Delphi 2010 differs in Canvas transparency compared to Delphi 7?
- by Tom1952
I'm porting some very old code from Delph7 to Delphi2010 with a few changes as possible to the existing code base for the usual reasons.
First: the good news for anyone who hasn't jumped yet: it's not as daunting as it may look! I'm actually pleased (& surprised) at how easy 1,000,000+ lines of code have moved across. And what a relief to be back on the leading edge! Delphi 2010 has so many great enhancements.
However, I'm having a cosmetic problem with some TStringGrids and TDbGrids descendants.
In the last century (literally!) someone wrote the two methods below.
The first method is used to justify text. When run in Delphi 2010, the new text and the unjustified text to both appear in the cells written to. Of course it's a mess visually, almost illegible. Sometimes, as a result of the second method is use, the grid cells are actually semi-transparent, with text from the window below showing through. (Again, not pretty!)
It appears to me that Delphi 2010's TDbGrid and TStringGrid have some differences in the way they handle transparency?
I haven't much experience in this area of Delphi (in fact, I have no idea what the 2nd method is actually doing!) and was hoping someone could give me some pointers on what's going on and how to fix it.
TIA!
Method 1
procedure TForm1.gridDrawCell(Sender: TObject; Col, Row: Integer;
Rect: TRect; State: TGridDrawState);
{Used to align text in cells.}
var
x: integer;
begin
if (Row > 0) AND (Col > 0) then
begin
SetTextAlign(grdTotals.Canvas.Handle, TA_RIGHT);
x := Rect.Right - 2;
end
else
begin
SetTextAlign(grdTotals.Canvas.Handle, TA_CENTER);
x := (Rect.Left + Rect.Right) div 2;
end;
grdTotals.Canvas.TextRect(Rect, x, Rect.Top+2, grdTotals.Cells[Col,Row]);
end;
Method 2
procedure WriteText(ACanvas: TCanvas; ARect: TRect; DX, DY: Integer; const Text: string;
TitleBreak: TTitleBreak; 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
ABitmap: TBitmap;
AdjustBy: Integer;
B, R: TRect;
WordBreak: Integer;
begin
WordBreak := 0;
if (TitleBreak = tbAlways) or ((TitleBreak = tbDetect) and (Pos(Chr(13) + Chr(10), Text) = 0))
then
WordBreak := DT_WORDBREAK;
ABitmap := TBitmap.Create;
try
ABitmap.Canvas.Lock;
try
AdjustBy := 1;
if (Alignment = taRightJustify) then
Inc(AdjustBy);
with ABitmap, ARect do
begin
Width := Max(Width, Right - Left);
Height := Max(Height, Bottom - Top);
R := Rect(DX, DY, Right - Left - AdjustBy, Bottom - Top - 1); { @@@ }
B := Rect(0, 0, Right - Left, Bottom - Top);
end;
with ABitmap.Canvas do
begin
Font := ACanvas.Font;
Brush := ACanvas.Brush;
Brush.Style := bsSolid;
FillRect(B);
SetBkMode(Handle, TRANSPARENT);
DrawText(Handle, PChar(Text), Length(Text), R, AlignFlags[Alignment] or WordBreak);
end;
ACanvas.CopyRect(ARect, ABitmap.Canvas, B);
finally
ABitmap.Canvas.Unlock;
end;
finally
ABitmap.Free;
end;
end;
