Drawing Paths

Functions to draw polygons into a graphics context. More...

Collaboration diagram for Drawing Paths:

Classes
struct	GPathInfo
struct	GPath

Typedefs
typedef struct GPathInfo	GPathInfo
typedef struct GPath	GPath

Functions
GPath *	gpath_create (const GPathInfo *init)
void	gpath_destroy (GPath *gpath)
	Free a dynamically allocated gpath created with gpath_create()
void	gpath_draw_filled (GContext *ctx, GPath *path)
void	gpath_draw_outline (GContext *ctx, GPath *path)
void	gpath_rotate_to (GPath *path, int32_t angle)
void	gpath_move_to (GPath *path, GPoint point)
void	gpath_draw_outline_open (GContext *ctx, GPath *path)

Detailed Description

Functions to draw polygons into a graphics context.

Code example:

static GPath *s_my_path_ptr = NULL;
 
static const GPathInfo BOLT_PATH_INFO = {
  .num_points = 6,
  .points = (GPoint []) {{21, 0}, {14, 26}, {28, 26}, {7, 60}, {14, 34}, {0, 34}}
};
 
// .update_proc of my_layer:
void my_layer_update_proc(Layer *my_layer, GContext* ctx) {
  // Fill the path:
  graphics_context_set_fill_color(ctx, GColorWhite);
  gpath_draw_filled(ctx, s_my_path_ptr);
  // Stroke the path:
  graphics_context_set_stroke_color(ctx, GColorBlack);
  gpath_draw_outline(ctx, s_my_path_ptr);
}
 
void setup_my_path(void) {
  s_my_path_ptr = gpath_create(&BOLT_PATH_INFO);
  // Rotate 15 degrees:
  gpath_rotate_to(s_my_path_ptr, TRIG_MAX_ANGLE / 360 * 15);
  // Translate by (5, 5):
  gpath_move_to(s_my_path_ptr, GPoint(5, 5));
}
 
// For brevity, the setup of my_layer is not written out...

Typedef Documentation

GPath

typedef struct GPath GPath

Data structure describing a path, plus its rotation and translation.

Note

See the remark with GPathInfo

GPathInfo

typedef struct GPathInfo GPathInfo

Data structure describing a naked path

Note

Note that this data structure only refers to an array of points; the points are not stored inside this data structure itself. In most cases, one cannot use a stack-allocated array of GPoints. Instead one often needs to provide longer-lived (static or "global") storage for the points.

Function Documentation

gpath_create()

GPath* gpath_create

(

const GPathInfo *

init

)

Creates a new GPath on the heap based on a series of points described by a GPathInfo.

Values after initialization:

• num_points and points pointer: copied from the GPathInfo.
• rotation: 0
• offset: (0, 0)

  Returns

  A pointer to the GPath. NULL if the GPath could not be created

gpath_draw_filled()

void gpath_draw_filled	(	GContext *	ctx,
		GPath *	path
	)

Draws the fill of a path into a graphics context, using the current fill color, relative to the drawing area as set up by the layering system.

Parameters

ctx	The graphics context to draw into
path	The path to fill

See also

graphics_context_set_fill_color()

gpath_draw_outline()

void gpath_draw_outline	(	GContext *	ctx,
		GPath *	path
	)

Draws the outline of a path into a graphics context, using the current stroke color and width, relative to the drawing area as set up by the layering system. The first and last points in the path do have a line between them.

Parameters

ctx	The graphics context to draw into
path	The path to draw

See also

graphics_context_set_stroke_color()

gpath_draw_outline_open()

gpath_draw_outline_open()

void gpath_draw_outline_open	(	GContext *	ctx,
		GPath *	path
	)

Draws an open outline of a path into a graphics context, using the current stroke color and width, relative to the drawing area as set up by the layering system. The first and last points in the path do not have a line between them.

Parameters

ctx	The graphics context to draw into
path	The path to draw

See also

graphics_context_set_stroke_color()

gpath_draw_outline()

gpath_move_to()

void gpath_move_to	(	GPath *	path,
		GPoint	point
	)

Sets the absolute offset of the path. The current translation will be replaced by the specified offset.

Parameters

path	The path onto which to set the translation
point	The point which is used as the vector for the translation.

Note

Setting a translation does not affect the points in the path directly. The translation is applied on-the-fly during drawing, either using gpath_draw_filled() or gpath_draw_outline().

gpath_rotate_to()

void gpath_rotate_to	(	GPath *	path,
		int32_t	angle
	)

Sets the absolute rotation of the path. The current rotation will be replaced by the specified angle.

Parameters

path	The path onto which to set the rotation
angle	The absolute angle of the rotation. The angle is represented in the same way that is used with sin_lookup(). See TRIG_MAX_ANGLE for more information.

Note

Setting a rotation does not affect the points in the path directly. The rotation is applied on-the-fly during drawing, either using gpath_draw_filled() or gpath_draw_outline().