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Using Enhanced Font Interfaces

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Vincent Wei edited this page Jul 24, 2019 · 8 revisions

Understand and use enhanced font intefaces of MiniGUI 4.0.

Table of Contents

Overview

In order to support complex or mixed scripts, we tuned and enhanced MiniGUI's font interfaces in version 4.0.0.

Before we continue, we need to clarify a few terms and concepts:

  • devfont: a device font object. It is the underlying object containing the glyphs of all or some characters in specific language or script.
  • logfont: a logical font object. It is the real object used by MiniGUI app to render paragraphs, words, or characters.

Generally, a MiniGUI app creates one or more logfonts by specifying the family, style, size, and charset/encoding, and calls GDI functions to lay out, shape, and render the text.

When creating a logfont object, MiniGUI retrieves the devfonts which matched the family, style, size, and character/encoding for the requested logfont object in the devfonts base, which is loaded in the start stage of MiniGUI.

However, one logfont object does not always correspond to a devfont object, but rather to multiple devfont objects.

For example, when we want to show a text like below:

“对暴徒仁慈就是对良民的残忍”
    -- Anonym

It is well known that, a font is often designed for a particular language/script or a few similar languages/scripts. So MiniGUI may retrieve the glyphs for the characters in the first line (they are all in Chinese) in a font file named 宋体.ttf, while in another font file named Arial.ttf for the characters in the second line (they are all in English).

Therefore, a logfont object actually corresponds to a collection of devfont objects, which match the logfont's family, style, size, and charset/encoding.

Before version 4.0.0, a logfont object can be represented by one or two devfont objects. Therefore, MiniGUI can easily handle standard languages/scripts, like Chinese, Japanese, English (Latin).

However, when we want to handle a text in the complex and mixed scripts like Arabic and Indic, the old logfont/devfont facility will not work.

Therefore, we tuned and enhanced the font interfaces in version 4.0.0. But don't worry, the tuned or enhanced interfaces kept the backward compatibility.

Enhancements of Font Name

Devfont name

You know that we often use a string to specify the family name, style, size, and charsets of a devfont object:

ttf-Arial-rrncnn-0-0-ISO8859-1,UTF-8

It means that the devfont is a TrueType vector font, the family name of the devfont is Arial, the style is represented by a string rrncnn, the size can be any value (e vector font can be arbitrarily scaled to meet different size requirements.), and the charsets/encodings of the devfont are ISO8859-1 and UTF-8.

Since 4.0.0, you can specify the aliases for the family name of a devfont:

<fonttype>-<family[,aliase]*>-<styles>-<width>-<height>-<charset[,charset]*>

For example:

ttf-Arial,Sans Serif-rrncnn-0-0-ISO8859-1,UTF-8
ttf-courier,monospace,serif-rrncnn-0-0-ISO8859-1,UTF-8

Note that the length of one devfont name can not exceed 255 bytes.

Logfont name

When we create a logfont object, we generally call CreateLogFontByName function. The logfont name uses the similar format as devfont name:

<fonttype>-<family-name[,family-nameN]*>-<styles>-<width|orientation>-<height>-charset

Since version 4.0.0, you can specify up to 7 family names for a logfont name, for example:

ttf-Courier,宋体,Naskh,SansSerif-rrncns-U-16-UTF-8

In this way, you can specify a logfont to use multiple devfonts to render a complex text.

Moreover, the previous width field of a logfont name is used for the glyph orientation:

  • U: Glyphs stand upright (default).
  • S: Glyphs are rotated 90 degrees clockwise (sideways).
  • D: Glyphs are upside-down.
  • L: Glyphs are rotated 90 degrees counter-clockwise (sideways left).

Font style

As you seen in above font names, we use a style string (six ASCII characters) to define the style of a font in font name.

In version 4.0.0, we tuned the meaning of each character in the style string.

The format of the style string changed from

<weight><slant><flipping><other><underline><struckout>

to

<weight><slant><flipping><other><decoration><rendering>

The differences are as follow:

  • The new <rendering> style added.
  • <underline> and <struckout> are merged to <decoration> in order to keep the style string is still 6-character long.
  • For <weight>, we redefined the weight styles follow OpenType specification.

The following words describe the detailed information about the changes of style:

  • Introduced new rendering style:
    1. FS_RENDER_MONO: represented by ASCII character n.
    2. FS_RENDER_GREY: represented by ASCII character g.
    3. FS_RENDER_SUBPIXEL: represented by ASCII character s.
  • The following old styles are deprecated:
    1. FS_WEIGHT_BOOK; use FS_RENDER_GREY instead.
    2. FS_WEIGHT_SUBPIXEL; use FS_RENDER_SUBPIXEL instead.
  • Introduced New weight style:
    1. FONT_WEIGHT_THIN: Thin; represented by ASCII character t.
    2. FONT_WEIGHT_EXTRA_LIGHT: Extra light (Ultra Light); represented by ASCII character e.
    3. FONT_WEIGHT_LIGHT: Light; represented by ASCII character l.
    4. FONT_WEIGHT_NORMAL: Normal; represented by ASCII character n.
    5. FONT_WEIGHT_REGULAR: Regular; represented by ASCII character r.
    6. FONT_WEIGHT_MEDIUM: Medium; represented by ASCII character m.
    7. FONT_WEIGHT_DEMIBOLD: Demi Bold (Semi Bold); represented by ASCII character d.
    8. FONT_WEIGHT_BOLD: Bold; represented by ASCII character b.
    9. FONT_WEIGHT_EXTRA_BOLD: Extra Bold (Ultra Bold); represented by ASCII character x.
    10. FONT_WEIGHT_BLACK: Black (Heavy); represented by ASCII character c.
  • Introduce the new decoration styles and replace FONT_UNDERLINE_LINE and FONT_STRUCKOUT_LINE with them:
    1. FONT_DECORATE_NONE: without any decoration; represented by ASCII character n.
    2. FONT_DECORATE_UNDERLINE: glyphs are underscored represented by ASCII character u.
    3. FONT_DECORATE_STRUCKOUT: glyphs are overstruck represented by ASCII character s.
    4. FONT_DECORATE_US: Both FONT_DECORATE_UNDERLINE and FONT_DECORATE_STRUCKOUT; represented by ASCII character U.
    5. FONT_DECORATE_REVERSE: Glyphs have their foreground and background reversed (r); Reserved for future.
    6. FONT_DECORATE_OUTLINE: Outline (hollow) glyphs (o); Reserved for future.
  • The following style are deprecated:
    1. FONT_OTHER_LCDPORTRAIT
    2. FONT_OTHER_LCDPORTRAITKERN

As an example, if you want to use the rendering method SUPIXEL for a TTF font, please define the logfont name in the following way:

ttf-Courier-rrncns-*-16-UTF-8

API Enhancements

For a new app, you should use the new function CreateLogFontEx to create a logfont, and specify the weight and rendering method of the glyph:

m_btnFont = CreateLogFontEx ("ttf", "helvetica", "UTF-8",
        FONT_WEIGHT_REGULAR,
        FONT_SLANT_ROMAN,
        FONT_FLIP_NONE,
        FONT_OTHER_NONE,
        FONT_DECORATE_NONE, FONT_RENDER_SUBPIXEL,
        SETTING_OK_BTN_TEXT_H, 0);

For the backward compatibility, you can still use CreateLogFont to create a new logfont. However, FS_WEIGHT_BOOK will be treated FS_WEIGHT_REGULAR and FS_RENDER_GREY, while FS_WEIGHT_SUBPIXEL will be treated FS_WEIGHT_REGULAR and FS_RENDER_SUBPIXEL.

You can still use CreateLogFontByName to create a new logfont. But you should make sure to define the new logfont name in new format.

We also introduced the following new functions in version 4.0.0:

  • CreateLogFontIndirectEx: to create a new logfont object by using the properties of an existing logfont object, but with a new rotation argument. This function is a supplementary of CreateLogFontIndirect.
  • CreateLogFontForMChar2UChar: to create a logfont in order to convert a multi-byte character string to Uchar32 string.
  • LoadDevFontFromIncoreData: to load a devfont from a file. This function is a supplementary of LoadDevFontFromFile.

Example

For complete usage example of new font API, you can refer to:

https://github.com/VincentWei/mg-tests/blob/master/4.0/createlogfontex.c

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