Removing and Replacing Items in a Picture (IM: XG)

Inside Macintosh: QuickDraw GX Graphics /: Chapter 6 - Picture Shapes / Using Picture Shapes

Removing and Replacing Items in a Picture
You can use the GXSetPicture function or the GXSetPictureParts function to replace items in a picture.
The GXSetPicture function removes every item in a picture and inserts a new list of items. The GXSetPictureParts function allows you more control in replacing items. With this function, you can replace a subset of the items in a picture with another set of items. The inserted set does not have to have the same number of items as the replaced set.
As a simple example, you can use the GXSetPictureParts function to remove a single item from a picture. Listing 6-6 shows how to use the GXSetPictureParts function to remove the chimney, which is item number 3, from the house picture shown in
Figure 6-21.
Listing 6-6 Removing an item from a picture
GXSetPictureParts(housePicture, 
                  3,   /* start editing at item 3 */
                  1,   /* remove 1 item */
                  0,   /* insert 0 items */
                  nil, /* no shapes to insert */
                  nil, nil, nil); /* no overrides */
The resulting picture is shown in Figure 6-22.
Figure 6-22 A house with chimney removed

You can also use the GXSetPictureParts function to replace items in a picture; with a single call to GXSetPictureParts, you can remove items from a picture and insert new items into a picture.
Like the sample code in Listing 6-6, the sample code in Listing 6-7 uses the GXSetPictureParts function to remove the chimney shape from the house picture. However, this call to the GXSetPictureParts function inserts a new chimney into the house picture at the same time.
Listing 6-7 Replacing one shape with another
   gxShape newChimneyRectangle;

   gxRectangle newChimneyGeometry = {ff(170), ff(50),
                                     ff(180), ff(80)};
   . 
   . 
   .
   newChimneyRectangle = GXNewRectangle(&newChimneyGeometry);
   SetShapeCommonColor(newChimneyRectangle, dark + gxGray);
   
   GXSetPictureParts(housePicture, 
                     3,  /* start editing at item 3 */
                     1,  /* remove 1 item */
                     1,  /* insert 1 item */
                     &newChimneyRectangle,  /* shape to insert */
                     nil, nil, nil);  /* no overrides */
   
   GXDisposeShape(newChimneyRectangle);
The resulting house picture is shown in Figure 6-23.
Figure 6-23 A house with the chimney replaced

For more information about the GXSetPictureParts function, see page 6-65.