Interface ExtendedMetrics

The read-only actualBoundingBoxAscent property of the TextMetrics interface is a double giving the distance from the horizontal line indicated by the CanvasRenderingContext2D.textBaseline attribute to the top of the bounding rectangle used to render the text, in CSS pixels.

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The read-only actualBoundingBoxDescent property of the TextMetrics interface is a double giving the distance from the horizontal line indicated by the CanvasRenderingContext2D.textBaseline attribute to the bottom of the bounding rectangle used to render the text, in CSS pixels.

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The read-only actualBoundingBoxLeft property of the TextMetrics interface is a double giving the distance parallel to the baseline from the alignment point given by the CanvasRenderingContext2D.textAlign property to the left side of the bounding rectangle of the given text, in CSS pixels; positive numbers indicating a distance going left from the given alignment point.

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The read-only actualBoundingBoxRight property of the TextMetrics interface is a double giving the distance parallel to the baseline from the alignment point given by the CanvasRenderingContext2D.textAlign property to the right side of the bounding rectangle of the given text, in CSS pixels.

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The read-only alphabeticBaseline property of the TextMetrics interface is a double giving the distance from the horizontal line indicated by the CanvasRenderingContext2D.textBaseline property to the alphabetic baseline of the line box, in CSS pixels.

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The font's ascent above the baseline in whole px at the measured size — GDI's tmAscent, which is what Excel lays text out with (the OS/2 winAscent, hinted where the font has a VDMX table).

The baseline's offset from the top of a lineHeight box, in px: where a renderer that paints the line as a box (a CSS line box) puts the alphabetic baseline.

The font's descent below the baseline in whole px — GDI's tmDescent (OS/2 winDescent).

The read-only emHeightAscent property of the TextMetrics interface returns the distance from the horizontal line indicated by the CanvasRenderingContext2D.textBaseline property to the top of the em square in the line box, in CSS pixels.

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The read-only emHeightDescent property of the TextMetrics interface returns the distance from the horizontal line indicated by the CanvasRenderingContext2D.textBaseline property to the bottom of the em square in the line box, in CSS pixels.

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The read-only fontBoundingBoxAscent property of the TextMetrics interface returns the distance from the horizontal line indicated by the CanvasRenderingContext2D.textBaseline attribute, to the top of the highest bounding rectangle of all the fonts used to render the text, in CSS pixels.

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The read-only fontBoundingBoxDescent property of the TextMetrics interface returns the distance from the horizontal line indicated by the CanvasRenderingContext2D.textBaseline attribute to the bottom of the bounding rectangle of all the fonts used to render the text, in CSS pixels.

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The read-only hangingBaseline property of the TextMetrics interface is a double giving the distance from the horizontal line indicated by the CanvasRenderingContext2D.textBaseline property to the hanging baseline of the line box, in CSS pixels.

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The read-only ideographicBaseline property of the TextMetrics interface is a double giving the distance from the horizontal line indicated by the CanvasRenderingContext2D.textBaseline property to the ideographic baseline of the line box, in CSS pixels.

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The read-only width property of the TextMetrics interface contains the text's advance width (the width of that inline box) in CSS pixels.

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