nLine=52, const wchar_t * szModule=0x00000000, const wchar_t * szFormat=0x0f77127c, ...) Line 279   C++
msvcr110d.dll!operator delete(void * pUserData=0x031392e0) Line 52  C++
QtGuid4.dll!QPenPrivate::`scalar deleting destructor'(unsigned int) C++
QtGuid4.dll!QPen::~QPen() Line 346  C++
QtGuid4.dll!QPaintEngineExPrivate::~QPaintEngineExPrivate() Line 172    C++
QtGuid4.dll!QRasterPaintEnginePrivate::~QRasterPaintEnginePrivate() C++
QtGuid4.dll!QRasterPaintEnginePrivate::`scalar deleting destructor'(unsigned int)   C++
QtGuid4.dll!QScopedPointerDeleter<QPaintEnginePrivate>::cleanup(QPaintEnginePrivate * pointer=0x03135d80) Line 62   C++
QtGuid4.dll!QScopedPointer<QPaintEnginePrivate,QScopedPointerDeleter<QPaintEnginePrivate> >::~QScopedPointer<QPaintEnginePrivate,QScopedPointerDeleter<QPaintEnginePrivate> >() Line 100    C++
QtGuid4.dll!QPaintEngine::~QPaintEngine() Line 723  C++
QtGuid4.dll!QPaintEngineEx::~QPaintEngineEx()   C++
QtGuid4.dll!QRasterPaintEngine::~QRasterPaintEngine() Line 428  C++
QtGuid4.dll!QRasterPaintEngine::`scalar deleting destructor'(unsigned int)  C++
QtGuid4.dll!QImageData::~QImageData() Line 224  C++
QtGuid4.dll!QImageData::`scalar deleting destructor'(unsigned int)  C++
QtGuid4.dll!QImage::~QImage() Line 1283 C++
SystemDesigner_d.exe!Parts::Tool::paintEvent(QPaintEvent * e=0x0029f238) Line 39    C++

有人能理解这个吗？

- jasonlg3d

---

尝试在绘制事件之外渲染图像，并仅在绘制事件期间绘制预先渲染的图像。即使那不是问题，也不要在绘制事件期间打开文件。它应该尽快完成。 - Kuba hasn't forgotten Monica

Answer 1

我找到了一种方法。在对象构造时，我使用 .svg 文件创建了一个 QIcon。然后我使用 QPainter.drawPixmap 来绘制 QIcon 的 pixmap。

在初始化列表中使用 m_icon(QString(m_part_dir.c_str()) + "\\icon.svg")

在 Paint 事件中：

void Tool::paintEvent(QPaintEvent *e) {
    QPainter painter(this);
    painter.setPen(QPen(Qt::gray, 1));
    painter.drawRect(0, 0, TOOL_WIDTH-1, TOOL_HEIGHT);

    //QIcon icon(QString(m_part_dir.c_str()) + "\\icon.svg");
    painter.drawPixmap(4, 4, 32, 32, m_icon.pixmap(QSize(32,32)));

    int text_y = TOOL_HEIGHT / 2 + 3;
    painter.setPen(QPen(Qt::black, 1));
    QString name(m_data["name"].c_str());
    painter.drawText(40, text_y, name);
}

感谢 Kuba Ober 的建议。

- jasonlg3d