Changeset 421 for trunk/Components/RichTextLayoutUnit.pas

Timestamp:

Mar 1, 2019, 8:09:20 PM (6 years ago)

Author:

ataylor

Message:

DBCS character boundary detection for cursor positioning logic.

File:

• trunk/Components/RichTextLayoutUnit.pas (modified) (8 diffs)

trunk/Components/RichTextLayoutUnit.pas

@@ -75 +75 @@
 
     Codepage:    ULong;       // ALT
+
+// TEMP (ALT)
+    DebugLog: TextFile;
+// TEMP (ALT)
+
 
     // Drawing functions
@@ -121 +126 @@
     Function GetTextEnd: longint;
 
+    // ALT
+    Function FindCharacterBoundary(    TextPointer: PChar;
+                                   var Index:       LongInt;
+                                       Advance:     Boolean; ): LongInt;
+
   Public
     constructor Create( Text: PChar;
@@ -177 +187 @@
   FRichTextSettings := RichTextSettings;
 
+{
+AssignFile( DebugLog, 'parse.txt');
+ReWrite( DebugLog );
+WriteLn( DebugLog, 'Opened log for writing.');
+}
+
   FImages := Images;
 
@@ -212 +228 @@
   FreeMem( Flines, FAllocatedNumLines * sizeof( TLayoutLine ) );
   FLinks.Destroy;
+
+{
+// TEMP (ALT)
+WriteLn( DebugLog, '=============================');
+CloseFile( DebugLog );
+// TEMP (ALT)
+}
 
   Inherited Destroy;
@@ -932 +955 @@
   Style: TTextDrawStyle;
   NewMarginX: longint;
+  InsideDBC:   Boolean;     // ALT
 begin
   Line := FLines[ LineIndex ];
@@ -941 +965 @@
 
   StartedDrawing := false;
+  InsideDBC := false;       // ALT
 
   while P < EndP do
   begin
     Element := ExtractNextTextElement( P, NextP );
+    CheckSpecialElementType( Element.Character, Element.ElementType, InsideDBC, Codepage );   // ALT
 
     case Element.ElementType of
       teWordBreak,
       teText,
+      teWrapChar,       // ALT
+      teLeadByte,       // ALT
       teImage:
       begin
@@ -967 +995 @@
 
         // Now find out how wide the thing is
-        inc( X, GetElementWidth( Element ) );
-
-      end;
+        if (( Element.ElementType = teLeadByte ) And ( EndP > P )) then    // ALT
+          inc( X, FFontManager.CJKTextWidth( 2, P ))
+        else
+          inc( X, GetElementWidth( Element ) );
+
+      end;
+
+      // teSecondByte: do nothing and continue to next byte (ALT)
 
       teStyle:
@@ -1205 +1238 @@
 end;
 
+// ALT begins
+//
+// Given a text position, check if it's in the middle of a double-byte
+// character; if so, shift the position one byte forwards or backwards.
+//
+function TRichTextLayout.FindCharacterBoundary(     TextPointer: PChar;     // pointer to text
+                                                var Index:       LongInt;   // position (byte index) within text
+                                                    Advance:     Boolean;   // whether to adjust position forward
+                                              ): LongInt;                   // returns new offset within line
+var
+  P:         PChar;             // pointer to current character in string
+  NextP:     PChar;             // pointer to the following character, if any
+  Element:   TTextElement;      // element data about the current character
+  CurrentPos:  LongInt;           // index of first character of line
+  Line:      LongInt;           // current line number
+  Offset:    LongInt;           // offset position within current line
+  InsideDBC: boolean;
+begin
+  if ( Offset > 0 ) and
+     ( Codepage in [ 932, 936, 942, 943, 949, 950, 1381, 1386 ]) then
+  begin
+    // Because parsing of byte types is state based, we must verify every
+    // byte's type from the beginning of the line until we reach the target.
+    //
+    Line := GetLineFromCharIndex( Index );
+    CurrentPos := GetCharIndex( FLines[ Line ].Text );
+    P := TextPointer + CurrentPos;
+    Offset := 0;
+    InsideDBC := false;
+
+    while CurrentPos < Index do
+    begin
+      Element := ExtractNextTextElement( P, NextP );
+      CheckSpecialElementType( Element.Character, Element.ElementType, InsideDBC, Codepage );
+      CurrentPos := CurrentPos + PCharPointerDiff( NextP, P );
+      Offset := Offset + PCharPointerDiff( NextP, P );
+      P := NextP;
+    end;
+
+    // We've reached the target position, and the current parsing state should
+    // be correctly set. So now we can safely determine the target byte's type.
+    //
+    Element := ExtractNextTextElement( P, NextP );
+    CheckSpecialElementType( Element.Character, Element.ElementType, InsideDBC, Codepage );
+
+    if Element.ElementType = teSecondByte then
+    begin
+      // If we are inside a a double byte character, shift position by one.
+      if Advance Then
+      Begin
+        inc( Index );
+        inc( Offset );
+      End
+      Else
+      Begin
+        dec( Index );
+        dec( Offset );
+      End
+    end;
+
+  end;
+
+  Result := Offset;
+end;
+//
+// ALT ends
+
 Initialization
 End.