Inno Setup - how to center an animated gif in resized wizard

Question

I would like to center my animated gif right in the middle of all pages in my installer ( WizardSizePercent=150) without using values.

Here is my code:

var
  ParentForm: TSetupForm;

begin
  TimerID := 0;
  SlideID := 0;
  ContentHeight := ParentForm.Top + ParentForm.Height;
  ExtractTemporaryFile('Image1.bmp');
  ExtractTemporaryFile('Image2.bmp');
  ExtractTemporaryFile('Image3.bmp');
  ExtractTemporaryFile('Image4.bmp');
  ExtractTemporaryFile('Image5.bmp');
  ExtractTemporaryFile('Image6.bmp');


  Panel := TPanel.Create(ParentForm);
  Panel.Parent := ParentForm;
  Panel.Left := 185;
  Panel.Top := ParentForm.Top + 130;
  Panel.Width := 1000;
  Panel.Height := 380;
  Panel.Visible := True;

  BackImage := TBitmapImage.Create(ParentForm);
  BackImage.Parent := Panel;
  BackImage.Width:= 1000;
  BackImage.Height:= 380;
  BackImage.Left := (Panel.Height - BackImage.Height) div 2;
  BackImage.Top := (Panel.Height - BackImage.Height) div 2;
  BackImage.Bitmap.LoadFromFile(ExpandConstant('{tmp}\Image1.bmp'));
  StartSlideTimer;
end;

How do I have to change the values of ContentHeight, Panel and BackImage?

Martin Prikryl · Accepted Answer · 2022-01-26T11:05:13.320

The WizardSizePercent (both explicit and implied by WizardStyle=modern) apply only after the InitializeWizard. So the controls explicitly positioned in InitializeWizard can become misplaced afterwards.

Either position the image only after the WizardSizePercent is applied. So e.g. in the CurPageChanged, not in InitializeWizard.

Or better, to have a more robust solution, that works e.g. even with WizardResizable, respond to WizardForm.OnResize by updating the image coordinates (or rather the Panel coordinates – though I do not understand its purpose). For an example, see Setting control width to half of custom page SurfaceWidth does not work correctly in Inno Setup.

In many cases, you can also use Anchors property to have the control resize automatically. For some example, see Inno Setup - aligning custom button with the Cancel button.

Also note that you cannot use constant coordinates. Your image would not center correctly on high DPI displays. Either scale the coordinates – for that check for example Inno Setup Placing image/control on custom page. Or in your case, it would be better, if you calculate the centered coordinates programmatically based on the image and window sizes – for that, check the In Inno Setup, how do I center some text in the window?

Inno Setup - how to center an animated gif in resized wizard

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