BLF: Public Function to Return Maximum Glyph Bounds

This BLF adds a public function that returns the maximum extext of a
font's glyphs. BLF_bounds_max returns a rctf of the minimum rect that
can contain any of the font's glyphs. Can be useful to know when sizing
a bitmap without knowing the final string contents.

Pull Request: https://projects.blender.org/blender/blender/pulls/145016

source/blender/blenfont/BLF_api.hh

@@ -30,6 +30,7 @@
 struct ListBase;
 struct ResultBLF;
 struct rcti;
+struct rctf;
 
 namespace blender::ocio {
 class ColorSpace;
@@ -293,6 +294,17 @@ int BLF_width_max(int fontid) ATTR_WARN_UNUSED_RESULT;
 int BLF_descender(int fontid) ATTR_WARN_UNUSED_RESULT;
 int BLF_ascender(int fontid) ATTR_WARN_UNUSED_RESULT;
 
+/**
+ * Returns the minimum bounding box that can enclose all glyphs in the font at
+ * the current size. Expect negative values as Y=0 is the baseline, X=0 is normal
+ * advance position (glyphs can have negative bearing and positioning). There
+ * should be little use for this as it is best to measure the bounds of the actual
+ * text to be drawn. These values (unscaled) are set in the font file, not calculated
+ * from the actual glyphs at load time. This should be considered correct but it is
+ * possible, although very unlikely, for a defective font to contain incorrect values.
+ */
+bool BLF_bounds_max(int fontid, rctf *r_bounds) ATTR_NONNULL(2);
+
 /**
  * The following function return the width and height of the string, but
  * just in one call, so avoid extra freetype2 stuff.

source/blender/blenfont/intern/blf.cc

@@ -891,6 +891,15 @@ int BLF_ascender(int fontid)
   return 0.0f;
 }
 
+bool BLF_bounds_max(int fontid, rctf *r_bounds)
+{
+  FontBLF *font = blf_get(fontid);
+  if (font) {
+    return blf_font_bounds_max(font, r_bounds);
+  }
+  return false;
+}
+
 void BLF_rotation(int fontid, float angle)
 {
   FontBLF *font = blf_get(fontid);

source/blender/blenfont/intern/blf_font.cc

@@ -1588,6 +1588,19 @@ int blf_font_ascender(FontBLF *font)
   return ft_pix_to_int((ft_pix)font->ft_size->metrics.ascender);
 }
 
+bool blf_font_bounds_max(FontBLF *font, rctf *r_bounds)
+{
+  if (!blf_ensure_face(font)) {
+    return false;
+  }
+
+  r_bounds->xmin = float(font->face->bbox.xMin) / float(font->face->units_per_EM) * font->size;
+  r_bounds->xmax = float(font->face->bbox.xMax) / float(font->face->units_per_EM) * font->size;
+  r_bounds->ymin = float(font->face->bbox.yMin) / float(font->face->units_per_EM) * font->size;
+  r_bounds->ymax = float(font->face->bbox.yMax) / float(font->face->units_per_EM) * font->size;
+  return true;
+}
+
 char *blf_display_name(FontBLF *font)
 {
   if (!blf_ensure_face(font) || !font->face->family_name) {

source/blender/blenfont/intern/blf_internal.hh

@@ -20,6 +20,7 @@ struct GlyphCacheBLF;
 struct ListBase;
 struct ResultBLF;
 struct rcti;
+struct rctf;
 enum class BLFWrapMode;
 
 /**
@@ -153,6 +154,7 @@ int blf_font_height_max(FontBLF *font);
 int blf_font_width_max(FontBLF *font);
 int blf_font_descender(FontBLF *font);
 int blf_font_ascender(FontBLF *font);
+bool blf_font_bounds_max(FontBLF *font, rctf *r_bounds);
 
 char *blf_display_name(FontBLF *font);