Add TTF_GetFontBBox() which returns font's extremum bounding box

Author: ivan-mogilko

SDL_ttf.c

@@ -3035,6 +3035,16 @@ void TTF_SetFontKerning(TTF_Font *font, int allowed)
 #endif
 }
 
+void TTF_GetFontBBox(const TTF_Font *font, TTF_BBox *bbox)
+{
+    /* Recalculate FT_Face's bbox from font units to pixels */
+    const FT_Face face = font->face;
+    bbox->xmax = FT_MulFix(FT_DivFix(face->bbox.xMax, face->units_per_EM), face->size->metrics.x_ppem);
+    bbox->xmin = FT_MulFix(FT_DivFix(face->bbox.xMin, face->units_per_EM), face->size->metrics.x_ppem);
+    bbox->ymax = FT_MulFix(FT_DivFix(face->bbox.yMax, face->units_per_EM), face->size->metrics.y_ppem);
+    bbox->ymin = FT_MulFix(FT_DivFix(face->bbox.yMin, face->units_per_EM), face->size->metrics.y_ppem);
+}
+
 long TTF_FontFaces(const TTF_Font *font)
 {
     return font->face->num_faces;

SDL_ttf.h

@@ -164,6 +164,15 @@ extern DECLSPEC void SDLCALL TTF_ByteSwappedUNICODE(SDL_bool swapped);
  */
 typedef struct TTF_Font TTF_Font;
 
+/**
+ * A bounding box, represented in pixel offsets.
+ */
+typedef struct TTF_BBox
+{
+    int xmin, xmax;
+    int ymin, ymax;
+} TTF_BBox;
+
 /**
  * Initialize SDL_ttf.
  *
@@ -678,6 +687,21 @@ extern DECLSPEC int SDLCALL TTF_GetFontKerning(const TTF_Font *font);
  */
 extern DECLSPEC void SDLCALL TTF_SetFontKerning(TTF_Font *font, int allowed);
 
+/**
+ * Query the font bounding box.
+ * 
+ * The bounding box defines bounds large enough to contain any glyph from
+ * the font. It is expressed in pixel offsets from glyph's origin (0,0),
+ * with Y axis pointing upwards. Thus ymax offset may be seen as the
+ * "maximal ascender" and ymin offset - as the "maximal descender".
+ *
+ * \param font the font to query.
+ * \param bbox the TTF_BBox struct to fill.
+ *
+ * \since This function is available since SDL_ttf 2.26.0.
+ */
+extern DECLSPEC void SDLCALL TTF_GetFontBBox(const TTF_Font *font, TTF_BBox *bbox);
+
 /**
  * Query the number of faces of a font.
  *