37 KiB
Handling and Rendering of Text
- Charset and Encoding
- Device Font
- Logical font
- Text Analysis
- Text Transformation
- Text Output
- Special Render Effects of Font Glyph
- Usage of
BIDItext - Enhancements in MiniGUI 4.0
As discussed before, the handling and rendering of text has some of their own
features in MiniGUI. We will elaborate the concepts related to text handling
and introduce the relevant APIs in this chapter.
Charset and Encoding
Charset (character set) is a collection of characters defined to represent
certain language; Encoding is the coding rules set to represent characters in
certain charset. Encoding usually ranks the character by fixed order and uses
them as the internal features of recording, storing, transfer and exchange.
People who have conducted computer know the ASCII code defined by the US
National Standard Authorization. ASCII code can be understood as an encoding
format of American English charset; this coding format uses one 7-bit byte to
represent one character scoped from 0x00 to 0x7F.
NOTE Type man ascii to get the definition of ASCII on Linux command
line.
ASCII cannot meet the requirement of non-English speakers as the use of
computer has spreads to the entire world. Therefore, almost all countries
define the standard of charset and encoding based on their own official
languages. The well-known standard GB2312-80 is the simplified Chinese
charset standard defined by China government. GB2312-80 includes 682 symbols
and 6763 Chinese words. It has 87 divisions, each of which has 94 characters.
There are other standards, such as ISO8859 used for the single-byte charsets,
JISX0201, JISX0208 charset defined by Japan, BIG5 traditional Chinese
charset, and so on.
One charset can have different encoding format. Usually we use EUC encode
(extended UNIX code) for GB2312 charset. EUC encodes each GB2312
charset as 2 bytes scoped in 0xA1~0xFE. The higher byte represents GB2312
area code while the lower one represents GB2312 position code. Another
popular GB2312 code is HZ code, which removes the highest bit of EUC
code, thus using ASCII to represent Chinese characters. For example, the code
of Chinese word “啊” is 0xB1A1 in EUC encoding, while in HZ encoding the
character is {1!}.
With the publication and update of the charset of each country and area, the
problem of compatibility rises. For example, a text file that uses GB2312
EUC code cannot be properly displayed on BIG5 system. Therefore, some
international organizations begin to develop the globally universal charset
standard, that is, the well-known UNICODE charset.
The international standard organization established ISO/IEC JTC1/SC2/WG2
work group in April 1984. This group is responsible for integrating different
characters and symbols of different countries. In 1991, some American companies
established Unicode Consortium and got agreement with WG2 to use the same
code-set in October 1991. At present, UNICODE 2.0 version includes 6811
characters, 20902 Chinese characters, 11172 Korean characters, 6400 make-up
divisions and 20249 reserved characters, totally 65534 characters. UNICODE
charset has multiple encoding formats, the most popular one is using 16-bit
double bytes to express one character; it is also called USC2; another is
UTF8 encoding format, which can be compatible with ASCII and ISO8859-1
charset. The byte-count used to represent a character is variable.
PROMPT Type man unicode and man utf-8 on Linux command line can get the
information of UNICODE charset and UTF8 encoding.
UNICODE can solve the compatibility problem of charsets. However, most
countries and regions do not recognize UNICODE charset. For example, China
government asks all OS software products must support GB18030 charset, not
the UNICODE charset. The reason is that GB18030 is compatible with GB2312
and GBK charset popularly used in China main land areas, but not compatible
with UNICODE.
UNICODE provides a way to solve charset compatibility problem for
general-purpose operating systems. However, it is not the best way for the
embedded systems. MiniGUI uses the internal code that is completely consistent
with the default code of that charset to represent. Then, the abstract
interfaces provide an universal analysis interface to text in any charset. This
interface can be used to analyze both of the font module and the multi-byte
character string. So far MiniGUI can support ISO8859-x (single-byte
charsets), GB2312, GBK, GB18030, BIG5, EUCKR, Shift-JIS, and EUCJP
(multi-byte charsets). MiniGUI also support UTF-8 and UTF-16 encode of
UNICODE charset through the abstract interface of charset.
PROMPT The charset support of MiniGUI can be also understood as the support of certain encoding format of that charset.
MiniGUI uses logical font interface to support multi-byte charset. When application displays text, it usually needs to set logical font and assign the encoding name of chosen charset. After creating logical font, application can use it to display text or analyze text string.
Device Font
Device font is a data structure which associates with font under layer. Each
device font has a set of operation (font_ops) which includes some abstract
interfaces, such as get_char_width, get_char_bitmap. Each type of font,
which is supported by MiniGUI, has a set of operation. By using this set of
operation, we can get any character's dot-matrix (for raster font) or glyph
(for vector font). Then, GDIs of MiniGUI can output these dot-matrix to
screen. These are the characters we can see from the screen.
To correctly display text needs to get the shape data corresponding to each
character. These shape data is called glyph and is saved in a file of certain
type, which is usually called a font file. The most popular type of font file
is dot-matrix (bitmap) font, which uses bitmap to store the information of
dot-matrix glyph of each character. Another popular type is vector font, which
stores the frame information of each character and can be zoomed by certain
algorithms. The popular types of vector font are TrueType and Adobe Type 1.
Similar to charset, MiniGUI defines a series of abstract interfaces for font.
Now MiniGUI can support RBF, VBF (two MiniGUI-defined dot-matrix font
formats), TrueType and Adobe Type 1 fonts. MiniGUI can also support QPF (Qt
Pre-rendered Fonts) font. MiniGUI can enlarge dot-matrix (bitmap) font
automatically and provide Anti-aliased feature for TV or other specified
display device.
Besides, MiniGUI implements bitmap font which is a device font by using
BITMAP to show characters. This font can make glyph according to customized
bitmap, and is provided to application and controls like other logical font
interface.
VBF V3.0 font is an upgrade version of V2.0, it enlarges the range of
character set. There is no limited for the character set which is for Latin
system, and the number of glyph in one VBF font can be greater than 255.
UPF font is an enhancement version of QPF font, it is convenience for
MiniGUI uses the font by memory mapping. It reduces memory usage when using
QPF font in MiniGUI-Processes mode. It supports BIDI text, such as Arabic
and Hebrew.
We can enable or disable any device font in MiniGUI by changing configuration options for configure script. The followings are the options for each device font:
--enable-rbfsupportIt is the option forRBFfont. MiniGUI supports it by default. If you don't want to support it, please use--disable-rbfsupportto disable it.--enable-vbfsupportIt is the option forVBFfont. MiniGUI supports it by default. If you don't want to support it, please use--disable-vbfsupportto disable it.--enable-upfsupportIt is the option forUPFfont. MiniGUI supports it by default. If you don't want to support it, please use--disable-upfsupportto disable it.--enable-qpfsupportIt is the option forQPFfont. MiniGUI supports it by default. If you don't want to support it, please use--disable-qpfsupportto disable it.--with-ttfsupport=ft1/ft2/noneIt is the option for vector font. There are two versions of vector font engines in MiniGUI, one is freetype 1.3.1, another is freetype 2.0. Please use--with-ttfsupport=ft1option for using 1.3.1 version and use--with-ttfsupport=ft2to support 2.0. MiniGUI doesn't support vector font in default, so you must useft1orft2to enable vector font support. It is important to note, you must install freetype library before enable vector font support. Otherwise, you can not enable it.
When initializing MiniGUI, it is needed to read MiniGUI.cfg and load certain
font files. The loaded font is internally called device font. Device font
defines the format name, type, size and its supported charset. According to the
loaded device font and the font type, name, size and character information
assigned by application program, MiniGUI searches the proper device font to
display text.
The following functions provide the support for loading and destroying dynamically font (ttf or qpf) :
BOOL GUIAPI LoadDevFontFromFile(const char *devfont_name,
const char *file_name, DEVFONT** devfont);
void GUIAPI DestroyDynamicDevFont (DEVFONT **devfont);
Bitmap device font
Bitmap device font is different than other device fonts which can be configured
in MiniGUI.cfg, it is created in application. The followings are related
functions.
DEVFONT *CreateBMPDevFont (const char *bmpfont_name, const BITMAP* glyph_bmp,
const char* start_mchar, int nr_glyphs, int glyph_width);
BOOL AddGlyphsToBMPFont (DEVFONT* dev_font, BITMAP* glyph_bmp,
const char* start_mchar, int nr_glyphs, int glyph_width)
void DestroyBMPFont (DEVFONT* dev_font)
CreateBMPDevFontIt creates bitmap device font and insert the device font which is successfully created into device font list. The arguments need to be passed are font's type, name, style, size and font name of supported character set, bitmap structure pointer, the first character of device font, the number of characters in device font, width of every character. It is important to note, the characters in each bitmap of bitmap device font must be continuous and have the same width.AddGlyphsToBMPFontIt adds characters in bitmap device font which already has been created. So bitmap font can display more characters. The first argument is device font pointer, other arguments are as same asCreateBMPDevFont.DestroyBMPFontIt destroys bitmap device font.
In the following codes, it creates bitmap device font which can display '0' to '9' firstly, then adds 'ABCDEFG' and '+' into device font. Finally, it creates logical font with 'led' style.
#define BMP_FILE_DIGIT "digits1.png"
#define BMP_FILE_LETTER "digits2.png"
#define BMP_FILE_SYMBOL "digits3.png"
#define BMP_FILE_DDOT "digits4.png"
static LOGFONT *logfont, *old ;
static DEVFONT *dev_font;
...
if (LoadBitmap (HDC_SCREEN, &digit_bmp, BMP_FILE_DIGIT)) {
fprintf (stderr, "Fail to load bitmap. \n");
return 1;
}
if (LoadBitmap (HDC_SCREEN, &letter_bmp, BMP_FILE_LETTER)) {
fprintf (stderr, "Fail to load bitmap. \n");
return 1;
}
if (LoadBitmap (HDC_SCREEN, &symbol_bmp, BMP_FILE_SYMBOL)) {
fprintf (stderr, "Fail to load bitmap. \n");
return 1;
}
if (LoadBitmap (HDC_SCREEN, &ddot_bmp, BMP_FILE_DDOT)) {
fprintf (stderr, "Fail to load bitmap. \n");
return 1;
}
dev_font = CreateBMPDevFont ("bmp-led-rrncnn-10-15-ISO8859-1",
&letter_bmp, "A", 6, 10);
AddGlyphsToBMPFont (dev_font, &digit_bmp, "0", 10, 10);
AddGlyphsToBMPFont (dev_font, &symbol_bmp, "+", 4, 10);
AddGlyphsToBMPFont (dev_font, &ddot_bmp, ":", 1, 10);
logfont = CreateLogFont (FONT_TYPE_NAME_BITMAP_BMP, "led",
"ISO8859-1",
FONT_WEIGHT_REGULAR, FONT_SLANT_ROMAN,
FONT_SETWIDTH_NORMAL, FONT_SPACING_CHARCELL,
FONT_UNDERLINE_NONE, FONT_STRUCKOUT_NONE,
10, 0);
The following images are used in above codes.
PROMPT The information of definition, name and format of device font is described in 3.1.4 of MiniGUI User Manual.
Logical font
Logical font is a GDI object, its symbol is stored in HFONT variable.
Logical font is description of font. It is abstract object, just like logical
pen and logical brush. It becomes real object only when application calls
SelectObject to select it into device context.
The logical font of MiniGUI has strong functions, including abundant
information such as charset, font type, and style. It can be used not only to
render text, but also to analyze the text string. This is very useful in most
text edition applications. Before using its logical font, you need firstly
build it and choose it to the device context, which will use this logical font
to output text. The default logical font of each device context is the default
system-defined font in MiniGUI.cfg. You can establish the logical font by
calling CreateLogFont, CreateLogFontByName, and CreateLogFontIndirect.
You can also use function SelectFont to select a logical font to a device
context. It is DestroyLogFont that is used to destroy logical font. However,
you cannot destroy the selected logical font. The prototypes of these functions
are as follow (minigui/gdi.h):
PLOGFONT GUIAPI CreateLogFont (const char* type, const char* family,
const char* charset, char weight, char slant, char flip,
char other, char underline, char struckout,
int size, int rotation);
PLOGFONT GUIAPI CreateLogFontByName (const char* font_name);
PLOGFONT GUIAPI CreateLogFontIndirect (LOGFONT* logfont);
void GUIAPI DestroyLogFont (PLOGFONT log_font);
void GUIAPI GetLogFontInfo (HDC hdc, LOGFONT* log_font);
PLOGFONT GUIAPI GetSystemFont (int font_id);
PLOGFONT GUIAPI GetCurFont (HDC hdc);
PLOGFONT GUIAPI SelectFont (HDC hdc, PLOGFONT log_font);
The following code fragment creates multiple logical fonts:
static LOGFONT *logfont, *logfontgb12, *logfontbig24;
logfont = CreateLogFont (NULL, "SansSerif", "ISO8859-1",
FONT_WEIGHT_REGULAR, FONT_SLANT_ITALIC, FONT_FLIP_NIL,
FONT_OTHER_NIL, FONT_UNDERLINE_NONE, FONT_STRUCKOUT_LINE,
16, 0);
logfontgb12 = CreateLogFont (NULL, "song", "GB2312",
FONT_WEIGHT_REGULAR, FONT_SLANT_ROMAN, FONT_FLIP_NIL,
FONT_OTHER_NIL, FONT_UNDERLINE_LINE, FONT_STRUCKOUT_LINE,
12, 0);
logfontbig24 = CreateLogFont (NULL, "ming", "BIG5",
FONT_WEIGHT_REGULAR, FONT_SLANT_ROMAN, FONT_FLIP_NIL,
FONT_OTHER_AUTOSCALE, FONT_UNDERLINE_LINE, FONT_STRUCKOUT_NONE,
24, 0);
The first font, logfont, belongs to ISO8859-1 charset and uses SansSerif
with the height of 16 pixels; logfontgb12 belongs to GB2312 charset and uses
Song with the height of 12 pixels; logfontbig24 belongs to BIG5 charset and
uses Ming. The desired size of the last font is 24 pixels, and we use
FONT_OTHER_AUTOSCALE style to create the logical font. The style
FONT_OTHER_AUTOSCALE tells MiniGUI to auto-scale the font glyph to meet the
desired font size.
We can also call GetSystemFont function to return a system logical font, the
argument font_id in that can be one of the following values:
SYSLOGFONT_DEFAULT: System default font, it has to be a single-byte charset logical font and must be formed byRBFdevice font.SYSLOGFONT_WCHAR_DEF: System default multi-byte charset font. It is usually formed byRBFdevice font. Its width is twice of theSYSLOGFONT_DEFAULTlogical font.SYSLOGFONT_FIXED: System font with fixed width.SYSLOGFONT_CAPTION: The logical font used to display text on caption bar.SYSLOGFONT_MENU: The logical font used to display menu text.SYSLOGFONT_CONTROL: The default logical font used by controls.
The system logical fonts above are created corresponding to definition of
MiniGUI.cfg when MiniGUI is initialized.
PROMPT The information of definition, name and format of system logical font is described in 3.1.5 of MiniGUI User Manual.
GetCurFont function returns current logical font in a device context. You
cannot call DestroyLogFont to destroy a system logical font.
Text Analysis
After establishing logical font, the application program can use logical font
to analyze multi-language-mixed text. Here the multi-language-mixed text means
the character string formed by two non-intersected charset texts, such as
GB2312 and ISO8859-1, or BIG5 and ISO8859-2. You can use the following
functions to analyze the text constitutes of multi-language-mixed text
(minigui/gdi.h):
// Text parse support
int GUIAPI GetTextMCharInfo (PLOGFONT log_font, const char* mstr, int len,
int* pos_chars);
int GUIAPI GetTextWordInfo (PLOGFONT log_font, const char* mstr, int len,
int* pos_words, WORDINFO* info_words);
int GUIAPI GetFirstMCharLen (PLOGFONT log_font, const char* mstr, int len);
int GUIAPI GetFirstWord (PLOGFONT log_font, const char* mstr, int len,
WORDINFO* word_info);
GetTextMCharInfo returns the byte address of each character of the
multi-language-mixed text. For example, for the string “ABC汉语”, this function
will return {0, 1, 2, 3, 5} five values in pos_chars. GetTextWordInfo will
analyze the place of each word of the multi-language-mixed text. As for
single-byte charset text, we use blank and TAB key as the delimiter; as for
multi-byte charset text, the word uses single-byte character as the delimiter.
GetFirstMCharLen returns the byte length of the first character.
GetFirstWord returns the word information of the first word.
Text Transformation
MiniGUI provides the functions of converting multi-byte charset text to wide
charset text in UCS or wide charset text in UCS to multi-byte charset text.
typedef unsigned short UChar16;
typedef signed int UChar32;
int GUIAPI MB2WCEx (PLOGFONT log_font, void* dest, BOOL wc32,
const unsigned char* mstr, int n);
#define MB2WC(log_font, dest, mstr, n) \
MB2WCEx (log_font, dest, sizeof(wchar_t) == 4, mstr, n)
int GUIAPI WC2MBEx (PLOGFONT log_font, unsigned char *s, UChar32 wc);
#define WC2MB(log_font, s, wc) \
WC2MBEx (log_font, s, (UChar32)wc);
int GUIAPI MBS2WCSEx (PLOGFONT log_font, void* dest, BOOL wc32,
const unsigned char* mstr, int mstr_len, int n,
int* conved_mstr_len);
#define MBS2WCS(log_font, dest, mstr, mstr_len, n) \
MBS2WCSEx(log_font, dest, sizeof (wchar_t) == 4, mstr, \
mstr_len, n, NULL)
int GUIAPI WCS2MBSEx (PLOGFONT log_font, unsigned char* dest,
const void *wcs, int wcs_len, BOOL wc32, int n,
int* conved_wcs_len);
#define WCS2MBS(log_font, dest, wcs, wcs_len, n) \
WCS2MBSEx (log_font, dest, wcs, wcs_len, sizeof (wchar_t) == 4, \
n, NULL)
MB2WCEx is used to convert a multi-byte character (GB2312, ISO8859, UTF-8,
GBK, BIG5, etc) to a wide character in UCS according to the
charset/encoding of the logical font. And MBS2WCSEx is used to convert a
multi-byte string (GB2312, ISO8859, UTF-8, GBK, BIG5, etc) to a wide
string in UCS according to the charset/encoding of the logical font.
WC2MBEx is used to convert a wide character in UCS to a multi-byte character
(GB2312, ISO8859, UTF-8, GBK, BIG5, etc) according to the
charset/encoding of the logical font. And WCS2MBSEx is used to convert a wide
string in UCS to a multi-byte string (GB2312, ISO8859, UTF-8, GBK,
BIG5, etc) according to the charset/encoding of the logical font.
Text Output
The following functions can be used to calculate the output length and width of
text (minigui/gdi.h):
int GUIAPI GetTextExtentPoint (HDC hdc, const char* text, int len, int max_extent,
int* fit_chars, int* pos_chars, int* dx_chars, SIZE* size);
int GUIAPI GetTabbedTextExtentPoint (HDC hdc, const char *text, int len, int max_extent,
int *fit_chars, int *pos_chars, int *dx_chars, SIZE *size);
// Text output support
int GUIAPI GetFontHeight (HDC hdc);
int GUIAPI GetMaxFontWidth (HDC hdc);
void GUIAPI GetTextExtent (HDC hdc, const char* spText, int len, SIZE* pSize);
void GUIAPI GetTabbedTextExtent (HDC hdc, const char* spText, int len, SIZE* pSize);
GetTextExtentPoint is used to calculate the maximal number of the characters
can be output, the byte place of each character, the output place of each
character, and the actual output width and height of multi-byte text in a given
output width (that is, the width of the output character is limited in a
certain extent). GetTextExtentPoint is an integrated function, which is very
useful for editor-type application. For example, in the single-line and
multi-line edit box control; MiniGUI uses this function to calculate the
position of the caret.
On the basis of GetTextExtentPoint function, handles for 'enter', 'newline'
,'TAB' and other formatting characters were added in GetTabbedTextExtentPoint
function.
GetFontHeight and GetMaxFontWidth return the height and maximum width of a
font. GetTextExtent calculates the output width and height of text.
GetTabbedTextExtent returns the output width and height of formatted text
string.
The following function is used to output text (minigui/gdi.h):
int GUIAPI TextOutLen (HDC hdc, int x, int y, const char* spText, int len);
int GUIAPI TabbedTextOutLen (HDC hdc, int x, int y, const char* spText, int len);
int GUIAPI TabbedTextOutEx (HDC hdc, int x, int y, const char* spText, int nCount,
int nTabPositions, int *pTabPositions, int nTabOrigin);
void GUIAPI GetLastTextOutPos (HDC hdc, POINT* pt);
// Compatiblity definitions
#define TextOut(hdc, x, y, text) TextOutLen (hdc, x, y, text, -1)
#define TabbedTextOut(hdc, x, y, text) TabbedTextOutLen (hdc, x, y, text, -1)
# #define DrawText(hdc, text, n, rc, format) DrawTextEx2 (hdc, text, n, rc, 0, format, NULL)
- [Charset and Encoding](#charset-and-encoding)
- [Device Font](#device-font)
+ [Bitmap device font](#bitmap-device-font)
- [Logical font](#logical-font)
- [Text Analysis](#text-analysis)
- [Text Transformation](#text-transformation)
- [Text Output](#text-output)
- [Special Render Effects of Font Glyph](#special-render-effects-of-font-glyph)
- [Usage of `BIDI` text](#usage-of-bidi-text)
- [Enhancements in MiniGUI 4.0](#enhancements-in-minigui-40)
#define DrawTextEx(hdc, text, n, rc, indent, format) DrawTextEx2 (hdc, text, n, rc, indent, format, NULL)
...
int GUIAPI DrawTextEx2 (HDC hdc, const char *pText, int nCount, RECT *pRect, int nIndent,
UINT nFormat, DTFIRSTLINE *firstline);
TextOutLen is used to output a certain text with appropriate length at given
position. If length is -1, the character string must terminate with '\0'.
TabbedTextOutLen is used to output formatted text string. TabbedTextOutEx
is used to output formatted character string, but also can specify the position
of each TAB character in the text string.
Figure 1 is the output of TextOut, TabbedTextOut, and TabbedTextOutEx
functions.
Figure 1 Output of TextOut, TabbedTextOut, and TabbedTextOutEx functions
DrawText is the most complicated text output function, which can use
different ways to output text in a given rectangle.
On the basis of DrawText, DrawTextEx can configure the number of characters
of text-indent.
On the basis of first two functions, DrawTextEx2 can calculate the number of
characters in first line. It is very useful for multi-line-edit. Because
multi-line-edit needs to know the width of edit to calculate how many
characters can be displayed in first line, so the character which is the first
one in second line can be known. The argument, firstline, includes the number
of characters in first line and display it.
Now, DrawText doesn't support UTF-16 text. Table 1 lists the formats
supported by DrawText.
Table 1 Output formats of DrawText function
| Format identifier | Meaning | Note |
|---|---|---|
DT_TOP |
Top-justifies the text. | single line only (DT_SINGLELINE) |
DT_VCENTER |
Centers text vertically. | ^ |
DT_BOTTOM |
Justifies the text to the bottom of the rectangle. | ^ |
DT_LEFT |
Aligns text to the left. | |
DT_CENTER |
Aligns text in the center. | |
DT_RIGHT |
Aligns text to the right. | |
DT_WORDBREAK |
Lines are automatically broken between words if a word would extend past the edge of the rectangle specified by the pRect parameter. |
|
DT_CHARBREAK |
Lines are automatically broken between characters if a character would extend past the edge of the rectangle specified by the pRect parameter. |
|
DT_SINGLELINE |
Displays text on the single line only. Carriage returns and line feeds do not break the line. | The vertical align flag will be ignored when there is not this flag |
DT_EXPANDTABS |
Expands TAB characters. |
|
DT_TABSTOP |
Sets tab stops. Bits 15-8 (high-order byte of the low-order word) of the uFormat parameter specify the number of characters for each TAB. |
|
DT_NOCLIP |
Draws without clipping. Output will be clipped to the specified rectangle by default. | |
DT_CALCRECT |
Do not output actually, only calculate the size of output rectangle. |
Code in List 1 calls DrawText function to perform aligned text output,
according to the description of character to be output. Please refer to
fontdemo.c program in mg-samples for complete code of the program.
Figure 2 shows the output effect of the program.
List 1 Using DrawText function
void OnModeDrawText (HDC hdc)
{
RECT rc1, rc2, rc3, rc4;
const char* szBuff1 = "This is a good day. \n"
"这是利用 DrawText 绘制的文本, 使用字体 GB2312 Song 12. "
"文本垂直靠上, 水平居中";
const char* szBuff2 = "This is a good day. \n"
"这是利用 DrawText 绘制的文本, 使用字体 GB2312 Song 16. "
"文本垂直靠上, 水平靠右";
const char* szBuff3 = "单行文本垂直居中, 水平居中";
const char* szBuff4 =
"这是利用 DrawTextEx 绘制的文本, 使用字体 GB2312 Song 16. "
"首行缩进值为 32. 文本垂直靠上, 水平靠左";
rc1.left = 1; rc1.top = 1; rc1.right = 401; rc1.bottom = 101;
rc2.left = 0; rc2.top = 110; rc2.right = 401; rc2.bottom = 351;
rc3.left = 0; rc3.top = 361; rc3.right = 401; rc3.bottom = 451;
rc4.left = 0; rc4.top = 461; rc4.right = 401; rc4.bottom = 551;
SetBkColor (hdc, COLOR_lightwhite);
Rectangle (hdc, rc1.left, rc1.top, rc1.right, rc1.bottom);
Rectangle (hdc, rc2.left, rc2.top, rc2.right, rc2.bottom);
Rectangle (hdc, rc3.left, rc3.top, rc3.right, rc3.bottom);
Rectangle (hdc, rc4.left, rc4.top, rc4.right, rc4.bottom);
InflateRect (&rc1, -1, -1);
InflateRect (&rc2, -1, -1);
InflateRect (&rc3, -1, -1);
InflateRect (&rc4, -1, -1);
SelectFont (hdc, logfontgb12);
DrawText (hdc, szBuff1, -1, &rc1, DT_NOCLIP | DT_CENTER | DT_WORDBREAK);
SelectFont (hdc, logfontgb16);
DrawText (hdc, szBuff2, -1, &rc2, DT_NOCLIP | DT_RIGHT | DT_WORDBREAK);
SelectFont (hdc, logfontgb24);
DrawText (hdc, szBuff3, -1, &rc3, DT_NOCLIP | DT_SINGLELINE | DT_CENTER | DT_VCENTER);
SelectFont (hdc, logfontgb16);
DrawTextEx (hdc, szBuff4, -1, &rc4, 32, DT_NOCLIP | DT_LEFT | DT_WORDBREAK);
}
Figure 2 The output of DrawText function
Besides the above output functions, MiniGUI also provides functions listed in Table 2, which can be used to set or get the extra space between characters and lines.
Table 2 Functions to set/get extra space between characters and lines
| Function | Meaning |
|---|---|
GetTextCharacterExtra |
Get the extra space between characters |
SetTextCharacterExtra |
Set the extra space between characters |
GetTextAboveLineExtra |
Get the extra space above line |
SetTextAboveLineExtra |
Set the extra space above line |
GetTextBellowLineExtra |
Get the extra space bellow line |
SetTextBellowLineExtra |
Set the extra space bellow line |
The more usage of logical font and text output functions is illustrated in
fontdemo.c file of mg-samples.
Special Render Effects of Font Glyph
MiniGUI provides many special effects to render the font glyphs. For example,
you can specify the logical font style to render the glyph with bold, italic,
underline, and/or strikeout line. In version 2.0.3/1.6.9, MiniGUI provides
anti-aliased effect by using low-pass filter, to flip the glyph vertically
and/or horizontally, and to scale the glyph to meet the desired logical font
size when using bitmap font. In version 2.0.4/1.6.10/3.0, MiniGUI provides
FreeType2 support, and it makes that user can choose sub-pixel render using
FreeType2 or MiniGUI; Before using sub-pixel render, please confirm that you
have opened FT_CONFIG_OPTION_SUBPIXEL_RENDERING macro in FreeType2.
List 2 Using sub-pixel render
LOGFONT* mg_font;
mg_font = CreateLogFont (FONT_TYPE_NAME_SCALE_TTF, "times", "ISO8859-1",
FONT_WEIGHT_SUBPIXEL, FONT_SLANT_ROMAN, FONT_FLIP_NIL,
FONT_OTHER_NIL, FONT_UNDERLINE_NONE, FONT_STRUCKOUT_NONE,
15, 0);
...........
SelectFont(hdc, mg_font);
ft2SetLcdFilter (mg_font, MG_SMOOTH_NONE);
TextOut(hdc, 0,0, "text with MiniGUI sub-pixels smooth");
......
ft2SetLcdFilter (mg_font, MG_SMOOTH_DEFAULT);
TextOut(hdc, 0,0, "text with FreeType2 sub-pixels smooth");
The render effects are specified through the logical font style when you create
the logical font. For example, if you specify FS_WEIGHT_BOOK style, MiniGUI
will use low-pass filter to handle the edge of the vectorial font glyph in
order to anti-aliase. When MiniGUI scales the font glyph of bitmap font, this
style also can be used to anti-aliase. Table 3 illustrates the render effects
supported by MiniGUI.
Table 3 The font glyph render effects of MiniGUI
| Style of logical font | Style character in logical font name | Style value of logical font | Meaning |
|---|---|---|---|
weight：FONT_WEIGHT_REGULAR |
First char is ‘r’ | FS_WEIGHT_REGULAR |
No any weight effect |
weight：FONT_WEIGHT_BOLD |
First char is ‘b’ | FS_WEIGHT_BOLD |
Bold |
weight：FONT_WEIGHT_LIGHT |
First char is ‘l’ | FS_WEIGHT_LIGHT |
To render glyph edge with the background color |
weight：FONT_WEIGHT_BOOK |
First char is ’b’ | FS_WEIGHT_BOOK |
To handle to glyph edge by using the low-pass filter to anti-aliased |
weight：FONT_WEIGHT_DEMIBOLD |
Fist char is ‘d’ | FS_WEIGHT_DEMIBOLD |
Both FS_WEIGHT_BOLD and FS_WEIGHT_BOOK |
weight：FONT_WEIGHT_SUBPIXEL |
Fist char is ‘s’ | FS_WEIGHT_SUBPIXEL |
To handle to glyph by using sub-pixel render |
slant：FONT_SLANT_ROMAN |
Second char is ‘r’ | FONT_SLANT_ROMAN |
No any slant effect |
slant：FONT_SLANT_ITALIC |
Second char is ‘i’ | FONT_SLANT_ITALIC |
Italic |
flip：FONT_OTHER_NIL |
Third char is any letter but H/V/T | N/A | No any flipping effect |
flip：FONT_FLIP_HORZ |
Third char is ‘H’ | FS_FLIP_HORZ |
To flip the glyph horizontally |
flip：FONT_FLIP_VERT |
Third char is ‘V’ | FS_FLIP_VERT |
To flip the glyph vertically |
flip：FONT_FLIP_HORZVERT |
Third char is ‘T’ | FS_FLIP_HORZVERT |
Both FS_FLIP_HORZ and FS_FLIP_VERT |
other：FONT_OTHER_NIL |
Forth char is any letter but S/N | N/A | No any other effect |
other：FONT_OTHER_AUTOSCALE |
Forth char is ‘S’ | FS_OTHER_AUTOSCALE |
To scale the glyph to meet the desired logical font size, only good for bitmap font. |
other：FONT_OTHER_TTFNOCACHE |
Forth char is ‘N’ | FS_OTHER_TTFNOCACHE |
To close the cache when render glyph by using TrueType font. |
other：FONT_OTHER_LCDPORTRAIT |
Forth char is ‘P’ | FS_OTHER_LCDPORTRAIT |
Using portrait LCD when render glyph by using TrueType font. |
underline：FONT_UNDERLINE_NONE |
Fifth char is ‘n’ | FS_UNDERLINE_NONE |
No underline |
underline：FONT_UNDERLINE_LINE |
Fifth char is ‘u’ | FS_UNDERLINE_LINE |
Underline |
strikeout：FONT_STRUCKOUT_NONE |
Sixth char is ’n’ | FS_STRUCKOUT_NONE |
No strikeout line |
strikeout：FONT_STRUCKOUT_LINE |
Sixth char is ’s’ | FS_STRUCKOUT_LINE |
strikeout line |
The style character given by Table 3 can be used to define the logical font name.
Usage of BIDI text
In generally, Latin and many texts store and display from left to right, but
some central Asian countries' languages (Arabic) display from right to left.
BIDI text problem occurs when these texts are mixed together.
To support BIDI text, please enable related character set and configure the
fonts. The following is the example for Arabic font:
- enable iso8859-6 character set support, MiniGUI supports Arabic font in default
- Configure vbf font in MiniGUI configuration file
[varbitmapfonts]
font_number=1
name0=vbf-naskhi-rrncnn-18-21-ISO8859-6
fontfile0=/usr/local/share/minigui/res/font/naskhi-18-21-iso8859-6.vbf
Arabic demo is shown as below:
Figure 3 Arabic font demo
Enhancements in MiniGUI 4.0
In MiniGUI 4.0, we enhanced and tuned the APIs related to text rendering in order that MiniGUI can handle complex font systems (scripts) like Arabic and Indic:
-
MiniGUI now provides complete APIs for Unicode character processing. These APIs conform to Unicode 12.0, including Unicode Bidirectional Algorithm (UAX#9), Unicode Line Breaking Algorithm (UAX#14), Unicode Normalization Forms (UAX#15), Unicode Script Property (UAX#24), Unicode Text Segmentation (UAX#29), Unicode Vertical Text Layout (UAX#50), and so on.
-
MiniGUI also provides new APIs to lay out, shape, and render glyphs from complex and mixed scripts, such as Arabic, Thai, and Indic. The new APIs also conform to the specifications of [CSS Text Module Level 3] and [CSS Writing Modes Level 3].
-
We tuned and optimized the logfont and devfont interfaces to support the new features above.
For the usage of the new APIs, please refer to the following supplementary documents:
<< Graphics Device Interfaces | Table of Contents | Advanced GDI Functions Based on NEWGAL >>