如何在Delphi中获得TEdit的画布？

Question

我想缩短文件名以适应TEdit,比如

Edit1.Text := MinimizeName(FileName, Edit1.Canvas, Edit1.Width);

不幸的是,这不能编译,因为TEdit Canvas直接拥有属性.其字体指标需要画布.如何访问TEdit的画布？

(MinimizeName在Vcl.FileCtrl中声明.)

Answer 1

你可以用TControlCanvas.您还应该考虑控件的Font.

例如:

var
  Canvas: TControlCanvas;

Canvas := TControlCanvas.Create;
try
  Canvas.Control := Edit1;
  Canvas.Font.Assign(Edit1.Font); 

  // Do something with Canvas... 
finally
  Canvas.Free;
end;

Answer 2

好的，我找到了。对于那些有兴趣的人：

procedure TForm1.Button1Click(Sender: TObject);  
var  
  aCanvas: TCanvas;  
begin  
  if FileOpenDialog1.Execute then begin  
    aCanvas := TCanvas.Create;  
    try  
      aCanvas.Handle := GetDC(Edit1.Handle);  
      Edit1.Text := MinimizeName(FileOpenDialog1.FileName, aCanvas, Edit1.Width - 8);  
    finally  
      ReleaseDC(Edit1.Handle, aCanvas.Handle);
      aCanvas.Free;  
    end;  
  end;  
end;