View source for RTL (Right-to-Left) based GUI

==RTL GUI Overview==

'''What is this about?'''<br>
The latest developmental build of ScummVM now supports an RTL based GUI. The main purpose of this is to adapt to RTL languages such as Hebrew, Arabic, etc.<br>
RTL means Right-To-Left. RTL users read their content beginning from the right and then moving towards the left.

<br>'''In ScummVM'''<br>
If you want to preview how it looks (keep in mind that these will work on the latest developmental branch), you can add a "guiRTL = true" key in the scummvm.ini configuration file to force RTL. Or, you can switch a native RTL language. (Currently, it is only enabled for Hebrew)

<br>'''How does it work?'''<br>
The main constructs to enable RTL, within the code are:<br>
# Main GUI-RTL, which you can check via g_gui.useRTL(). This is currently only enabled for Hebrew, but more languages can be added in GuiManager::setLanguageRTL() (located in gui/gui-manager.cpp) 
# RTL for an individual widget, which is checked via _useRTL (for each GUI object). <br>_useRTL is true by default. This shouldn't be a concern, because it always checks g_gui.useRTL() whenever working in an RTL based GUI.
# Overlaying Offset - this is used in the context of a stacked dialog. More information below.

<br>'''I am adding some things to GUI, I would also like them to support RTL.'''<br>
The following section has some notes that are needed to be kept in mind when designing new items or additions to the GUI - to adapt to RTL also.


==RTL based GUI in code:==
===General notes===
- The mouse coordinates are not calculated differently for RTL based GUI. They are just flipped from the normal GUI, so this shouldn't be a problem when creating new things within the GUI.<br>
- Everything in the normal GUI will basically be flipped around, by calculating the reverse coordinates on the go.<br>

===Stacked Dialogs===
If you are creating a stacked dialog, you will need to do the following things to adapt it for the RTL counterpart:<br>

# Navigate to ThemeLayout.cpp, in <code>ThemeLayoutMain::reflowLayout()</code><br>
# Within there, you'll see a check like <code>if (g_gui.useRTL) then if (_name......)</code><br>
# Simply add the name of the stacked dialog here like:
<code>this->_name == "stacked-dialog-name"</code><br>

This sets the left+right coordinates of the stacked dialog.
(Picture below)<br><br>

# Navigate to Widget.cpp, in <code>Widget::draw()</code>. <br>
# Within there, you'll see a check like <code>if (g_gui.useRTL()) then if (_name.....) </code><br>
# Simply add the name of the stacked dialog here like:
<code>this->_name.contains("stacked-dialog-name")</code> <br>

<br>'''Why do I need to add these things for stacked dialogs?'''<br>
The reason why we make this modification in Widget::draw(), is to shift the widgets when a stacked dialog is opened. This shift is added by calling g_gui.getOverlayOffset(), which is set when the name of the stacked dialog is added in ThemeLayout.cpp. This is set to 0 when the stacked dialog is closed.


==RTL Widgets:==

Some widgets are supposed to look differently for RTL. Here is an example:

If you're adding in support for a new widget, and also want to add in support for it's RTL counterpart - but wish to keep it disabled by default:
Navigate to the ..._layout.stx and set
<code>rtl = 'no'</code>

This will disable _useRTL, effectively disabling it by default. One such example currently is SliderWidgets.