cross-platform techniques to determine screen dimensions - perl

Question

Is there a good cross-platform way of getting the screen dimensions?
Frequently I do this with PerlTk:
use Tk;
my $mw = MainWindow->new;
my $screen_width = $mw->screenwidth();
my $screen_height = $mw->screenheight();
But it'd be better to not have to load all of Tk just to do this.
This looks like a good X11 specific way of doing these things (GetRootWindow should work for screen dimensions):
Perl: Getting the geometry of a window with X11 WindowID
But I think a cross-platform approach would be better.
Specifically, I'm looking for ways to determine the monitor dimensions in pixels, which is what Tk's screenwidth and screenheight return.

Answer 1

On most POSIX-y systems:
use Curses ();
my $screen_width = $Curses::COLS;
my $screen_height = $Curses::LINES;
These values don't update automatically when the screen is resized.

Answer 2

The best I can see for getting display/screen resolution is to combine OS-specific tools.
On X11 the best bet is probably xrandr† while on Windows it'd be Win32::GUI or Win32::API.
Then wrap it in a sub that checks for the OS (using $^O or such) and selects a tool to use.
(Or of course use a GUI package, like Perl/Tk that OP is using)
† For example
for my $line_out ( qx(xrandr) ) {
#print "--> $line_out";
if ( my ($wt, $ht) = $line_out =~ /^\s+([0-9]+)\s*x\s*([0-9]+)/ ) {
say "Width: $wt, height: $ht";
last;
}
}
There are many ways to parse that, and in principle I recommend using libraries to manage external programs (in particular in order to get their output/errors etc); this is a quick demo.
On my system the xrandr output is like
Screen 0: minimum 8 x 8, current 5040 x 1920, maximum 32767 x 32767
DP-0 connected primary 1920x1200+3120+418 (normal left inverted right x axis y axis) 519mm x 320mm
1920x1200 59.95*+
1600x1200 60.00
1280x1024 75.02 60.02
1152x864 75.00
...
and it keeps going, and then for all displays.
So I pick the top resolution for the first listed one ("primary")