using own font in lv-micropython. Please, how to properly use lv.font_t to make own font?
Platform
ESP32
Code:
mvfont = b'...data'
def get_font_char(font, c):
return glyph_data_with_header
def get_glyph_dsc_cb(self, dsc_out, unicode_letter, unicode_letter_next):
ch = get_font_char(mvfont, unicode_letter)
if not ch:
return False
dsc_out.adv_w = ch[5] #/*Horizontal space required by the glyph in [px]*/
dsc_out.box_h = ch[3] #/*Height of the bitmap in [px]*/
dsc_out.box_w = ch[2] #/*Width of the bitmap in [px]*/
dsc_out.ofs_x = ch[4] #/*X offset of the bitmap in [pf]*/
dsc_out.ofs_y = ch[1] #/*Y offset of the bitmap measured from the as line*/
dsc_out.bpp = 1 #/*Bits per pixel: 1/2/4/8*/
return True
def get_glyph_bitmap_cb(self, unicode_letter):
ch = get_font_char(mvfont, unicode_letter)
y_offset, width, height, x_offset, x_delta = struct.unpack('>5B', ch[1:6])
d,m = divmod(width*height, 8)
chr_size = d+1 if m else d
return ch[5: 5+chr_size]
rcl56 = lv.font_t()
rcl56.get_glyph_dsc = get_glyph_dsc_cb #/*Set a callback to get info about gylphs*/
rcl56.get_glyph_bitmap = get_glyph_bitmap_cb #/*Set a callback to get bitmap of a glyp*/
rcl56.line_height = 58 #/*The real line height where any text fits*/
rcl56.base_line = 47 #/*Base line measured from the top of line_height*/
rcl56.dsc = None #/*Store any implementation specific data here*/
rcl56.user_data = None
I never tried adding a new font format, I only used lvgl fonts created with LittlevGL font converter.
Any reason you don’t want to use lvgl font system? They put a lot of work in it, it supports advanced features such as compression, kerning etc. and you can convert any TTF font to lvgl font using the font converter tool.
Regarding your crash, I suggest you try to debugging it. The backtrace you got is a good starting point:
thanks for reply. I have no problem to use lvgl font system, I have converted font etc… BUT if I understand this process well, I must compile my font as a part of lv-mpy. This means, I must recompile and reflash mpy each time I need some change in fonts. This means keep changes in repo for future updates and this is not so simply…
My font format is able to handle kerning too, is probably very similar to format used in lvgl, but uses python structures.
My goal is rewrite existing application to use lvgl. I have very simple lib for display (ili9341), which is written in mpy and is very slow (to redraw all things on screen it needs more then 2s, so it is not usable to print time with seconds, and no, I am not redrawing whole screen each time change ). I want to use lvgl for faster drawing… and add some interactivity in future… My question is “Is there some mpy example of using own font? Or, what I am doing wrong?”
But, if recommended way is use of build-in fonts, I can live with this…
Currently you must compile and reflash after updating or adding font.
We plan to support dynamic font loading in the future, which would allow loading the font on runtime from a file.
I’m not sure when I’ll have time to work on this, but I’ve opened a github issue for tracking it.
I’m not aware of any micropython example (or C example) that implements a new font. As far as I know, the only implementation is lvgl’s font system.
I’m not sure what you are doing wrong, if you want to find out I suggest you try debugging it.
Our ili9341 driver allows more than 30FPS, even when the whole screen is redrawn. It’s using DMA, double buffering, critical part are written in C, etc.
I also recommend using the built-in font system. I think it will cost you a lot less time to use it than to integrate your own font format, especially since you are using MicroPython and not C (although, with all the effort @amirgon has put into making the MicroPython binding so stable, maybe the difference is irrelevant.)
I started with Loboris mpy, which uses parts written in C, DMA, etc… too, but is very buggy and no more developed, so I switched to clear mpy and written my display driver. I optimized them for memory usage (I had ESP32 without psram), but it is very slow. Then I found lvgl, it looks like good solution for my speed troubles (and as bonus, this is the first system, where is working touch layer).
Embeddedt:
I undrestand and it looks like way which I will go. For now
BTW. I have build-in my fonts now and I must say, this fonts looks much more better…
). I want to use lvgl for faster drawing… and add some interactivity in future… My question is “Is there some mpy example of using own font? Or, what I am doing wrong?”