[css-fonts-5] Start level 5 as CSSWG resolved to put stuff there today w3c#126

Author: svgeesus

css-fonts-5/Overview.bs

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+
+Title: CSS Fonts Module Level 5
+Shortname: css-fonts
+Level: 5
+Status: ED
+Work Status: exploring
+Group: CSSWG
+ED: https://drafts.csswg.org/css-fonts-5/
+TR: https://www.w3.org/TR/css-fonts-5/
+!Delta Spec: yes
+Editor: Myles C. Maxfield, Apple Inc., [email protected], w3cid 77180
+Editor: Chris Lilley, W3C, http://svgees.us, w3cid 1438
+Abstract: This specification defines modifications to the existing CSS Fonts 4 specification along with additional features.
+Repository: w3c/csswg-drafts
+Inline Github Issues: title
+Default Highlight: css
+Warning: Not Ready
+
+
+
+spec:css-color-4; type:property; text:color
+spec:css-values; type:value; text:ex
+spec:css22; type:value; for:/; text:block
+spec:html; type:element; text:font
+spec:css-fonts-4; type:descriptor; text:font-language-override
+
+
+
+
+Introduction
+
+The CSS Fonts Level 4 specification ([[!CSS-FONTS-4]]) describes the
+controls CSS provides for selecting and using fonts within documents,
+including support for variable fonts and color fonts.
+The ideas here are additions or modifications to the properties and
+rules defined in CSS Fonts Level 4.
+
+This specification is currently a delta to the CSS Fonts Level 4 specification.
+Do not assume that if something is not here, it has been dropped.
+
+
+
+
+Value Definitions
+
+This specification follows the CSS property definition conventions from [[!CSS2]]
+using the value definition syntax from [[!CSS-VALUES-3]].
+Value types not defined in this specification are defined in CSS Values & Units [[!CSS-VALUES-3]].
+Combination with other CSS modules may expand the definitions of these value types.
+
+In addition to the property-specific values listed in their definitions,
+all properties defined in this specification
+also accept the CSS-wide keywords as their property value.
+For readability they have not been repeated explicitly.
+
+
+Basic Font Properties
+
+
+    Font family: the 'font-family!!property' property
+
+
+Generic font families
+
+In addition to the [[css-fonts-4#generic-font-families]]
+in CSS Fonts Level 4, the following new generic font families are also defined.
+
+Issue(4910):
+
+Issue(5054):
+
+    
+        xxx
+        
+            Placeholder text for the xxx generic font family.
+
+
+    
+
+Issue(4566):
+
+Font weight: the 'font-weight!!property' property
+
+Issue(2690):
+
+
+
+Font style: the 'font-style!!property' property
+
+Issue(4044):
+
+
+
+Relative sizing: the 'font-size-adjust' property
+
+Issue(5539):
+
+
+
+Font Resources
+
+
+The ''@font-face'' rule
+
+Issue(5518):
+
+
+
+Font property descriptors: the 'font-size!!descriptor'
+
+
+Issue(806):
+
+Issue(731):
+
+Issue(5892):
+
+
+
+
+
+Default font metrics overriding:
+the 'ascent-override', 'descent-override' and 'line-gap-override' descriptors
+
+
+Name: ascent-override
+Value: normal | <>
+For: @font-face
+Initial: normal
+
+
+
+Name: descent-override
+Value: normal | <>
+For: @font-face
+Initial: normal
+
+
+
+Name: line-gap-override
+Value: normal | <>
+For: @font-face
+Initial: normal
+
+
+The 'ascent-override', 'descent-override' and 'line-gap-override' descriptors define the
+ascent metric, descent metric and
+line gap metric of the font, respectively.
+
+When the descriptor value is 'normal', the corresponding metric value is obtained from the
+font file directly.
+
+Note: User agents may draw data from different places from the font file as the metric values,
+which results in different text layouts.
+
+When the descriptor value is a percentage, the corresponding metric value is resolved as the
+given percentage multiplied by the used font size. Negative values are invalid at parse time.
+
+
+	The percentage is resolved against different font sizes for different elements.
+
+
+@font-face {
+  font-family: overridden-font;
+  ascent-override: 50%;
+  ...
+}
+
+<span style="font-family: overridden-font; font-size: 20px;">
+  Outer span content
+  <span style="font-size: 150%;">Inner span content</span>
+</span>
+
+
+	The outer span uses an ascent value of
+	10px, whereas the inner span uses 15px.
+
+
+
+
+	We may override the metrics of a local fallback font to match the primary font, which
+	is a web font. This reduces layout shifting when switching from fallback to the
+	primary font.
+
+
+@font-face {
+  font-family: cool-web-font;
+  src: url("https://example.com/font.woff");
+}
+
+@font-face {
+  font-family: fallback-to-local;
+  src: local(Some Local Font);
+  /* Override metric values to match cool-web-font */
+  ascent-override: 125%;
+  descent-override: 25%;
+  line-gap-override: 0%;
+}
+
+<div style="font-family: cool-web-font, fallback-to-local">Title goes here</div>
+<img src="https://example.com/largeimage" alt="A large image that you don't want to shift">
+
+
+	The image will not be vertically shifted when the user agent finishes loading and
+	switches to use the web font.
+
+
+
+
+    Default font metrics overriding:
+    the 'superscript-position-override', 'subscript-position-override','superscript-size-override' and 'subscript-size-override' descriptors
+
+Issue(5518):
+
+    
+        Name: superscript-position-override
+        Value: normal | <>
+        For: @font-face
+        Initial: normal
+    
+
+    
+        Name: subscript-position-override
+        Value: normal | <>
+        For: @font-face
+        Initial: normal
+    
+
+    
+        Name: superscript-size-override
+        Value: normal | <>
+        For: @font-face
+        Initial: normal
+    
+
+    
+        Name: subscript-size-override
+        Value: normal | <>
+        For: @font-face
+        Initial: normal
+    
+
+
+
+
+Font Feature Properties
+
+
+Font language override: the 'font-language-override' property
+
+Issue(5484):
+
+
+
+Font Feature and Variation Resolution
+
+Issue(5635):
+
+
+
+Font Variation Properties
+
+
+
+Optical sizing control: the 'font-optical-sizing' property
+
+Issue(5466):
+
+
+
+
+
+
+
+Security and Privacy Considerations
+
+
+No new security or privacy considerations have been raised on this specification.
+
+
+
+Acknowledgments
+
+The CSS Working group would like to thank:
+
+
+
+Changes
+
+-->