Difference between revisions of "SynEdit Highlighter"

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There is no such thing as a MaxLvl, because folds that start and end on the same line can not be folded anyway. No need to detect them.
 
There is no such thing as a MaxLvl, because folds that start and end on the same line can not be folded anyway. No need to detect them.
 
   if a then begin b:=1; c:=2; end; // no fold on that line
 
   if a then begin b:=1; c:=2; end; // no fold on that line
 +
 +
 +
= References =
 +
Threads on the forum:
 +
 +
http://www.lazarus.freepascal.org/index.php/topic,10260.0.html
 +
http://www.lazarus.freepascal.org/index.php/topic,7879.0.html
 +
http://www.lazarus.freepascal.org/index.php/topic,7338.0.html
 +
http://www.lazarus.freepascal.org/index.php/topic,10959.msg54714

Revision as of 22:18, 30 October 2010

Understanding the SynEdit Highlighter

SynEdit - Highlighter relationship

SynEdit <-> Highlighter have a n to 1 relationship.

  • 1 (instance of a) Highlighter can serve n (many) (instances of) SynEdits
  • Each SynEdit only has one Highlighter

As a result of this:

  • no Highlighter Instance has a (fixed) reference to the SynEdit.
(Highlighters however keep a list of SynEditTextBuffers to which they are attached)
  • All data for the Highlighter is (and must be) stored on the SynEdit (actually on the TextBuffer of SynEdit (referred to as "Lines").

However SynEdit ensures before each call to the Highlighter that Highlighter.CurrentLines is set to the current SynEdits Lines. This way the highlighter can access the data whenever needed. The Format of the data-storage is determined by the highlighter (TSynCustomHighlighter.AttachToLines)

Scanning and Returning Highlight attributes

The Highlighter is expected to work on a per Line base.

If any text was modified, SynEdit will call (TSynCustomHighlighter.ScanFrom / Currently called from TSynEdit.ScanFrom) with the line range. The Highlighter should know the state of the previous line.

If Highlight attributes are required SynEdit will request them per Line too. SynEdit will loop through individual tokens on a line. This currently happens from nested proc PaintLines in SynEdit.PaintTextLines. It calls TSynCustomHighlighter.StartAtLineIndex, followed by HL.GetTokenEx/HL.GetTokenAttribute for as long as HL.GetEol is false

Also the BaseClass for the Highlighter's data (see AttachToLines) is based on per line storage, and SynEdit's TextBuffer (Lines) do maintenance on this data to keep it synchronized. That is when ever lines of text are inserted or removed, so are entries inserted or removed from the highlighters data (hence it must have one entry per line).

Usually Highlighters store the end-of-line-status in this field. So if the highlighter is going to work on a line, it will continue with the state-entry from the previous line.

Folding

SynEdit's folding is handled by unit SynEditFoldedView and SynGutterCodeFolding. Highlighter that implement folding are to be based on TSynCustomFoldHighlighter

The basic information for communication between SynEditFoldedView and the HL requires 2 values stored for each line. (Of course the highlighter itself can store more information):

  • FoldLevel at the end of line
  • Minimum FoldLevel encountered anywhere on the line

The Foldlevel indicates how many (nested) folds exist. It goes up whenever a fold begins, and down when a fold ends

                           EndLvl   MinLvl
 Procedure a;               1 -      0
 Begin                      2 --     1 -
   b:= 1;                   2 --     2 --
   if c > b then begin      3 ---    2 --
     c:=b;                  3 ---    3 ---
   end else begin           3 ---    2 --
     b:=c;                  3 ---    3 ---
   end;                     2 --     2 --
 end;                       0        0  // The end closes both: begin and procedure fold

In the line

 Procedure a;               1 -      0

the MinLvl is 0, because the line started with a Level of 0 (and it never went down / no folds closed). Similar in all lines where there is only an opening fold keyword ("begin").

But the line

   end else begin           3 ---    2 --

starts with a level of 3, and also ends with it (one close, one open). But since it went down first, the minimum level encountered anywhere on the line is 2.

Without the MinLvl it would not be possible to tell, that a fold ends in this line.

There is no such thing as a MaxLvl, because folds that start and end on the same line can not be folded anyway. No need to detect them.

 if a then begin b:=1; c:=2; end; // no fold on that line


References

Threads on the forum:

http://www.lazarus.freepascal.org/index.php/topic,10260.0.html http://www.lazarus.freepascal.org/index.php/topic,7879.0.html http://www.lazarus.freepascal.org/index.php/topic,7338.0.html http://www.lazarus.freepascal.org/index.php/topic,10959.msg54714