Related Info: Color Quickdraw

Tips &Tidbits

By Scott T Boyd, Editor

Tip Of The Month

White-Bordered Black Text Mode

A recent thread on comp.sys.mac.programmer prompted this little code snippet to work around a glaring omission on QuickDraw text modes. This is actual, tested, working code to draw a white outline around black characters. The trick is in the use of CharExtra, a Color QuickDraw routine that’s worth reading about in Inside Macintosh.

/* 1 */
void
Outline (
        short x ,
        short y ,
        Ptr text ,
        short length )
{
        long w1 , w2 , ce ;

        TextMode ( srcBic ) ;
        TextFace ( outline ) ;
        w1 = TextWidth ( text , 0 , length ) ;
        MoveTo ( x , y ) ;
        DrawText ( text , 0 , length ) ;

        TextMode ( srcOr ) ;
        TextFace ( normal ) ;
        w2 = TextWidth ( text , 0 , length ) ;
        ce = ( w1 - w2 ) * 0x10000L / length ;
        CharExtra ( ce ) ;
        SpaceExtra ( ce ) ;
        MoveTo ( x , y ) ;
        DrawText ( text , 0 , length ) ;

        CharExtra ( 0 ) ;
        SpaceExtra ( 0 ) ;
}

It only works in color GrafPorts, but that’s to be expected since CharExtra requires Color Quickdraw.

- Jon Wätte (h+@nada.kth.se)

Auntie Flicker

Many operations, especially moving and sizing of controls, cause a lot of flicker on the screen. Some of this can be avoided by hiding the control, moving and sizing it, and bringing it back, but even then there is more drawing to the screen than is really necessary.

The trick to avoiding all this unnecessary drawing is to temporarily turn off drawing during the operations which cause flicker, and then turn it on again. To do this, simply replace the visRgn with a null region temporarily, i.e.:

/* 2 */
RgnHandle vis;

...

vis = window->visRgn;
window->visRgn = NewRgn();

... operations which would normally cause flicker ...

DisposeRgn(window->visRgn);
window->visRgn = vis;

... don’t forget to redraw or invalidate appropriately here!

- Jorg ‘jbx’ Brown