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The OnKeyDown event of an object allows you to check what key the user has pressed.
Note that the procedure keeps track of shift/alt/ctrl etc keys separately (in Shift) from the "regular" keys (in Key) - see the procedure signature in the example.
Note: OnKeyDown doesn't support Unicode characters. If you need Unicode characters but no control characters, use OnUTF8KeyPress.
Note: When a key is held down, the OnKeyDown event is re-triggered. The first re-triggering event is after approx 500 ms and the next ones cycle between 30 and 50 ms.
uses ...LCLType, Dialogs, ...; ... procedure TForm1.Edit1KeyDown(Sender: TObject; var Key: Word; Shift: TShiftState); begin // Example: checking for simple keys: if (Key = VK_DOWN) or (Key = VK_UP) then ShowMessage('Pressed arrow up or down key'); // Check for Alt-F2 if (Key = VK_F2) and (ssAlt in Shift) then ShowMessage('Alt F2 was pressed') Key := 0; // Necessary for some widgetsets, e.g. Cocoa, in order to disable processing in subsequent elements. end;
- Description of keyboard events in Delphi; should be applicable to Lazarus, as well.
- LCL Key Handling Detailed background on key handling in the LCL.