Fix EVR page freeze issue

[saba-ja]

Originating Project/Creator	F Prime
Affected Component	GDS
Affected Architectures(s)	-
Related Issue(s)	-
Has Unit Tests (y/n)	No
Builds Without Errors (y/n)	Yes
Unit Tests Pass (y/n)	NA
Documentation Included (y/n)	Yes

---

Change Description

Current GDS Event page freezes when the number of EVRs in the event table reaches a certain size.
This issue makes the entire webpage irresponsive.

Rationale

The issue is DOM rendering is computationally expensive and having too many HTML elements in the DOM can effect browser's performance. To fix the issue this PR adds lazy loading of EVRs. Events are only added up to a certain number. After the maximum size user has to scroll down to the bottom of the page to load the next group of EVRs. Upon adding the new group the previous EVRs are removed from the DOM.

Testing/Review Recommendations

Manually tested and verified root cause of the slow down is the number of HTML elements and not memory issues.
GDS with issue

Manually verified GDS functionality after the fix. As shown in the video below the EVR table had ~28K EVRs and the page did not show any sign of slow down:
GDS EVR fixed

Functionalities:

• Load next EVR group after scrolling down.
• Load prev EVR group after scrolling up.
• Can use First button to move to the top of the list.
• Can use Last button to move to the bottom of the list.
• Can stay at the bottom when pressing Last button or scrolling down to the last element of the list.
• Will activate auto update when at the end of the list. Shows a green flag to indicate auto update is enabled.
• Shows total size of EVR list.
• Show start and end of current EVR window.

Future Work

NA

[github-actions]

Misspellings found, please review:

• milisecond
• scrollability

To accept these changes, run the following commands from this repository on this branch

pushd $(git rev-parse --show-toplevel)
perl -e '
my $new_expect_file=".github/actions/spelling/expect.txt";
use File::Path qw(make_path);
make_path ".github/actions/spelling";
open FILE, q{<}, $new_expect_file; chomp(my @words = <FILE>); close FILE;
my @add=qw('"milisecond scrollability "');
my %items; @items{@words} = @words x (1); @items{@add} = @add x (1);
@words = sort {lc($a) cmp lc($b)} keys %items;
open FILE, q{>}, $new_expect_file; for my $word (@words) { print FILE "$word\n" if $word =~ /\w/; };
close FILE;'
popd

[github-actions]

Misspellings found, please review:

• bbb
• ccc
• ddd
• eee
• fff
• ggg
• HHH
• jjj
• kkk
• lll
• mmm
• nnn
• ooo
• ppp
• qqq
• rrr
• SUUU
• ttt
• UUU
• VVV
• yyy
• zzz

To accept these changes, run the following commands from this repository on this branch

pushd $(git rev-parse --show-toplevel)
perl -e '
my $new_expect_file=".github/actions/spelling/expect.txt";
use File::Path qw(make_path);
make_path ".github/actions/spelling";
open FILE, q{<}, $new_expect_file; chomp(my @words = <FILE>); close FILE;
my @add=qw('"bbb ccc ddd eee fff ggg HHH jjj kkk lll mmm nnn ooo ppp qqq rrr SUUU ttt UUU VVV yyy zzz "');
my %items; @items{@words} = @words x (1); @items{@add} = @add x (1);
@words = sort {lc($a) cmp lc($b)} keys %items;
open FILE, q{>}, $new_expect_file; for my $word (@words) { print FILE "$word\n" if $word =~ /\w/; };
close FILE;'
popd

[github-actions]

Misspellings found, please review:

• bbb
• ccc
• ddd
• eee
• fff
• ggg
• HHH
• jjj
• kkk
• lll
• mmm
• nnn
• ooo
• ppp
• qqq
• rrr
• SUUU
• ttt
• UUU
• VVV
• yyy
• zzz

To accept these changes, run the following commands from this repository on this branch

pushd $(git rev-parse --show-toplevel)
perl -e '
my $new_expect_file=".github/actions/spelling/expect.txt";
use File::Path qw(make_path);
make_path ".github/actions/spelling";
open FILE, q{<}, $new_expect_file; chomp(my @words = <FILE>); close FILE;
my @add=qw('"bbb ccc ddd eee fff ggg HHH jjj kkk lll mmm nnn ooo ppp qqq rrr SUUU ttt UUU VVV yyy zzz "');
my %items; @items{@words} = @words x (1); @items{@add} = @add x (1);
@words = sort {lc($a) cmp lc($b)} keys %items;
open FILE, q{>}, $new_expect_file; for my $word (@words) { print FILE "$word\n" if $word =~ /\w/; };
close FILE;'
popd

[github-actions]

Misspellings found, please review:

• bbb
• ccc
• ddd
• eee
• ggg
• HHH
• jjj
• kkk
• lll
• mmm
• nnn
• ooo
• ppp
• qqq
• rrr
• SUUU
• ttt
• UUU
• VVV
• yyy
• zzz

To accept these changes, run the following commands from this repository on this branch

pushd $(git rev-parse --show-toplevel)
perl -e '
my $new_expect_file=".github/actions/spelling/expect.txt";
use File::Path qw(make_path);
make_path ".github/actions/spelling";
open FILE, q{<}, $new_expect_file; chomp(my @words = <FILE>); close FILE;
my @add=qw('"bbb ccc ddd eee ggg HHH jjj kkk lll mmm nnn ooo ppp qqq rrr SUUU ttt UUU VVV yyy zzz "');
my %items; @items{@words} = @words x (1); @items{@add} = @add x (1);
@words = sort {lc($a) cmp lc($b)} keys %items;
open FILE, q{>}, $new_expect_file; for my $word (@words) { print FILE "$word\n" if $word =~ /\w/; };
close FILE;'
popd

[LeStarch]

The video really helped!