Converting LTR to RTL? - c++

Question

As you know many ui components and dev tools doesn't support rtl , we can call it flipping text , cause result is same example :
LTR
سلام salam متن راهنما word
RTL
word متن راهنما salam سلام
is there anyway to convert this LTR to RTL , i don't have any idea and language doesn't matter
Actually i am seeking for a solution to get this done in RAD Studio Firemonkey Application , as you may know firemonkey apps doesn't support rtl it's in roadmap of rad studio but not implemented yet

Answer 1

Under Windows, you can do that via the UniScribe API.
I've used this to convert Unicode text into set of glyphs, for our Open Source PDF writer.
You have source code sample in SynPdf.pas unit. See the TPdfWrite.AddUnicodeHexTextUniScribe method:
function TPdfWrite.AddUnicodeHexTextUniScribe(PW: PWideChar;
WinAnsiTTF: TPdfFontTrueType; NextLine: boolean; Canvas: TPdfCanvas): boolean;
var L, i,j: integer;
res: HRESULT;
max, count, numSp: integer;
Sp: PScriptPropertiesArray;
W: PWideChar;
items: array of TScriptItem;
level: array of byte;
VisualToLogical: array of integer;
psc: pointer; // opaque Uniscribe font metric cache
complex,R2L: boolean;
complexs: array of byte;
glyphs: array of TScriptVisAttr;
glyphsCount: integer;
OutGlyphs, LogClust: array of word;
procedure Append(i: Integer);
// local procedure used to add glyphs from items[i] to the PDF content stream
var L: integer;
W: PWideChar;
procedure DefaultAppend;
var tmpU: array of WideChar;
begin
SetLength(tmpU,L+1); // we need the text to be ending with #0
move(W^,tmpU[0],L*2);
AddUnicodeHexTextNoUniScribe(pointer(tmpU),WinAnsiTTF,false,Canvas);
end;
begin
L := items[i+1].iCharPos-items[i].iCharPos; // length of this shapeable item
if L=0 then
exit; // nothing to append
W := PW+items[i].iCharPos;
if not GetBit(complexs[0],i) then begin
// not complex items are rendered as fast as possible
DefaultAppend;
exit;
end;
res := ScriptShape(0,psc,W,L,max,#items[i].a,
pointer(OutGlyphs),pointer(LogClust),pointer(glyphs),glyphsCount);
case res of
E_OUTOFMEMORY: begin // max was not big enough (should never happen)
DefaultAppend;
exit;
end;
E_PENDING, USP_E_SCRIPT_NOT_IN_FONT: begin // need HDC and a selected font object
res := ScriptShape(Canvas.FDoc.GetDCWithFont(WinAnsiTTF),
psc,W,L,max,#items[i].a,
pointer(OutGlyphs),pointer(LogClust),pointer(glyphs),glyphsCount);
if res<>0 then begin // we won't change font if necessary, sorry
// we shall implement the complex technic as stated by
// http://msdn.microsoft.com/en-us/library/dd374105(v=VS.85).aspx
DefaultAppend;
exit;
end;
end;
0: ; // success -> will add glyphs just below
else exit;
end;
// add glyphs to the PDF content
// (NextLine has already been handled: not needed here)
AddGlyphs(pointer(OutGlyphs),glyphsCount,Canvas);
end;
begin
result := false; // on UniScribe error, handle as Unicode
// 1. Breaks a Unicode string into individually shapeable items
L := StrLenW(PW)+1; // include last #0
max := L+2; // should be big enough
SetLength(items,max);
count := 0;
if ScriptItemize(PW,L,max,nil,nil,pointer(items),count)<>0 then
exit; // error trying processing Glyph Shaping -> fast return
// 2. guess if requiring glyph shaping or layout
SetLength(complexs,(count shr 3)+1);
ScriptGetProperties(sP,numSp);
complex := false;
R2L := false;
for i := 0 to Count-2 do // don't need Count-1 = Terminator
if fComplex in sP^[items[i].a.eScript and (1 shl 10-1)]^.fFlags then begin
complex := true;
SetBit(complexs[0],i);
end else
if fRTL in items[i].a.fFlags then
R2L := true;
if not complex then begin
// no glyph shaping -> fast append as normal Unicode Text
if R2L then begin
// handle Right To Left but not Complex text
W := pointer(items); // there is enough temp space in items[]
W[L] := #0;
dec(L);
for i := 0 to L do
W[i] := PW[L-i];
AddUnicodeHexTextNoUniScribe(W,WinAnsiTTF,NextLine,Canvas);
result := true; // mark handled here
end;
exit;
end;
// 3. get Visual Order, i.e. how to render the content from left to right
SetLength(level,count);
for i := 0 to Count-1 do
level[i] := items[i].a.s.uBidiLevel;
SetLength(VisualToLogical,count);
if ScriptLayout(Count,pointer(level),pointer(VisualToLogical),nil)<>0 then
exit;
// 4. now we have enough information to start drawing
result := true;
if NextLine then
Canvas.MoveToNextLine; // manual NextLine handling
// 5. add glyphs for all shapeable items
max := (L*3)shr 1+32; // should be big enough - allocate only once
SetLength(glyphs,max);
SetLength(OutGlyphs,max);
SetLength(LogClust,max);
psc := nil; // cached for the same character style used
if Canvas.RightToLeftText then
// append from right to left visual order
for j := Count-2 downto 0 do // Count-2: ignore last ending item
Append(VisualToLogical[j]) else
// append from left to right visual order
for j := 0 to Count-2 do // Count-2: ignore last ending item
Append(VisualToLogical[j]);
end;
Of course, this is under Windows only. So it won't work on Mac OS X. You'll have to use another library under Mac OS X...

Answer 2

It's complicated. If you want to do it correctly, you must use the Bidi Library from the International Components for Unicode.

Answer 3

If you use MFC, here is how to set both righting direction and alignment. Assuming your CEdit control is named m_TextEdit:
void MyDialog::SetLangDirection(bool RTL)
{
DWORD w_dwStyle;
w_dwStyle = GetWindowLong(m_TextEdit.GetSafeHwnd(), GWL_EXSTYLE);
if (RTL)
{
w_dwStyle -= WS_EX_LEFT | WS_EX_LTRREADING;
w_dwStyle |= WS_EX_RIGHT | WS_EX_RTLREADING;
}
else
{
w_dwStyle -= WS_EX_RIGHT | WS_EX_RTLREADING;
w_dwStyle |= WS_EX_LEFT | WS_EX_LTRREADING;
}
SetWindowLong(m_TextEdit.GetSafeHwnd(), GWL_EXSTYLE, w_dwStyle);
}
See my tip.