Many fonts include glyphs for the basic ASCII characters in addition to the characters of the writing system they are primarily intended to support.

So whether you see characters in Sinhalese script or Latin characters depends on what text you type to be displayed in the font.

Sinhala MN, I see, is one of the standard fonts included with OS X 10.6 and greater.

Just copy and paste Sinhalese text and it should be displayed correctly (or at least the characters should be sinhalese; if your software cannot handle indic script, the characters may come out in the wrong order).

I just checked and Sinhala MN on my mac is an AAT font. I don't know if Illustrator supports AAT fonts (for which ligatures, reorderings etc. are performed by finite state machines).

AFAIK none of the Adobe Apps support AAT.

André

First time poster. Little late to the party, but just tested Sinhala on Illustrator, Photoshop and Indesign (CC 2014) on Mavericks, and it displays correctly. But you have to enable Adobe Word Ready Paragraph Composer on Indesign, Show Indic Options on Illustrator and Middle East and South Asian on Photoshop. See attached sample.

It is my feeling the text should more likely look like this (on OS X 10.9.4 with textedit) Here is the text itself: විකිපීඩියා, නිදහස් විශ්වකෝෂය වෙතින් and now the textedit rendering;

You are correct Michel. I guess I posted too soon. When I try on Windows 8.1 using Iskoola Pota, it resembles the original.

You could try the fonts on the ICTA (Information and Communication Technology Agency of Sri Lanka) site: Stylized Sinhala Unicode Fonts. They appear to be opentype fonts and are likely to behave better with Adobe products than AAT fonts. I tried WARNA.ttf. It does not work with textedit. Here is what I get with XeLaTeX.

To select it, I had to call it "ICTA Large Font". I don't know where the system finds that name; I had to use the command ftxinstalledfonts to find that. Here it the trace of execution in a terminal window:

% ftxinstalledfonts -f -l | grep -i warna
824 ICTA Large Font /Library/Fonts/1090_WARNA.ttf

Here is the XeLaTeX source code

\documentclass{article}
\usepackage{fontspec}
\setmainfont{ICTA Large Font}
\begin{document}
විකිපීඩියා, නිදහස් විශ්වකෝෂය වෙතින්
\end{document}

Weird!

Correction: if I replace "ICTA Large Font" by WARNA in setmainfont, XeLaTeX actually takes it. I just don't see WARNA listed in the fonts when I use TextEdit which only knows about "ICTA Large Font" but can't render it properly.

There's also Bhashitha and Malithi that seem to work: http://www.locallanguages.lk/sinhala_unicode_converters

I don't know the sinhala script nor where to find tests. The font Bhashitha looks interesting because it contains both AAT and opentype tables; Malithi contains only opentype tables. Both fonts may work fine with Adobe applications but Bhashitha appears to also work with TextEdit. Here is a grab from textedit; I just used the sequence of characters වෙතින්.

As you can see the first two characters are not reordered by TextEdit with Malithi as they are with Bhashitha and Sinhala MN. Any further comment should be made by someone that knows the fonts and the language or at least the Sinhala script.