{"id":2323,"date":"2013-12-19T07:00:00","date_gmt":"2013-12-19T07:00:00","guid":{"rendered":"https:\/\/blogs.msdn.microsoft.com\/oldnewthing\/2013\/12\/19\/how-do-i-display-an-rtl-string-in-a-notification-balloon-on-an-ltr-system\/"},"modified":"2013-12-19T07:00:00","modified_gmt":"2013-12-19T07:00:00","slug":"how-do-i-display-an-rtl-string-in-a-notification-balloon-on-an-ltr-system","status":"publish","type":"post","link":"https:\/\/devblogs.microsoft.com\/oldnewthing\/20131219-00\/?p=2323","title":{"rendered":"How do I display an RTL string in a notification balloon on an LTR system?"},"content":{"rendered":"

\nSuppose you have a program that is written in Arabic or Hebrew\nand you want to render some text.\nNo problem.\nYou just call\nExt­Text­Out<\/code> and pass the\nETO_RTL­READING<\/code> flag to say,\n“Please render this string in an RTL context.”\nMany other text-rendering functions have a similar flag,\nsuch as\nDT_RTL­READING<\/code> for\nDraw­Text<\/code>.\n<\/p>\n

\nBut what if you don’t control the call to\nExt­Text­Out<\/code> or Draw­Text<\/code>\nor whatever other function is being used to render the text.\nIf you don’t control the call, then you can’t pass along the\nmagic “Please render this string in an RTL context” flag.\n<\/p>\n

\nIf you’re lucky, the component that is doing the rendering has\nsome analogous flag that tells it to render in RTL context.\nIf the component is a control,\nthis flag may be implicit in the\nWS_EX_RTL­READING<\/code> extended style\non the control window itself.\nFor some components, the secret signal is\n\nthe presence of two RLM characters (U+200F) at the beginning of the string<\/a>.\n<\/p>\n

\nIf you’re not lucky, then the component that is doing the rendering\ngives you no way to convince or cajole it into rendering text\nin an RTL context.\nBut all hope is not lost:\nThe\n(possibly\nnon-intuitive<\/a>)\nUnicode Bidi algorithm comes to the rescue!\n<\/p>\n

\nWhat you can do is place the RLE control character (U+202B)\nat the start of the string.\nThe RIGHT-TO-LEFT EMBEDDING control character means\n“Treat the text that follows in an RTL context until further instructions.”\n(You cancel the effect of an RLE by a PDF (POP DIRECTIONAL\nFORMATTING, U+202C).)\n<\/p>\n

\nLet’s demonstrate in our\n\nscratch program<\/a>.\n<\/p>\n

\n#define THESTRING L\"\\x0639\\x0644\\x0649 \\x0633\\x0628\\x064a\\x0644 \" \\\n                  L\"\\x0627\\x0644\\x0645\\x062b\\x0627\\x0644: \" \\\n                  L\"Dear \\x0623\\x0634\\x0631\\x0641 \" \\\n                  L\"\\x0645\\x0627\\x0647\\x0631\"\n#define RLE L\"\\x202b\"\nvoid ShowString(HDC hdc, int y, PCWSTR psz, UINT format)\n{\n RECT rc = { 0, y, 500, y+100 };\n DrawTextW(hdc, psz, -1, &rc, format);\n}\nvoid\nPaintContent(HWND hwnd, PAINTSTRUCT *pps)\n{\n ShowString(pps->hdc, 0, THESTRING, 0);\n ShowString(pps->hdc, 100, THESTRING, DT_RTLREADING);\n ShowString(pps->hdc, 200, RLE THESTRING, 0);\n}\n<\/pre>\n
\nThis sample program takes\n\na string in Arabic<\/a>\n(with a little bit of English thrown in just to make the difference\nmore noticeable)\nand renders it three ways:\n<\/p>\n