CODEWITHSUNDEEP
c++svgdirect2dpathgeometry
NoName
NoName

Reputation: 8025

Draw a SVG path with Direct2D: Can't draw elliptical arc

I have following SVG path:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.1//EN" "http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd">
<svg xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" version="1.1" width="24" height="24" viewBox="0 0 24 24">
    <path d="M6,2C4.89,2 4,2.89 4,4V20A2,2 0 0,0 6,22H18A2,2 0 0,0 20,20V8L14,2H6Z" />
</svg>

For easy of reading:

M 6, 2
C 4.89, 2 4,2.89 4,4
V 20
A 2,2 0 0,0 6,22
H 18
A 2,2 0 0,0 20,20
V 8L14,2
H 6
Z

I'm trying to convert this to a ID2D1PathGeometry. Here is the code:

ID2D1PathGeometry *geo = NULL;
ID2D1GeometrySink *pSink = NULL;
d2DFactory->CreatePathGeometry(&geo);
geo->Open(&pSink);
pSink->SetFillMode(D2D1_FILL_MODE_WINDING);

pSink->BeginFigure({ 6.00f, 2.00f }, D2D1_FIGURE_BEGIN_FILLED);
pSink->AddBezier({ { 4.89f, 2.00f },{ 4.00f, 2.89f },{ 4.00f, 4.00f } });
pSink->AddLine({ 4.00f, 20.00f });
{
    D2D1_ARC_SEGMENT arc;
    arc.point.x = 6.00f;
    arc.point.y = 22.00f;
    arc.size.width = 2.00f;
    arc.size.height = 2.00f;
    arc.rotationAngle = 0.00f;
    arc.sweepDirection = D2D1_SWEEP_DIRECTION_CLOCKWISE;
    pSink->AddArc(&arc);
}
pSink->AddLine({ 18.00f, 22.00f });
{
    D2D1_ARC_SEGMENT arc;
    arc.point.x = 6.00f;
    arc.point.y = 22.00f;
    arc.size.width = 2.00f;
    arc.size.height = 2.00f;
    arc.rotationAngle = 0.00f;
    arc.sweepDirection = D2D1_SWEEP_DIRECTION_CLOCKWISE;
    pSink->AddArc(&arc);
}
pSink->AddLine({ 20.00f, 8.00f });
pSink->AddLine({ 14.00f, 2.00f });
pSink->AddLine({ 6.00f, 2.00f });
pSink->EndFigure(D2D1_FIGURE_END_CLOSED);

pSink->Close();
pSink->Release();

pRT->DrawGeometry(geo, brushBlack);

While I can convert lines and bezier successfully, I failed to convert Arcs.
For example, the code above will not draw anything, but if I comments following lines:

// pSink->AddArc(&arc);

It will draw a shape, but certainly will not exactly what is output by Chrome browser, because of lack some segments.

Question:

1.

What is the error in my code that prevent me draw geometry with Arcs segment? How to fix it?

2.

In w3.org document, an Arc segment have follwing value:

rx, ry, x_axis_rotation, large_arc_flag, sweep_flag, x, y

While I can set rx, ry, x_axis_rotation, sweep_flag, x, y, I don't see the member large_arc_flag in D2D1_ARC_SEGMENT struct. How can I adapt it to my code?

Upvotes: 0

Views: 578

Answers (1)

user7860670
user7860670

Reputation: 37587

  1. You should inspect the value returned by pSink->Close(); to determine what went wrong.
  2. D2D1_ARC_SEGMENT::arcSize that you don't initialize at all causing UB and potentially causing code to fail to add arc since flag value most likely turns to be invalid.

Upvotes: 1

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