Hi Steve,

This seems to be SDF imprecisions. I will analyze it carefully, but probably we will need to increase SDF resolution.

Is this happening on trunk or in the Arabic branch?

Hey Jesus, yes, this is in the Arabic branch, but I'm pretty sure this issue was present in the build prior to integrating the Arabic branch as well.

Yes, that makes sense.

I am finishing an important crash you have in the Arabic branch (VGLTextLayout::HitTestTextPosition) and will jump to this ASAP.

Awesome, much appreciated. And yes, those HitTestTextPosition bugs take precedence over this issue for us, this is just a slight graphical issue that's fairly low priority, the other issues are causing glyphs to be rendered in the incorrect location so we're getting overlapping prompts which will cause compliancy failures.

Thank you for your help Jesús! Much appreciated.

Hi Steve, I see similar artifacts even without stroking. This is a limitation of the current technique we are using for rendering text, each font is internally rasterized to a distance field of size 54. If you double this size, you will see everything improves:

Index: VGLContext.cpp
===================================================================
--- VGLContext.cpp  (revision 11207)
+++ VGLContext.cpp  (working copy)
@@ -3709,7 +3709,7 @@
 #if 1
     // Render glyph SDF at a fixed resolution
     NS_UNUSED(scale);
-    float renderSize = 54.0f;
+    float renderSize = 54.0f * 2;
 #else
     // Render glyph SDF at the next power of two needed resolution
     float renderSize = (float)Clip(NextPow2(uint32_t(p.size * scale)), 1U, 54U);

But doing this has tricky implications. Right now, by default our glyph cache uses an internal texture of 1024 x 1024 with tiles of 512 x 512 (tiles are entirely discarded when there is not enough space in the atlas using a LRU algorithm).

The resolution of 1024 x 1024 can be changed by clients (not sure if your game is doing that), but the 512 x 512 is hardcoded in a macro (TILE_SIZE). The patch provided above should probably also increase TILE_SIZE. But this also depends on how heavy is your game about text.

Not sure yet what's the best way to expose this to client code. Tile size can be exposed the same as atlas size, and probably we can expose a size threshold for glyphs, if the size of the glyph (in your case is 200) is greater than that we can increase the rasterized distance field.

I need to think more about this, but feedback is welcome.

PS: thanks for the amazing repro-case, as always, you always make things so easy for us :)