Chapter 5: Writing and using fonts

What you need:
SoftwareSourceDescription
sdl_ttf.pphttp://cvs.sourceforge.net/viewcvs.py/sdl4fp/extras/
Downloads		Unit file to handle fonts.
SDL_ttf.dllhttp://www.freetype.org/index2.html
Windows: http://gnuwin32.sourceforge.net/packages/freetype.htm 		This is the corresponding dynamic link library file.


This chapter will introduce you on how to load fonts and write to the screen. There are two things to do for preparation. First of all we have to change the compiler settings because a new unit, called SDL_TTF, gets included. This unit uses the "result" command to return values of functions. This is a command from Object Pascal. So the compiler has to support it's syntax otherwise he won't accept this command. To let the compiler support the Object Pascal syntax go to "Options" and then "Compiler..." A new window will pop up. From "Syntax" mark the option "Object pascal support". Now SDL_TTF can be used.

In version 1.2.0.0 of SDL4Freepascal this unit isn't included. It has to be separately downloaded. You can download it here: http://cvs.sourceforge.net/viewcvs.py/sdl4fp/extras/ or from the download section. The file "sdl_ttf.pp" has to be copied to the sdl unit folder where all the other sdl units are located (e.g. C:\FPC\units\).

Analogous to SDL.dll in chapter 1 you have to download the last stable release of FreeType which can be found here: http://www.freetype.org/index2.html (Windows: http://gnuwin32.sourceforge.net/packages/freetype.htm ). You should extract the file and get two files. A text file and the important SDL_ttf.dll. These files you copy to the system32-folder.

Now let's begin with the interessting part. The goal is to get a text with a certain font and colour to the screen. Of course we need the screen surface again and a surface onto which can be written. Furthermore the new unit has to be loaded.

PROGRAM chap5;
USES crt, SDL, SDL_VIDEO, SDL_TTF;

VAR
screen,fontface:pSDL_SURFACE;

BEGIN
CLRSCR;
SDL_INIT(SDL_INIT_VIDEO);
screen:=SDL_SETVIDEOMODE(200,200,8,SDL_SWSURFACE);
if screen=nil then HALT;

readln;
SDL_FREESURFACE(screen);
SDL_FREESURFACE(fontface);
SDL_QUIT;
END.


To initialize the TTF (True type font) system you have to use TTF_INIT which returns -1 if something goes wrong. Notice that the whole true type support is an own additional project to the SDL library, so this has not to be initilized by the SDL_INIT command.

To load a certain font you use TTF_OPENFONT(font,point size). This command is a function that returns a usual pointer! The parameters are the path to the font (e.g. C:\WINDOWS\fonts\arial.ttf) and the point size which detemines the size of the letters. Furthermore as SDL surface has to be free'd and SDL system has to be quit so has TTF system. The commands TTF_CLOSEFONT(font) and TTF_QUIT have to be used to do this.

PROGRAM chap5;
USES crt, SDL, SDL_VIDEO, SDL_TTF;

VAR
screen,fontface:pSDL_SURFACE;
loaded_font:pointer;

BEGIN
CLRSCR;
SDL_INIT(SDL_INIT_VIDEO);
screen:=SDL_SETVIDEOMODE(200,200,8,SDL_SWSURFACE);
if screen=nil then HALT;

if TTF_INIT=-1 then HALT(1);
loaded_font:=TTF_OPENFONT('C:\WINDOWS\fonts\arial.ttf',12);

 readln;
SDL_FREESURFACE(screen);
SDL_FREESURFACE(fontface);
TTF_CLOSEFONT(loaded_font);
TTF_QUIT;
 SDL_QUIT;
END.


So next we have to determine the colour of the letters and the messege itself. The colour is determined by a pSDL_COLOR record, which is of course kind of pointer. In pSDL_COLOR record there are three elements (actually four, but the forth is unused) which can be accessed by .r,.g and .b and determine as common the shares of red, green and blue colour. You will agree that writing a function for this can be senseful, especially if you have to handle many different colours. The fact that pSDL_COLOR is a pointer type we have to set up it by NEW command and free it finally by DISPOSE. This commands you should familiar with because they are usual Pascal commands.

PROGRAM chap5;
USES crt, SDL, SDL_VIDEO, SDL_TTF;

VAR
screen,fontface:pSDL_SURFACE;
loaded_font:pointer;
colour_font:pSDL_COLOR;

BEGIN
CLRSCR;
SDL_INIT(SDL_INIT_VIDEO);
screen:=SDL_SETVIDEOMODE(200,200,8,SDL_SWSURFACE);
if screen=nil then HALT;

if TTF_INIT=-1 then HALT;
loaded_font:=TTF_OPENFONT('C:\WINDOWS\fonts\arial.ttf',12);

NEW(colour_font);
 colour_font^.r:=255; colour_font^.g:=0; colour_font^.b:=0;

 readln;
DISPOSE(colour_font);
SDL_FREESURFACE(screen);
SDL_FREESURFACE(fontface);
TTF_CLOSEFONT(loaded_font);
TTF_QUIT;
SDL_QUIT;
END.


Now we use TTF_RENDERTEXT_SOLID which returns a pSDL_SURFACE. We return it to fontface. The parameters are the used font as pointer (loaded_font), the messege string and the colour as value of pSDL_COLOR (colour_font).

Finally we have to blit the fontface surface, on which now the messege is written, to the screen surface and update the screen surface.

PROGRAM chap5;
USES crt, SDL, SDL_VIDEO, SDL_TTF;

VAR
screen,fontface:pSDL_SURFACE;
loaded_font:pointer;
colour_font:pSDL_COLOR;

BEGIN
CLRSCR;
SDL_INIT(SDL_INIT_VIDEO);
screen:=SDL_SETVIDEOMODE(200,200,8,SDL_SWSURFACE);
if screen=nil then HALT;

if TTF_INIT=-1 then HALT;
loaded_font:=TTF_OPENFONT('C:\WINDOWS\fonts\arial.ttf',12);

NEW(colour_font);
colour_font^.r:=255; colour_font^.g:=0; colour_font^.b:=0;

fontface:=TTF_RENDERTEXT_SOLID(loaded_font,'HELLO WORLD',colour_font^);

SDL_BLITSURFACE(fontface,NIL,screen,NIL);
SDL_UPDATERECT(screen,0,0,0,0);

 readln;
DISPOSE(colour_font);
SDL_FREESURFACE(screen);
SDL_FREESURFACE(fontface);
TTF_CLOSEFONT(loaded_font);
TTF_QUIT;
SDL_QUIT;
END.


Now you are able to write ;).

This file contains the source code: chap5.pas (right click and "save as")
This file is the executable: chap5.exe (right click and "save as")



















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Creation/Updates: 20/3/2006; 15/10/2005
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