Gets or sets a value that specifies an aspect value for an element that will effectively preserve the x-height of the first choice font, whether it is substituted or not.
HRESULT IHTMLCSSStyleDeclaration::get_fontSizeAdjust(VARIANT *p);HRESULT IHTMLCSSStyleDeclaration::put_fontSizeAdjust(VARIANT v);
- Pointer to a variable of type VARIANT that receives one of the values listed in Possible Values.
- VARIANT that specifies one of the values listed in Possible Values.
none Default. Indicates the font's x-height should not be preserved. inherit Indicates that the property takes the same computed value as the property for the element's parent. number Specifies the aspect value. For the adjusted font size calculation, see Remarks.
Returns S_OK if successful, or an error value otherwise.
For any given font size, the apparent size and legibility of text varies across fonts. For scripts such as Latin or Cyrillic that distinguish between uppercase and lowercase letters, the relative height of lowercase letters compared to their uppercase counterparts is a determining factor of legibility. This is commonly referred to as the aspect value . Precisely defined, it is equal to the x-height of a font (the height of a font's lowercase 'x' character) divided by the font size.
In situations where font fallback occurs, fallback fonts cannot share the same aspect ratio as the desired font family and thus appear less legible. Font fallback occurs when the specified font is not available and the client uses a fallback font, or a replacement font. The IHTMLCSSStyleDeclaration::fontSizeAdjust property is a way to preserve the legibility of text when font fallback occurs. It does this by adjusting the font size so that the x-height is the same regardless of the font that is used.
The following calculation uses the number value to calculate the adjusted font size:
c = ( a / a' ) s
In this equation,
sis the font-size value,
ais the number value of the IHTMLCSSStyleDeclaration::fontSizeAdjust property,
a'is the aspect value of the actual font, and
cis the adjusted font size to use.
This property applies to any font that is selected, but in typical usage it should be based on the aspect value of the first font in the font-family list. If this is specified accurately, the (
a/a') term in the formula listed previously is 1 for the first font and no adjustment occurs. If the value is specified inaccurately, text that is rendered by using the first font in the family list displays differently in earlier versions of Internet Explorer, which do not support the IHTMLCSSStyleDeclaration::fontSizeAdjust property .