Inconsistent behavior of Font.get_char_size for different TextServer

[dalexeev]

Godot version

v4.0.dev.custom_build [340883636]

System information

Kubuntu 21.10

Issue description

Font.get_char_size returns different results for TextServerAdvanced and TextServerFallback (internationalization/rendering/text_driver setting).

TextServerAdvanced:

(0, 7) # Wrong width
(4.15625, 23)

TextServerFallback:

(6, 7)
(4.15625, 23)

Note that the result is different for the attached font, but not for the standard font. My font is generated by my script, which is written similar to the Image Font importer. But a different result for different TextServer is still a bug in this case.

Steps to reproduce

See the issue description and MRP.

Minimal reproduction project

get_char_size.zip

[dalexeev]

Related (internationalization/rendering/text_driver = Fallback)?

Peek.2021-12-30.21-02.mp4

[bruvzg]

Font.get_char_size returns different results for TextServerAdvanced

Missing return value for the bitmap font in the font_get_glyph_index.

@@ -2573,7 +2573,7 @@ int32_t TextServerAdvanced::font_get_glyph_index(RID p_font_rid, int p_size, cha
 			return FT_Get_Char_Index(fd->cache[size]->face, p_char);
 		}
 	} else {
-		return 0;
+		return (int32_t)p_char;
 	}
 #else
 	return (int32_t)p_char;

Related (internationalization/rendering/text_driver = Fallback)?

Probably unrelated, seems like a rounding error in the Fallback text server or TextEdit. I'll take a look at it on Monday.