Difference between revisions of "Font rendering"

Revision as of 14:52, 30 October 2015

µGFX comes with a built-in support of mcufont. The author of the mcufont project provides a re-licensed version of his works to the µGFX projects.

Features

The µGFX font rendering engine provides the following features:

Word-Wrapping

ToDo

Unicode

Unicode support can be enabled by setting GDISP_NEED_TEXT_UTF8 to TRUE.

For information about cyrillic font support, see Cyrillic.

Anti-Aliasing

To use the anti-aliasing font feature, the following three conditions have to be fulfilled:

1. Using an anti-aliased font
2. GDISP_NEED_ANTIALIAS needs to be set to TRUE
3. Either have GDISP_NEED_PIXELREAD set to TRUE or using one of the text drawing functions that have a background color parameter.

Note that you can use normal (not anti-aliased) fonts along with anti-aliased ones without any problems.

Kerning

Kerning support can be enabled by setting GDISP_NEED_TEXT_KERNING to TRUE.

TrueType-Font support

Any TrueType-Font available in a *.ttf or a *.bdf file format can be used in uGFX. See Adding Fonts.

Fonts

Every font that's available in a .ttf or .bdf format can be displayed through µGFX. However, we already added a bunch of fonts in different sizes and versions which should cover most use cases. Use the Font name as the parameter of the gdispOpenFont() routine.

Note that each of these fonts has to be enabled in your configuration file.

The UI fonts are created by the µGFX developers to provide a default font. The UI fonts stand under the GFX license and should therefore be used in preference to other fonts if suitable. The other fonts are under their own respective licenses.

Usage

Before you can use a font, you first have to open it by calling gdispOpenFont().

font_t font = gdispOpenFont("DejaVuSans32_aa");

Note: When the font name specified could not be found, the last enabled font in the configuration file will be used.

You should call gdispCloseFont() to release any allocated resources if you don't need a font any longer:

gdispCloseFont(font);

After opening a font, the font variable can now be passed to any API call that takes a font parameter. You may start by reading through the basic GDISP text drawing routines before you take a look at the different GWIN system.

Adding fonts

The following step-by-step guide will lead you through the process of adding a custom *.ttf font. This guide works for every font, not only ASCII but also cyrillic and any other unicode compatible ones.

1. Acquire a font

First of all, you'll need a font in the *.ttf source. You can find plenty of these using google. Please notice their licenses.

2. Convert the font

The next step is to convert the font into a format that can be understood by the µGFX decoder. This can be done very easily using our online converter. The converter allows you to set the font size, enable or disable anti-aliasing and filter for certain characters. Filtering un-needed characters is essential to keep the font size low. This table might help you choose the correct character range. A click on the button «Get .c file» will offer you a C file to download after a few moments. Please click that button just once. It can take up to a minute to convert a larger font.

3. Implement the font

Place the downloaded c file inside your project directory and name it userfonts.h. Alternatively write a userfonts.h file that includes each of your downloaded font c files. In your gfxconf.h, enable the following setting:

#define GDISP_INCLUDE_USER_FONTS	TRUE

4. Open the font

You can now open and use this font as any other one. If you're curious about the parameter of gdispOpenFont(), you can either use the full_name or the short_name field that can be found in the struct at the very bottom of the C file (first and second entry). Please note that you need to configure your text editor to operate in UTF-8 mode, when you want to display those fonts successfully.

For a more detailed guide on how to add your own font, see Cyrillic.

Font metrics

The GDISP API provides several function to retrieve information about font metrics:

typedef enum fontmetric { fontHeight, fontDescendersHeight, fontLineSpacing, fontCharPadding, fontMinWidth, fontMaxWidth } fontmetric_t;
 
coord_t gdispGetFontMetric(font_t font, fontmetric_t metric);
coord_t gdispGetCharWidth(char c, font_t font);
coord_t gdispGetStringWidth(const char* str, font_t font);