[ViewVC] Diff of: cvs/rxvt-unicode/src/perl/background

Comparing rxvt-unicode/src/perl/background (file contents):
Revision 1.45 by root, Sun Jun 10 11:53:32 2012 UTC vs.
Revision 1.77 by root, Tue Sep 4 11:21:11 2012 UTC

…		…
1	#! perl	1	#! perl
2		2
3	#:META:X_RESOURCE:%.expr:string:background expression	3	#:META:X_RESOURCE:%.expr:string:background expression
4	#:META:X_RESOURCE:%.border.:boolean:respect the terminal border	4	#:META:X_RESOURCE:%.border:boolean:respect the terminal border
5		5	#:META:X_RESOURCE:%.interval:seconds:minimum time between updates
6	#TODO: once, rootalign
7		6
8	=head1 NAME	7	=head1 NAME
9		8
10	background - manage terminal background	9	background - manage terminal background
11		10
12	=head1 SYNOPSIS	11	=head1 SYNOPSIS
13		12
14	urxvt --background-expr 'background expression'	13	urxvt --background-expr 'background expression'
15	--background-border	14	--background-border
		15	--background-interval seconds
		16
		17	=head1 QUICK AND DIRTY CHEAT SHEET
		18
		19	Just load a random jpeg image and tile the background with it without
		20	scaling or anything else:
		21
		22	load "/path/to/img.jpg"
		23
		24	The same, but use mirroring/reflection instead of tiling:
		25
		26	mirror load "/path/to/img.jpg"
		27
		28	Load an image and scale it to exactly fill the terminal window:
		29
		30	scale keep { load "/path/to/img.jpg" }
		31
		32	Implement pseudo-transparency by using a suitably-aligned root pixmap
		33	as window background:
		34
		35	rootalign root
		36
		37	Likewise, but keep a blurred copy:
		38
		39	rootalign keep { blur 10, root }
16		40
17	=head1 DESCRIPTION	41	=head1 DESCRIPTION
18		42
19	This extension manages the terminal background by creating a picture that	43	This extension manages the terminal background by creating a picture that
20	is behind the text, replacing the normal background colour.	44	is behind the text, replacing the normal background colour.
26	to be as simple as possible.	50	to be as simple as possible.
27		51
28	For example, to load an image and scale it to the window size, you would	52	For example, to load an image and scale it to the window size, you would
29	use:	53	use:
30		54
31	urxvt --background-expr 'scale load "/path/to/mybg.png"'	55	urxvt --background-expr 'scale keep { load "/path/to/mybg.png" }'
32		56
33	Or specified as a X resource:	57	Or specified as a X resource:
34		58
35	URxvt.background-expr: scale load "/path/to/mybg.png"	59	URxvt.background-expr: scale keep { load "/path/to/mybg.png" }
36		60
37	=head1 THEORY OF OPERATION	61	=head1 THEORY OF OPERATION
38		62
39	At startup, just before the window is mapped for the first time, the	63	At startup, just before the window is mapped for the first time, the
40	expression is evaluated and must yield an image. The image is then	64	expression is evaluated and must yield an image. The image is then
…		…
53	If any of the parameters that the expression relies on changes (when the	77	If any of the parameters that the expression relies on changes (when the
54	window is moved or resized, its position or size changes; when the root	78	window is moved or resized, its position or size changes; when the root
55	pixmap is replaced by another one the root background changes; or when the	79	pixmap is replaced by another one the root background changes; or when the
56	timer elapses), then the expression will be evaluated again.	80	timer elapses), then the expression will be evaluated again.
57		81
58	For example, an expression such as C<scale load "$HOME/mybg.png"> scales the	82	For example, an expression such as C<scale keep { load "$HOME/mybg.png"
59	image to the window size, so it relies on the window size and will	83	}> scales the image to the window size, so it relies on the window size
60	be reevaluated each time it is changed, but not when it moves for	84	and will be reevaluated each time it is changed, but not when it moves for
61	example. That ensures that the picture always fills the terminal, even	85	example. That ensures that the picture always fills the terminal, even
62	after it's size changes.	86	after its size changes.
63		87
64	=head2 EXPRESSIONS	88	=head2 EXPRESSIONS
65		89
66	Expressions are normal Perl expressions, in fact, they are Perl blocks -	90	Expressions are normal Perl expressions, in fact, they are Perl blocks -
67	which means you could use multiple lines and statements:	91	which means you could use multiple lines and statements:
68		92
		93	scale keep {
69	again 3600;	94	again 3600;
70	if (localtime now)[6]) {	95	if (localtime now)[6]) {
71	return scale load "$HOME/weekday.png";	96	return load "$HOME/weekday.png";
72	} else {	97	} else {
73	return scale load "$HOME/sunday.png";	98	return load "$HOME/sunday.png";
		99	}
74	}	100	}
75		101
76	This expression gets evaluated once per hour. It will set F<sunday.png> as	102	This inner expression is evaluated once per hour (and whenever the
		103	terminal window is resized). It sets F<sunday.png> as background on
77	background on Sundays, and F<weekday.png> on all other days.	104	Sundays, and F<weekday.png> on all other days.
78		105
79	Fortunately, we expect that most expressions will be much simpler, with	106	Fortunately, we expect that most expressions will be much simpler, with
80	little Perl knowledge needed.	107	little Perl knowledge needed.
81		108
82	Basically, you always start with a function that "generates" an image	109	Basically, you always start with a function that "generates" an image
…		…
115	horizontal and vertical dimensions. For example, this halves the image	142	horizontal and vertical dimensions. For example, this halves the image
116	width and doubles the image height:	143	width and doubles the image height:
117		144
118	scale 0.5, 2, load "$HOME/mypic.png"	145	scale 0.5, 2, load "$HOME/mypic.png"
119		146
120	Other effects than scalign are also readily available, for exmaple, you can	147	IF you try out these expressions, you might suffer from some sluggishness,
121	tile the image to fill the whole window, instead of resizing it:	148	because each time the terminal is resized, it loads the PNG image again
		149	and scales it. Scaling is usually fast (and unavoidable), but loading the
		150	image can be quite time consuming. This is where C<keep> comes in handy:
122		151
		152	scale 0.5, 2, keep { load "$HOME/mypic.png" }
		153
		154	The C<keep> operator executes all the statements inside the braces only
		155	once, or when it thinks the outcome might change. In other cases it
		156	returns the last value computed by the brace block.
		157
		158	This means that the C<load> is only executed once, which makes it much
		159	faster, but also means that more memory is being used, because the loaded
		160	image must be kept in memory at all times. In this expression, the
		161	trade-off is likely worth it.
		162
		163	But back to effects: Other effects than scaling are also readily
		164	available, for example, you can tile the image to fill the whole window,
		165	instead of resizing it:
		166
123	tile load "$HOME/mypic.png"	167	tile keep { load "$HOME/mypic.png" }
124		168
125	In fact, images returned by C<load> are in C<tile> mode by default, so the C<tile> operator	169	In fact, images returned by C<load> are in C<tile> mode by default, so the
126	is kind of superfluous.	170	C<tile> operator is kind of superfluous.
127		171
128	Another common effect is to mirror the image, so that the same edges touch:	172	Another common effect is to mirror the image, so that the same edges
		173	touch:
129		174
130	mirror load "$HOME/mypic.png"	175	mirror keep { load "$HOME/mypic.png" }
131		176
132	This is also a typical background expression:	177	Another common background expression is:
133		178
134	rootalign root	179	rootalign root
135		180
136	It first takes a snapshot of the screen background image, and then	181	This one first takes a snapshot of the screen background image, and then
137	moves it to the upper left corner of the screen - the result is	182	moves it to the upper left corner of the screen (as opposed to the upper
138	pseudo-transparency, as the image seems to be static while the window is	183	left corner of the terminal window)- the result is pseudo-transparency:
139	moved around.	184	the image seems to be static while the window is moved around.
140		185
141	=head2 CYCLES AND CACHING	186	=head2 COLOUR SPECIFICATIONS
142		187
143	As has been mentioned before, the expression might be evaluated multiple	188	Whenever an operator expects a "colour", then this can be specified in one
144	times. Each time the expression is reevaluated, a new cycle is said to	189	of two ways: Either as string with an X11 colour specification, such as:
145	have begun. Many operators cache their results till the next cycle.
146		190
147	For example, the C<load> operator keeps a copy of the image. If it is	191	"red" # named colour
148	asked to load the same image on the next cycle it will not load it again,	192	"#f00" # simple rgb
149	but return the cached copy.	193	"[50]red" # red with 50% alpha
		194	"TekHVC:300/50/50" # anything goes
150		195
151	This only works for one cycle though, so as long as you load the same	196	OR as an array reference with one, three or four components:
152	image every time, it will always be cached, but when you load a different
153	image, it will forget about the first one.
154		197
155	This allows you to either speed things up by keeping multiple images in	198	[0.5] # 50% gray, 100% alpha
156	memory, or comserve memory by loading images more often.	199	[0.5, 0, 0] # dark red, no green or blur, 100% alpha
		200	[0.5, 0, 0, 0.7] # same with explicit 70% alpha
157		201
158	For example, you can keep two images in memory and use a random one like	202	=head2 CACHING AND SENSITIVITY
159	this:
160		203
161	my $img1 = load "img1.png";	204	Since some operations (such as C<load> and C<blur>) can take a long time,
162	my $img2 = load "img2.png";	205	caching results can be very important for a smooth operation. Caching can
163	(0.5 > rand) ? $img1 : $img2	206	also be useful to reduce memory usage, though, for example, when an image
		207	is cached by C<load>, it could be shared by multiple terminal windows
		208	running inside urxvtd.
164		209
165	Since both images are "loaded" every time the expression is evaluated,	210	=head3 C<keep { ... }> caching
166	they are always kept in memory. Contrast this version:
167		211
168	my $path1 = "img1.png";	212	The most important way to cache expensive operations is to use C<keep {
169	my $path2 = "img2.png";	213	... }>. The C<keep> operator takes a block of multiple statements enclosed
170	load ((0.5 > rand) ? $path1 : $path2)	214	by C<{}> and keeps the return value in memory.
171		215
172	Here, a path is selected randomly, and load is only called for one image,	216	An expression can be "sensitive" to various external events, such as
173	so keeps only one image in memory. If, on the next evaluation, luck	217	scaling or moving the window, root background changes and timers. Simply
174	decides to use the other path, then it will have to load that image again.	218	using an expression (such as C<scale> without parameters) that depends on
		219	certain changing values (called "variables"), or using those variables
		220	directly, will make an expression sensitive to these events - for example,
		221	using C<scale> or C<TW> will make the expression sensitive to the terminal
		222	size, and thus to resizing events.
		223
		224	When such an event happens, C<keep> will automatically trigger a
		225	reevaluation of the whole expression with the new value of the expression.
		226
		227	C<keep> is most useful for expensive operations, such as C<blur>:
		228
		229	rootalign keep { blur 20, root }
		230
		231	This makes a blurred copy of the root background once, and on subsequent
		232	calls, just root-aligns it. Since C<blur> is usually quite slow and
		233	C<rootalign> is quite fast, this trades extra memory (for the cached
		234	blurred pixmap) with speed (blur only needs to be redone when root
		235	changes).
		236
		237	=head3 C<load> caching
		238
		239	The C<load> operator itself does not keep images in memory, but as long as
		240	the image is still in memory, C<load> will use the in-memory image instead
		241	of loading it freshly from disk.
		242
		243	That means that this expression:
		244
		245	keep { load "$HOME/path..." }
		246
		247	Not only caches the image in memory, other terminal instances that try to
		248	C<load> it can reuse that in-memory copy.
175		249
176	=head1 REFERENCE	250	=head1 REFERENCE
177		251
178	=head2 COMMAND LINE SWITCHES	252	=head2 COMMAND LINE SWITCHES
179		253
…		…
189	overwriting borders and any other areas, such as the scrollbar.	263	overwriting borders and any other areas, such as the scrollbar.
190		264
191	Specifying this flag changes the behaviour, so that the image only	265	Specifying this flag changes the behaviour, so that the image only
192	replaces the background of the character area.	266	replaces the background of the character area.
193		267
		268	=item --background-interval seconds
		269
		270	Since some operations in the underlying XRender extension can effectively
		271	freeze your X-server for prolonged time, this extension enforces a minimum
		272	time between updates, which is normally about 0.1 seconds.
		273
		274	If you want to do updates more often, you can decrease this safety
		275	interval with this switch.
		276
194	=back	277	=back
195		278
196	=cut	279	=cut
197		280
		281	our %_IMG_CACHE;
198	our $HOME;	282	our $HOME;
199	our ($self, $old, $new);	283	our ($self, $frame);
200	our ($x, $y, $w, $h);	284	our ($x, $y, $w, $h);
201		285
202	# enforce at least this interval between updates	286	# enforce at least this interval between updates
203	our $MIN_INTERVAL = 1/100;	287	our $MIN_INTERVAL = 6/59.951;
204		288
205	{	289	{
206	package urxvt::bgdsl; # background language	290	package urxvt::bgdsl; # background language
		291
		292	sub FR_PARENT() { 0 } # parent frame, if any - must be #0
		293	sub FR_CACHE () { 1 } # cached values
		294	sub FR_AGAIN () { 2 } # what this expr is sensitive to
		295	sub FR_STATE () { 3 } # watchers etc.
207		296
208	use List::Util qw(min max sum shuffle);	297	use List::Util qw(min max sum shuffle);
209		298
210	=head2 PROVIDERS/GENERATORS	299	=head2 PROVIDERS/GENERATORS
211		300
…		…
218	=item load $path	307	=item load $path
219		308
220	Loads the image at the given C<$path>. The image is set to plane tiling	309	Loads the image at the given C<$path>. The image is set to plane tiling
221	mode.	310	mode.
222		311
223	Loaded images will be cached for one cycle.	312	If the image is already in memory (e.g. because another terminal instance
		313	uses it), then the in-memory copy us returned instead.
224		314
		315	=item load_uc $path
		316
		317	Load uncached - same as load, but does not cache the image, which means it
		318	is I<always> loaded from the filesystem again, even if another copy of it
		319	is in memory at the time.
		320
225	=cut	321	=cut
		322
		323	sub load_uc($) {
		324	$self->new_img_from_file ($_[0])
		325	}
226		326
227	sub load($) {	327	sub load($) {
228	my ($path) = @_;	328	my ($path) = @_;
229		329
230	$new->{load}{$path} = $old->{load}{$path} \|\| $self->new_img_from_file ($path);	330	$_IMG_CACHE{$path} \|\| do {
		331	my $img = load_uc $path;
		332	Scalar::Util::weaken ($_IMG_CACHE{$path} = $img);
		333	$img
		334	}
231	}	335	}
232		336
233	=item root	337	=item root
234		338
235	Returns the root window pixmap, that is, hopefully, the background image	339	Returns the root window pixmap, that is, hopefully, the background image
236	of your screen. The image is set to extend mode.	340	of your screen.
237		341
238	This function makes your expression root sensitive, that means it will be	342	This function makes your expression root sensitive, that means it will be
239	reevaluated when the bg image changes.	343	reevaluated when the bg image changes.
240		344
241	=cut	345	=cut
242		346
243	sub root() {	347	sub root() {
244	$new->{rootpmap_sensitive} = 1;	348	$frame->[FR_AGAIN]{rootpmap} = 1;
245	die "root op not supported, exg, we need you";	349	$self->new_img_from_root
246	}	350	}
247		351
248	=item solid $colour	352	=item solid $colour
249		353
250	=item solid $width, $height, $colour	354	=item solid $width, $height, $colour
…		…
258	=cut	362	=cut
259		363
260	sub solid($;$$) {	364	sub solid($;$$) {
261	my $colour = pop;	365	my $colour = pop;
262		366
263	my $img = $self->new_img (urxvt::PictStandardARGB32, $_[0] \|\| 1, $_[1] \|\| 1);	367	my $img = $self->new_img (urxvt::PictStandardARGB32, 0, 0, $_[0] \|\| 1, $_[1] \|\| 1);
264	$img->fill ($colour);	368	$img->fill ($colour);
265	$img	369	$img
266	}	370	}
267		371
268	=item clone $img	372	=item clone $img
…		…
272		376
273	=cut	377	=cut
274		378
275	sub clone($) {	379	sub clone($) {
276	$_[0]->clone	380	$_[0]->clone
		381	}
		382
		383	=item merge $img ...
		384
		385	Takes any number of images and merges them together, creating a single
		386	image containing them all. The tiling mode of the first image is used as
		387	the tiling mode of the resulting image.
		388
		389	This function is called automatically when an expression returns multiple
		390	images.
		391
		392	=cut
		393
		394	sub merge(@) {
		395	return $_[0] unless $#_;
		396
		397	# rather annoyingly clumsy, but optimisation is for another time
		398
		399	my $x0 = +1e9;
		400	my $y0 = +1e9;
		401	my $x1 = -1e9;
		402	my $y1 = -1e9;
		403
		404	for (@_) {
		405	my ($x, $y, $w, $h) = $_->geometry;
		406
		407	$x0 = $x if $x0 > $x;
		408	$y0 = $y if $y0 > $y;
		409
		410	$x += $w;
		411	$y += $h;
		412
		413	$x1 = $x if $x1 < $x;
		414	$y1 = $y if $y1 < $y;
		415	}
		416
		417	my $base = $self->new_img (urxvt::PictStandardARGB32, $x0, $y0, $x1 - $x0, $y1 - $y0);
		418	$base->repeat_mode ($_[0]->repeat_mode);
		419	$base->fill ([0, 0, 0, 0]);
		420
		421	$base->draw ($_)
		422	for @_;
		423
		424	$base
277	}	425	}
278		426
279	=back	427	=back
280		428
281	=head2 TILING MODES	429	=head2 TILING MODES
…		…
314	become transparent. This mode is most useful when you want to place an	462	become transparent. This mode is most useful when you want to place an
315	image over another image or the background colour while leaving all	463	image over another image or the background colour while leaving all
316	background pixels outside the image unchanged.	464	background pixels outside the image unchanged.
317		465
318	Example: load an image and display it in the upper left corner. The rest	466	Example: load an image and display it in the upper left corner. The rest
319	of the space is left "empty" (transparent or wahtever your compisotr does	467	of the space is left "empty" (transparent or whatever your compositor does
320	in alpha mode, else background colour).	468	in alpha mode, else background colour).
321		469
322	pad load "mybg.png"	470	pad load "mybg.png"
323		471
324	=item extend $img	472	=item extend $img
325		473
326	Extends the image over the whole plane, using the closest pixel in the	474	Extends the image over the whole plane, using the closest pixel in the
327	area outside the image. This mode is mostly useful when you more complex	475	area outside the image. This mode is mostly useful when you use more complex
328	filtering operations and want the pixels outside the image to have the	476	filtering operations and want the pixels outside the image to have the
329	same values as the pixels near the edge.	477	same values as the pixels near the edge.
330		478
331	Example: just for curiosity, how does this pixel extension stuff work?	479	Example: just for curiosity, how does this pixel extension stuff work?
332		480
…		…
381	Using these functions make your expression sensitive to window moves.	529	Using these functions make your expression sensitive to window moves.
382		530
383	These functions are mainly useful to align images to the root window.	531	These functions are mainly useful to align images to the root window.
384		532
385	Example: load an image and align it so it looks as if anchored to the	533	Example: load an image and align it so it looks as if anchored to the
386	background.	534	background (that's exactly what C<rootalign> does btw.):
387		535
388	move -TX, -TY, load "mybg.png"	536	move -TX, -TY, keep { load "mybg.png" }
389		537
390	=item TW	538	=item TW
		539
		540	=item TH
391		541
392	Return the width (C<TW>) and height (C<TH>) of the terminal window (the	542	Return the width (C<TW>) and height (C<TH>) of the terminal window (the
393	terminal window is the full window by default, and the character area only	543	terminal window is the full window by default, and the character area only
394	when in border-respect mode).	544	when in border-respect mode).
395		545
…		…
399	the window size to conserve memory.	549	the window size to conserve memory.
400		550
401	Example: take the screen background, clip it to the window size, blur it a	551	Example: take the screen background, clip it to the window size, blur it a
402	bit, align it to the window position and use it as background.	552	bit, align it to the window position and use it as background.
403		553
404	clip move -TX, -TY, blur 5, root	554	clip move -TX, -TY, keep { blur 5, root }
405		555
406	=cut	556	=cut
407		557
408	sub TX() { $new->{position_sensitive} = 1; $x }	558	sub TX() { $frame->[FR_AGAIN]{position} = 1; $x }
409	sub TY() { $new->{position_sensitive} = 1; $y }	559	sub TY() { $frame->[FR_AGAIN]{position} = 1; $y }
410	sub TW() { $new->{size_sensitive} = 1; $w }	560	sub TW() { $frame->[FR_AGAIN]{size} = 1; $w }
411	sub TH() { $new->{size_sensitive} = 1; $h }	561	sub TH() { $frame->[FR_AGAIN]{size} = 1; $h }
412		562
413	=item now	563	=item now
414		564
415	Returns the current time as (fractional) seconds since the epoch.	565	Returns the current time as (fractional) seconds since the epoch.
416		566
…		…
423	C<$seconds> seconds.	573	C<$seconds> seconds.
424		574
425	Example: load some image and rotate it according to the time of day (as if it were	575	Example: load some image and rotate it according to the time of day (as if it were
426	the hour pointer of a clock). Update this image every minute.	576	the hour pointer of a clock). Update this image every minute.
427		577
		578	again 60;
428	again 60; rotate TW, TH, 50, 50, (now % 86400) * -720 / 86400, scale load "myclock.png"	579	rotate 50, 50, (now % 86400) * -72 / 8640, scale keep { load "myclock.png" }
429		580
430	=item counter $seconds	581	=item counter $seconds
431		582
432	Like C<again>, but also returns an increasing counter value, starting at	583	Like C<again>, but also returns an increasing counter value, starting at
433	0, which might be useful for some simple animation effects.	584	0, which might be useful for some simple animation effects.
…		…
435	=cut	586	=cut
436		587
437	sub now() { urxvt::NOW }	588	sub now() { urxvt::NOW }
438		589
439	sub again($) {	590	sub again($) {
440	$new->{again} = $_[0];	591	$frame->[FR_AGAIN]{time} = $_[0];
441	}	592	}
442		593
443	sub counter($) {	594	sub counter($) {
444	$new->{again} = $_[0];	595	$frame->[FR_AGAIN]{time} = $_[0];
445	$self->{counter} + 0	596	$frame->[FR_STATE]{counter} + 0
446	}	597	}
447		598
448	=back	599	=back
449		600
450	=head2 SHAPE CHANGING OPERATORS	601	=head2 SHAPE CHANGING OPERATORS
…		…
470	assumed.	621	assumed.
471		622
472	Example: load an image, blur it, and clip it to the window size to save	623	Example: load an image, blur it, and clip it to the window size to save
473	memory.	624	memory.
474		625
475	clip blur 10, load "mybg.png"	626	clip keep { blur 10, load "mybg.png" }
476		627
477	=cut	628	=cut
478		629
479	sub clip($;$$;$$) {	630	sub clip($;$$;$$) {
480	my $img = pop;	631	my $img = pop;
…		…
553		704
554	Example: move the image right by 20 pixels and down by 30.	705	Example: move the image right by 20 pixels and down by 30.
555		706
556	move 20, 30, ...	707	move 20, 30, ...
557		708
		709	=item align $xalign, $yalign, $img
		710
		711	Aligns the image according to a factor - C<0> means the image is moved to
		712	the left or top edge (for C<$xalign> or C<$yalign>), C<0.5> means it is
		713	exactly centered and C<1> means it touches the right or bottom edge.
		714
		715	Example: remove any visible border around an image, center it vertically but move
		716	it to the right hand side.
		717
		718	align 1, 0.5, pad $img
		719
558	=item center $img	720	=item center $img
559		721
560	=item center $width, $height, $img	722	=item center $width, $height, $img
561		723
562	Centers the image, i.e. the center of the image is moved to the center of	724	Centers the image, i.e. the center of the image is moved to the center of
563	the terminal window (or the box specified by C<$width> and C<$height> if	725	the terminal window (or the box specified by C<$width> and C<$height> if
564	given).	726	given).
		727
		728	Example: load an image and center it.
		729
		730	center keep { pad load "mybg.png" }
565		731
566	=item rootalign $img	732	=item rootalign $img
567		733
568	Moves the image so that it appears glued to the screen as opposed to the	734	Moves the image so that it appears glued to the screen as opposed to the
569	window. This gives the illusion of a larger area behind the window. It is	735	window. This gives the illusion of a larger area behind the window. It is
570	exactly equivalent to C<move -TX, -TY>, that is, it moves the image to the	736	exactly equivalent to C<move -TX, -TY>, that is, it moves the image to the
571	top left of the screen.	737	top left of the screen.
572		738
573	Example: load a background image, put it in mirror mode and root align it.	739	Example: load a background image, put it in mirror mode and root align it.
574		740
575	rootalign mirror load "mybg.png"	741	rootalign keep { mirror load "mybg.png" }
576		742
577	Example: take the screen background and align it, giving the illusion of	743	Example: take the screen background and align it, giving the illusion of
578	transparency as long as the window isn't in front of other windows.	744	transparency as long as the window isn't in front of other windows.
579		745
580	rootalign root	746	rootalign root
581		747
582	=cut	748	=cut
583		749
584	sub move($$;$) {	750	sub move($$;$) {
585	my $img = pop->clone;	751	my $img = pop->clone;
586	$img->move ($_[0], $_[1]);	752	$img->move ($_[0], $_[1]);
587	$img	753	$img
588	}	754	}
589		755
		756	sub align($;$$) {
		757	my $img = pop;
		758
		759	move $_[0] * (TW - $img->w),
		760	$_[1] * (TH - $img->h),
		761	$img
		762	}
		763
590	sub center($;$$) {	764	sub center($;$$) {
591	my $img = pop;	765	my $img = pop;
592	my $w = $_[0] \|\| TW;	766	my $w = $_[0] \|\| TW;
593	my $h = $_[0] \|\| TH;	767	my $h = $_[1] \|\| TH;
594		768
595	move 0.5 * ($w - $img->w), 0.5 * ($h - $img->h), $img	769	move 0.5 * ($w - $img->w), 0.5 * ($h - $img->h), $img
596	}	770	}
597		771
598	sub rootalign($) {	772	sub rootalign($) {
599	move -TX, -TY, $_[0]	773	move -TX, -TY, $_[0]
600	}	774	}
601		775
		776	=item rotate $center_x, $center_y, $degrees, $img
		777
		778	Rotates the image clockwise by C<$degrees> degrees, around the point at
		779	C<$center_x> and C<$center_y> (specified as factor of image width/height).
		780
		781	Example: rotate the image by 90 degrees around it's center.
		782
		783	rotate 0.5, 0.5, 90, keep { load "$HOME/mybg.png" }
		784
		785	=cut
		786
		787	sub rotate($$$$) {
		788	my $img = pop;
		789	$img->rotate (
		790	$_[0] * ($img->w + $img->x),
		791	$_[1] * ($img->h + $img->y),
		792	$_[2] * (3.14159265 / 180),
		793	)
		794	}
		795
602	=back	796	=back
603		797
604	=head2 COLOUR MODIFICATIONS	798	=head2 COLOUR MODIFICATIONS
605		799
606	The following operators change the pixels of the image.	800	The following operators change the pixels of the image.
607		801
608	=over 4	802	=over 4
		803
		804	=item tint $color, $img
		805
		806	Tints the image in the given colour.
		807
		808	Example: tint the image red.
		809
		810	tint "red", load "rgb.png"
		811
		812	Example: the same, but specify the colour by component.
		813
		814	tint [1, 0, 0], load "rgb.png"
		815
		816	=cut
		817
		818	sub tint($$) {
		819	$_[1]->tint ($_[0])
		820	}
609		821
610	=item contrast $factor, $img	822	=item contrast $factor, $img
611		823
612	=item contrast $r, $g, $b, $img	824	=item contrast $r, $g, $b, $img
613		825
…		…
640		852
641	Values less than 0 reduce brightness, while values larger than 0 increase	853	Values less than 0 reduce brightness, while values larger than 0 increase
642	it. Useful range is from -1 to 1 - the former results in a black, the	854	it. Useful range is from -1 to 1 - the former results in a black, the
643	latter in a white picture.	855	latter in a white picture.
644		856
645	Due to idiosynchrasies in the underlying XRender extension, biases less	857	Due to idiosyncrasies in the underlying XRender extension, biases less
646	than zero can be I<very> slow.	858	than zero can be I<very> slow.
		859
		860	You can also try the experimental(!) C<muladd> operator.
647		861
648	=cut	862	=cut
649		863
650	sub contrast($$;$$;$) {	864	sub contrast($$;$$;$) {
651	my $img = pop;	865	my $img = pop;
652	my ($r, $g, $b, $a) = @_;	866	my ($r, $g, $b, $a) = @_;
653		867
654	($g, $b) = ($r, $r) if @_ < 4;	868	($g, $b) = ($r, $r) if @_ < 3;
655	$a = 1 if @_ < 5;	869	$a = 1 if @_ < 4;
656		870
657	$img = $img->clone;	871	$img = $img->clone;
658	$img->contrast ($r, $g, $b, $a);	872	$img->contrast ($r, $g, $b, $a);
659	$img	873	$img
660	}	874	}
661		875
662	sub brightness($$;$$;$) {	876	sub brightness($$;$$;$) {
663	my $img = pop;	877	my $img = pop;
664	my ($r, $g, $b, $a) = @_;	878	my ($r, $g, $b, $a) = @_;
665		879
666	($g, $b) = ($r, $r) if @_ < 4;	880	($g, $b) = ($r, $r) if @_ < 3;
667	$a = 1 if @_ < 5;	881	$a = 1 if @_ < 4;
668		882
669	$img = $img->clone;	883	$img = $img->clone;
670	$img->brightness ($r, $g, $b, $a);	884	$img->brightness ($r, $g, $b, $a);
671	$img	885	$img
		886	}
		887
		888	=item muladd $mul, $add, $img # EXPERIMENTAL
		889
		890	First multipliesthe pixels by C<$mul>, then adds C<$add>. This cna be used
		891	to implement brightness and contrast at the same time, with a wider value
		892	range than contrast and brightness operators.
		893
		894	Due to numerous bugs in XRender implementations, it can also introduce a
		895	number of visual artifacts.
		896
		897	Example: increase contrast by a factor of C<$c> without changing image
		898	brightness too much.
		899
		900	muladd $c, (1 - $c) * 0.5, $img
		901
		902	=cut
		903
		904	sub muladd($$$) {
		905	$_[2]->muladd ($_[0], $_[1])
672	}	906	}
673		907
674	=item blur $radius, $img	908	=item blur $radius, $img
675		909
676	=item blur $radius_horz, $radius_vert, $img	910	=item blur $radius_horz, $radius_vert, $img
…		…
688	sub blur($$;$) {	922	sub blur($$;$) {
689	my $img = pop;	923	my $img = pop;
690	$img->blur ($_[0], @_ >= 2 ? $_[1] : $_[0])	924	$img->blur ($_[0], @_ >= 2 ? $_[1] : $_[0])
691	}	925	}
692		926
693	=item rotate $new_width, $new_height, $center_x, $center_y, $degrees
694
695	Rotates the image by C<$degrees> degrees, counter-clockwise, around the
696	pointer at C<$center_x> and C<$center_y> (specified as factor of image
697	width/height), generating a new image with width C<$new_width> and height
698	C<$new_height>.
699
700	#TODO# new width, height, maybe more operators?
701
702	Example: rotate the image by 90 degrees
703
704	=cut
705
706	sub rotate($$$$$$) {
707	my $img = pop;
708	$img->rotate (
709	$_[0],
710	$_[1],
711	$_[2] * $img->w,
712	$_[3] * $img->h,
713	$_[4] * (3.14159265 / 180),
714	)
715	}
716
717	=back	927	=back
718		928
		929	=head2 OTHER STUFF
		930
		931	Anything that didn't fit any of the other categories, even after applying
		932	force and closing our eyes.
		933
		934	=over 4
		935
		936	=item keep { ... }
		937
		938	This operator takes a code block as argument, that is, one or more
		939	statements enclosed by braces.
		940
		941	The trick is that this code block is only evaluated when the outcome
		942	changes - on other calls the C<keep> simply returns the image it computed
		943	previously (yes, it should only be used with images). Or in other words,
		944	C<keep> I<caches> the result of the code block so it doesn't need to be
		945	computed again.
		946
		947	This can be extremely useful to avoid redoing slow operations - for
		948	example, if your background expression takes the root background, blurs it
		949	and then root-aligns it it would have to blur the root background on every
		950	window move or resize.
		951
		952	Another example is C<load>, which can be quite slow.
		953
		954	In fact, urxvt itself encloses the whole expression in some kind of
		955	C<keep> block so it only is reevaluated as required.
		956
		957	Putting the blur into a C<keep> block will make sure the blur is only done
		958	once, while the C<rootalign> is still done each time the window moves.
		959
		960	rootalign keep { blur 10, root }
		961
		962	This leaves the question of how to force reevaluation of the block,
		963	in case the root background changes: If expression inside the block
		964	is sensitive to some event (root background changes, window geometry
		965	changes), then it will be reevaluated automatically as needed.
		966
		967	=cut
		968
		969	sub keep(&) {
		970	my $id = $_[0]+0;
		971
		972	local $frame = $self->{frame_cache}{$id} \|\|= [$frame];
		973
		974	unless ($frame->[FR_CACHE]) {
		975	$frame->[FR_CACHE] = [ $_[0]() ];
		976
		977	my $self = $self;
		978	my $frame = $frame;
		979	Scalar::Util::weaken $frame;
		980	$self->compile_frame ($frame, sub {
		981	# clear this frame cache, also for all parents
		982	for (my $frame = $frame; $frame; $frame = $frame->[0]) {
		983	undef $frame->[FR_CACHE];
		984	}
		985
		986	$self->recalculate;
		987	});
		988	};
		989
		990	# in scalar context we always return the first original result, which
		991	# is not quite how perl works.
		992	wantarray
		993	? @{ $frame->[FR_CACHE] }
		994	: $frame->[FR_CACHE][0]
		995	}
		996
		997	# sub keep_clear() {
		998	# delete $self->{frame_cache};
		999	# }
		1000
		1001	=back
		1002
719	=cut	1003	=cut
720		1004
721	}	1005	}
722		1006
723	sub parse_expr {	1007	sub parse_expr {
724	my $expr = eval "sub {\npackage urxvt::bgdsl;\n#line 0 'background expression'\n$_[0]\n}";	1008	my $expr = eval
		1009	"sub {\n"
		1010	. "package urxvt::bgdsl;\n"
		1011	. "#line 0 'background expression'\n"
		1012	. "$_[0]\n"
		1013	. "}";
725	die if $@;	1014	die if $@;
726	$expr	1015	$expr
727	}	1016	}
728		1017
729	# compiles a parsed expression	1018	# compiles a parsed expression
730	sub set_expr {	1019	sub set_expr {
731	my ($self, $expr) = @_;	1020	my ($self, $expr) = @_;
732		1021
		1022	$self->{root} = []; # the outermost frame
733	$self->{expr} = $expr;	1023	$self->{expr} = $expr;
734	$self->recalculate;	1024	$self->recalculate;
		1025	}
		1026
		1027	# takes a hash of sensitivity indicators and installs watchers
		1028	sub compile_frame {
		1029	my ($self, $frame, $cb) = @_;
		1030
		1031	my $state = $frame->[urxvt::bgdsl::FR_STATE] \|\|= {};
		1032	my $again = $frame->[urxvt::bgdsl::FR_AGAIN];
		1033
		1034	# don't keep stuff alive
		1035	Scalar::Util::weaken $state;
		1036
		1037	if ($again->{nested}) {
		1038	$state->{nested} = 1;
		1039	} else {
		1040	delete $state->{nested};
		1041	}
		1042
		1043	if (my $interval = $again->{time}) {
		1044	$state->{time} = [$interval, urxvt::timer->new->after ($interval)->interval ($interval)]
		1045	if $state->{time}[0] != $interval;
		1046
		1047	# callback might have changed, although we could just rule that out
		1048	$state->{time}[1]->cb (sub {
		1049	++$state->{counter};
		1050	$cb->();
		1051	});
		1052	} else {
		1053	delete $state->{time};
		1054	}
		1055
		1056	if ($again->{position}) {
		1057	$state->{position} = $self->on (position_change => $cb);
		1058	} else {
		1059	delete $state->{position};
		1060	}
		1061
		1062	if ($again->{size}) {
		1063	$state->{size} = $self->on (size_change => $cb);
		1064	} else {
		1065	delete $state->{size};
		1066	}
		1067
		1068	if ($again->{rootpmap}) {
		1069	$state->{rootpmap} = $self->on (rootpmap_change => $cb);
		1070	} else {
		1071	delete $state->{rootpmap};
		1072	}
735	}	1073	}
736		1074
737	# evaluate the current bg expression	1075	# evaluate the current bg expression
738	sub recalculate {	1076	sub recalculate {
739	my ($arg_self) = @_;	1077	my ($arg_self) = @_;
…		…
749		1087
750	$arg_self->{next_refresh} = urxvt::NOW + $MIN_INTERVAL;	1088	$arg_self->{next_refresh} = urxvt::NOW + $MIN_INTERVAL;
751		1089
752	# set environment to evaluate user expression	1090	# set environment to evaluate user expression
753		1091
754	local $self = $arg_self;	1092	local $self = $arg_self;
755
756	local $HOME = $ENV{HOME};	1093	local $HOME = $ENV{HOME};
757	local $old = $self->{state};	1094	local $frame = $self->{root};
758	local $new = my $state = $self->{state} = {};
759		1095
760	($x, $y, $w, $h) =
761	$self->background_geometry ($self->{border});	1096	($x, $y, $w, $h) = $self->background_geometry ($self->{border});
762		1097
763	# evaluate user expression	1098	# evaluate user expression
764		1099
765	my $img = eval { $self->{expr}->() };	1100	my @img = eval { $self->{expr}->() };
766	warn $@ if $@;#d#	1101	die $@ if $@;
		1102	die "background-expr did not return anything.\n" unless @img;
		1103	die "background-expr: expected image(s), got something else.\n"
767	die if !UNIVERSAL::isa $img, "urxvt::img";	1104	if grep { !UNIVERSAL::isa $_, "urxvt::img" } @img;
768		1105
769	$state->{size_sensitive} = 1	1106	my $img = urxvt::bgdsl::merge @img;
		1107
		1108	$frame->[FR_AGAIN]{size} = 1
770	if $img->repeat_mode != urxvt::RepeatNormal;	1109	if $img->repeat_mode != urxvt::RepeatNormal;
771		1110
772	# if the expression is sensitive to external events, prepare reevaluation then	1111	# if the expression is sensitive to external events, prepare reevaluation then
773		1112	$self->compile_frame ($frame, sub { $arg_self->recalculate });
774	my $repeat;
775
776	if (my $again = $state->{again}) {
777	$repeat = 1;
778	my $self = $self;
779	$state->{timer} = $again == $old->{again}
780	? $old->{timer}
781	: urxvt::timer->new->after ($again)->interval ($again)->cb (sub {
782	++$self->{counter};
783	$self->recalculate
784	});
785	}
786
787	if (delete $state->{position_sensitive}) {
788	$repeat = 1;
789	$self->enable (position_change => sub { $_[0]->recalculate });
790	} else {
791	$self->disable ("position_change");
792	}
793
794	if (delete $state->{size_sensitive}) {
795	$repeat = 1;
796	$self->enable (size_change => sub { $_[0]->recalculate });
797	} else {
798	$self->disable ("size_change");
799	}
800
801	if (delete $state->{rootpmap_sensitive}) {
802	$repeat = 1;
803	$self->enable (rootpmap_change => sub { $_[0]->recalculate });
804	} else {
805	$self->disable ("rootpmap_change");
806	}
807		1113
808	# clear stuff we no longer need	1114	# clear stuff we no longer need
809		1115
810	%$old = ();	1116	# unless (%{ $frame->[FR_STATE] }) {
811
812	unless ($repeat) {
813	delete $self->{state};	1117	# delete $self->{state};
814	delete $self->{expr};	1118	# delete $self->{expr};
815	}	1119	# }
816		1120
817	# set background pixmap	1121	# set background pixmap
818		1122
819	$self->set_background ($img, $self->{border});	1123	$self->set_background ($img, $self->{border});
820	$self->scr_recolour (0);	1124	$self->scr_recolour (0);
…		…
822	}	1126	}
823		1127
824	sub on_start {	1128	sub on_start {
825	my ($self) = @_;	1129	my ($self) = @_;
826		1130
827	my $expr = $self->x_resource ("background.expr")	1131	my $expr = $self->x_resource ("%.expr")
828	or return;	1132	or return;
829		1133
		1134	$self->has_render
		1135	or die "background extension needs RENDER extension 0.10 or higher, ignoring background-expr.\n";
		1136
830	$self->set_expr (parse_expr $expr);	1137	$self->set_expr (parse_expr $expr);
831	$self->{border} = $self->x_resource_boolean ("background.border");	1138	$self->{border} = $self->x_resource_boolean ("%.border");
		1139
		1140	$MIN_INTERVAL = $self->x_resource ("%.interval");
832		1141
833	()	1142	()
834	}	1143	}
835		1144

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Comparing rxvt-unicode/src/perl/background (file contents): Revision 1.45 by root, Sun Jun 10 11:53:32 2012 UTC vs. Revision 1.77 by root, Tue Sep 4 11:21:11 2012 UTC

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Comparing rxvt-unicode/src/perl/background (file contents):
Revision 1.45 by root, Sun Jun 10 11:53:32 2012 UTC vs.
Revision 1.77 by root, Tue Sep 4 11:21:11 2012 UTC