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delphikeypress

Backspace press detection

Is there a possibility for detection backspace key pressing (like an event) only while a cursor is over Timage component? This shortcut has to trigger dedicated image-processing related to TImage.

Solution

  • I would just enable/disable they key-pressing detection event when the mouse enters or leaves the image (OnMouseEnter, OnMouseLeave).

    You just need to have a BackDetection function (compatible with TKeyEvent) on your Form :

    procedure MyForm.BackDetection(Sender: TObject; var Key: word; Shift: TShiftState);
begin
  if Key = VK_BACK then begin
    ... 
    ... Your image-processing code
    ...
  end;   
end;

    This does require that KeyPreview is True.

    Then you just set this event, or disable it, when the mouse enter or leaves your image.

    procedure MyForm.MyImageOnMouseEnter(Sender: TObject);
begin
  OnKeyPress := BackDetection;
end;

procedure MyForm.MyImageOnMouseLeave(Sender: TObject);
begin
  OnKeyPress := nil;
end;