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Considerations When Dynamically Resizing Forms and Controls

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If the forms and visual controls for an application are dynamically resized, accommodate all aspects of the resizing process to ensure optimal appearance of the application under all possible screen resolutions. Here are some factors to consider when dynamically resizing the visual elements of an application:

  • The resizing of forms and visual controls is done at a ratio calculated by comparing the screen resolution of the development computer to that of the computer onto which the application installed. Use a constant to represent one dimension of the screen resolution on the development computer: either the height or the width, in pixels. Retrieve the same dimension for the user's computer at run time using the TScreen.Height or TScreen.Width property. Divide the value for the development computer by the value for the user's computer to derive the difference ratio between the two computers' screen resolutions.
  • Resize the visual elements of the application (forms and controls) by reducing or increasing the size of the elements and their positions on forms. This resizing is proportional to the difference between the screen resolutions on the development and user computers. Resize and reposition visual controls on forms automatically by setting the CustomForm.Scaled form's Scaled property to True and calling TWinControl.ScaleBy its ScaleBy method . The ScaleBy method does not change the form's height and width, though. Do this manually by multiplying the current values for the Height and Width properties by the screen resolution difference ratio.
  • The controls on a form can be resized manually, instead of automatically with the TWinControl.ScaleBy method , by referencing each visual control in a loop and setting its dimensions and position. The Height and Width property values for visual controls are multiplied by the screen resolution difference ratio. Reposition visual controls proportional to screen resolution differences by multiplying the Top and Left property values by the same ratio.
  • If an application is designed on a computer configured for a higher screen resolution than that on the user's computer, font sizes will be reduced in the process of proportionally resizing visual controls. If the size of the font at design time is too small, the font as resized at run time may be unreadable. For example, the default font size for a form is 8. If the development computer has a screen resolution of 1024x768 and the user's computer 640x480, visual control dimensions will be reduced by a factor of 0.625 (640 / 1024 = 0.625). The original font size of 8 is reduced to 5 (8 * 0.625 = 5). Text in the application appears jagged and unreadable as it is displayed in the reduced font size.
  • Some visual controls, such as TLabel and TEdit, dynamically resize when the size of the font for the control changes. This can affect deployed applications when forms and controls are dynamically resized. The resizing of the control due to font size changes are in addition to size changes due to proportional resizing for screen resolutions. This effect is offset by setting the AutoSize property of these controls to False.
  • Avoid making use of explicit pixel coordinates, such as when drawing directly to a canvas. Instead, modify the coordinates by a ratio proportionate to the screen resolution difference ratio between the development and user computers. For example, if the application draws a rectangle to a canvas ten pixels high by twenty wide, instead multiply the ten and twenty by the screen resolution difference ratio. This ensures that the rectangle visually appears the same size under different screen resolutions.

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