c++regexdelphiuniscribe

Converting LTR to RTL?


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


Solution

  • 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...