one , describe
1, establish QFont Object time , You can specify the various properties you want the font to have .Qt The font with the specified attribute will be used , Or if there is no matching font ,Qt The most matching installed font will be used . The font properties actually used can be found from
QFontInfo Object retrieval . use QFontMetricsF Get measured value , for example , use QFontMetrics::width() Gets the pixel length of the string .
2, To load a specific physical font （ Usually represented by a single file ）, Please use QRawFont.
3, Must exist QGuiApplication Instance can only be used QFont. have access to QGuiApplication::setFont() Sets the default font for the application .
4, If the selected font does not contain all the characters that need to be displayed ,QFont Attempts to find characters in the closest equivalent font . When QPainter
When drawing characters from a font , If there is no such character ,QPainter An unfilled square is drawn .
5, The overhead of loading fonts can be expensive .QFont Contains a large number of optimizations , Can copy quickly QFont object .
two , Type member
1,QFont::Capitalization： Font case policy
* MixedCase： Normal text rendering , Keep it as it is .
* AllUppercase： All text is rendered in uppercase .
* AllLowercase： All contents of the text are rendered in lowercase .
* SmallCaps： The text is rendered in substantially lowercase .
* Capitalize： The first letter of each word is capitalized .
2,QFont::SpacingType： Spacing type
* PercentageSpacing： value 100 The spacing will remain the same ; value 200 After, the space between characters is expanded to the width of the character itself .
* AbsoluteSpacing： Positive values increase the letter spacing of the corresponding pixel ; Negative values reduce spacing .（ The apparent value is the pixel value of the interval ）
3,QFont::Stretch： Stretch type （ Stretching factor ）. follow CSS Predefined stretch values for naming conventions . The higher the value , The more stretched the text is .（ The default value is 0）
* AnyStretch：0
* UltraCondensed：50
* ExtraCondensed：62
* Condensed：75
* SemiCondensed：87
* Unstretched：100
* SemiExpanded：112
* Expanded：125
* ExtraExpanded：150
* UltraExpanded：200
4,QFont::Style： Font style .
* StyleNormal： normal .
* StyleItalic： Italics .
* StyleOblique： oblique .（ Not as oblique as italics ）
5,QFont::Weight： Weight type .Qt Use from 0 reach 99 Weighted proportion of , Weight is 0 Indicates thin , and 99 Indicates extreme darkness .
* Thin：0
* ExtraLight：12
* Light：25
* Normal：50
* Medium：57
* DemiBold：63
* Bold：75
* ExtraBold：81
* Black：87
three , Member function
1,bool bold()
Is it bold . If the value of the weight > QFont::Medium return true, Otherwise return false.
2,QFont::Capitalization capitalization()
Get case policy .
3,QString defaultFamily()
4,bool exactMatch()
If a system font that exactly matches the settings of this font is available , Then return true.
5,bool fixedPitch()
Is a fixed font width set .
6,bool isCopyOf(const QFont &f)
If this font and f Are copies of each other , That is, one is created as a copy of the other , And it hasn't been modified since , Then return true.
7,bool italic()
If the font style is not QFont::StyleNormal, Then return true.（ That is, italics ）
8,bool kerning()
If use kerning is set , Then return true.
9,qreal letterSpacing()
Get letter spacing .
10,QFont::SpacingType letterSpacingType()
Gets the type of spacing setting .
11,bool overline()
Is the upper dash set .
12,int pixelSize()
* If the font is setPixelSize() Set , Returns the pixel size of the font .
* If the size is in setPointSize() or setPointSizeF() Set , Then return -1.
13,int pointSize()
Returns the point size of the font . If you specify the font size in pixels , Then return -1.
14,qreal pointSizeF()
Returns the point size of the font . If you specify the font size in pixels , Then return -1.
15,QFont resolve(const QFont &other)
Returns a new QFont, Should QFont Contains properties copied from other fonts .
16,void setBold(bool enable)
Set whether to bold , It's actually a setup QFont::Bold and QFont::Normal.
19,void setItalic(bool enable)
Sets whether to use italics . It's actually a setup QFont::StyleNormal / QFont::StyleItalic.
20,void setPixelSize(int pixelSize)
Set font size to pixel size . Use this function to make the font device dependent （ Different devices have different resolutions ）.
21,void setPointSize(int pointSize)
Sets the point size of the font . The point size must be greater than zero .
22,void setPointSizeF(qreal pointSize)
ditto , However, not all platforms support this accuracy .
23,bool strikeOut()
Is a strikethrough set .
24,bool underline()
Is underline set .
25,qreal wordSpacing()
Gets the spacing between words .
four , Related nonmember functions
1,uint qHash(const QFont &font, uint seed = 0)
Gets the hash value of the font .（QFont The hash value changes as the setting of changes ）
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