Right-to-Left problem

Hi

i'm using the persian language, and when i want to change the direction to "RTL", it doesn't work.

but when i click the "LTR" button, it's work.

i have to go to source and change the direction to "RTL".

it's like below:

<p>Hello</p>

when i click the "LTR" button it change to:

<p dir="ltr">Hello</p>

but when i click the "RTL" button it change to:

<p>Hello</p>

i want when i click the "RTL" button the direction change to "RTL"

how to fix this?

tnx