I had some time to spare and I thought I might take a shot at, my long
time desire of, getting rid of 'with's in VirtualTrees.pas
One thing I noticed is this: If the with block is more involved than a
simple element, such as this:
with Owner, FHeader, FFixedAreaConstraints, TreeView do begin
you have to start 'exploding' from the right-most element and work your
way to the left-most one. Otherwise, the resulting code can become
meaningless/uncompilable.
Since there's that workaround, I can live with that caveat.
But, I think the one below is a bug:
Here is the original code:
procedure TVirtualTreeColumns.UpdatePositions(Force: Boolean = False);
var
I, RunningPos: Integer;
begin
if not FNeedPositionsFix and (Force or (UpdateCount = 0)) then begin
RunningPos := 0;
for I := 0 to High(FPositionToIndex) do
*with Items[FPositionToIndex[I]] do **begin*
FPosition := I;
FLeft := RunningPos;
if coVisible in FOptions then Inc(RunningPos, FWidth);
*end*;
end;
end;
when I explode 'Items[FPositionToIndex[I]]' it becomes this:
procedure TVirtualTreeColumns.UpdatePositions(Force: Boolean = False);
var
I, RunningPos: Integer;
begin
if not FNeedPositionsFix and (Force or (UpdateCount = 0)) then begin
RunningPos := 0;
*for I := 0 to High(FPositionToIndex) do**
** Items[FPositionToIndex[I]].FPosition := I;*
Items[FPositionToIndex[I]].FLeft := RunningPos;
if coVisible in Items[FPositionToIndex[I]].FOptions then
Inc(RunningPos, Items[FPositionToIndex[I]].FWidth);
end;
end;
At first sight, it looks OK. It compiles.
But, it has, silently, intoduced a bug: It has removed the 'begin end'
block that belonged to the 'with' and did not shift it back to the 'for'
loop.
IOW, it should have been like this. Notice that 'begin' moved to back to
the for-loop block.
procedure TVirtualTreeColumns.UpdatePositions(Force: Boolean = False);
var
I, RunningPos: Integer;
begin
if not FNeedPositionsFix and (Force or (UpdateCount = 0)) then begin
RunningPos := 0;
*for I := 0 to High(FPositionToIndex) do begin*
Items[FPositionToIndex[I]].FPosition := I;
Items[FPositionToIndex[I]].FLeft := RunningPos;
if coVisible in Items[FPositionToIndex[I]].FOptions then
Inc(RunningPos, Items[FPositionToIndex[I]].FWidth);
*end*;
end;
end;
--
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