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Appendix A — The geometry in SWF — Coordinates

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.

SWF Sound Info (swf_sound_info)

SWF Structure Info
Tag Flash Version: 
1
SWF Structure: 
struct swf_soundinfo {
	unsigned short		f_sound_id_ref;
	unsigned		f_reserved : 2;
	unsigned		f_stop_playback : 1;
	unsigned		f_no_multiple : 1;
	unsigned		f_has_envelope : 1;
	unsigned		f_has_loops : 1;
	unsigned		f_has_out_point : 1;
	unsigned		f_has_in_point : 1;
	if(f_has_in_point) {
		unsigned long	f_in_point;
	}
	if(f_has_out_point) {
		unsigned long	f_out_point;
	}
	if(f_has_loop_count) {
		unsigned short	f_loop_count;
	}
	if(f_has_envelope) {
		unsigned char	f_envelope_count;
		swf_envelope	f_envelope[f_envelope_count];
	}
};

Information on how to playback a sound effect. These are found in a StartSound and a DefineButtonSound.

The f_sound_id_ref is a reference to an earlier DefineSound tag.

The f_stop_playback can be set to 1 in which case the sound stops as soon as the next ShowFrame is reached. All the other flags should be set to 0 when this one is 1.

The f_no_multiple flag indicates whether the same sound effect can be played more than once at a time.

The f_in/out_point indicate the start and end points where the sound should start playing and where it will end. f_in_point should always be smaller than ...

SWF Action 3 (swf_action3)

SWF Structure Info
Tag Flash Version: 
9
SWF Structure: 

Not documented here yet.

Since Flash version 9, actions can be saved in a new format named abcFormat by the Tamarin project from the Mozilla organization.

The code itself (action script) is the same, but the structure of an swf_action3 holds object oriented information about classes, methods and such in a really clean way (really! in comparison to the old way, that's dead clean!).

At this time, the swf_action3 structure is documented in the abcFormat.html file.

I will duplicate and test the structures at a later time.

SWF Any Filter (swf_any_filter)

SWF Structure Info
Tag Flash Version: 
8
SWF Structure: 
/* the filter type */
struct swf_filter_type {
	unsigned char	f_type;
};

struct swf_filter_glow {
	swf_filter_type	f_type;		/* 0, 2, 3, 4 or 7 */
	if(f_type == GradientGlow || f_type == GradientBevel) {
		unsigned char		f_count;
	}
	else {
		f_count = 1;
	}
	swf_rgba		f_rgba[f_count];
	if(f_type == Bevel) {
		swf_rgba		f_highlight_rgba[f_count];
	}
	if(f_type == GradientGlow || f_type == GradientBevel) {
		unsigned char		f_position[f_count];
	}
	signed long fixed	f_blur_horizontal;
	signed long fixed	f_blur_vertical;
	if(f_type != Glow) {
		signed long fixed	f_radian_angle;
		signed long fixed	f_distance;
	}
	signed short fixed	f_strength;
	unsigned		f_inner_shadow : 1;
	unsigned		f_knock_out : 1;
	unsigned		f_composite_source : 1;
	if(f_type == Bevel) {
		unsigned		f_on_top : 1;
	}
	else {
		unsigned		f_reserved : 1;
	}
	if(f_type == GradientGlow || f_type == GradientBevel) {
		unsigned		f_passes : 4;
	}
	else {
		unsigned		f_reserved : 4;
	}
};

struct swf_filter_blur {
	swf_filter_type		f_type;	/* 1 */
	unsigned long fixed	f_blur_horizontal;
	unsigned long fixed	f_blur_vertical;
	unsigned		f_passes : 5;
	unsigned		f_reserved : 3;
};

struct swf_filter_convolution {
	swf_filter_type	f_type;		/* 5 */
	unsigned char	f_columns;
	unsigned char	f_rows;
	long float	f_divisor;
	long float	f_bias;
	long float	f_weights[f_columns × f_rows];
	swf_rgba	f_default_color;
	unsigned	f_reserved : 6;
	unsigned	f_clamp : 1;
	unsigned	f_preserve_alpha : 1;
};

struct swf_filter_colormatrix {
	swf_filter_type	f_type;		/* 6 */
	long float	f_matrix[20];
};

struct swf_any_filter {
	swf_filter_type			f_fitler_type;
	swf_filter_blur			f_filter_blur;
	swf_filter_colormatrix		f_filter_colormatrix;
	swf_filter_convolution		f_filter_convolution;
	swf_filter_glow			f_filter_glow;
};

A filter defines how to transform the objects it is attached to. The first byte is the filter type. The data following depend on the type. Because each filter is much different, they are defined in separate structures. You can attach a filter to an object using an ActionScript or the PlaceObject3 tag.

The following describes the different filters available since version 8.

...
Value Name Version
0 Drop Shadow 8

SWF Shape Record (swf_shape_record)

SWF Structure Info
Tag Flash Version: 
1
SWF Structure: 
/* if f_shape_record_type = 0 & f_end_of_shape = 0
  then that's the end of the list of shape records */
struct swf_shape_record_end {
	unsigned		f_shape_record_type : 1;
	unsigned		f_end_of_shape : 5;
};

/* f_shape_record_type = 0 & at least one of the following five bits is not zero
  then change style, fill and position setup */
struct swf_shape_record_setup {
	unsigned		f_shape_record_type : 1;
	if(f_tag == DefineShape) {1
		unsigned	f_shape_reserved : 1;		/* always zero */
	}
	else {
		unsigned	f_shape_has_new_styles : 1;
	}
	unsigned		f_shape_has_line_style : 1;
	unsigned		f_shape_has_fill_style1 : 1;
	unsigned		f_shape_has_fill_style0 : 1;
	unsigned		f_shape_has_move_to : 1;
	if(f_shape_has_move_to) {
		unsigned	f_shape_move_size : 5;
		signed twips	f_shape_move_x : f_shape_move_size;
		signed twips	f_shape_move_y : f_shape_move_size;
	}
	if(f_shape_has_fill_style0) {
		unsigned	f_shape_fill_style0 : f_fill_bits_count;
	}
	if(f_shape_has_fill_style1) {
		unsigned	f_shape_fill_style1 : f_fill_bits_count;
	}
	if(f_shape_has_line_style) {
		unsigned	f_shape_line_style : f_line_bits_count;
	}
	if(f_shape_has_new_styles) {
		swf_styles	f_styles;
	}
};

/* f_shape_record_type = 1 -- edge record */
struct swf_shape_record_edge {
	unsigned		f_shape_record_type : 1;
	unsigned		f_shape_edge_type : 1;
	unsigned		f_shape_coord_size : 4;
	f_shape_coord_real_size = f_shape_coord_size + 2;
	if(f_shape_edge_type == 0) {
		signed twips	f_shape_control_delta_x : f_shape_coord_real_size;
		signed twips	f_shape_control_delta_y : f_shape_coord_real_size;
		signed twips	f_shape_anchor_delta_x : f_shape_coord_real_size;
		signed twips	f_shape_anchor_delta_y : f_shape_coord_real_size;
	}
	else {
		unsigned	f_shape_line_has_x_and_y : 1;
		if(f_shape_line_has_x_and_y == 1) {
			signed twips	f_shape_delta_x : f_shape_coord_real_size;
			signed twips	f_shape_delta_y : f_shape_coord_real_size;
		}
		else {
			unsigned	f_shape_line_has_x_or_y : 1;
			if(f_shape_line_has_x_or_y == 0) {
				signed twips	f_shape_delta_x : f_shape_coord_real_size;
			}
			else {
				signed twips	f_shape_delta_y : f_shape_coord_real_size;
			}
		}
	}
};

union swf_shape_record {
	swf_shape_record_end	f_shape_end;
	swf_shape_record_setup	f_shape_setup;
	swf_shape_record_edge	f_shape_edge;
};
  • 1. From my tests with the official Macromedia Flash plugin, it looks that there is always a bit at this position. It seems however that it cannot be set to 1 in v1.0 of the tag (i.e. when the DefineShape tag is used).

The shape records are typed. Depending on that type, the contents vary. The following defines one structure for each type. The shape record is a union of these structures.

It is important to note that the f_shape_move_x and f_shape_move_y are not deltas from the current point, but a position from the current shape origin. All the other positions are defined as deltas from the previous position, including the anchors which are deltas from the control point position!

SoundStreamBlock

Tag Info
Tag Number: 
19
Tag Type: 
Define
Tag Flash Version: 
2
Brief Description: 

A block of sound data (i.e. audio samples.) The size of this block of data is defined in the previous SoundStreamHead tag. It is used to download sound samples on a per frame basis instead of all at once.

Tag Structure: 
struct swf_soundstreamblock {
	swf_long_tag		f_tag;		/* 19 */
	unsigned char		f_sound_data[variable size];
};

The SoundStreamBlock tag defines the data of a sound effect previously defined with a SoundStreamHead or a SoundStreamHead2 tag.

WARNING: This tag requires you to save the swf_tag structure in long format whatever the size of the data (i.e. f_tag_and_size & 0x3F == 0x3F always true even if the size is 62 or less.)

The data depends on the SoundStreamHead[2] definition and is variable in size. Please, see the DefineSound tag for more information about sound data.

DefineButtonSound

Tag Info
Tag Number: 
17
Tag Type: 
Define
Tag Flash Version: 
2
Brief Description: 

Defines how to play a sound effect for when an event occurs on the referenced button.

Tag Structure: 
enum {
	DEFINE_BUTTON_SOUND_CONDITION_POINTER_LEAVE = 0,
	DEFINE_BUTTON_SOUND_CONDITION_POINTER_ENTER = 1,
	DEFINE_BUTTON_SOUND_CONDITION_POINTER_PUSH = 2,
	DEFINE_BUTTON_SOUND_CONDITION_POINTER_RELEASE_INSIDE = 3,
	DEFINE_BUTTON_SOUND_CONDITION_MAX = 4
};

struct swf_definebuttonsound {
	swf_tag			f_tag;		/* 17 */
	unsigned short		f_button_id_ref;
	swf_sound_info		f_button_sound_condition[DEFINE_BUTTON_SOUND_CONDITION_MAX];
};

The DefineButtonSound can be used to emit a sound when an event occur on the specified button. It is likely better to use sprites that you display using actions than to use this tag. You will have access to more events and conditions, plus this tag always includes four sound effect references.

The f_button_id_ref is a reference to the button given sound effects.

[un]signed long fixed

Tag Flash Version: 
1
Used by PushData Action: 
Not available in PushData Action

A short fixed value1 is a 32 bit (or less) number representing a value with 16 bits on the left of the decimal point and 16 bits on the right.

When the value is smaller than 32 bits, we assume that only the least significant bits were defined (quite often only those after the decimal point.)

For more information about bit fields, check out the [un]signed type.

  • 1. The fixed long type exists since version 1, although it was properly named as such only in version 8 of Flash.

[un]signed short fixed

Tag Flash Version: 
1
Used by PushData Action: 
Not available in PushData Action

A short fixed value1 is a 16 bit (or less) number representing a value with 8 bits on the left of the decimal point and 8 bits on the right.

When the value is smaller than 16 bits, we assume that only the least significant bits were defined (quite often only those after the decimal point.)

For more information about bit fields, check out the [un]signed type.

  • 1. The fixed short type exists since version 1, although it was properly named as such only in version 8 of Flash.

[un]signed twips

Tag Flash Version: 
1
Used by PushData Action: 
Not available in PushData Action

A bit field variable defined as TWIPS represents a floating point defined in TWIPS. Load the value as a signed or unsigned integer and then divide it by 20. The floating point result is a precise dimension in pixel.

Please, see the [un]signed type for more information about fields.