Change font size for a TextView widget in a running Gtk3 Perl app - perl

Question

I'm trying to modify the font size, in a TextView widget, in a running Perl application and I'm having a difficult time of it. Here's one of my attempts(the relevant code is in the function setFontSize).
#! /usr/bin/env perl
use feature qw(state);
use local::lib;
use warnings;
use strict;
use utf8;
use constant MAX_FONT_SIZE => 200;
use constant MIN_FONT_SIZE => 12;
use constant FONT_UNIT => 4;
use Glib qw(TRUE FALSE);
use Gtk3 qw(init);
use Pango;
sub killKey {
my ($object, $event) = #_;
my $c = lc chr ($event->keyval);
Gtk3->main_quit if $c eq 'q';
FALSE;
}
sub setFontSize {
my ($tView, $font_size) = #_;
my $pCont = $tView->get_pango_context();
my $fDescr = $pCont->get_font_description();
$fDescr->set_absolute_size($font_size * Pango::SCALE);
my $buf = $tView->get_buffer();
my $end = $buf->get_end_iter();
my $start = $buf->get_start_iter();
my $str = $buf->get_text($start, $end, TRUE);
my $newBuf = Gtk3::TextBuffer->new();
$newBuf->set_text($str);
#$buf->set_text($buf->get_text($start, $end, TRUE), -1);
$tView->set_buffer($newBuf);
STDOUT->print("called: ", $fDescr->to_string(),"\n");
# {
# no strict "refs";
#
# for my $elem (sort keys %{ref($fDescr)."::"}) {
# STDOUT->print("${elem}\n");
# }
# }
}
sub catchScroll {
my ($object, $event, $tView) = #_;
state $font_size = 40;
my $dir = $event->direction;
my ($ctrl, $mod) = #{$event->state};
if ($ctrl eq q<control-mask> && $mod eq q<mod2-mask>) {
if ($dir eq q<up>) {
$font_size += FONT_UNIT if $font_size < MAX_FONT_SIZE;
setFontSize($tView, $font_size);
return FALSE;
}elsif ($dir eq q<down>) {
$font_size -= FONT_UNIT if $font_size > MIN_FONT_SIZE;
setFontSize($tView, $font_size);
return FALSE;
}
}
FALSE;
}
my $window = Gtk3::Window->new(q<toplevel>);
my $scrWin = Gtk3::ScrolledWindow->new();
my $tView = Gtk3::TextView->new();
my $provider = Gtk3::CssProvider->new();
$provider->load_from_path("the.css");
my $style = $tView->get_style_context();
$style->add_provider($provider, 600);
my $str = qx(perldoc -T -t -f split 2>&1);
my $buf = $tView->get_buffer();
$buf->set_text($str);
my $sIter = $buf->get_start_iter();
$buf->place_cursor($sIter);
#$tView->set_editable(FALSE);
$window->add_events(q<GDK_KEY_PRESS_MASK>);
$window->add_events(q<GDK_SCROLL_MASK>);
$window->signal_connect(delete_event => sub{Gtk3->main_quit; FALSE});
$window->signal_connect(key_press_event => \&killKey);
$window->signal_connect(scroll_event => \&catchScroll, $tView);
$window->set_border_width(0);
$window->fullscreen();
$window->set_decorated(FALSE);
$scrWin->add($tView);
$window->add($scrWin);
$window->show_all;
Gtk3->main;
I can hack the font values from the provider and it works perfectly... Kind of makes you wonder why the Gtk3 folks don't have that functionality available for these types of problems.
the.css
text {
background-color: rgb(0,0,0);
color: rgb(0, 255, 0);
}
textview {
font-size: 40px;
}
The final version: I added CSS::Tiny to handle the css in provider and added functionality to freeze the vertical scroll bar while I modify the font size with Ctrl+mouse wheel.
#! /usr/bin/env perl
use feature qw(state);
use warnings;
use strict;
use utf8;
use constant MAX_FONT_SIZE => 200;
use constant MIN_FONT_SIZE => 20;
use constant FONT_UNIT => 4;
use constant FONT_START_SIZE => 40;
use CSS::Tiny;
use Glib qw(TRUE FALSE);
use Gtk3 qw(init);
sub killKey {
my ($object, $event) = #_;
my $c = lc chr ($event->keyval);
Gtk3->main_quit if $c eq 'q';
}
sub changeFontSize {
my ($style, $provider, $font_size) = #_;
my $cssStr = $provider->to_string();
my $css = CSS::Tiny->new();
$css = CSS::Tiny->read_string($cssStr);
$css->{textview}->{q<font-size>} = "${font_size}px";
$style->remove_provider($provider);
$provider = Gtk3::CssProvider->new();
$provider->load_from_data($css->write_string());
$style->add_provider($provider, 600);
}
sub catchScroll {
my ($object, $event, $data) = #_;
my ($style, $provider, $vadj) = #{$data};
my ($ctrl, $mod) = #{$event->state};
my $dir = $event->direction;
my $retval = Gtk3::get_current_event();
state $font_size = FONT_START_SIZE;
if ($ctrl eq q<control-mask> && $mod eq q<mod2-mask>) {
if ($dir eq q<up>) {
$font_size += FONT_UNIT if $font_size < MAX_FONT_SIZE;
changeFontSize($style, $provider, $font_size);
}elsif ($dir eq q<down>) {
$font_size -= FONT_UNIT if $font_size > MIN_FONT_SIZE;
changeFontSize($style, $provider, $font_size);
}else {
}
$vadj->set_value(0.0);
}
FALSE;
}
my $window = Gtk3::Window->new(q<toplevel>);
my $scrWin = Gtk3::ScrolledWindow->new();
my $tView = Gtk3::TextView->new();
my $provider = Gtk3::CssProvider->new();
$provider->load_from_path(q<the.css>);
my $style = $tView->get_style_context();
$style->add_provider($provider, 600);
my $str = qx(perldoc -T -t -f split 2>&1);
my $buf = $tView->get_buffer();
$buf->set_text($str);
my $sIter = $buf->get_start_iter();
$buf->place_cursor($sIter);
$tView->set_editable(FALSE);
$window->add_events(q<GDK_KEY_PRESS_MASK>);
$window->add_events(q<GDK_SCROLL_MASK>);
$window->signal_connect(delete_event => sub{Gtk3->main_quit; FALSE});
$window->signal_connect(key_press_event => \&killKey);
$window->signal_connect(
scroll_event =>
\&catchScroll,
[$style, $provider, $scrWin->get_vadjustment()]
);
$window->set_border_width(0);
$window->set_position(q<center>);
$window->fullscreen();
$window->set_decorated(FALSE);
$scrWin->add($tView);
$window->add($scrWin);
$window->show_all();
Gtk3->main;
the.css
text {
background-color: rgb(0, 0, 0);
color: rgb(0, 255, 0);
}
textview {
font-size: 40px;
}

Answer 1

Currently I am not able to make the Pango font description to work either. Seems like it is difficult to find a good documentation of how this is supposed to work :)
Anyway, as a workaround, a CSS provider can be used:
sub setFontSize {
my ($tView, $font_size) = #_;
state $provider;
my $context = $tView->get_style_context();
if ( $provider ) {
$context->remove_provider( $provider );
}
$provider = Gtk3::CssProvider->new();
my $css = sprintf "textview {font-size: %spx;}", $font_size;
$provider->load_from_data($css);
$context->add_provider($provider, Gtk3::STYLE_PROVIDER_PRIORITY_APPLICATION);
}