Drawing Tracks

The Appearance Manager provides a variety of functions that you can use to make your program's tracks--that is, its scroll bars, sliders, and progress bars--theme-compliant. You can use the Appearance Manager to handle most aspects of drawing, obtaining values for, and checking for mouse-down events on tracks and their related parts (such as the indicator on a scroll bar or slider, a scroll bar's arrows, or the tick marks on a slider).

Your application can use the function DrawThemeTrack to draw a theme-compliant slider, progress bar, or scroll bar. If you use DrawThemeTrack to draw a scroll bar, use the function DrawThemeScrollBarArrows to draw the scroll bar's arrows; see Listing 3-7 for an example of using these two functions together to draw a complete scroll bar. If you use DrawThemeTrack to draw a slider, use DrawThemeTrackTickMarks if you need to draw tick marks for the slider.

Listing 3-7 Drawing a scroll bar with arrows



 
Rect bounds;

ThemeTrackDrawInfo drawInfo;

OSStatus err;



SetRect (&bounds, 10, 10, 200, 26);



/* Draw the arrows and pass the actual track rect into the

drawInfo structure for DrawThemeTrack to use */

err = DrawThemeScrollBarArrows (&bounds, kThemeTrackActive, 0, true, &drawInfo.bounds);



if (err == noErr)

{

    drawInfo.kind = kThemeScrollBar;

    /* drawInfo.bounds is set to the modified bounds, with the arrows removed,

    on exit from DrawThemeScrollBarArrows */

    drawInfo.min = 0;

    drawInfo.max = 100;

    drawInfo.value = 65;

    drawInfo.attributes = kThemeTrackHorizontal | kThemeTrackShowThumb;

    drawInfo.enableState = kThemeTrackActive;

    drawInfo.trackInfo.scrollbar.viewsize = 0;

    drawInfo.trackInfo.scrollbar.pressState = 0;



    err = DrawThemeTrack (&drawInfo, NULL, NULL, 0);

}