SkFont Reference
===
class SkFont {
// SkFont interface
};
Font_Size adjusts the overall text size in points.
Font_Size can be set to any positive value or zero.
Font_Size defaults to 12.
Font_Size
Font_Scale_X adjusts the text horizontal scale.
Text scaling approximates condensed and expanded type faces when the actual face
is not available.
Font_Scale_X can be set to any value.
Font_Scale_X defaults to 1.
Font_Skew_X adjusts the text horizontal slant.
Text skewing approximates italic and oblique type faces when the actual face
is not available.
Font_Skew_X can be set to any value.
Font_Skew_X defaults to 0.
Font_Embolden approximates the bold font style accompanying a normal font when a bold font face
is not available. Skia does not provide font substitution; it is up to the client to find the
bold font face using the platform Font_Manager.
Use Font_Skew_X to approximate an italic font style when the italic font face
is not available.
A FreeType based port may define SK_USE_FREETYPE_EMBOLDEN at compile time to direct
the font engine to create the bold Glyphs. Otherwise, the extra bold is computed
by increasing the stroke width and setting the SkPaint::Style to
SkPaint::kStrokeAndFill_Style as needed.
Font_Embolden is disabled by default.
If Hinting is set to SkFontHinting::kFull, Hinting_Spacing adjusts the character
spacing by the difference of the hinted and unhinted Left_Side_Bearing and
Right_Side_Bearing. Hinting_Spacing only applies to platforms that use
FreeType as their Font_Engine.
Hinting_Spacing is not related to text kerning, where the space between
a specific pair of characters is adjusted using data in the font kerning tables.
Font_Linear selects whether text is rendered as a Glyph or as a Path.
If Font_Linear is set, it has the same effect as setting Hinting to SkFontHinting::kNormal.
If Font_Linear is clear, it is the same as setting Hinting to SkFontHinting::kNone.
Font_Subpixel uses the pixel transparency to represent a fractional offset.
As the opaqueness of the color increases, the edge of the glyph appears to move
towards the outside of the pixel.
When set, Anti_Alias positions glyphs within a pixel, using alpha and
possibly RGB striping. It can take advantage of the organization of RGB stripes
that create a color, and relies on the small size of the stripe and visual perception
to make the color fringing imperceptible.
Anti_Alias can be enabled on devices that orient stripes horizontally
or vertically, and that order the color components as RGB or BGR. Internally, the
glyph cache may store multiple copies of the same glyph with different sub-pixel
positions, requiring more memory.
If Hinting is set to SkFontHinting::kNormal or SkFontHinting::kFull, Force_Hinting
instructs the Font_Manager to always hint Glyphs.
Force_Hinting has no effect if Hinting is set to SkFontHinting::kNone or
SkFontHinting::kSlight.
Force_Hinting only affects platforms that use FreeType as the Font_Manager.
Embedded_Bitmaps allows selecting custom sized bitmap Glyphs.
Embedded_Bitmaps when set chooses an embedded bitmap glyph over an outline contained
in a font if the platform supports this option.
FreeType selects the bitmap glyph if available when Embedded_Bitmaps is set, and selects
the outline glyph if Embedded_Bitmaps is clear.
Windows may select the bitmap glyph but is not required to do so.
OS_X and iOS do not support this option.
---
SkFont controls options applied when drawing and measuring text.
class SkFont {
enum class Edging {
kAlias,
kAntiAlias,
kSubpixelAntiAlias,
};
SkFont();
SkFont(sk_sp<SkTypeface> typeface, SkScalar size);
SkFont(sk_sp<SkTypeface> typeface, SkScalar size, SkScalar scaleX, SkScalar skewX);
bool operator==(const SkFont& font) const;
bool isForceAutoHinting() const;
bool isEmbeddedBitmaps() const;
bool isSubpixel() const;
bool isLinearMetrics() const;
bool isEmbolden() const;
void setForceAutoHinting(bool forceAutoHinting);
void setEmbeddedBitmaps(bool embeddedBitmaps);
void setSubpixel(bool subpixel);
void setLinearMetrics(bool linearMetrics);
void setEmbolden(bool embolden);
Edging getEdging() const;
void setEdging(Edging edging);
void setHinting(SkFontHinting hintingLevel);
SkFontHinting getHinting() const;
SkFont makeWithSize(SkScalar size) const;
SkTypeface* getTypeface() const;
SkScalar getSize() const;
SkScalar getScaleX() const;
SkScalar getSkewX() const;
sk_sp<SkTypeface> refTypeface() const;
void setTypeface(sk_sp<SkTypeface> tf);
void setSize(SkScalar textSize);
void setScaleX(SkScalar scaleX);
void setSkewX(SkScalar skewX);
int textToGlyphs(const void* text, size_t byteLength, SkTextEncoding encoding,
SkGlyphID glyphs[], int maxGlyphCount) const;
uint16_t unicharToGlyph(SkUnichar uni) const;
int countText(const void* text, size_t byteLength, SkTextEncoding encoding) const;
bool containsText(const void* text, size_t byteLength, SkTextEncoding encoding) const;
size_t breakText(const void* text, size_t length, SkTextEncoding encoding, SkScalar maxWidth,
SkScalar* measuredWidth = nullptr) const;
SkScalar measureText(const void* text, size_t byteLength, SkTextEncoding encoding,
SkRect* bounds = nullptr) const;
bool getPath(uint16_t glyphID, SkPath* path) const;
void getPaths(const uint16_t glyphIDs[], int count,
void (*glyphPathProc)(const SkPath* pathOrNull, const SkMatrix& mx, void* ctx),
void* ctx) const;
SkScalar getMetrics(SkFontMetrics* metrics) const;
SkScalar getSpacing() const;
};
---
enum class Edging {
kAlias,
kAntiAlias,
kSubpixelAntiAlias,
};
Whether edge pixels draw opaque or with partial transparency.
### Constants
### Example
### See Also
incomplete
---
SkFont()
Constructs SkFont with default values.
### Return Value
default initialized SkFont
### Example
### See Also
incomplete
---
SkFont(sk_sp<SkTypeface> typeface, SkScalar size)
Constructs SkFont with default values with SkTypeface and size in points.
### Parameters
### Return Value
initialized SkFont
### Example
### See Also
incomplete
---
SkFont(sk_sp<SkTypeface> typeface, SkScalar size, SkScalar scaleX, SkScalar skewX)
Constructs SkFont with default values with SkTypeface and size in points,
horizontal scale, and horizontal skew. Horizontal scale emulates condensed
and expanded fonts. Horizontal skew emulates oblique fonts.
### Parameters
### Return Value
initialized SkFont
### Example
### See Also
incomplete
---
bool operator==(const SkFont& font)const
Compares SkFont and font, and returns true if they are equivalent.
May return false if SkTypeface has identical contents but different pointers.
### Parameters
### Return Value
true if SkFont pair are equivalent
### Example
### See Also
incomplete
---
bool isForceAutoHinting()const
If true, instructs the font manager to always hint glyphs.
Returned value is only meaningful if platform uses FreeType as the font manager.
### Return Value
true if all glyphs are hinted
### Example
### See Also
incomplete
---
bool isEmbeddedBitmaps()const
Returns true if font engine may return glyphs from font bitmaps instead of from outlines.
### Return Value
true if glyphs may be font bitmaps
### Example
### See Also
incomplete
---
bool isSubpixel()const
Returns true if glyphs at different sub-pixel positions may differ on pixel edge coverage.
### Return Value
true if glyph positioned in pixel using transparency
### Example
### See Also
incomplete
---
bool isLinearMetrics()const
Returns true if text is converted to SkPath before drawing and measuring.
### Return Value
true glyph hints are never applied
### Example
### See Also
incomplete
---
bool isEmbolden()const
Returns true if bold is approximated by increasing the stroke width when creating glyph
bitmaps from outlines.
### Return Value
bold is approximated through stroke width
### Example
### See Also
incomplete
---
void setForceAutoHinting(bool forceAutoHinting)
Sets whether to always hint glyphs.
If forceAutoHinting is set, instructs the font manager to always hint glyphs.
Only affects platforms that use FreeType as the font manager.
### Parameters
### Example
### See Also
incomplete
---
void setEmbeddedBitmaps(bool embeddedBitmaps)
Requests, but does not require, to use bitmaps in fonts instead of outlines.
### Parameters
### Example
### See Also
incomplete
---
void setSubpixel(bool subpixel)
Requests, but does not require, that glyphs respect sub-pixel positioning.
### Parameters
### Example
### See Also
incomplete
---
void setLinearMetrics(bool linearMetrics)
Requests, but does not require, that glyphs are converted to SkPath
before drawing and measuring.
### Parameters
### Example
### See Also
incomplete
---
void setEmbolden(bool embolden)
Increases stroke width when creating glyph bitmaps to approximate a bold typeface.
### Parameters
### Example
### See Also
incomplete
---
Edging getEdging()const
Whether edge pixels draw opaque or with partial transparency.
### Return Value
one of: Edging::kAlias, Edging::kAntiAlias, Edging::kSubpixelAntiAlias
### Example
### See Also
incomplete
---
void setEdging(Edging edging)
Requests, but does not require, that edge pixels draw opaque or with
partial transparency.
### Parameters
### Example
### See Also
incomplete
---
void setHinting(SkFontHinting hintingLevel)
Sets level of glyph outline adjustment.
Does not check for valid values of hintingLevel.
### Parameters
SkFontHinting::kNormal, SkFontHinting::kFull
### Example
### See Also
incomplete
---
SkFontHinting getHinting()const
Returns level of glyph outline adjustment.
### Return Value
one of: SkFontHinting::kNone, SkFontHinting::kSlight, SkFontHinting::kNormal,
SkFontHinting::kFull
### Example
### See Also
incomplete
---
SkFont makeWithSize(SkScalar size)const
Returns a font with the same attributes of this font, but with the specified size.
Returns nullptr if size is less than zero, infinite, or NaN.
### Parameters
### Return Value
initialized SkFont
### Example
### See Also
incomplete
---
SkTypeface* getTypeface()const
Returns SkTypeface if set, or nullptr.
Does not alter SkTypeface SkRefCnt.
### Return Value
SkTypeface if previously set, nullptr otherwise
### Example
### See Also
incomplete
---
SkScalar getSize()const
Returns text size in points.
### Return Value
typographic height of text
### Example
### See Also
incomplete
---
SkScalar getScaleX()const
Returns text scale on x-axis.
Default value is 1.
### Return Value
text horizontal scale
### Example
### See Also
incomplete
---
SkScalar getSkewX()const
Returns text skew on x-axis.
Default value is zero.
### Return Value
additional shear on x-axis relative to y-axis
### Example
### See Also
incomplete
---
sk_sp<SkTypeface> refTypeface()const
Increases SkTypeface SkRefCnt by one.
### Return Value
SkTypeface if previously set, nullptr otherwise
### Example
### See Also
incomplete
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void setTypeface(sk_sp<SkTypeface> tf)
Sets SkTypeface to typeface, decreasing SkRefCnt of the previous SkTypeface.
Pass nullptr to clear SkTypeface and use the default typeface. Increments
tf SkRefCnt by one.
### Parameters
### Example
### See Also
incomplete
---
void setSize(SkScalar textSize)
Sets text size in points.
Has no effect if textSize is not greater than or equal to zero.
### Parameters
### Example
### See Also
incomplete
---
void setScaleX(SkScalar scaleX)
Sets text scale on x-axis.
Default value is 1.
### Parameters
### Example
### See Also
incomplete
---
void setSkewX(SkScalar skewX)
Sets text skew on x-axis.
Default value is zero.
### Parameters
skewX |
additional shear on x-axis relative to y-axis |
### Example
### See Also
incomplete
---
int textToGlyphs(const void* text, size_t byteLength, SkTextEncoding encoding, SkGlyphID glyphs[],
int maxGlyphCount)const
Converts text into glyph indices.
Returns the number of glyph indices represented by text.
SkTextEncoding specifies how text represents characters or glyphs.
glyphs may be nullptr, to compute the glyph count.
Does not check text for valid character codes or valid glyph indices.
If byteLength equals zero, returns zero.
If byteLength includes a partial character, the partial character is ignored.
If encoding is kUTF8_SkTextEncoding and text contains an invalid UTF-8 sequence,
zero is returned.
If maxGlyphCount is not sufficient to store all the glyphs, no glyphs are copied.
The total glyph count is returned for subsequent buffer reallocation.
### Parameters
kUTF32_SkTextEncoding, kGlyphID_SkTextEncoding
### Parameters
### Return Value
number of glyphs represented by text of length byteLength
### Example
### See Also
incomplete
---
uint16_t unicharToGlyph(SkUnichar uni)const
Returns glyph index for Unicode character.
### Parameters
### Return Value
glyph index
### Example
### See Also
incomplete
---
int countText(const void* text, size_t byteLength, SkTextEncoding encoding)const
Returns number of glyphs represented by text.
### Parameters
kUTF32_SkTextEncoding, kGlyphID_SkTextEncoding
### Return Value
number of glyphs represented by text of length byteLength
### Example
### See Also
incomplete
---
bool containsText(const void* text, size_t byteLength, SkTextEncoding encoding)const
Returns true if all text corresponds to a non-zero glyph index.
Returns false if any characters in text are not supported in
SkTypeface.
If SkTextEncoding is kGlyphID_SkTextEncoding,
returns true if all glyph indices in text are non-zero;
does not check to see if text contains valid glyph indices for SkTypeface.
Returns true if byteLength is zero.
### Parameters
### Return Value
true if all text corresponds to a non-zero glyph index
### Example
### See Also
incomplete
---
size_t breakText(const void* text, size_t length, SkTextEncoding encoding, SkScalar maxWidth,
SkScalar* measuredWidth = nullptr)const
Returns the bytes of text that fit within maxWidth.
The text fragment fits if its advance width is less than or equal to maxWidth.
Measures only while the advance is less than or equal to maxWidth.
Returns the advance or the text fragment in measuredWidth if it not nullptr.
Uses encoding to decode text, SkTypeface to get the font metrics,
and text size to scale the metrics.
Does not scale the advance or bounds by fake bold.
### Parameters
### Return Value
bytes of text that fit, always less than or equal to length
### Example
Line under "Breakfast" shows desired width, shorter than available characters.
Line under "Bre" shows measured width after breaking
text.
### See Also
incomplete
---
SkScalar measureText(const void* text, size_t byteLength, SkTextEncoding encoding,
SkRect* bounds = nullptr)const
Returns the advance width of text.
The advance is the normal distance to move before drawing additional text.
Returns the bounding box of text if bounds is not nullptr.
### Parameters
kUTF32_SkTextEncoding, kGlyphID_SkTextEncoding
### Parameters
bounds |
returns bounding box relative to (0, 0) if not nullptr |
### Return Value
number of glyphs represented by text of length byteLength
### Example
### See Also
incomplete
---
bool getPath(uint16_t glyphID, SkPath* path)const
Returns path corresponding to glyph outline.
If glyph has an outline, copies outline to path and returns true.
path returned may be empty.
If glyph is described by a bitmap, returns false and ignores path parameter.
### Parameters
### Return Value
true if glyphID is described by path
### Example
### See Also
incomplete
---
void getPaths(const uint16_t glyphIDs[], int count, void (*glyphPathProc) (const SkPath* pathOrNull,
const SkMatrix& mx, void* ctx) , void* ctx)const
Returns path corresponding to glyph array.
### Parameters
### Example
### See Also
incomplete
---
SkScalar getMetrics(SkFontMetrics* metrics)const
Returns SkFontMetrics associated with SkTypeface.
The return value is the recommended spacing between lines: the sum of metrics
descent, ascent, and leading.
If metrics is not nullptr, SkFontMetrics is copied to metrics.
Results are scaled by text size but does not take into account
dimensions required by text scale, text skew, fake bold,
style stroke, and SkPathEffect.
### Parameters
### Return Value
recommended spacing between lines
### Example
### See Also
incomplete
---
SkScalar getSpacing()const
Returns the recommended spacing between lines: the sum of metrics
descent, ascent, and leading.
Result is scaled by text size but does not take into account
dimensions required by stroking and SkPathEffect.
Returns the same result as getMetrics().
### Return Value
recommended spacing between lines
### Example
### See Also
incomplete