Add a family of functions for opening fonts for non-square displays

FreeType natively supports font rendering for displays with non square pixels. This commit adds the following 4 functions: TTF_OpenFontDPI TTF_OpenFontDPIRW TTF_OpenFontIndexDPI TTF_OpenFontIndexDPIRW They are equivalent to the functions without the DPI suffix but accept 2 additional arguments, horizontal and vertical DPI resolution respectively.
libsdl-org · Dec 28, 2019 · 8642e6d · 8642e6d
1 parent 83cf252
commit 8642e6d
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Showing 2 changed files with 34 additions and 5 deletions.
diff --git a/SDL_ttf.c b/SDL_ttf.c
@@ -371,7 +371,7 @@ static unsigned long RWread(
 	return SDL_RWread( src, buffer, 1, (int)count );
 }
 
-TTF_Font* TTF_OpenFontIndexRW( SDL_RWops *src, int freesrc, int ptsize, long index )
+TTF_Font* TTF_OpenFontIndexDPIRW( SDL_RWops *src, int freesrc, int ptsize, long index, unsigned int hdpi, unsigned int vdpi )
 {
 	TTF_Font* font;
 	FT_Error error;
@@ -463,8 +463,10 @@ TTF_Font* TTF_OpenFontIndexRW( SDL_RWops *src, int freesrc, int ptsize, long ind
 	/* Make sure that our font face is scalable (global metrics) */
 	if ( FT_IS_SCALABLE(face) ) {
 
-		/* Set the character size and use default DPI (72) */
-		error = FT_Set_Char_Size( font->face, 0, ptsize * 64, 0, 0 );
+		/* Set the character size using the provided DPI.  If a zero DPI
+		 * is provided, then the other DPI setting will be used.  If both
+		 * are zero, then Freetype's default 72 DPI will be used.  */
+		error = FT_Set_Char_Size( font->face, 0, ptsize * 64, hdpi, vdpi );
 		if( error ) {
 			TTF_SetFTError( "Couldn't set font size", error );
 			TTF_CloseFont( font );
@@ -539,19 +541,39 @@ TTF_Font* TTF_OpenFontIndexRW( SDL_RWops *src, int freesrc, int ptsize, long ind
 	return font;
 }
 
+TTF_Font* TTF_OpenFontDPIRW(SDL_RWops *src, int freesrc, int ptsize, unsigned int hdpi, unsigned int vdpi)
+{
+	return TTF_OpenFontIndexDPIRW(src, freesrc, ptsize, 0, hdpi, vdpi);
+}
+
+TTF_Font* TTF_OpenFontIndexRW( SDL_RWops *src, int freesrc, int ptsize, long index )
+{
+	return TTF_OpenFontIndexDPIRW(src, freesrc, ptsize, index, 0, 0);
+}
+
 TTF_Font* TTF_OpenFontRW( SDL_RWops *src, int freesrc, int ptsize )
 {
 	return TTF_OpenFontIndexRW(src, freesrc, ptsize, 0);
 }
 
-TTF_Font* TTF_OpenFontIndex( const char *file, int ptsize, long index )
+TTF_Font* TTF_OpenFontIndexDPI(const char *file, int ptsize, long index, unsigned int hdpi, unsigned int vdpi)
 {
 	SDL_RWops *rw = SDL_RWFromFile(file, "rb");
 	if ( rw == NULL ) {
 		TTF_SetError(SDL_GetError());
 		return NULL;
 	}
-	return TTF_OpenFontIndexRW(rw, 1, ptsize, index);
+	return TTF_OpenFontIndexDPIRW(rw, 1, ptsize, index, hdpi, vdpi);
+}
+
+TTF_Font* TTF_OpenFontIndex( const char *file, int ptsize, long index )
+{
+	return TTF_OpenFontIndexDPI(file, ptsize, index, 0, 0);
+}
+
+TTF_Font* TTF_OpenFontDPI( const char *file, int ptsize, unsigned int hdpi, unsigned int vdpi )
+{
+	return TTF_OpenFontIndexDPI(file, ptsize, 0, hdpi, vdpi);
 }
 
 TTF_Font* TTF_OpenFont( const char *file, int ptsize )

diff --git a/SDL_ttf.h b/SDL_ttf.h
@@ -88,6 +88,13 @@ extern DECLSPEC TTF_Font * SDLCALL TTF_OpenFontIndex(const char *file, int ptsiz
 extern DECLSPEC TTF_Font * SDLCALL TTF_OpenFontRW(SDL_RWops *src, int freesrc, int ptsize);
 extern DECLSPEC TTF_Font * SDLCALL TTF_OpenFontIndexRW(SDL_RWops *src, int freesrc, int ptsize, long index);
 
+/* Opens a font using the given horizontal and vertical target resolutions (in DPI).
+ * DPI scaling only applies to scalable fonts (e.g. TrueType). */
+extern DECLSPEC TTF_Font * SDLCALL TTF_OpenFontDPI(const char *file, int ptsize, unsigned int hdpi, unsigned int vdpi);
+extern DECLSPEC TTF_Font * SDLCALL TTF_OpenFontDPIRW(SDL_RWops *src, int freesrc, int ptsize, unsigned int hdpi, unsigned int vdpi);
+extern DECLSPEC TTF_Font * SDLCALL TTF_OpenFontIndexDPI(const char *file, int ptsize, long index, unsigned int hdpi, unsigned int vdpi);
+extern DECLSPEC TTF_Font * SDLCALL TTF_OpenFontIndexDPIRW(SDL_RWops *src, int freesrc, int ptsize, long index, unsigned int hdpi, unsigned int vdpi);
+
 /* Set and retrieve the font style */
 #define TTF_STYLE_NORMAL	0x00
 #define TTF_STYLE_BOLD		0x01