Combining characters leave remnants if the main character stays the same
after redraw. I have tested with a number of fonts, notably "-fn 9x15",
"-fn xft:FreeMono", "-fn xft:DejaVuSansMono", and
"-fn xft:LiberationMono-Regular". They all behave exactly the same.
The following contrived code illustrates the issue using the keycap combining
char. The keycap is drawn over the final "t" in the string "test". It will
only be removed when that character changes to a character other than "t".
The problem appears to be localized to wide Combining characters, like
those in the "Combining Diacritical Marks for Symbols" range (20DD-20EF).
#!/usr/bin/perl
binmode(STDOUT, ':utf8');
system("clear");
print "\n\n\t\ttest \N{U+20E3}\nPress Enter to continue...\n";
<STDIN>;
system("clear");
print "\n\n\t\ttest \nPress Enter to continue...\n";
<STDIN>;
system("clear");
print "\n\n\t\ttesT \nPress Enter to continue...\n";
<STDIN>;
system("clear");
print "\n\n\t\tteST \n\n";
__END__
Using '-lsp' and '-letsp', the issue can be localized to only the character
overlaid by the combining character (as is their purpose). But, the main
issue continues to exist.
Please note that this doesn't happen with the ucs-fonts (e.g. font choice of
"-fn -Misc-Fixed-Medium-R-Normal--15-140-75-75-C-90-ISO10646-1"), as they use
a smaller negative kerning value to place the keycap over the directly
preceding character. As such, it may be your opinion that this is a font
issue. But, I wanted to bring it up, nonetheless.
Environment:
Arch Linux: current, using AUR rxvt-unicode-256xresources 9.21-1
rxvt-unicode (urxvt) v9.21 - released: 2014-12-31
options:
perl,xft,styles,combining,blink,iso14755,encodings=eu+vn+jp+jp-ext+kr+zh+zh-ext,fade,transparent,tint,pixbuf,XIM,frills,selectionscrolling,wheel,slipwheel,smart-resize,cursorBlink,pointerBlank,scrollbars=plain+rxvt+NeXT+xterm
Thanks.
--
Totten, William David (Bill)
totten @ pobox . com
http://pobox.com/~totten/
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