3D Text: improvements to vertical alignment

They way Blender handles vertical alignment is very buggy:

- Top-Base: It works perfectly.

- Bottom: It is actually bottom-baseline,
  and it fails when line size is != 1.0 when working with text boxes.

- Top: Poorly implemented, it should use font's ascent
  (recommended distance from baseline),
  so it has room for accents,
  but it's not one line distance far from the origin (as it is now).

- Center: Poorly implemented.
  This is tricky since there is no silver bullet.

To clear this situation I created a new option (Bottom-Baseline),
and addressed the issues above.
I'm getting the ascent and descent from freetype2,
and use this for padding above/below the text.
Also for vertically centering the text.

1 files changed, 17 insertions, 0 deletions

diff --git a/source/blender/blenlib/intern/freetypefont.c b/source/blender/blenlib/intern/freetypefont.c
index c7604b3cd6d..3f3868bea45 100644
--- a/source/blender/blenlib/intern/freetypefont.c
+++ b/source/blender/blenlib/intern/freetypefont.c
@@ -359,10 +359,27 @@ static VFontData *objfnt_to_ftvfontdata(PackedFile *pf)
 		lcode = charcode = FT_Get_First_Char(face, &glyph_index);
 	}
 
+	/* Blender default BFont is not "complete". */
+	const bool complete_font = (face->ascender != 0) && (face->descender != 0) &&
+	                           (face->ascender != face->descender);
+
+	if (complete_font) {
+		/* We can get descender as well, but we simple store descender in relation to the ascender.
+		 * Also note that descender is stored as a negative number. */
+		vfd->ascender = (float)face->ascender / (face->ascender - face->descender);
+	}
+	else {
+		vfd->ascender = 0.8f;
+		vfd->em_height = 1.0f;
+	}
 
 	/* Adjust font size */
 	if (face->bbox.yMax != face->bbox.yMin) {
 		vfd->scale = (float)(1.0 / (double)(face->bbox.yMax - face->bbox.yMin));
+
+		if (complete_font) {
+			vfd->em_height = (float)(face->ascender - face->descender) / (face->bbox.yMax - face->bbox.yMin);
+		}
 	}
 	else {
 		vfd->scale = 1.0f / 1000.0f;