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

Comparing rxvt-unicode/src/perl/background (file contents):
Revision 1.63 by root, Tue Jun 19 18:17:56 2012 UTC vs.
Revision 1.81 by sf-exg, Wed Oct 24 11:20:28 2012 UTC

…		…
4	#:META:X_RESOURCE:%.border:boolean:respect the terminal border	4	#:META:X_RESOURCE:%.border:boolean:respect the terminal border
5	#:META:X_RESOURCE:%.interval:seconds:minimum time between updates	5	#:META:X_RESOURCE:%.interval:seconds:minimum time between updates
6		6
7	=head1 NAME	7	=head1 NAME
8		8
9	background - manage terminal background	9	background - manage terminal background
10		10
11	=head1 SYNOPSIS	11	=head1 SYNOPSIS
12		12
13	urxvt --background-expr 'background expression'	13	urxvt --background-expr 'background expression'
14	--background-border	14	--background-border
15	--background-interval seconds	15	--background-interval seconds
16		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 }
		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.
21		45
…		…
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 its 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 is 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 scaling are also readily available, for example, 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	=head3 C<load> et al.	188	Whenever an operator expects a "colour", then this can be specified in one
		189	of two ways: Either as string with an X11 colour specification, such as:
144		190
145	As has been mentioned before, the expression might be evaluated multiple	191	"red" # named colour
146	times. Each time the expression is reevaluated, a new cycle is said to	192	"#f00" # simple rgb
147	have begun. Many operators cache their results till the next cycle.	193	"[50]red" # red with 50% alpha
		194	"TekHVC:300/50/50" # anything goes
148		195
149	For example, the C<load> operator keeps a copy of the image. If it is	196	OR as an array reference with one, three or four components:
150	asked to load the same image on the next cycle it will not load it again,
151	but return the cached copy.
152		197
153	This only works for one cycle though, so as long as you load the same	198	[0.5] # 50% gray, 100% alpha
154	image every time, it will always be cached, but when you load a different	199	[0.5, 0, 0] # dark red, no green or blur, 100% alpha
155	image, it will forget about the first one.	200	[0.5, 0, 0, 0.7] # same with explicit 70% alpha
156		201
157	This allows you to either speed things up by keeping multiple images in	202	=head2 CACHING AND SENSITIVITY
158	memory, or conserve memory by loading images more often.
159		203
160	For example, you can keep two images in memory and use a random one like	204	Since some operations (such as C<load> and C<blur>) can take a long time,
161	this:	205	caching results can be very important for a smooth operation. Caching can
		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.
162		209
163	my $img1 = load "img1.png";	210	=head3 C<keep { ... }> caching
164	my $img2 = load "img2.png";
165	(0.5 > rand) ? $img1 : $img2
166		211
167	Since both images are "loaded" every time the expression is evaluated,	212	The most important way to cache expensive operations is to use C<keep {
168	they are always kept in memory. Contrast this version:
169
170	my $path1 = "img1.png";
171	my $path2 = "img2.png";
172	load ((0.5 > rand) ? $path1 : $path2)
173
174	Here, a path is selected randomly, and load is only called for one image,
175	so keeps only one image in memory. If, on the next evaluation, luck
176	decides to use the other path, then it will have to load that image again.
177
178	=head3 C<once { ... }>
179
180	Another way to cache expensive operations is to use C<once { ... }>. The
181	C<once> operator takes a block of multiple statements enclosed by C<{}>	213	... }>. The C<keep> operator takes a block of multiple statements enclosed
182	and evaluates it only.. once, returning any images the last statement	214	by C<{}> and keeps the return value in memory.
183	returned. Further calls simply produce the values from the cache.
184		215
		216	An expression can be "sensitive" to various external events, such as
		217	scaling or moving the window, root background changes and timers. Simply
		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
185	This is most useful for expensive operations, such as C<blur>:	227	C<keep> is most useful for expensive operations, such as C<blur>:
186		228
187	rootalign once { blur 20, root }	229	rootalign keep { blur 20, root }
188		230
189	This makes a blurred copy of the root background once, and on subsequent	231	This makes a blurred copy of the root background once, and on subsequent
190	calls, just root-aligns it. Since C<blur> is usually quite slow and	232	calls, just root-aligns it. Since C<blur> is usually quite slow and
191	C<rootalign> is quite fast, this trades extra memory (For the cached	233	C<rootalign> is quite fast, this trades extra memory (for the cached
192	blurred pixmap) with speed (blur only needs to be redone when root	234	blurred pixmap) with speed (blur only needs to be redone when root
193	changes).	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.
194		249
195	=head1 REFERENCE	250	=head1 REFERENCE
196		251
197	=head2 COMMAND LINE SWITCHES	252	=head2 COMMAND LINE SWITCHES
198		253
…		…
252	=item load $path	307	=item load $path
253		308
254	Loads the image at the given C<$path>. The image is set to plane tiling	309	Loads the image at the given C<$path>. The image is set to plane tiling
255	mode.	310	mode.
256		311
257	Loaded images will be cached for one cycle, and shared between temrinals	312	If the image is already in memory (e.g. because another terminal instance
258	running in the same process (e.g. in C<urxvtd>).	313	uses it), then the in-memory copy us returned instead.
259		314
260	#=item load_uc $path	315	=item load_uc $path
261	#	316
262	#Load uncached - same as load, but does not cache the image. This function	317	Load uncached - same as load, but does not cache the image, which means it
263	#is most useufl if you want to optimise a background expression in some	318	is I<always> loaded from the filesystem again, even if another copy of it
264	#way.	319	is in memory at the time.
265		320
266	=cut	321	=cut
		322
		323	sub load_uc($) {
		324	$self->new_img_from_file ($_[0])
		325	}
267		326
268	sub load($) {	327	sub load($) {
269	my ($path) = @_;	328	my ($path) = @_;
270		329
271	$_IMG_CACHE{$path} \|\| do {	330	$_IMG_CACHE{$path} \|\| do {
272	my $img = $self->new_img_from_file ($path);	331	my $img = load_uc $path;
273	Scalar::Util::weaken ($_IMG_CACHE{$path} = $img);	332	Scalar::Util::weaken ($_IMG_CACHE{$path} = $img);
274	$img	333	$img
275	}	334	}
276	}	335	}
277		336
…		…
323		382
324	=item merge $img ...	383	=item merge $img ...
325		384
326	Takes any number of images and merges them together, creating a single	385	Takes any number of images and merges them together, creating a single
327	image containing them all. The tiling mode of the first image is used as	386	image containing them all. The tiling mode of the first image is used as
328	the tiling mdoe of the resulting image.	387	the tiling mode of the resulting image.
329		388
330	This function is called automatically when an expression returns multiple	389	This function is called automatically when an expression returns multiple
331	images.	390	images.
332		391
333	=cut	392	=cut
…		…
362	$base->draw ($_)	421	$base->draw ($_)
363	for @_;	422	for @_;
364		423
365	$base	424	$base
366	}	425	}
		426
		427	=back
367		428
368	=head2 TILING MODES	429	=head2 TILING MODES
369		430
370	The following operators modify the tiling mode of an image, that is, the	431	The following operators modify the tiling mode of an image, that is, the
371	way that pixels outside the image area are painted when the image is used.	432	way that pixels outside the image area are painted when the image is used.
…		…
468	Using these functions make your expression sensitive to window moves.	529	Using these functions make your expression sensitive to window moves.
469		530
470	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.
471		532
472	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
473	background.	534	background (that's exactly what C<rootalign> does btw.):
474		535
475	move -TX, -TY, load "mybg.png"	536	move -TX, -TY, keep { load "mybg.png" }
476		537
477	=item TW	538	=item TW
		539
		540	=item TH
478		541
479	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
480	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
481	when in border-respect mode).	544	when in border-respect mode).
482		545
…		…
486	the window size to conserve memory.	549	the window size to conserve memory.
487		550
488	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
489	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.
490		553
491	clip move -TX, -TY, once { blur 5, root }	554	clip move -TX, -TY, keep { blur 5, root }
492		555
493	=cut	556	=cut
494		557
495	sub TX() { $frame->[FR_AGAIN]{position} = 1; $x }	558	sub TX() { $frame->[FR_AGAIN]{position} = 1; $x }
496	sub TY() { $frame->[FR_AGAIN]{position} = 1; $y }	559	sub TY() { $frame->[FR_AGAIN]{position} = 1; $y }
…		…
510	C<$seconds> seconds.	573	C<$seconds> seconds.
511		574
512	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
513	the hour pointer of a clock). Update this image every minute.	576	the hour pointer of a clock). Update this image every minute.
514		577
		578	again 60;
515	again 60; rotate 50, 50, (now % 86400) * -720 / 86400, scale load "myclock.png"	579	rotate 50, 50, (now % 86400) * -72 / 8640, scale keep { load "myclock.png" }
516		580
517	=item counter $seconds	581	=item counter $seconds
518		582
519	Like C<again>, but also returns an increasing counter value, starting at	583	Like C<again>, but also returns an increasing counter value, starting at
520	0, which might be useful for some simple animation effects.	584	0, which might be useful for some simple animation effects.
…		…
549	Clips an image to the given rectangle. If the rectangle is outside the	613	Clips an image to the given rectangle. If the rectangle is outside the
550	image area (e.g. when C<$x> or C<$y> are negative) or the rectangle is	614	image area (e.g. when C<$x> or C<$y> are negative) or the rectangle is
551	larger than the image, then the tiling mode defines how the extra pixels	615	larger than the image, then the tiling mode defines how the extra pixels
552	will be filled.	616	will be filled.
553		617
554	If C<$x> an C<$y> are missing, then C<0> is assumed for both.	618	If C<$x> and C<$y> are missing, then C<0> is assumed for both.
555		619
556	If C<$width> and C<$height> are missing, then the window size will be	620	If C<$width> and C<$height> are missing, then the window size will be
557	assumed.	621	assumed.
558		622
559	Example: load an image, blur it, and clip it to the window size to save	623	Example: load an image, blur it, and clip it to the window size to save
560	memory.	624	memory.
561		625
562	clip blur 10, load "mybg.png"	626	clip keep { blur 10, load "mybg.png" }
563		627
564	=cut	628	=cut
565		629
566	sub clip($;$$;$$) {	630	sub clip($;$$;$$) {
567	my $img = pop;	631	my $img = pop;
…		…
577	=item scale $width_factor, $height_factor, $img	641	=item scale $width_factor, $height_factor, $img
578		642
579	Scales the image by the given factors in horizontal	643	Scales the image by the given factors in horizontal
580	(C<$width>) and vertical (C<$height>) direction.	644	(C<$width>) and vertical (C<$height>) direction.
581		645
582	If only one factor is give, it is used for both directions.	646	If only one factor is given, it is used for both directions.
583		647
584	If no factors are given, scales the image to the window size without	648	If no factors are given, scales the image to the window size without
585	keeping aspect.	649	keeping aspect.
586		650
587	=item resize $width, $height, $img	651	=item resize $width, $height, $img
…		…
661	the terminal window (or the box specified by C<$width> and C<$height> if	725	the terminal window (or the box specified by C<$width> and C<$height> if
662	given).	726	given).
663		727
664	Example: load an image and center it.	728	Example: load an image and center it.
665		729
666	center pad load "mybg.png"	730	center keep { pad load "mybg.png" }
667		731
668	=item rootalign $img	732	=item rootalign $img
669		733
670	Moves the image so that it appears glued to the screen as opposed to the	734	Moves the image so that it appears glued to the screen as opposed to the
671	window. This gives the illusion of a larger area behind the window. It is	735	window. This gives the illusion of a larger area behind the window. It is
672	exactly equivalent to C<move -TX, -TY>, that is, it moves the image to the	736	exactly equivalent to C<move -TX, -TY>, that is, it moves the image to the
673	top left of the screen.	737	top left of the screen.
674		738
675	Example: load a background image, put it in mirror mode and root align it.	739	Example: load a background image, put it in mirror mode and root align it.
676		740
677	rootalign mirror load "mybg.png"	741	rootalign keep { mirror load "mybg.png" }
678		742
679	Example: take the screen background and align it, giving the illusion of	743	Example: take the screen background and align it, giving the illusion of
680	transparency as long as the window isn't in front of other windows.	744	transparency as long as the window isn't in front of other windows.
681		745
682	rootalign root	746	rootalign root
…		…
707		771
708	sub rootalign($) {	772	sub rootalign($) {
709	move -TX, -TY, $_[0]	773	move -TX, -TY, $_[0]
710	}	774	}
711		775
712	=item rotate $center_x, $center_y, $degrees	776	=item rotate $center_x, $center_y, $degrees, $img
713		777
714	Rotates the image by C<$degrees> degrees, counter-clockwise, around the	778	Rotates the image clockwise by C<$degrees> degrees, around the point at
715	pointer at C<$center_x> and C<$center_y> (specified as factor of image	779	C<$center_x> and C<$center_y> (specified as factor of image width/height).
716	width/height).
717		780
718	#TODO# new width, height, maybe more operators?
719
720	Example: rotate the image by 90 degrees	781	Example: rotate the image by 90 degrees around its center.
		782
		783	rotate 0.5, 0.5, 90, keep { load "$HOME/mybg.png" }
721		784
722	=cut	785	=cut
723		786
724	sub rotate($$$$) {	787	sub rotate($$$$) {
725	my $img = pop;	788	my $img = pop;
…		…
736		799
737	The following operators change the pixels of the image.	800	The following operators change the pixels of the image.
738		801
739	=over 4	802	=over 4
740		803
		804	=item tint $color, $img
		805
		806	Tints the image in the given colour.
		807
		808	Example: tint the image red.
		809
		810	tint "red", load "rgb.png"
		811
		812	Example: the same, but specify the colour by component.
		813
		814	tint [1, 0, 0], load "rgb.png"
		815
		816	=cut
		817
		818	sub tint($$) {
		819	$_[1]->tint ($_[0])
		820	}
		821
741	=item contrast $factor, $img	822	=item contrast $factor, $img
742		823
743	=item contrast $r, $g, $b, $img	824	=item contrast $r, $g, $b, $img
744		825
745	=item contrast $r, $g, $b, $a, $img	826	=item contrast $r, $g, $b, $a, $img
…		…
774	latter in a white picture.	855	latter in a white picture.
775		856
776	Due to idiosyncrasies in the underlying XRender extension, biases less	857	Due to idiosyncrasies in the underlying XRender extension, biases less
777	than zero can be I<very> slow.	858	than zero can be I<very> slow.
778		859
		860	You can also try the experimental(!) C<muladd> operator.
		861
779	=cut	862	=cut
780		863
781	sub contrast($$;$$;$) {	864	sub contrast($$;$$;$) {
782	my $img = pop;	865	my $img = pop;
783	my ($r, $g, $b, $a) = @_;	866	my ($r, $g, $b, $a) = @_;
…		…
798	$a = 1 if @_ < 4;	881	$a = 1 if @_ < 4;
799		882
800	$img = $img->clone;	883	$img = $img->clone;
801	$img->brightness ($r, $g, $b, $a);	884	$img->brightness ($r, $g, $b, $a);
802	$img	885	$img
		886	}
		887
		888	=item muladd $mul, $add, $img # EXPERIMENTAL
		889
		890	First multiplies the pixels by C<$mul>, then adds C<$add>. This can be used
		891	to implement brightness and contrast at the same time, with a wider value
		892	range than contrast and brightness operators.
		893
		894	Due to numerous bugs in XRender implementations, it can also introduce a
		895	number of visual artifacts.
		896
		897	Example: increase contrast by a factor of C<$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])
803	}	906	}
804		907
805	=item blur $radius, $img	908	=item blur $radius, $img
806		909
807	=item blur $radius_horz, $radius_vert, $img	910	=item blur $radius_horz, $radius_vert, $img
…		…
828	Anything that didn't fit any of the other categories, even after applying	931	Anything that didn't fit any of the other categories, even after applying
829	force and closing our eyes.	932	force and closing our eyes.
830		933
831	=over 4	934	=over 4
832		935
833	=item once { ... }	936	=item keep { ... }
834		937
835	This function takes a code block as argument, that is, one or more	938	This operator takes a code block as argument, that is, one or more
836	statements enclosed by braces.	939	statements enclosed by braces.
837		940
838	The trick is that this code block is only evaluated once - future calls	941	The trick is that this code block is only evaluated when the outcome
839	will simply return the original image (yes, it should only be used with	942	changes - on other calls the C<keep> simply returns the image it computed
840	images).	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.
841		946
842	This can be extremely useful to avoid redoing the same slow operations	947	This can be extremely useful to avoid redoing slow operations - for
843	again and again- for example, if your background expression takes the root	948	example, if your background expression takes the root background, blurs it
844	background, blurs it and then root-aligns it it would have to blur the	949	and then root-aligns it it would have to blur the root background on every
845	root background on every window move or resize.	950	window move or resize.
		951
		952	Another example is C<load>, which can be quite slow.
846		953
847	In fact, urxvt itself encloses the whole expression in some kind of	954	In fact, urxvt itself encloses the whole expression in some kind of
848	C<once> block so it only is reevaluated as required.	955	C<keep> block so it only is reevaluated as required.
849		956
850	Putting the blur into a C<once> block will make sure the blur is only done	957	Putting the blur into a C<keep> block will make sure the blur is only done
851	once:	958	once, while the C<rootalign> is still done each time the window moves.
852		959
853	rootlign once { blur 10, root }	960	rootalign keep { blur 10, root }
854		961
855	This leaves the question of how to force reevaluation of the block,	962	This leaves the question of how to force reevaluation of the block,
856	in case the root background changes: If expression inside the block	963	in case the root background changes: If expression inside the block
857	is sensitive to some event (root background changes, window geometry	964	is sensitive to some event (root background changes, window geometry
858	changes), then it will be reevaluated automatically as needed.	965	changes), then it will be reevaluated automatically as needed.
859		966
860	=item once_again
861
862	Resets all C<once> block as if they had never been called, i.e. on the
863	next call they will be reevaluated again.
864
865	=cut	967	=cut
866		968
867	sub once(&) {	969	sub keep(&) {
868	my $id = $_[0]+0;	970	my $id = $_[0]+0;
869		971
870	local $frame = $self->{frame_cache}{$id} \|\|= [$frame];	972	local $frame = $self->{frame_cache}{$id} \|\|= [$frame];
871		973
872	unless ($frame->[FR_CACHE]) {	974	unless ($frame->[FR_CACHE]) {
…		…
879	# clear this frame cache, also for all parents	981	# clear this frame cache, also for all parents
880	for (my $frame = $frame; $frame; $frame = $frame->[0]) {	982	for (my $frame = $frame; $frame; $frame = $frame->[0]) {
881	undef $frame->[FR_CACHE];	983	undef $frame->[FR_CACHE];
882	}	984	}
883		985
884	unless ($self->{term}) {
885	use Data::Dump;
886	ddx $frame;
887	exit;
888	}
889
890	$self->recalculate;	986	$self->recalculate;
891	});	987	});
892	};	988	};
893		989
894	# in scalar context we always return the first original result, which	990	# in scalar context we always return the first original result, which
…		…
896	wantarray	992	wantarray
897	? @{ $frame->[FR_CACHE] }	993	? @{ $frame->[FR_CACHE] }
898	: $frame->[FR_CACHE][0]	994	: $frame->[FR_CACHE][0]
899	}	995	}
900		996
901	sub once_again() {	997	# sub keep_clear() {
902	delete $self->{frame_cache};	998	# delete $self->{frame_cache};
903	}	999	# }
904		1000
905	=back	1001	=back
906		1002
907	=cut	1003	=cut
908		1004
…		…
921		1017
922	# compiles a parsed expression	1018	# compiles a parsed expression
923	sub set_expr {	1019	sub set_expr {
924	my ($self, $expr) = @_;	1020	my ($self, $expr) = @_;
925		1021
926	$self->{root} = [];	1022	$self->{root} = []; # the outermost frame
927	$self->{expr} = $expr;	1023	$self->{expr} = $expr;
928	$self->recalculate;	1024	$self->recalculate;
929	}	1025	}
930		1026
931	# takes a hash of sensitivity indicators and installs watchers	1027	# takes a hash of sensitivity indicators and installs watchers
…		…
993		1089
994	# set environment to evaluate user expression	1090	# set environment to evaluate user expression
995		1091
996	local $self = $arg_self;	1092	local $self = $arg_self;
997	local $HOME = $ENV{HOME};	1093	local $HOME = $ENV{HOME};
998	local $frame = [];	1094	local $frame = $self->{root};
999		1095
1000	($x, $y, $w, $h) = $self->background_geometry ($self->{border});	1096	($x, $y, $w, $h) = $self->background_geometry ($self->{border});
1001		1097
1002	# evaluate user expression	1098	# evaluate user expression
1003		1099

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Comparing rxvt-unicode/src/perl/background (file contents): Revision 1.63 by root, Tue Jun 19 18:17:56 2012 UTC vs. Revision 1.81 by sf-exg, Wed Oct 24 11:20:28 2012 UTC

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Comparing rxvt-unicode/src/perl/background (file contents):
Revision 1.63 by root, Tue Jun 19 18:17:56 2012 UTC vs.
Revision 1.81 by sf-exg, Wed Oct 24 11:20:28 2012 UTC