Including Bi-directional Functionality in Applications

Some languages do not follow the left to right reading order commonly found in western languages, but rather read words right to left and numbers left to right. These languages are termed bi-directional (BiDi) because of this separation. The most common bi-directional languages are Arabic and Hebrew, although other Middle East languages are also bi-directional.

TApplication has two properties, BiDiKeyboard and NonBiDiKeyboard, that allow you to specify the keyboard layout. In addition, the VCL supports bi-directional localization through the BiDiMode and ParentBiDiMode properties.

Note: Bi-directional properties are not available for cross-platform applications.

The BiDiMode property controls the reading order for the text, the placement of the vertical scrollbar, and whether the alignment is changed. Controls that have a text property, such as Name, display the BiDiMode property on the Object Inspector.

The BiDiMode property is a new enumerated type, TBiDiMode, with four states: bdLeftToRight, bdRightToLeft, bdRightToLeftNoAlign, and bdRightToLeftReadingOnly.

bdLeftToRight

bdLeftToRight draws text using left to right reading order. The alignment and scroll bars are not changed. For instance, when entering right to left text, such as Arabic or Hebrew, the cursor goes into push mode and the text is entered right to left. Latin text, such as English or French, is entered left to right. bdLeftToRight is the default value.

bdRightToLeft

bdRightToLeft draws text using right to left reading order, the alignment is changed and the scroll bar is moved. Text is entered as normal for right-to-left languages such as Arabic or Hebrew. When the keyboard is changed to a Latin language, the cursor goes into push mode and the text is entered left to right.

bdRightToLeftNoAlign

bdRightToLeftNoAlign draws text using right to left reading order, the alignment is not changed, and the scroll bar is moved.

bdRightToLeftReadingOnly

bdRightToLeftReadingOnly draws text using right to left reading order, and the alignment and scroll bars are not changed.