/usr/lib/urxvt/perl/background is in rxvt-unicode 9.19-1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572 573 574 575 576 577 578 579 580 581 582 583 584 585 586 587 588 589 590 591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612 613 614 615 616 617 618 619 620 621 622 623 624 625 626 627 628 629 630 631 632 633 634 635 636 637 638 639 640 641 642 643 644 645 646 647 648 649 650 651 652 653 654 655 656 657 658 659 660 661 662 663 664 665 666 667 668 669 670 671 672 673 674 675 676 677 678 679 680 681 682 683 684 685 686 687 688 689 690 691 692 693 694 695 696 697 698 699 700 701 702 703 704 705 706 707 708 709 710 711 712 713 714 715 716 717 718 719 720 721 722 723 724 725 726 727 728 729 730 731 732 733 734 735 736 737 738 739 740 741 742 743 744 745 746 747 748 749 750 751 752 753 754 755 756 757 758 759 760 761 762 763 764 765 766 767 768 769 770 771 772 773 774 775 776 777 778 779 780 781 782 783 784 785 786 787 788 789 790 791 792 793 794 795 796 797 798 799 800 801 802 803 804 805 806 807 808 809 810 811 812 813 814 815 816 817 818 819 820 821 822 823 824 825 826 827 828 829 830 831 832 833 834 835 836 837 838 839 840 841 842 843 844 845 846 847 848 849 850 851 852 853 854 855 856 857 858 859 860 861 862 863 864 865 866 867 868 869 870 871 872 873 874 875 876 877 878 879 880 881 882 883 884 885 886 887 888 889 890 891 892 893 894 895 896 897 898 899 900 901 902 903 904 905 906 907 908 909 910 911 912 913 914 915 916 917 918 919 920 921 922 923 924 925 926 927 928 929 930 931 932 933 934 935 936 937 938 939 940 941 942 943 944 945 946 947 948 949 950 951 952 953 954 955 956 957 958 959 960 961 962 963 964 965 966 967 968 969 970 971 972 973 974 975 976 977 978 979 980 981 982 983 984 985 986 987 988 989 990 991 992 993 994 995 996 997 998 999 1000 1001 1002 1003 1004 1005 1006 1007 1008 1009 1010 1011 1012 1013 1014 1015 1016 1017 1018 1019 1020 1021 1022 1023 1024 1025 1026 1027 1028 1029 1030 1031 1032 1033 1034 1035 1036 1037 1038 1039 1040 1041 1042 1043 1044 1045 1046 1047 1048 1049 1050 1051 1052 1053 1054 1055 1056 1057 1058 1059 1060 1061 1062 1063 1064 1065 1066 1067 1068 1069 1070 1071 1072 1073 1074 1075 1076 1077 1078 1079 1080 1081 1082 1083 1084 1085 1086 1087 1088 1089 1090 1091 1092 1093 1094 1095 1096 1097 1098 1099 1100 1101 1102 1103 1104 1105 1106 1107 1108 1109 1110 1111 1112 1113 1114 1115 1116 1117 1118 1119 1120 1121 1122 1123 1124 1125 1126 1127 1128 1129 1130 1131 1132 1133 1134 1135 1136 1137 1138 1139 1140 1141 1142 1143 1144 1145 1146 1147 1148 1149 1150 1151 1152 1153 1154 1155 1156 1157 1158 1159 1160 1161 1162 1163 1164 1165 1166 1167 1168 1169 1170 1171 1172 1173 1174 1175 1176 1177 1178 1179 1180 1181 1182 1183 1184 1185 1186 1187 1188 1189 1190 1191 1192 1193 1194 1195 1196 1197 1198 1199 1200 1201 1202 1203 1204 1205 1206 1207 1208 1209 1210 | #! perl
#:META:X_RESOURCE:%.expr:string:background expression
#:META:X_RESOURCE:%.border:boolean:respect the terminal border
#:META:X_RESOURCE:%.interval:seconds:minimum time between updates
=head1 NAME
background - manage terminal background
=head1 SYNOPSIS
urxvt --background-expr 'background expression'
--background-border
--background-interval seconds
=head1 QUICK AND DIRTY CHEAT SHEET
Just load a random jpeg image and tile the background with it without
scaling or anything else:
load "/path/to/img.jpg"
The same, but use mirroring/reflection instead of tiling:
mirror load "/path/to/img.jpg"
Load an image and scale it to exactly fill the terminal window:
scale keep { load "/path/to/img.jpg" }
Implement pseudo-transparency by using a suitably-aligned root pixmap
as window background:
rootalign root
Likewise, but keep a blurred copy:
rootalign keep { blur 10, root }
=head1 DESCRIPTION
This extension manages the terminal background by creating a picture that
is behind the text, replacing the normal background colour.
It does so by evaluating a Perl expression that I<calculates> the image on
the fly, for example, by grabbing the root background or loading a file.
While the full power of Perl is available, the operators have been design
to be as simple as possible.
For example, to load an image and scale it to the window size, you would
use:
urxvt --background-expr 'scale keep { load "/path/to/mybg.png" }'
Or specified as a X resource:
URxvt.background-expr: scale keep { load "/path/to/mybg.png" }
=head1 THEORY OF OPERATION
At startup, just before the window is mapped for the first time, the
expression is evaluated and must yield an image. The image is then
extended as necessary to cover the whole terminal window, and is set as a
background pixmap.
If the image contains an alpha channel, then it will be used as-is in
visuals that support alpha channels (for example, for a compositing
manager). In other visuals, the terminal background colour will be used to
replace any transparency.
When the expression relies, directly or indirectly, on the window size,
position, the root pixmap, or a timer, then it will be remembered. If not,
then it will be removed.
If any of the parameters that the expression relies on changes (when the
window is moved or resized, its position or size changes; when the root
pixmap is replaced by another one the root background changes; or when the
timer elapses), then the expression will be evaluated again.
For example, an expression such as C<scale keep { load "$HOME/mybg.png"
}> scales the image to the window size, so it relies on the window size
and will be reevaluated each time it is changed, but not when it moves for
example. That ensures that the picture always fills the terminal, even
after its size changes.
=head2 EXPRESSIONS
Expressions are normal Perl expressions, in fact, they are Perl blocks -
which means you could use multiple lines and statements:
scale keep {
again 3600;
if (localtime now)[6]) {
return load "$HOME/weekday.png";
} else {
return load "$HOME/sunday.png";
}
}
This inner expression is evaluated once per hour (and whenever the
terminal window is resized). It sets F<sunday.png> as background on
Sundays, and F<weekday.png> on all other days.
Fortunately, we expect that most expressions will be much simpler, with
little Perl knowledge needed.
Basically, you always start with a function that "generates" an image
object, such as C<load>, which loads an image from disk, or C<root>, which
returns the root window background image:
load "$HOME/mypic.png"
The path is usually specified as a quoted string (the exact rules can be
found in the L<perlop> manpage). The F<$HOME> at the beginning of the
string is expanded to the home directory.
Then you prepend one or more modifiers or filtering expressions, such as
C<scale>:
scale load "$HOME/mypic.png"
Just like a mathematical expression with functions, you should read these
expressions from right to left, as the C<load> is evaluated first, and
its result becomes the argument to the C<scale> function.
Many operators also allow some parameters preceding the input image
that modify its behaviour. For example, C<scale> without any additional
arguments scales the image to size of the terminal window. If you specify
an additional argument, it uses it as a scale factor (multiply by 100 to
get a percentage):
scale 2, load "$HOME/mypic.png"
This enlarges the image by a factor of 2 (200%). As you can see, C<scale>
has now two arguments, the C<200> and the C<load> expression, while
C<load> only has one argument. Arguments are separated from each other by
commas.
Scale also accepts two arguments, which are then separate factors for both
horizontal and vertical dimensions. For example, this halves the image
width and doubles the image height:
scale 0.5, 2, load "$HOME/mypic.png"
IF you try out these expressions, you might suffer from some sluggishness,
because each time the terminal is resized, it loads the PNG image again
and scales it. Scaling is usually fast (and unavoidable), but loading the
image can be quite time consuming. This is where C<keep> comes in handy:
scale 0.5, 2, keep { load "$HOME/mypic.png" }
The C<keep> operator executes all the statements inside the braces only
once, or when it thinks the outcome might change. In other cases it
returns the last value computed by the brace block.
This means that the C<load> is only executed once, which makes it much
faster, but also means that more memory is being used, because the loaded
image must be kept in memory at all times. In this expression, the
trade-off is likely worth it.
But back to effects: Other effects than scaling are also readily
available, for example, you can tile the image to fill the whole window,
instead of resizing it:
tile keep { load "$HOME/mypic.png" }
In fact, images returned by C<load> are in C<tile> mode by default, so the
C<tile> operator is kind of superfluous.
Another common effect is to mirror the image, so that the same edges
touch:
mirror keep { load "$HOME/mypic.png" }
Another common background expression is:
rootalign root
This one first takes a snapshot of the screen background image, and then
moves it to the upper left corner of the screen (as opposed to the upper
left corner of the terminal window)- the result is pseudo-transparency:
the image seems to be static while the window is moved around.
=head2 COLOUR SPECIFICATIONS
Whenever an operator expects a "colour", then this can be specified in one
of two ways: Either as string with an X11 colour specification, such as:
"red" # named colour
"#f00" # simple rgb
"[50]red" # red with 50% alpha
"TekHVC:300/50/50" # anything goes
OR as an array reference with one, three or four components:
[0.5] # 50% gray, 100% alpha
[0.5, 0, 0] # dark red, no green or blur, 100% alpha
[0.5, 0, 0, 0.7] # same with explicit 70% alpha
=head2 CACHING AND SENSITIVITY
Since some operations (such as C<load> and C<blur>) can take a long time,
caching results can be very important for a smooth operation. Caching can
also be useful to reduce memory usage, though, for example, when an image
is cached by C<load>, it could be shared by multiple terminal windows
running inside urxvtd.
=head3 C<keep { ... }> caching
The most important way to cache expensive operations is to use C<keep {
... }>. The C<keep> operator takes a block of multiple statements enclosed
by C<{}> and keeps the return value in memory.
An expression can be "sensitive" to various external events, such as
scaling or moving the window, root background changes and timers. Simply
using an expression (such as C<scale> without parameters) that depends on
certain changing values (called "variables"), or using those variables
directly, will make an expression sensitive to these events - for example,
using C<scale> or C<TW> will make the expression sensitive to the terminal
size, and thus to resizing events.
When such an event happens, C<keep> will automatically trigger a
reevaluation of the whole expression with the new value of the expression.
C<keep> is most useful for expensive operations, such as C<blur>:
rootalign keep { blur 20, root }
This makes a blurred copy of the root background once, and on subsequent
calls, just root-aligns it. Since C<blur> is usually quite slow and
C<rootalign> is quite fast, this trades extra memory (for the cached
blurred pixmap) with speed (blur only needs to be redone when root
changes).
=head3 C<load> caching
The C<load> operator itself does not keep images in memory, but as long as
the image is still in memory, C<load> will use the in-memory image instead
of loading it freshly from disk.
That means that this expression:
keep { load "$HOME/path..." }
Not only caches the image in memory, other terminal instances that try to
C<load> it can reuse that in-memory copy.
=head1 REFERENCE
=head2 COMMAND LINE SWITCHES
=over 4
=item --background-expr perl-expression
Specifies the Perl expression to evaluate.
=item --background-border
By default, the expression creates an image that fills the full window,
overwriting borders and any other areas, such as the scrollbar.
Specifying this flag changes the behaviour, so that the image only
replaces the background of the character area.
=item --background-interval seconds
Since some operations in the underlying XRender extension can effectively
freeze your X-server for prolonged time, this extension enforces a minimum
time between updates, which is normally about 0.1 seconds.
If you want to do updates more often, you can decrease this safety
interval with this switch.
=back
=cut
our %_IMG_CACHE;
our $HOME;
our ($self, $frame);
our ($x, $y, $w, $h, $focus);
# enforce at least this interval between updates
our $MIN_INTERVAL = 6/59.951;
{
package urxvt::bgdsl; # background language
sub FR_PARENT() { 0 } # parent frame, if any - must be #0
sub FR_CACHE () { 1 } # cached values
sub FR_AGAIN () { 2 } # what this expr is sensitive to
sub FR_STATE () { 3 } # watchers etc.
use List::Util qw(min max sum shuffle);
=head2 PROVIDERS/GENERATORS
These functions provide an image, by loading it from disk, grabbing it
from the root screen or by simply generating it. They are used as starting
points to get an image you can play with.
=over 4
=item load $path
Loads the image at the given C<$path>. The image is set to plane tiling
mode.
If the image is already in memory (e.g. because another terminal instance
uses it), then the in-memory copy is returned instead.
=item load_uc $path
Load uncached - same as load, but does not cache the image, which means it
is I<always> loaded from the filesystem again, even if another copy of it
is in memory at the time.
=cut
sub load_uc($) {
$self->new_img_from_file ($_[0])
}
sub load($) {
my ($path) = @_;
$_IMG_CACHE{$path} || do {
my $img = load_uc $path;
Scalar::Util::weaken ($_IMG_CACHE{$path} = $img);
$img
}
}
=item root
Returns the root window pixmap, that is, hopefully, the background image
of your screen.
This function makes your expression root sensitive, that means it will be
reevaluated when the bg image changes.
=cut
sub root() {
$frame->[FR_AGAIN]{rootpmap} = 1;
$self->new_img_from_root
}
=item solid $colour
=item solid $width, $height, $colour
Creates a new image and completely fills it with the given colour. The
image is set to tiling mode.
If C<$width> and C<$height> are omitted, it creates a 1x1 image, which is
useful for solid backgrounds or for use in filtering effects.
=cut
sub solid($;$$) {
my $colour = pop;
my $img = $self->new_img (urxvt::PictStandardARGB32, 0, 0, $_[0] || 1, $_[1] || 1);
$img->fill ($colour);
$img
}
=item clone $img
Returns an exact copy of the image. This is useful if you want to have
multiple copies of the same image to apply different effects to.
=cut
sub clone($) {
$_[0]->clone
}
=item merge $img ...
Takes any number of images and merges them together, creating a single
image containing them all. The tiling mode of the first image is used as
the tiling mode of the resulting image.
This function is called automatically when an expression returns multiple
images.
=cut
sub merge(@) {
return $_[0] unless $#_;
# rather annoyingly clumsy, but optimisation is for another time
my $x0 = +1e9;
my $y0 = +1e9;
my $x1 = -1e9;
my $y1 = -1e9;
for (@_) {
my ($x, $y, $w, $h) = $_->geometry;
$x0 = $x if $x0 > $x;
$y0 = $y if $y0 > $y;
$x += $w;
$y += $h;
$x1 = $x if $x1 < $x;
$y1 = $y if $y1 < $y;
}
my $base = $self->new_img (urxvt::PictStandardARGB32, $x0, $y0, $x1 - $x0, $y1 - $y0);
$base->repeat_mode ($_[0]->repeat_mode);
$base->fill ([0, 0, 0, 0]);
$base->draw ($_)
for @_;
$base
}
=back
=head2 TILING MODES
The following operators modify the tiling mode of an image, that is, the
way that pixels outside the image area are painted when the image is used.
=over 4
=item tile $img
Tiles the whole plane with the image and returns this new image - or in
other words, it returns a copy of the image in plane tiling mode.
Example: load an image and tile it over the background, without
resizing. The C<tile> call is superfluous because C<load> already defaults
to tiling mode.
tile load "mybg.png"
=item mirror $img
Similar to tile, but reflects the image each time it uses a new copy, so
that top edges always touch top edges, right edges always touch right
edges and so on (with normal tiling, left edges always touch right edges
and top always touch bottom edges).
Example: load an image and mirror it over the background, avoiding sharp
edges at the image borders at the expense of mirroring the image itself
mirror load "mybg.png"
=item pad $img
Takes an image and modifies it so that all pixels outside the image area
become transparent. This mode is most useful when you want to place an
image over another image or the background colour while leaving all
background pixels outside the image unchanged.
Example: load an image and display it in the upper left corner. The rest
of the space is left "empty" (transparent or whatever your compositor does
in alpha mode, else background colour).
pad load "mybg.png"
=item extend $img
Extends the image over the whole plane, using the closest pixel in the
area outside the image. This mode is mostly useful when you use more complex
filtering operations and want the pixels outside the image to have the
same values as the pixels near the edge.
Example: just for curiosity, how does this pixel extension stuff work?
extend move 50, 50, load "mybg.png"
=cut
sub pad($) {
my $img = $_[0]->clone;
$img->repeat_mode (urxvt::RepeatNone);
$img
}
sub tile($) {
my $img = $_[0]->clone;
$img->repeat_mode (urxvt::RepeatNormal);
$img
}
sub mirror($) {
my $img = $_[0]->clone;
$img->repeat_mode (urxvt::RepeatReflect);
$img
}
sub extend($) {
my $img = $_[0]->clone;
$img->repeat_mode (urxvt::RepeatPad);
$img
}
=back
=head2 VARIABLE VALUES
The following functions provide variable data such as the terminal window
dimensions. They are not (Perl-) variables, they just return stuff that
varies. Most of them make your expression sensitive to some events, for
example using C<TW> (terminal width) means your expression is evaluated
again when the terminal is resized.
=over 4
=item TX
=item TY
Return the X and Y coordinates of the terminal window (the terminal
window is the full window by default, and the character area only when in
border-respect mode).
Using these functions makes your expression sensitive to window moves.
These functions are mainly useful to align images to the root window.
Example: load an image and align it so it looks as if anchored to the
background (that's exactly what C<rootalign> does btw.):
move -TX, -TY, keep { load "mybg.png" }
=item TW
=item TH
Return the width (C<TW>) and height (C<TH>) of the terminal window (the
terminal window is the full window by default, and the character area only
when in border-respect mode).
Using these functions makes your expression sensitive to window resizes.
These functions are mainly useful to scale images, or to clip images to
the window size to conserve memory.
Example: take the screen background, clip it to the window size, blur it a
bit, align it to the window position and use it as background.
clip move -TX, -TY, keep { blur 5, root }
=item FOCUS
Returns a boolean indicating whether the terminal window has keyboard
focus, in which case it returns true.
Using this function makes your expression sensitive to focus changes.
A common use case is to fade the background image when the terminal loses
focus, often together with the C<-fade> command line option. In fact,
there is a special function for just that use case: C<focus_fade>.
Example: use two entirely different background images, depending on
whether the window has focus.
FOCUS ? keep { load "has_focus.jpg" } : keep { load "no_focus.jpg" }
=cut
sub TX () { $frame->[FR_AGAIN]{position} = 1; $x }
sub TY () { $frame->[FR_AGAIN]{position} = 1; $y }
sub TW () { $frame->[FR_AGAIN]{size} = 1; $w }
sub TH () { $frame->[FR_AGAIN]{size} = 1; $h }
sub FOCUS() { $frame->[FR_AGAIN]{focus} = 1; $focus }
=item now
Returns the current time as (fractional) seconds since the epoch.
Using this expression does I<not> make your expression sensitive to time,
but the next two functions do.
=item again $seconds
When this function is used the expression will be reevaluated again in
C<$seconds> seconds.
Example: load some image and rotate it according to the time of day (as if it were
the hour pointer of a clock). Update this image every minute.
again 60;
rotate 50, 50, (now % 86400) * -72 / 8640, scale keep { load "myclock.png" }
=item counter $seconds
Like C<again>, but also returns an increasing counter value, starting at
0, which might be useful for some simple animation effects.
=cut
sub now() { urxvt::NOW }
sub again($) {
$frame->[FR_AGAIN]{time} = $_[0];
}
sub counter($) {
$frame->[FR_AGAIN]{time} = $_[0];
$frame->[FR_STATE]{counter} + 0
}
=back
=head2 SHAPE CHANGING OPERATORS
The following operators modify the shape, size or position of the image.
=over 4
=item clip $img
=item clip $width, $height, $img
=item clip $x, $y, $width, $height, $img
Clips an image to the given rectangle. If the rectangle is outside the
image area (e.g. when C<$x> or C<$y> are negative) or the rectangle is
larger than the image, then the tiling mode defines how the extra pixels
will be filled.
If C<$x> and C<$y> are missing, then C<0> is assumed for both.
If C<$width> and C<$height> are missing, then the window size will be
assumed.
Example: load an image, blur it, and clip it to the window size to save
memory.
clip keep { blur 10, load "mybg.png" }
=cut
sub clip($;$$;$$) {
my $img = pop;
my $h = pop || TH;
my $w = pop || TW;
$img->sub_rect ($_[0], $_[1], $w, $h)
}
=item scale $img
=item scale $size_factor, $img
=item scale $width_factor, $height_factor, $img
Scales the image by the given factors in horizontal
(C<$width>) and vertical (C<$height>) direction.
If only one factor is given, it is used for both directions.
If no factors are given, scales the image to the window size without
keeping aspect.
=item resize $width, $height, $img
Resizes the image to exactly C<$width> times C<$height> pixels.
=item fit $img
=item fit $width, $height, $img
Fits the image into the given C<$width> and C<$height> without changing
aspect, or the terminal size. That means it will be shrunk or grown until
the whole image fits into the given area, possibly leaving borders.
=item cover $img
=item cover $width, $height, $img
Similar to C<fit>, but shrinks or grows until all of the area is covered
by the image, so instead of potentially leaving borders, it will cut off
image data that doesn't fit.
=cut
sub scale($;$;$) {
my $img = pop;
@_ == 2 ? $img->scale ($_[0] * $img->w, $_[1] * $img->h)
: @_ ? $img->scale ($_[0] * $img->w, $_[0] * $img->h)
: $img->scale (TW, TH)
}
sub resize($$$) {
my $img = pop;
$img->scale ($_[0], $_[1])
}
sub fit($;$$) {
my $img = pop;
my $w = ($_[0] || TW) / $img->w;
my $h = ($_[1] || TH) / $img->h;
scale +(min $w, $h), $img
}
sub cover($;$$) {
my $img = pop;
my $w = ($_[0] || TW) / $img->w;
my $h = ($_[1] || TH) / $img->h;
scale +(max $w, $h), $img
}
=item move $dx, $dy, $img
Moves the image by C<$dx> pixels in the horizontal, and C<$dy> pixels in
the vertical.
Example: move the image right by 20 pixels and down by 30.
move 20, 30, ...
=item align $xalign, $yalign, $img
Aligns the image according to a factor - C<0> means the image is moved to
the left or top edge (for C<$xalign> or C<$yalign>), C<0.5> means it is
exactly centered and C<1> means it touches the right or bottom edge.
Example: remove any visible border around an image, center it vertically but move
it to the right hand side.
align 1, 0.5, pad $img
=item center $img
=item center $width, $height, $img
Centers the image, i.e. the center of the image is moved to the center of
the terminal window (or the box specified by C<$width> and C<$height> if
given).
Example: load an image and center it.
center keep { pad load "mybg.png" }
=item rootalign $img
Moves the image so that it appears glued to the screen as opposed to the
window. This gives the illusion of a larger area behind the window. It is
exactly equivalent to C<move -TX, -TY>, that is, it moves the image to the
top left of the screen.
Example: load a background image, put it in mirror mode and root align it.
rootalign keep { mirror load "mybg.png" }
Example: take the screen background and align it, giving the illusion of
transparency as long as the window isn't in front of other windows.
rootalign root
=cut
sub move($$;$) {
my $img = pop->clone;
$img->move ($_[0], $_[1]);
$img
}
sub align($;$$) {
my $img = pop;
move $_[0] * (TW - $img->w),
$_[1] * (TH - $img->h),
$img
}
sub center($;$$) {
my $img = pop;
my $w = $_[0] || TW;
my $h = $_[1] || TH;
move 0.5 * ($w - $img->w), 0.5 * ($h - $img->h), $img
}
sub rootalign($) {
move -TX, -TY, $_[0]
}
=item rotate $center_x, $center_y, $degrees, $img
Rotates the image clockwise by C<$degrees> degrees, around the point at
C<$center_x> and C<$center_y> (specified as factor of image width/height).
Example: rotate the image by 90 degrees around its center.
rotate 0.5, 0.5, 90, keep { load "$HOME/mybg.png" }
=cut
sub rotate($$$$) {
my $img = pop;
$img->rotate (
$_[0] * ($img->w + $img->x),
$_[1] * ($img->h + $img->y),
$_[2] * (3.14159265 / 180),
)
}
=back
=head2 COLOUR MODIFICATIONS
The following operators change the pixels of the image.
=over 4
=item tint $color, $img
Tints the image in the given colour.
Example: tint the image red.
tint "red", load "rgb.png"
Example: the same, but specify the colour by component.
tint [1, 0, 0], load "rgb.png"
=cut
sub tint($$) {
$_[1]->tint ($_[0])
}
=item shade $factor, $img
Shade the image by the given factor.
=cut
sub shade($$) {
$_[1]->shade ($_[0])
}
=item contrast $factor, $img
=item contrast $r, $g, $b, $img
=item contrast $r, $g, $b, $a, $img
Adjusts the I<contrast> of an image.
The first form applies a single C<$factor> to red, green and blue, the
second form applies separate factors to each colour channel, and the last
form includes the alpha channel.
Values from 0 to 1 lower the contrast, values higher than 1 increase the
contrast.
Due to limitations in the underlying XRender extension, lowering contrast
also reduces brightness, while increasing contrast currently also
increases brightness.
=item brightness $bias, $img
=item brightness $r, $g, $b, $img
=item brightness $r, $g, $b, $a, $img
Adjusts the brightness of an image.
The first form applies a single C<$bias> to red, green and blue, the
second form applies separate biases to each colour channel, and the last
form includes the alpha channel.
Values less than 0 reduce brightness, while values larger than 0 increase
it. Useful range is from -1 to 1 - the former results in a black, the
latter in a white picture.
Due to idiosyncrasies in the underlying XRender extension, biases less
than zero can be I<very> slow.
You can also try the experimental(!) C<muladd> operator.
=cut
sub contrast($$;$$;$) {
my $img = pop;
my ($r, $g, $b, $a) = @_;
($g, $b) = ($r, $r) if @_ < 3;
$a = 1 if @_ < 4;
$img = $img->clone;
$img->contrast ($r, $g, $b, $a);
$img
}
sub brightness($$;$$;$) {
my $img = pop;
my ($r, $g, $b, $a) = @_;
($g, $b) = ($r, $r) if @_ < 3;
$a = 1 if @_ < 4;
$img = $img->clone;
$img->brightness ($r, $g, $b, $a);
$img
}
=item muladd $mul, $add, $img # EXPERIMENTAL
First multiplies the pixels by C<$mul>, then adds C<$add>. This can be used
to implement brightness and contrast at the same time, with a wider value
range than contrast and brightness operators.
Due to numerous bugs in XRender implementations, it can also introduce a
number of visual artifacts.
Example: increase contrast by a factor of C<$c> without changing image
brightness too much.
muladd $c, (1 - $c) * 0.5, $img
=cut
sub muladd($$$) {
$_[2]->muladd ($_[0], $_[1])
}
=item blur $radius, $img
=item blur $radius_horz, $radius_vert, $img
Gaussian-blurs the image with (roughly) C<$radius> pixel radius. The radii
can also be specified separately.
Blurring is often I<very> slow, at least compared or other
operators. Larger blur radii are slower than smaller ones, too, so if you
don't want to freeze your screen for long times, start experimenting with
low values for radius (<5).
=cut
sub blur($$;$) {
my $img = pop;
$img->blur ($_[0], @_ >= 2 ? $_[1] : $_[0])
}
=item focus_fade $img
=item focus_fade $factor, $img
=item focus_fade $factor, $color, $img
Fades the image by the given factor (and colour) when focus is lost (the
same as the C<-fade>/C<-fadecolor> command line options, which also supply
the default values for C<factor> and C<$color>. Unlike with C<-fade>, the
C<$factor> is a real value, not a percentage value (that is, 0..1, not
0..100).
Example: do the right thing when focus fading is requested.
focus_fade load "mybg.jpg";
=cut
sub focus_fade($;$$) {
my $img = pop;
return $img
if FOCUS;
my $fade = @_ >= 1 ? $_[0] : defined $self->resource ("fade") ? $self->resource ("fade") * 0.01 : 0;
my $color = @_ >= 2 ? $_[1] : $self->resource ("color+" . urxvt::Color_fade);
$img = $img->tint ($color) if $color ne "rgb:00/00/00";
$img = $img->muladd (1 - $fade, 0) if $fade;
$img
}
=back
=head2 OTHER STUFF
Anything that didn't fit any of the other categories, even after applying
force and closing our eyes.
=over 4
=item keep { ... }
This operator takes a code block as argument, that is, one or more
statements enclosed by braces.
The trick is that this code block is only evaluated when the outcome
changes - on other calls the C<keep> simply returns the image it computed
previously (yes, it should only be used with images). Or in other words,
C<keep> I<caches> the result of the code block so it doesn't need to be
computed again.
This can be extremely useful to avoid redoing slow operations - for
example, if your background expression takes the root background, blurs it
and then root-aligns it it would have to blur the root background on every
window move or resize.
Another example is C<load>, which can be quite slow.
In fact, urxvt itself encloses the whole expression in some kind of
C<keep> block so it only is reevaluated as required.
Putting the blur into a C<keep> block will make sure the blur is only done
once, while the C<rootalign> is still done each time the window moves.
rootalign keep { blur 10, root }
This leaves the question of how to force reevaluation of the block,
in case the root background changes: If expression inside the block
is sensitive to some event (root background changes, window geometry
changes), then it will be reevaluated automatically as needed.
=cut
sub keep(&) {
my $id = $_[0]+0;
local $frame = $self->{frame_cache}{$id} ||= [$frame];
unless ($frame->[FR_CACHE]) {
$frame->[FR_CACHE] = [ $_[0]() ];
my $self = $self;
my $frame = $frame;
Scalar::Util::weaken $frame;
$self->compile_frame ($frame, sub {
# clear this frame cache, also for all parents
for (my $frame = $frame; $frame; $frame = $frame->[0]) {
undef $frame->[FR_CACHE];
}
$self->recalculate;
});
};
# in scalar context we always return the first original result, which
# is not quite how perl works.
wantarray
? @{ $frame->[FR_CACHE] }
: $frame->[FR_CACHE][0]
}
# sub keep_clear() {
# delete $self->{frame_cache};
# }
=back
=cut
}
sub parse_expr {
my $expr = eval
"sub {\n"
. "package urxvt::bgdsl;\n"
. "#line 0 'background expression'\n"
. "$_[0]\n"
. "}";
die if $@;
$expr
}
# compiles a parsed expression
sub set_expr {
my ($self, $expr) = @_;
$self->{root} = []; # the outermost frame
$self->{expr} = $expr;
$self->recalculate;
}
# takes a hash of sensitivity indicators and installs watchers
sub compile_frame {
my ($self, $frame, $cb) = @_;
my $state = $frame->[urxvt::bgdsl::FR_STATE] ||= {};
my $again = $frame->[urxvt::bgdsl::FR_AGAIN];
# don't keep stuff alive
Scalar::Util::weaken $state;
if ($again->{nested}) {
$state->{nested} = 1;
} else {
delete $state->{nested};
}
if (my $interval = $again->{time}) {
$state->{time} = [$interval, urxvt::timer->new->after ($interval)->interval ($interval)]
if $state->{time}[0] != $interval;
# callback *might* have changed, although we could just rule that out
$state->{time}[1]->cb (sub {
++$state->{counter};
$cb->();
});
} else {
delete $state->{time};
}
if ($again->{position}) {
$state->{position} = $self->on (position_change => $cb);
} else {
delete $state->{position};
}
if ($again->{size}) {
$state->{size} = $self->on (size_change => $cb);
} else {
delete $state->{size};
}
if ($again->{rootpmap}) {
$state->{rootpmap} = $self->on (rootpmap_change => $cb);
} else {
delete $state->{rootpmap};
}
if ($again->{focus}) {
$state->{focus} = $self->on (focus_in => $cb, focus_out => $cb);
} else {
delete $state->{focus};
}
}
# evaluate the current bg expression
sub recalculate {
my ($arg_self) = @_;
# rate limit evaluation
if ($arg_self->{next_refresh} > urxvt::NOW) {
$arg_self->{next_refresh_timer} = urxvt::timer->new->after ($arg_self->{next_refresh} - urxvt::NOW)->cb (sub {
$arg_self->recalculate;
});
return;
}
$arg_self->{next_refresh} = urxvt::NOW + $MIN_INTERVAL;
# set environment to evaluate user expression
local $self = $arg_self;
local $HOME = $ENV{HOME};
local $frame = $self->{root};
($x, $y, $w, $h) = $self->background_geometry ($self->{border});
$focus = $self->focus;
# evaluate user expression
my @img = eval { $self->{expr}->() };
die $@ if $@;
die "background-expr did not return anything.\n" unless @img;
die "background-expr: expected image(s), got something else.\n"
if grep { !UNIVERSAL::isa $_, "urxvt::img" } @img;
my $img = urxvt::bgdsl::merge @img;
$frame->[FR_AGAIN]{size} = 1
if $img->repeat_mode != urxvt::RepeatNormal;
# if the expression is sensitive to external events, prepare reevaluation then
$self->compile_frame ($frame, sub { $arg_self->recalculate });
# clear stuff we no longer need
# unless (%{ $frame->[FR_STATE] }) {
# delete $self->{state};
# delete $self->{expr};
# }
# set background pixmap
$self->set_background ($img, $self->{border});
$self->scr_recolour (0);
$self->want_refresh;
}
sub on_start {
my ($self) = @_;
my $expr = $self->x_resource ("%.expr")
or return;
$self->has_render
or die "background extension needs RENDER extension 0.10 or higher, ignoring background-expr.\n";
$self->set_expr (parse_expr $expr);
$self->{border} = $self->x_resource_boolean ("%.border");
$MIN_INTERVAL = $self->x_resource ("%.interval");
()
}
|