Resolution independent applications

Problem/Question/Abstract:

Have you ever wondered how to display your forms and components always the same size no matter what the screen resolution is?

Answer:

You have to modify your project�s DPR file to acomplish that:

// Modify your projects code to achieve resolution independent
// applications. I have found that this trick only works for
// resolutions greater than the resolution you design the forms, for
// example if you design at 800x600 you can use your application at
// a resolution of 1024 x 768 or greater.
// However it won�t run fine at 640x480 (altough, nowadays I don�t
// kwonw many people with thatv resolution, so I think 800X600 is
// fine)

program TestResolution;

uses
  Forms,
  Dialogs,
  Classes,
  TypInfo,
  Windows,
  Unit1 in 'Unit1.pas' {Form1},
  Unit2 in 'Unit2.pas' {Form2};

{$R *.RES}

const
  //If form is designed in 800 x 600 mode
  ScreenWidth: LongInt = 800;
  ScreenHeight: LongInt = 600;

var
  vi_Counter1, vi_Counter2: Integer;
  NewFormWidth: Integer;

begin
  Application.Initialize;
  Application.CreateForm(TForm1, Form1);
  Application.CreateForm(TForm2, Form2);
  NewFormWidth := GetSystemMetrics(0);

  with Application do
    for vi_Counter1 := 0 to ComponentCount - 1 do
    begin
      //Find all the Auto-create forms
      if Components[vi_Counter1] is TForm then
        with (Components[vi_Counter1] as TForm) do
        begin
          Scaled := True;
          if screen.Width <> ScreenWidth then
          begin
            Height := longint(Height) * longint(screen.Height) div
              ScreenHeight;
            Width := longint(Width) * longint(screen.Width) div
              ScreenWidth;
            ScaleBy(screen.Width, ScreenWidth);

            //Now Scale the Form�s component�s Font
            for vi_Counter2 := 0 to ControlCount - 1 do
              with Components[vi_Counter2] do
                //Use RTTI information to find for a Font property
                if GetPropInfo(ClassInfo, 'font') <> nil then
                  Font.Size := (NewFormWidth div ScreenWidth)
                    * font.Size;
          end;
        end;
    end;
  Application.Run;
end.

finally some aditional considerations:

You will have to scale every form create on the fly.
Use only TrueType fonts, not Bitmapped fonts to avoid problems.
Don�t set the Form�s Position property to poDesigned, when scalling it could be off the screen.
Don't change the PixelsPerInch property of the form.
Don't crowd controls on the form - leave at least 4 pixels between controls, so that a one pixel change in border  locations (due to scaling) won't show up as ugly overlapping  controls.