Text wrapping / Font Metrics in Display Rendering Engine?

ESPHome
1

Hi,
is there some way to calculate the length that a string would take up on the screen with a specific (non-fixed width) font?
Or a way to automatically split a string that is too long to be displayed in one row on the given display into suitable sub-strings?
(For example, the Qt library has QFontMetrics and the wordwrap property for QLabel to achieve this)
Any best practices for ESPhome?

1 Like
2

If there is a C++ library for that, then some sort of custom component may do it.

3

Digging deeper into the API, it looks like DisplayBuffer already has something like this:
esphome::display::DisplayBuffer::get_text_bounds()

That should allow to detect if a string is too large to be fully visible on a display.
Still need to act on that information though - either trying to split the string into smaller substrings and print them as rows, or maybe create some text scrolling animation. Not sure if that can be done in a lambda though. Would be nice if the Display rendering API would allow to call something like “Pan this (prerendered text) image in this rect on x-axis with this speed”.

4

Hi @code_talker, a bit too late to the party but I have answered this question here

1 Like
5

Thanks. Looks elegant.
For proper wrapping, the Position in the String would still have to be calculated somehow, maybe simply by iteratively checking the width, or some binary search strategy.
when I get around to revisit this project, I’ll Post an update.

6

the way I see it, the position is irrelevant, the width of a string does not change with the position, no matter where you place it :slight_smile:

What you need to care about is layouting. I have my own layout algorithm which requires knowing the width of the different objects I am displaying.