Hey there, let's clarify where that dy property comes from—it's actually not defined in the <gdLst> section of your LeftArrow shape, and that's intentional!

What is dy? #

dy is a predefined global geometric parameter in OpenXML DrawingML, meaning it's a universal value available to all preset shapes without needing to be explicitly declared in individual shape definitions. It represents half the total height of the shape, so mathematically:

dy = h / 2

Where h is another predefined parameter for the shape's full height.

Other Common Predefined Parameters #

You'll see many of these used in your LeftArrow code too:

• w: Total width of the shape
• h: Total height of the shape
• l: X-coordinate of the shape's left edge
• t: Y-coordinate of the shape's top edge
• r: X-coordinate of the shape's right edge
• b: Y-coordinate of the shape's bottom edge
• vc: Y-coordinate of the shape's vertical center (equals t + dy)
• hc: X-coordinate of the shape's horizontal center

Checking Your LeftArrow Code #

Looking at your formula for y1:

<gd name="y1" fmla="+- vc 0 dy" />

This simplifies to vc - dy, which equals t (the top edge of the shape)—perfectly aligns with what dy represents as half the height.

Your Original LeftArrow Shape Definition #

Here's your code formatted for clarity:

<leftArrow>
<avLst xmlns="http://schemas.openxmlformats.org/drawingml/2006/main">
<gd name="adj1" fmla="val 50000" />
<gd name="adj2" fmla="val 50000" />
</avLst>
<gdLst xmlns="http://schemas.openxmlformats.org/drawingml/2006/main">
<gd name="maxAdj2" fmla="*/ 100000 w ss" />
<gd name="a1" fmla="pin 0 adj1 100000" />
<gd name="a2" fmla="pin 0 adj2 maxAdj2" />
<gd name="dx2" fmla="*/ ss a2 100000" />
<gd name="x2" fmla="+- l dx2 0" />
<gd name="dy1" fmla="*/ h a1 200000" />
<gd name="y1" fmla="+- vc 0 dy" />
<!-- Where define the dy property -->
<gd name="y2" fmla="+- vc dy1 0" />
<gd name="dx1" fmla="*/ y1 dx2 hd2" />
<gd name="x1" fmla="+- x2 0 dx1" />
</gdLst>
<ahLst xmlns="http://schemas.openxmlformats.org/drawingml/2006/main">
<ahXY gdRefY="adj1" minY="0" maxY="100000">
<pos x="r" y="y1" />
</ahXY>
<ahXY gdRefX="adj2" minX="0" maxX="maxAdj2">
<pos x="x2" y="t" />
</ahXY>
</ahLst>
<cxnLst xmlns="http://schemas.openxmlformats.org/drawingml/2006/main">
<cxn ang="3cd4">
<pos x="x2" y="t" />
</cxn>
<cxn ang="cd2">
<pos x="l" y="vc" />
</cxn>
<cxn ang="cd4">
<pos x="x2" y="b" />
</cxn>
<cxn ang="0">
<pos x="r" y="vc" />
</cxn>
</cxnLst>
<rect l="x1" t="y1" r="r" b="y2" xmlns="http://schemas.openxmlformats.org/drawingml/2006/main" />
<pathLst xmlns="http://schemas.openxmlformats.org/drawingml/2006/main">
<path>
<moveTo>
<pt x="l" y="vc" />
</moveTo>
<lnTo>
<pt x="x2" y="t" />
</lnTo>
<lnTo>
<pt x="x2" y="y1" />
</lnTo>
<lnTo>
<pt x="r" y="y1" />
</lnTo>
<lnTo>
<pt x="r" y="y2" />
</lnTo>
<lnTo>
<pt x="x2" y="y2" />
</lnTo>
<lnTo>
<pt x="x2" y="b" />
</lnTo>
<close />
</path>
</pathLst>
</leftArrow>

内容的提问来源于stack exchange，提问作者lindexi