PgDrawArc(), PgDrawArcCx()

Draw an arc, pie, or chord

Synopsis:

int  PgDrawArc( PhPoint_t const *center,
                PhPoint_t const *radii,
                unsigned int start,
                unsigned int end,
                int flags );

int  PgDrawArcCx( void *dc,
                  PhPoint_t const *center,
                  PhPoint_t const *radii,
                  unsigned int start,
                  unsigned int end,
                  int flags );

Arguments:

dc

PgDrawArcCx() only. A void pointer to any type of draw context. Examples of draw contexts are:

• a PhDrawContext_t returned by PhDCCreate()
• a PmMemoryContext_t returned by PmMemCreateMC()
• a PpPrintContext_t returned by PpCreatePC()
• a PdOffscreenContext_t returned by PdCreateOffscreenContext()

center

A pointer to a PhPoint_t structure that specifies the center of the arc.

radii

A pointer to a PhPoint_t structure that specifies the x and y radii of the arc.

start, end

The start and end angles, in bi-grads (see below).

flags

Flags that control what type of arc is drawn; see below.

Library:

ph

Description:

These functions build a command in the draw buffer to draw an arc. PgDrawArc() works on the current draw context, while you can specify the draw context for PgDrawArcCx().

The arc is drawn counter-clockwise, from the start angle to the end angle. To draw a complete circle, make the two angles equal to each other. An angle of 0 bi-grads is on the horizon to the right of the center.

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A circle is divided into 65536 gradations called binary gradations or bi-grads. Thus, 0x2000 is 45 degrees, 0x4000 is 90 degrees, 0x8000 is 180 degrees, and 0xC000 is 270 degrees.

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The flags argument controls what type of arc is drawn:

Pg_ARC_CHORD

A curve with the end points connected by a straight line.

Pg_ARC_PIE

A curve with the end points connected to the arc's center.

Pg_ARC

The curve alone.

You can OR one of the following into any flags value:

• Pg_DRAW_STROKE — draw as a line.
• Pg_DRAW_FILL — fill the arc.
• Pg_DRAW_FILL_STROKE — fill the arc, then stroke it.

Returns:

0

Success.

-1

The draw buffer is too small to hold the current draw state and the draw command.

Examples:

The following example:

DrawFillArc() {
    PhPoint_t   c = { 80, 60 };
    PhPoint_t   r = { 72, 52 };

    PgSetFillColor( Pg_RED );
    PgDrawArc( &c, &r, 0x0000, 0x4000, Pg_DRAW_FILL |
                                       Pg_ARC_CHORD);
    PgSetFillColor( Pg_YELLOW );
    PgDrawArc( &c, &r, 0x5555, 0x9555, Pg_DRAW_FILL |
                                       Pg_ARC_PIE);
    PgSetStrokeColor( Pg_WHITE );
    PgSetFillColor( Pg_PURPLE );
    PgDrawArc( &c, &r, 0xAAAA, 0xEAAA,
               Pg_DRAW_FILL_STROKE | Pg_ARC_PIE);
}

will draw:

The following example:

DrawStrokeArc() {
    PhPoint_t   c = { 80, 60 };
    PhPoint_t   r = { 72, 52 };

    PgSetStrokeColor( Pg_WHITE );
    PgDrawArc( &c, &r, 0x0000, 0x4000, Pg_DRAW_STROKE |
                                       Pg_ARC_CHORD );
    PgSetStrokeColor( Pg_YELLOW );
    PgDrawArc( &c, &r, 0x5555, 0x9555, Pg_DRAW_STROKE |
                                       Pg_ARC_PIE );
    PgSetStrokeColor( Pg_YELLOW );
    PgDrawArc( &c, &r, 0xAAAA, 0xEAAA, Pg_DRAW_STROKE |
                                       Pg_ARC );
}

will draw:

Classification:

Photon

See also:

PhPoint_t

To draw stroked arcs, see also:

PgSetStrokeCap*(), PgSetStrokeColor*(), PgSetStrokeDash*(), PgSetStrokeDither*(), PgSetStrokeJoin*(), PgSetStrokeWidth*()

To draw filled arcs, see also:

PgSetFillColor*(), PgSetFillDither*(), PgSetFillTransPat*()

“Arcs, ellipses, polygons, and rectangles” in the Raw Drawing and Animation chapter of the Photon Programmer's Guide