Comment by zokier
1 day ago
> Embedded-graphics includes bitmap fonts that have a very limited set of characters to save space (ASCII, ISO 8859 or JIS X0201). This makes it impossible to draw most of Ratatui's widgets, which heavily use box-drawing glyphs, Braille, and other special characters
You have a bitmap display, you can just draw lines and stuff without needing to rely on font-based hacks.
Sure, but that's beside the point.
Text based graphics with fancy or custom fonts is just crazy efficient. That is exactly how we got the amazing graphics of The Last Ninja or Turrican on machines with less than 64KiB useable RAM.
Same for more modern embedded devices. If you constrain yourself to text you increase both runtime performance and your developer productivity.
It was crazy efficient on character or tile-based hardware. It makes no difference on bitmap displays, or rather adds some overhead.
At the end of the day it's always pixels - alway has been [1] - and the efficiency of storing and blitting a small number of fixed size rectangles is hard to beat if you can get away with it.
[1] Except for the early oscilloscope style vector displays maybe.
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Are you claiming that scrapping together boxes and whatnot with line drawing characters is more efficient than just drawing the lines directly?
I think they're claiming that having character-based pipelines and algorithms can be more efficient than doing everything on the level of pixels... I can't help but feel there's a middle-ground somewhere, though.
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The same isn't true for modern embedded devices, they don't have tile rendering hardware. If you connect a i2c/SPI screen (SSD1306, ST7735), you write all the pixels on the screen (or pixels to some subregion of the screen), these screens do have a backing memory in them.
So in order to draw a line, you will - objectively - have to copy/move more bytes if you approximate line with character symbols.
This isn't a big deal, but crazy efficient it is not.
All the efficiency when drawing on those screens mostly relies on how well you chain together DMA transfers to portions of the screen you want stuff to be drawn to, so that SPI transfers aren't blocking the CPU (that's assuming you don't have memory for a second full-screen buffer).
SSD1306 is a bit in the middle. It's technically a 128x64 monochrome bitmapped display, but it's organized as eight 128x8 "rows", with each byte representing a single 1x8 group of pixels. That organization really favors being treated as either four or eight lines of text - trying to use it as a generic bitmap display gets awkward, because it's only addressable at the level of those 1x8 groups.
ST7735 is more of a standard (color) bitmap display.
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