Performing Layout Calculations

[memononen]

Performing Layout Calculations

[memononen]

Hi,
You should use the same context for getting the text size too. Otherwise you will need to load the fonts twice, etc.

There are a couple of state helpers you can use to make sure that you don't mess things up. nvgSave() will save the current state (fonts, fills, etc), nvgReset() resets the state, nvgRestore() restores the state.

If that sounds too much trouble, I don't mind adding a font state struct and allow you to use that for text related query functions. nvgTextBounds() and nvgVertMetrics() do not issue any draw calls. They may update the font cache, which will update anyway when you render text.

[Ziflin]

It sounds like using the same context would cause problems with threaded rendering though? Similar issues with nvgTextBounds if they are updating textures or font related information. (This isn't a huge concern, but would have been nice to get setup.)

Was nvgTextBounds calculating the correct text size give the current transform scale and performing the pixel alignment? I'm about to look through the code, but it seemed like this would cause some "badness" if the drawing calculated a different final bounds due to the pixel alignment.

Thanks again for the help!

[memononen]

NanoVG rendering is not thread safe. So if you use multiple threads you should do some buffering or use multiple contexts (current fonts and images cannot be shared across contexts).

You are correct that nvgTextBounds takes current transform into account. Transform is part of the state so you can use the nvgSave(), nvgReset(), , nvgRestore() sequences to get a clean slate at any given time.

[Ziflin]

Ok, I assumed it was setup this way. At what point does the font texture get created? Just wondering if there's a way to not create the actual GL resource for my layout-only context. I wasn't sure if calculating the text bounds required the glyphs to be added to the font texture?

[memononen]

Currently the glyphs are generated on first access, including calculating text bounds. The magic happens in fontstash.h fons__getGlyph()

[Ziflin]

Ok thanks, I'll check it out more today.