Flash

/* f_type = 0x00 - solid fill */
struct swf_fill_style_solid {
	unsigned char		f_type;
	if(f_tag == DefineMorphShape || f_tag == DefineMorphShape2) {
		swf_rgba	f_rgba;
		swf_rgba	f_rgba_morph;
	}
	else if(f_tag == DefineShape3) {
		swf_rgba	f_rgba;
	}
	else {
		swf_rgb		f_rgb;
	}
};

/* f_type = 0x10 - linear gradient fill,
	    0x12 - radial gradient fill
	    0x13 - focal gradient fill (V8.0) */
struct swf_fill_style_gradient {
	unsigned char		f_type;
	swf_matrix			f_gradient_matrix;
	if(f_tag == DefineMorphShape || f_tag == DefineMorphShape2) {
		swf_matrix	f_gradient_matrix_morph;
	}
	swf_gradient		f_gradient;
};

/* f_type = 0x40 - tilled bitmap fill with smoothed edges,
	    0x41 - clipped bitmap fill with smoothed edges,
	    0x42 - tilled bitmap fill with hard edges (V7.0),
	    0x43 - clipped bitmap fill with hard edges (V7.0) */
struct swf_fill_style_bitmap {
	unsigned char		f_type;
	unsigned short		f_bitmap_ref;
	swf_matrix		f_bitmap_matrix;
	if(f_tag == DefineMorphShape || f_tag == DefineMorphShape2) {
		swf_matrix	f_bitmap_matrix_morph;
	}
};

union swf_fill_style {
	unsigned char		f_type;
	swf_fill_style_solid	f_solid;
	swf_fill_style_gradient	f_gradient;
	swf_fill_style_bitmap	f_bitmap;
};

The fill style is defined in the first byte. The values are defined below. Depending on that value, the fill style structure changes as shown below. swf_fill_style is a union of all the other structures.

Notice that types 0x42 and 0x43 are only available since version 7 and type 0x13 is only available since version 8.

Note that these values were introduced in Flash 7 but it looks like only player 8 supported the distinction between hard edges and smooth edges on a per shape basis. That would explain why I could not see any difference between smooth and hard shapes when I tested this feature ...

struct swf_placeobject2 {	/* and swf_placeobject3 */
	swf_tag			f_tag;		/* 26 or 70 */
	/* NOTE: the following flags can be read as one or two bytes also */
	if(version >= 8) {
		unsigned	f_place_reserved : 5;
		unsigned	f_place_bitmap_caching : 1;
		unsigned	f_place_blend_mode : 1;
		unsigned	f_place_filters : 1;
	}
	if(version >= 5) {
		unsigned	f_place_has_actions : 1;
	}
	else {
		unsigned	f_place_reserved : 1;
	}
	unsigned		f_place_has_clipping_depth : 1;
	unsigned		f_place_has_name : 1;
	unsigned		f_place_has_morph_position : 1;
	unsigned		f_place_has_color_transform : 1;
	unsigned		f_place_has_matrix : 1;
	unsigned		f_place_has_id_ref : 1;
	unsigned		f_place_has_move : 1;
	unsigned short		f_depth;
	if(f_place_has_id_ref) {
		unsigned short		f_object_id_ref;
	}
	if(f_place_has_matrix) {
		swf_matrix		f_matrix;
	}
	if(f_place_has_color_transform) {
		swf_color_transform	f_color_transform;
	}
	if(f_place_has_morph_position) {
		unsigned short		f_morph_position;
	}
	if(f_place_has_name) {
		string			f_name;
	}
	if(f_place_has_clipping_depth) {
		unsigned short		f_clipping_depth;
	}
	/* 3 next entries since v8.0 */
	if(f_place_filters) {
		unsigned char		f_filter_count;
		swf_any_filter		f_filter;
	}
	if(f_place_blend_mode) {
		unsigned char		f_blend_mode;
	}
	if(f_place_bitmap_caching) {
		/* WARNING: this is not defined in the Macromedia documentation
		 * it may be that it was part of the blend mode whenever the person
		 * who defined this byte was testing (I copied that from somewhere else!).
		 */
		unsigned char		f_bitmap_caching;
	}
	/* since v5.0 */
	if(f_place_has_actions) {
		unsigned short		f_reserved;
		if(version >= 6) {
			unsigned long	f_all_flags;
		}
		else {
			unsigned short	f_all_flags;
		}
		swf_event		f_event[<variable>];
		if(version >= 6) {
			unsigned long	f_end;	/* always zero */
		}
		else {
			unsigned short	f_end;	/* always zero */
		}
	}
};

This tag will be used to specify where and how to place an object in the next frame. The PlaceObject is much different and is presented separately.

The f_depth field is used to indicate at which depth the character is inserted in the current frame. There can be only one object per depth value (thus a maximum of 65536 objects can appear on a single frame).

The f_place_has_move and f_place_has_id_ref flags are used to indicate what to do at the given depth. The following table presents what happens depending on the current value.

f_place_has_move	...

A null terminated string of 8 bits characters (i.e. a C string.) You have to scan the string in order to skip it to the next element.

Flash also makes use of Pascal Strings. Those strings start with a size. In all instance, the size of the string is defined on one byte (char). In this case, we declare the string with a construct as follow:

  char f_string_size;
  char f_pascal_string[f_string_size];

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.

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.

A signed or unsigned bit field which width does not directly correspond to an existing C type.

In structures, the width of the field is specified after the field name like in C bit fields. In case of Flash, it can be dynamic in which case a variable name is specified.

Signed bit fields have an implied sign extend of the most significant bit of the bit field. So a signed bit field of 2 bits support the following values:

struct swf_definesound {
	swf_tag			f_tag;		/* 14 */
	unsigned short		f_sound_id;
	unsigned		f_sound_format : 4;
	unsigned		f_sound_rate : 2;
	unsigned		f_sound_is_16bits : 1;
	unsigned		f_sound_is_stereo : 1;
	unsigned long		f_sound_samples_count;
	unsigned char		f_sound_data[<variable size>];
};

A DefineSound tag declares a set of samples of a sound effect or a music.

The sound samples can be compressed or not, stereo or not and 8 or 16 bits. The different modes are not all available in version 2, although the same tag is used in newer versions with additional capabilities.

The f_sound_is_16bits is always set to 1 (16bits samples) if the samples are compressed (neither Rawnor Uncompressed).

The f_sound_rate represents the rate at which the samples are defined. The rate at which it will be played on the target computers may differ. The following equation can be used to determine the ...

struct swf_definefontinfo {
	swf_tag			f_tag;		/* 13 or 62 */
	unsigned short		f_font_info_id_ref;
	unsigned char		f_font_info_name_length;
	unsigned char		f_font_info_name[f_name_length];
	if(version >= 7 && f_tag.f_tag == DefineFontInfo2) {
		unsigned		f_font_info_reserved : 2;
		unsigned		f_font_info_small_text : 1;
		unsigned		f_font_info_reserved : 2;
	}
	else if(version >= 6 && f_tag.f_tag == DefineFontInfo2) {
		unsigned		f_font_info_reserved : 5;
	}
	else {
		unsigned		f_font_info_reserved : 2;
		unsigned		f_font_info_unicode : 1;
		unsigned		f_font_info_shiftjis : 1;
		unsigned		f_font_info_ansii : 1;
	}
	unsigned		f_font_info_italic : 1;
	unsigned		f_font_info_bold : 1;
	unsigned		f_font_info_wide : 1;	/* always 1 in v6.x+ */
	if(version >= 6 && f_tag.f_tag == DefineFontInfo2) {
		unsigned char		f_font_info_language;
	}
	if(f_font_info_wide) {
		unsigned short		f_font_info_map[f_font_glyphs_count];
	}
	else {
		unsigned char		f_font_info_map[f_font_glyphs_count];
	}
};

A DefineFontInfo tag will be used to complete the definition of a DefineFont tag. It uses the exact same identifier (f_font_info_id_ref = f_font_id). You must have the corresponding font definition appearing before the DefineFontInfo since it will use the number of glyphs defined in the DefineFont to know the size of the map definition in the DefineFontInfo tag.

When it looks like it perfectly matches an existing system font, the plugin may use that system font (as long as no rotation is used, it will work fine.) It is also possible to force the use of the system font by declaring an empty ...

struct swf_doaction {
	swf_tag			f_tag;		/* 12 and 59 */
	if(f_tag == DoInitAction) {
		unsigned short	f_action_sprite;
	}
	swf_action		f_action_record[variable];
};

The DoAction tag will be used to execute a set of actions in place. Usually, actions are used on buttons to add interactivity to the SWF movies. In version 1 you had only one dynamic branch (WaitForFrame). In version 4 you can test many different things such as a position, angle or sound track cursor position. Since version 5, SWF has a complete scripting language supporting string and arithmetic operations.

struct swf_definefont {
	swf_tag			f_tag;		/* 10 */
	unsigned short		f_font_id;
	/* there is always at least one glyph */
	f_font_glyphs_count = f_font_offsets[0] / 2;
	unsigned short		f_font_offsets[f_font_glyphs_count];
	swf_shape		f_font_shapes[f_font_glyphs_count];
};

It is common to use the DefineFont tag in order to create an array of shapes later re-used to draw strings of text on the screen. Note that the definition of the shape within a font is limited since it can't include any specific fill and/or line style. Also, each shape is assumed to be defined within a 1024x1024 square. This square is called the EM Square. Fig 1. below shows you the EM Square and how it is used. The characters baseline can be placed anywhere within the EM Square (it certainly can be outside too if you wish?!?).