TdxCustomForm.ScaleFactorChanged(Integer,Integer) Method

Automatically scales the form and components within it when the scale factor changes.

Declaration

procedure ScaleFactorChanged(M: Integer; D: Integer); virtual;

Parameters

Name	Type	Description
M	Integer	The new scale factor multiplier.
D	Integer	The new scale factor denominator.

Remarks

The ScaleFactorChanged procedure is called automatically every time the application accepts the WM_DPICHANGED^[1] system message if the Scaled property is set to True. ScaleFactorChanged calls the UpdateImageLists procedure to dynamically switch between multiple image lists with bitmap icons that target different DPIs.

For example you can override the ScaleFactorChanged procedure in a TdxCustomForm class descendant to execute custom actions when the ScaleFactor property value changes. To allow the custom form to switch between DPI-specific image lists, call the UpdateImageLists procedure within a custom ScaleFactorChanged procedure implementation.

Tip

This image list replacement technique is deprecated. We recommend that you use only SVG images as UI icons in projects that target multi-monitor high-DPI environments.

Code Example

The following code example demonstrates a custom ScaleFactorChanged procedure implementation that switches between multiple image lists based on DPI thresholds:

Delphi

function TMyForm.GetMostSuitableImageList: TcxImageList;
var
  ATargetDPI: Integer;
begin
  ATargetDPI := ScaleFactor.Apply(96);  // Calculates the current DPI
  if ATarget >= 192 then
    Result := ilImages200  // Chooses the icon set designed for 200% DPI
  else if ATargetDPI >= 144 then
    Result := ilImages150  // Chooses the icon set designed for 150% DPI
  else if ATargetDPI >= 120 then
    Result := ilImages125  // Chooses the icon set designed for 125% DPI
  else
    Result := ilImages;  // Chooses the icon set designed for 100% DPI (unscaled)
end;

procedure TMyForm.ScaleFactorChanged(M, D: Integer); // Overrides the ScaleFactorChanged procedure
var
  AImageList: Integer;
begin
  AImageList := GetMostSuitableImageList;  // Chooses a suitable replacement image list
  btnBMPGlyph.OptionsImage.Images := AImageList;  // Substitutes the button's image list
  AImageList.GetImage(0, btnBMPGlyph.OptionsImage.Glyph);  // Applies the first image as a button glyph
  btnBMPGlyph.OptionsImage.Glyph.SourceDPI := AImageList.SourceDPI; // Updates the glyph DPI
end;

C++

TcxImageList* __fastcall TMyForm::GetMostSuitableImageList(void)
{
  int ATargetDPI = ScaleFactor->Apply(96); // Calculates the form's DPI
  if(ATargetDPI >= 192) { return ilImages200; }  // Chooses the icon set designed for 200% DPI
  else if(ATargetDPI >= 144) { return ilImages150; }  // Chooses the icon set designed for 150% DPI
  else if(ATargetDPI >= 120) { return ilImages125; }  // Chooses the icon set designed for 125% DPI
  else { return ilImages; }  // Chooses the icon set designed for 100% DPI (unscaled)
}

void __fastcall TMyForm::ScaleFactorChanged(int M, int D)  // Overrides the ScaleFactorChanged procedure
{
  TcxImageList *AImageList = GetMostSuitableImageList();  // Chooses a suitable replacement image list
  btnBMPGlyph->OptionsImage->Images = AImageList;  // Substitutes the button's image list
  AImageList->GetImage(0, btnBMPGlyph->OptionsImage->Glyph);  // Applies the first image as a button glyph
  btnBMPGlyph->OptionsImage->Glyph->SourceDPI = AImageList->SourceDPI;  // Updates the glyph DPI
}

Footnotes

1. An application accepts the WM_DPICHANGED system message only if the application manifest includes the permonitor or permonitorv2 item.