SetTransformLocal question.

Question

Hello,

I have the following code;

IXpsOMMatrixTransform* rawGeomToPhys;
                            result = xpsObjectFactory->CreateMatrixTransform(&combinedMatrix, &rawGeomToPhys);

                            IXpsOMVisualCollection* pageVisuals;
                            result = page->GetVisuals(&pageVisuals);

                            result = pageVisuals->Append(scaleCanvas);

                            scaleCanvas->SetTransformLocal(rawGeomToPhys);

                            IXpsOMVisual* visual = NULL;
                            XPS_OBJECT_TYPE  visualType;

                            UINT32 count;
                            UINT32 thisVisual;

                            pageVisuals->GetCount(&count);
                            thisVisual = 0;
                            while (thisVisual < count) 
                            {
                                result = pageVisuals->GetAt(thisVisual, &visual);

                                result = visual->GetType(&visualType);

                                if (visualType == XPS_OBJECT_TYPE_CANVAS)
                                {
                                    result = visual->SetTransformLocal(rawGeomToPhys);
                                }

                                if (NULL != visual) { visual->Release(); visual = NULL; }
                                thisVisual++;
                            }

If I remove the following line;

scaleCanvas->SetTransformLocal(rawGeomToPhys);

the scale and translate on the matrix takes effect; however, the pages are produced upside down and content is mirrored.

If I keep the aforementioned line of code, the scale and translate on the matrix has no effect; however, the pages produced come out scaled to the page size and in proper format (upside and not mirrored) (must be using a default value for the scaling and translation)

How can I keep;

scaleCanvas->SetTransformLocal(rawGeomToPhys);

in my code but still apply the matrix scale and translate which is something like;

combinedMatrix.scale(0.5, 0.5);
combinedMatrix.translate(y, x);

Answer 1

Perhaps you should code according to the following code from chromium, especially the order of SetTransformLocal and Append, etc. I suppose there is no trick about SetTransformLocal.:

bool SkXPSDevice::endSheet() {
    //XPS is fixed at 96dpi (XPS Spec 11.1).
    static const float xpsDPI = 96.0f;
    static const float inchesPerMeter = 10000.0f / 254.0f;
    static const float targetUnitsPerMeter = xpsDPI * inchesPerMeter;
    const float scaleX = targetUnitsPerMeter
                       / SkScalarToFLOAT(this->fCurrentUnitsPerMeter.fX);
    const float scaleY = targetUnitsPerMeter
                       / SkScalarToFLOAT(this->fCurrentUnitsPerMeter.fY);
    //Create the scale canvas.
    SkTScopedComPtr<IXpsOMCanvas> scaleCanvas;
    HRBM(this->fXpsFactory->CreateCanvas(&scaleCanvas),
         "Could not create scale canvas.");
    SkTScopedComPtr<IXpsOMVisualCollection> scaleCanvasVisuals;
    HRBM(scaleCanvas->GetVisuals(&scaleCanvasVisuals),
         "Could not get scale canvas visuals.");
    SkTScopedComPtr<IXpsOMMatrixTransform> geomToPhys;
    XPS_MATRIX rawGeomToPhys = { scaleX, 0, 0, scaleY, 0, 0, };
    HRBM(this->fXpsFactory->CreateMatrixTransform(&rawGeomToPhys, &geomToPhys),
         "Could not create geometry to physical transform.");
    HRBM(scaleCanvas->SetTransformLocal(geomToPhys.get()),
         "Could not set transform on scale canvas.");
    //Add the content canvas to the scale canvas.
    HRBM(scaleCanvasVisuals->Append(this->fCurrentXpsCanvas.get()),
         "Could not add base canvas to scale canvas.");
    //Create the page.
    XPS_SIZE pageSize = {
        SkScalarToFLOAT(this->fCurrentCanvasSize.width()) * scaleX,
        SkScalarToFLOAT(this->fCurrentCanvasSize.height()) * scaleY,
    };
    SkTScopedComPtr<IXpsOMPage> page;
    HRB(this->createXpsPage(pageSize, &page));
    SkTScopedComPtr<IXpsOMVisualCollection> pageVisuals;
    HRBM(page->GetVisuals(&pageVisuals), "Could not get page visuals.");
    //Add the scale canvas to the page.
    HRBM(pageVisuals->Append(scaleCanvas.get()),
         "Could not add scale canvas to page.");
    //Create the package writer if it hasn't been created yet.
    if (NULL == this->fPackageWriter.get()) {
        SkTScopedComPtr<IXpsOMImageResource> image;
        //Ignore return, thumbnail is completely optional.
        this->createXpsThumbnail(page.get(), 0, &image);
        HRB(this->initXpsDocumentWriter(image.get()));
    }
    HRBM(this->fPackageWriter->AddPage(page.get(),
                                       &pageSize,
                                       NULL,
                                       NULL,
                                       NULL,
                                       NULL),
         "Could not write the page.");
    this->fCurrentXpsCanvas.reset();
    return true;
}

and

void SkXPSDevice::drawDevice(const SkDraw& d, SkBaseDevice* dev,
                             int x, int y,
                             const SkPaint&) {
    SkXPSDevice* that = static_cast<SkXPSDevice*>(dev);
    SkTScopedComPtr<IXpsOMMatrixTransform> xpsTransform;
    XPS_MATRIX rawTransform = {
        1.0f,
        0.0f,
        0.0f,
        1.0f,
        static_cast<FLOAT>(x),
        static_cast<FLOAT>(y),
    };
    HRVM(this->fXpsFactory->CreateMatrixTransform(&rawTransform, &xpsTransform),
         "Could not create layer transform.");
    HRVM(that->fCurrentXpsCanvas->SetTransformLocal(xpsTransform.get()),
         "Could not set layer transform.");
    //Get the current visual collection and add the layer to it.
    SkTScopedComPtr<IXpsOMVisualCollection> currentVisuals;
    HRVM(this->fCurrentXpsCanvas->GetVisuals(&currentVisuals),
         "Could not get current visuals for layer.");
    HRVM(currentVisuals->Append(that->fCurrentXpsCanvas.get()),
         "Could not add layer to current visuals.");
}