8.2 KiB
TTF font utility
introduction
This module is designed to perform two main task
- Load the font file
- Render text using a TTF font
The render system can be single or multiple, for example it is possible to have a bitmap render and a HW accelerated render.
TTF loader
This part of the module do a simple task, load a TTF file and preprocess all the loaded data in order to simplify the rendering phase.
Let's start with a simple snippet of code that load a font from the disk:
mut ttf_font := ttf.TTF_File{}
ttf_font.buf = os.read_bytes("arial.ttf") or { panic(err) }
ttf_font.init()
Note: the font must be passed to the TTF_file as RAM buffer.
At this point the font "arial" is loaded and parsed and if it is a valid TTF font it is
ready for the rendering.
We can get some quick info on the font as string using the get_info_string function:
println(ttf_font.get_info_string())
produces an output like this:
----- Font Info -----
font_family : Arial
font_sub_family : Normal
full_name : Arial
postscript_name : ArialMT
version : 1
font_revision : 5.06
magic_number : 5f0f3cf5
flags : 81b
created unixTS : 649950890
modified unixTS : 1282151447
units_per_em : 2048
box : [x_min:-1361, y_min:-665, x_Max:4096, y_Max:2060]
mac_style : 0
-----------------------
Once loaded a font the TTF_File struct is filled with the font data and texts can be rendered.
At high level no more action are required to use the loaded font.
Multiple fonts can be loaded without problems at the same time.
TTF Bitmap render
In this modue it is possible to have different renders running at the same time. At the present time all the rendering are made on the CPU, sokol is used only to draw the rendered text to the screen. Let's start with a simple snippet of code:
import os
import x.ttf
[console]
fn main() {
mut ttf_font := ttf.TTF_File{}
ttf_font.buf = os.read_bytes('arial.ttf') or { panic(err) }
ttf_font.init()
// print font info
println(ttf_font.get_info_string())
}
This simple code load a TTF font and display its basic informations.
draw_text
The draw text function draw simple strings without indentation or other imagination tasks. At this point we can render a simple text:
import os
import x.ttf
[console]
fn main() {
mut ttf_font := ttf.TTF_File{}
ttf_font.buf = os.read_bytes('arial.ttf') or { panic(err) }
ttf_font.init()
// print font info
println(ttf_font.get_info_string())
bmp_width := 200
bmp_heigth := 64
bmp_layers := 4 // number of planes for an RGBA buffer
// memory size of the buffer
bmp_size := bmp_width * bmp_heigth * bmp_layers
font_size := 32 // font size in points
device_dpi := 72 // default screen DPI
// Formula for scale calculation
// scaler := (font_size * device dpi) / (72dpi * em_unit)
scale := f32(font_size * device_dpi) / f32(72 * ttf_font.units_per_em)
// height of the font to use in the buffer to separate the lines
y_base := int((ttf_font.y_max - ttf_font.y_min) * scale)
// declare the bitmap struct
mut bmp := ttf.BitMap{
tf: &ttf_font
buf: malloc(bmp_size)
buf_size: bmp_size
width: bmp_width
height: bmp_heigth
bp: bmp_layers
color: 0x000000_FF // RGBA black
scale: scale
}
bmp.init_filler()
bmp.clear()
bmp.set_pos(10, y_base)
bmp.draw_text('Test Text!')
bmp.save_as_ppm('test.ppm')
}
This is the low level render that draw ther text on a bitmap and save the bitmap on a disk as
.ppm file.
Note: The render in this case is a raw rendering without any postfiltering or other processing.
Using the low level rendering you need to manage all the amenities like allocate and release memory and other tasks like calc the character dimensions.
You can specify the style for the text rendering in the BitMap struct::
enum Style {
outline
outline_aliased
filled // default syle
raw
}
Use this level only if you want achieve particular result on text rendering.
draw_text_block
Draw text block draw a justified and indented block of multiline text in the bitmap.
import os
import x.ttf
[console]
fn main() {
mut ttf_font := ttf.TTF_File{}
ttf_font.buf = os.read_bytes('arial.ttf') or { panic(err) }
ttf_font.init()
// print font info
println(ttf_font.get_info_string())
bmp_width := 200
bmp_heigth := 200
bmp_layers := 4 // number of planes for an RGBA buffer
// memory size of the buffer
bmp_size := bmp_width * bmp_heigth * bmp_layers
font_size := 32 // font size in points
device_dpi := 72 // default screen DPI
// Formula for scale calculation
// scaler := (font_size * device dpi) / (72dpi * em_unit)
scale := f32(font_size * device_dpi) / f32(72 * ttf_font.units_per_em)
// height of the font to use in the buffer to separate the lines
y_base := int((ttf_font.y_max - ttf_font.y_min) * scale)
text := "Today it is a good day!
Tomorrow I'm not so sure :(
But Vwill prevail for sure, V is the way!!
òàèì@ò!£$%&
"
// declare the bitmap struct
mut bmp := ttf.BitMap{
tf: &ttf_font
buf: malloc(bmp_size)
buf_size: bmp_size
width: bmp_width
height: bmp_heigth
bp: bmp_layers
color: 0x000000_FF // RGBA black
scale: scale
}
bmp.init_filler()
bmp.clear()
bmp.justify = true
bmp.align = .left
bmp.draw_text_block(text, x: 0, y: 0, w: bmp_width - 20, h: bmp_heigth)
bmp.save_as_ppm('test.ppm')
}
This is the low level render that draw text block on the bitmap.
A text block is defined from a Text_block struct:
struct Text_block {
x int // x postion of the left high corner
y int // y postion of the left high corner
w int // width of the text block
h int // heigth of the text block
cut_lines bool = true // force to cut the line if the length is over the text block width
}
and use the following bitmap fields:
style Style = .filled // default syle
align Text_align = .left // default text align
justify bool // justify text flag, default deactivated
justify_fill_ratio f32 = 0.5 // justify fill ratio, if the ratio of the filled
// row is >= of this then justify the text
It is possible to modify these parameters to obtain the desired effect on the text rendering.
TTF Sokol render
The sokol render use the bitmap render to create the text and the gg functions to render
the text to the screen.
It is mor esimpel to use in a gg app that the raw bitmap render.
Each single text rendered need its own reder to be declared, after you can modify it.
Here a simple example of the usage:
import gg
import gx
import sokol.sapp
import sokol.sgl
import x.ttf
import os
const (
win_width = 600
win_height = 700
bg_color = gx.white
font_paths = [
'arial.ttf',
]
)
struct App_data {
pub mut:
gg &gg.Context
sg_img C.sg_image
init_flag bool
frame_c int
tf []ttf.TTF_File
ttf_render []ttf.TTF_render_Sokol
}
fn my_init(mut app App_data) {
app.init_flag = true
}
fn draw_frame(mut app App_data) {
cframe_txt := 'Current Frame: $app.frame_c'
app.gg.begin()
sgl.defaults()
sgl.matrix_mode_projection()
sgl.ortho(0.0, f32(sapp.width()), f32(sapp.height()), 0.0, -1.0, 1.0)
// draw text only if the app is already initialized
if app.init_flag == true {
// update the text
mut txt1 := &app.ttf_render[0]
txt1.destroy_texture()
txt1.create_text(cframe_txt, 43)
txt1.create_texture()
txt1.draw_text_bmp(app.gg, 30, 60)
}
app.frame_c++
app.gg.end()
}
[console]
fn main() {
mut app := &App_data{
gg: 0
}
app.gg = gg.new_context(
width: win_width
height: win_height
create_window: true
window_title: 'Test TTF module'
user_data: app
bg_color: bg_color
frame_fn: draw_frame
init_fn: my_init
)
// load TTF fonts
for font_path in font_paths {
mut tf := ttf.TTF_File{}
tf.buf = os.read_bytes(font_path) or { panic(err) }
println('TrueTypeFont file [$font_path] len: $tf.buf.len')
tf.init()
println(tf.get_info_string())
app.tf << tf
}
// TTF render 0 Frame counter
app.ttf_render << &ttf.TTF_render_Sokol{
bmp: &ttf.BitMap{
tf: &(app.tf[0])
buf: unsafe { malloc(32000000) }
buf_size: (32000000)
color: 0xFF0000FF
// style: .raw
}
}
app.gg.run()
}