vg4->canvas->subcanvas()

Prepare for drawing a new sub-canvas upon a parent-canvas.

SYNTAX

struct VG_Position vg4->canvas->subcanvas(struct VG_Canvas *cvas, const struct VG_ImagecopyAttrPixel *iattr_pixel)

FUNCTION PARAMETERS

cvas	Parent-canvas
iattr_pixel	Pixel-modifying part of image-copy attributes, or NULL

RETURN VALUE

Returns position for sub-canvas (centered to parent-canvas)

DESCRIPTION

Prepare for drawing a new sub-canvas upon a parent-canvas. If a sub-canvas shall be drawn upon a parent-canvas, e.g. for typing a filename when clicked on a "create a new file", this function prepares the background, which is the parent-canvas, and calculates the position of the sub-canvas.

EXAMPLE

/* execute a sub-canvas cvas upon parent-canvas cvas_parent,
 * set selection in selname
 * return VG_TRUE = OK or VG_FALSE = exit request
 */

VG_BOOL
exec_subcanvas(struct VG_Canvas *cvas_parent, struct VG_Canvas *cvas, const char **selname)
{
  struct VG_Position possub;
  struct VG_Image *wclone;
  struct VG_ImagecopyAttrPixel iattr_pixel;

  *selname = NULL;

  /* reduce brightness */
  VG_IMAGECOPY_ATTRPIXEL_DEFAULT(&iattr_pixel);
  iattr_pixel.brightness = 60;

  /* get current background */
  wclone = vg4->window->clone(NULL, NULL);

  /* get position for sub-canvas and draw as background parent-canvas with reduced brightness */
  possub = vg4->canvas->subcanvas(cvas_parent, &iattr_pixel);

  /* execute sub-canvas */
  if (!vg4->canvas->exec(cvas, &possub, selname)) { return VG_FALSE; }

  /* restore background */
  vg4->window->clear();
  vg4->window->copy(wclone, NULL, NULL);
  vg4->image->destroy(wclone);

  return VG_TRUE;
}