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wrong hignlight in TDBGrid

zhuhail
zhuhail asked
on
Medium Priority
475 Views
Last Modified: 2010-04-06
A TDBGrid with dgMultiSelect = True and is connected to a database.
In run time, the rows may be highlighted when they are clicked and the corresponding records are selected, no problem.

However, when you scroll the grid, a row at the top or the bottow may also be highlighted automatically but the corresponding record is NOT be selected! So, some highlighted rows related to the records you selected but one highlighted row related to nothing in the same time.

How to avoid that?
Comment
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Commented:
I've tried what you said but I didn't see anything wrong. I've selected 3 rows and then scroll up and down but the 3 rows still were selected and only one else ,let's say selected (but not actually), it's the one where you are positioned in the table, but when you look for the selected ones via SelectedRows it isn't there.

Author

Commented:
Hi,

Let me give you more detail:

Delphi 2.0.
A TQuery + a TDBGrid (with dgMultiSelect = True).
They are connected to a database (the demo).
Bring all the records in the table of the database to the TDBGrid by SQL "%".
Click 3 rows (make sure they are far from the top or bottow) in the TDBGrid, 3 rows are highlighted and 3 corresponding records in the TQuery are selected.
  ("highlighted" means something happened in the TDBGrid.
   "selected" means something happened inside the TQuery.)
Roll one step up (or down) the TDBGrid, a row at the top (or bottow) will be highlighted automatically but its corresponding record in the TQuery is not been selected.
Now, 4 rows are highlighted but only 3 records are selected!
I want: Any row highlighted = the corresponding record selected.
Tech Director
CERTIFIED EXPERT
Commented:
Hi there,

First of all I would like to say that I agree with the comment
from javiertb, I tried what you suggested and :

Three rows selected: note all the columns in the selected rows are highlighted.
Then scrolling down: only one column in bottom row is highlighted
but not selected... you can tell the difference between highlited
and selected.... so three highlited across all columns and one is
highlited only across first column...


Any way you wanted a better answer:

The answer involves a whole lot of hard work, which I started on
and gave up cause, geeze for 50 points, or a max of 4*50=200 if
you rate it superbly... its not worth the effort.. any way..
What you should do is set

  Dbgrid.DefaultDrawing = False

and then write your routines to handle the drawing, you can get most of the needed stuff in the source code DBgrids.pas.. it will look very hairy and messy something like this:


if I were you I would just settle for what is supported. :)

*** Yuck ***



procedure TForm1.DBGrid1DrawColumnCell(Sender: TObject; const Rect: TRect;
  DataCol: Integer; Column: TColumn; State: TGridDrawState);
var
  Value: string;
begin
  Value := '';
  if Assigned(Column.Field) then
    Value := Column.Field.DisplayText;
  WriteText(Canvas, Rect, 0, 0, Value, Column.Alignment);
end;

procedure WriteText(ACanvas: TCanvas; ARect: TRect; DX, DY: Integer;
  const Text: string; Alignment: TAlignment);
const
  AlignFlags : array [TAlignment] of Integer =
    ( DT_LEFT or DT_WORDBREAK or DT_EXPANDTABS or DT_NOPREFIX,
      DT_RIGHT or DT_WORDBREAK or DT_EXPANDTABS or DT_NOPREFIX,
      DT_CENTER or DT_WORDBREAK or DT_EXPANDTABS or DT_NOPREFIX );
var
  B, R: TRect;
  I, Left: Integer;
begin
  I := ColorToRGB(ACanvas.Brush.Color);
  if GetNearestColor(ACanvas.Handle, I) = I then
  begin                       { Use ExtTextOut for solid colors }
    case Alignment of
      taLeftJustify:
        Left := ARect.Left + DX;
      taRightJustify:
        Left := ARect.Right - ACanvas.TextWidth(Text) - 3;
    else { taCenter }
      Left := ARect.Left + (ARect.Right - ARect.Left) shr 1
        - (ACanvas.TextWidth(Text) shr 1);
    end;
    ExtTextOut(ACanvas.Handle, Left, ARect.Top + DY, ETO_OPAQUE or
      ETO_CLIPPED, @ARect, PChar(Text), Length(Text), nil);
  end
  else begin                  { Use FillRect and Drawtext for dithered colors }
    with DrawBitmap, ARect do { Use offscreen bitmap to eliminate flicker and }
    begin                     { brush origin tics in painting / scrolling.    }
      Width := Max(Width, Right - Left);
      Height := Max(Height, Bottom - Top);
      R := Rect(DX, DY, Right - Left - 1, Bottom - Top - 1);
      B := Rect(0, 0, Right - Left, Bottom - Top);
    end;
    with DrawBitmap.Canvas do
    begin
      Font := ACanvas.Font;
      Font.Color := ACanvas.Font.Color;
      Brush := ACanvas.Brush;
      Brush.Style := bsSolid;
      FillRect(B);
      SetBkMode(Handle, TRANSPARENT);
      DrawText(Handle, PChar(Text), Length(Text), R, AlignFlags[Alignment]);
    end;
    ACanvas.CopyRect(ARect, DrawBitmap.Canvas, B);
  end;
end;




procedure TForm1.DBGrid1DrawDataCell(Sender: TObject; const Rect: TRect;
  Field: TField; State: TGridDrawState);
var
  Alignment: TAlignment;
  Value: string;
begin
  Alignment := taLeftJustify;
  Value := '';
  if Assigned(Field) then
  begin
    Alignment := Field.Alignment;
    Value := Field.DisplayText;
  end;
  WriteText(Canvas, Rect, 0, 0, Value, Alignment);
end;

Cheers,
Rob.







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Author

Commented:
Adjusted points to 70

Author

Commented:
Adjusted points to 75

Author

Commented:
Hi Rob,

Yes, that is what I need! Thank you very much.
I didn't expect the problem would be so difficult, sorry....The point is increasing :-)

Perhaps I missed something, when run your code, I got some error messages which are listed (with corresponding statements) as forllows:

with DrawBitmap, ARect do
     Undeclared identitier: 'DrawBitmap'.

FillRect(B);
     Incompatible types: 'Integer' and 'TRect'.

SetBkMode(Handle, TRANSPAPENT);
     Undeclared identifier: 'Handle'.

ACanvas.CapyRect(ARect, DrawBitmap.Canvas, B);
     Not enough actual parameters.

ACanvas.CapyRect(ARect, DrawBitmap.Canvas, B);
end;
end;
     '.' expected but ';'found. (reffers to the last line)
     
Can you help?

Regards.

Author

Commented:
Adjusted points to 85

Author

Commented:
Adjusted points to 90

Author

Commented:
Adjusted points to 100
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