مدرسه دلفي

How to clear a TCanvas very fast?

PatBlt(Image1.Canvas.Handle,0,0,Image1.Width,Image1.Height,WHITENESS); 

Image1.Refresh;

procedure TForm1.File2StringGrid(StringGrid: TStringGrid; FileName: String); 

var F: TextFile; 

    Tmp, x, y: Integer; 

    TmpStr: string; 

begin 

  AssignFile(F, FileName); 

  Reset(F); 

  Readln(F, Tmp); 

  StringGrid.ColCount:=Tmp; 

  Readln(F, Tmp); 

  StringGrid.RowCount:=Tmp; 

  for x:=0 to StringGrid.ColCount-1 do 

  for y:=0 to StringGrid.RowCount-1 do 

  begin 

    Readln(F, TmpStr); 

    StringGrid.Cells[x,y]:=TmpStr; 

  end; 

  CloseFile(F); 

end; 

procedure TForm1.StringGrid2File(StringGrid: TStringGrid; FileName: String); 

var F: TextFile; 

    x, y: Integer; 

begin 

  AssignFile(F, FileName); 

  Rewrite(F); 

  Writeln(F, StringGrid.ColCount); 

  Writeln(F, StringGrid.RowCount); 

  for x:=0 to StringGrid.ColCount-1 do 

  for y:=0 to StringGrid.RowCount-1 do 

     Writeln(F, StringGrid.Cells[x,y]); 

  CloseFile(F); 

end;

Runtime I/O errors

1   ¦Invalid function number
2   ¦File not found
3   ¦Path not found
4   ¦Too many open files
5   ¦File access denied
6   ¦Invalid file handle
12  ¦Invalid file access code
15  ¦Invalid drive number
16  ¦Cannot remove current directory
17  ¦Cannot rename across drives
18  ¦No more files
100 ¦Disk read error
101 ¦Disk write error
102 ¦File not assigned
103 ¦File not open
104 ¦File not open for input
105 ¦File not open for output
106 ¦Invalid numeric format
150 ¦Disk is write-protected
151 ¦Bad drive request struct length
152 ¦Drive not ready
154 ¦CRC error in data
156 ¦Disk seek error
157 ¦Unknown media type
158 ¦Sector Not Found
159 ¦Printer out of paper
160 ¦Device write fault
161 ¦Device read fault
162 ¦Hardware failure
200 ¦Division by zero
201 ¦Range check error
202 ¦Stack overflow error
203 ¦Heap overflow error
204 ¦Invalid pointer operation
205 ¦Floating point overflow
206 ¦Floating point underflow
207 ¦Invalid floating point operation
208 ¦Overlay manager not installed
209 ¦Overlay file read error
210 ¦Object not initialized
211 ¦Call to abstract method
212 ¦Stream registration error   
213 ¦Collection index out of range
214 ¦Collection overflow error
215 ¦Arithmetic overflow error
216 ¦General Protection fault

procedure TForm1.Button1Click(Sender: TObject); 

var Bitmap, Bitmap2: TBitmap; ButHandle: THandle; Rec: TRect; 

begin 

  Bitmap:=TBitmap.Create; 

  Bitmap2:=TBitmap.Create; 

  Bitmap2.LoadFromFile('c:\mybmp.bmp'); 

  Rec:=Rect(2, 2, Button1.Width-2, Button1.Height-2); 

  ButHandle:=GetDC(Button1.Handle); 

  Bitmap.Canvas.Handle:=ButHandle; 

  Bitmap.Canvas.StretchDraw(Rec, Bitmap2); 

end;