area

struct swf_definescalinggrid {
	swf_tag				f_tag;		/* 78 */
	unsigned short			f_button_id_ref;
	swf_rect			f_rect;
};

This definition is used so the scaling factors applied on an object affects only the center of the object fully. The borders are only affected in one direction and the corners are not scaled (note, restrictions apply, see below.) This is quite useful to draw a scalable button or window.

Fig 1 — Sample button being scaled with a scaling grid

Edges are used to define a shape vector based and also coordinates where images need to be drawn. The edges are always coordinates from where ever your last point was to where ever you want the next point to be (a little like a turtle in LOGO).

The most common and simple geometric information are the object coordinates on the output screen. These are defined in TWIPs. There are 20 twips per pixels. Note that an embedded SWF file can be enlarged and/or reduced thus changing this basic scaling factor. To have exactly 20 twips per pixel you must ensure that the EMBED and/or OBJECT tags use a WIDTH and HEIGHT with exactly the same value as in the rectangle defined in the SWF header file divided by 20.

struct swf_button {
	char align;
	unsigned		f_button_reserved : 2;
	if(version >= 8) {
		unsigned		f_button_blend_mode : 1;
		unsigned		f_button_filter_list : 1;
	}
	else {
		unsigned		f_button_reserved : 2;
	}
	unsigned		f_button_state_hit_test : 1;
	unsigned		f_button_state_down : 1;
	unsigned		f_button_state_over : 1;
	unsigned		f_button_state_up : 1;
	if(any f_button_state_... != 0) {
		unsigned short		f_button_id_ref;
		unsigned short		f_button_layer;
		swf_matrix		f_matrix;
		if(f_tag == DefineButton2) {
			swf_color_transform		f_color_transform;
		}
		if(f_button_filter_list) {
			unsigned char		f_filter_count;
			swf_any_filter		f_filter;
		}
		if(f_button_blend_mode) {
			unsigned char		f_blend_mode;
		}
	}
};

A button structure defines a state and a corresponding shape reference. The shape will be affected by the specified matrix whenever used.

There are many acceptable combinations. The object which is referenced is drawn when its state matches the current state of the button. If only the f_button_state_hit_test is set, then the shape is always displayed.