We use the Parent property to get or set the parent of the control. The parent of a control is the control that contains it. For example, if an application includes three radio buttons in a group box, the group box is the parent of the three radio buttons, and the radio buttons are the child controls of the group box.
To serve as a parent, a control must be an instance of a TWinControl…
We use TextRect to write a string inside a clipping rectangle or within a limited rectangular region. Any portions of the string that fall outside the rectangle passed in the Rect parameter are clipped and don’t appear. The upper left corner of the text is placed at…
OnClose event occurs when the form closes.
We use OnClose to perform special processing when the form closes. The OnClose event specifies which event handler to call when a form is about to close. The handler specified by OnClose might, for example, test to make sure…
OnSelectCell event occurs before a cell in the grid is selected.
Write an OnSelectCell event handler to specify whether any particular cell in the grid can be selected. The Col and Row parameters indicate the column and row indexes of the cell that is about to be selected. Set the CanSelect parameter to False to prevent the cell being selected.
Here is the working example of the…
OnDrawCell event Occurs when a cell in the grid needs to be drawn.
We write an OnDrawCell event handler to draw the contents of all the cells in the grid. Draw on the cell using the methods of the Canvas property. The Rect parameter indicates the location of the cell…
OnChange event occurs when the user changes the text displayed in the edit region.
We write an OnChange event handler to take specific action immediately after the user edits the text in the edit region or selects an item from the list. The Text property gives the new…
OnClick event occurs when the user clicks the control.
We use the OnClick event handler to respond when the user clicks the control. If the control has an associated action, and that action has an OnExecute method, the action’s OnExecute method responds to click events unless it is superseded by an OnClick event handler.
Usually, OnClick occurs when the user presses and…
BiDiMode property or DelphiVCL.Application.BiDiMode is used to indicate the layout of the application when running under Middle Eastern versions of Windows.
Use BiDiMode to specify the bi-directional mode for the application. The bi-directional mode controls the…
BiDiKeyboard property or DelphiVCL.Application.BiDiKeyboard is used to specify the name of the keyboard map that should be used in middle-east locales when text reads from right to left.
This name is a string composed of the hexadecimal value of the language…
BeginInvoke method or DelphiVCL.Application.BeginInvoke is used to perform an asynchronous call to the method specified by either AProc or AFunc.
The AContext parameter specifies the context where the method executes in. This context corresponds to the main thread. In case of a Tcontrol descendant, it executes in the context of the thread on which the closest window handle was…
