Make Delphi XE application DPI-unaware

Question

I just created a new application in Delphi and even though other applications written the same way, this new application does not get automatically scaled by Windows. All applications have exactly the same settings (e.g., scaled = false). And Windows usually scales them properly (otherwise they would be too small if scaling is set to 150% or higher).

I found out that using properties menu of the .exe file, tab "Compatibility", "Change HIGH-DPI settings" and set "Scaling by system" on bottom solves the issue and the application gets scaled properly.

But how can I either activate this option by default (Registry?) or how can I do it programmatically?

Are you really using XE (from 2010)? IIRC, XE apps were not DPI-aware to begin with. You had to write a custom app manifest, or make API calls explicitly, to enable DPI awareness. Its only in the last few years that Delphi has been getting proper DPI handling built-in — Remy Lebeau
– Remy Lebeau, Commented Jul 13, 2024 at 4:53
Perhaps there already exists a manifest claiming the app is dpi aware? — Uwe Raabe
– Uwe Raabe, Commented Jul 13, 2024 at 7:33
No, the problem was another DLL, which is loaded at program startup. It de-activates scaling because it needs an unscaled app to work properly. Costs me half the night to find out... — Andreas Ströbel
– Andreas Ströbel, Commented Jul 13, 2024 at 17:24

Remy Lebeau · Accepted Answer · 2024-07-13 18:25:59Z

You can provide your app with an app manifest that specifies <dpiAwareness>unaware</dpiAwareness> (Windows 10 v1607 and later), <gdiScaling>false</gdiScaling> (Windows 10 v1703 and later), and <dpiAware>false</dpiAware> (earlier versions), eg:

<?xml version="1.0" encoding="UTF-8" standalone="yes"?> <assembly xmlns="urn:schemas-microsoft-com:asm.v1" manifestVersion="1.0" xmlns:asmv3="urn:schemas-microsoft-com:asm.v3"> <application xmlns="urn:schemas-microsoft-com:asm.v3"> <windowsSettings> <dpiAware xmlns="http://schemas.microsoft.com/SMI/2005/WindowsSettings">false</dpiAware> <dpiAwareness xmlns="http://schemas.microsoft.com/SMI/2016/WindowsSettings">unaware</dpiAwareness> <gdiScaling xmlns="http://schemas.microsoft.com/SMI/2017/WindowsSettings">false</gdiScaling> </windowsSettings> </application> </assembly>

Alternatively, before creating any GUI windows at runtime, you can call either SetProcessDpiAwarenessContext(DPI_AWARENESS_CONTEXT_UNAWARE) (Windows 10 v1607 and later) or SetProcessDpiAwareness(PROCESS_DPI_UNAWARE) (earlier versions), eg:

program MyProject; uses Vcl.Forms, Winapi.Windows, MyMainForm in 'MainForm.pas' {MyMainForm}; {$R *.res} {$IF NOT DECLARED(DPI_AWARENESS)} type DPI_AWARENESS = ( DPI_AWARENESS_INVALID = -1, DPI_AWARENESS_UNAWARE = 0, DPI_AWARENESS_SYSTEM_AWARE = 1, DPI_AWARENESS_PER_MONITOR_AWARE = 2 ); {$IFEND} {$IF NOT DECLARED(DPI_AWARENESS_CONTEXT)} type DPI_AWARENESS_CONTEXT__ = record var unused: Integer; end; DPI_AWARENESS_CONTEXT = ^DPI_AWARENESS_CONTEXT__; const DPI_AWARENESS_CONTEXT_UNAWARE: DPI_AWARENESS_CONTEXT = DPI_AWARENESS_CONTEXT(-1); {$IFEND} type LPFN_SetProcessDpiAwarenessContext = function(value: DPI_AWARENESS_CONTEXT): BOOL; stdcall; LPFN_SetProcessDpiAwareness = function(value: PROCESS_DPI_AWARENESS): HRESULT; stdcall; var lpSetProcessDpiAwarenessContext: LPFN_SetProcessDpiAwarenessContext; lpSetProcessDpiAwareness: LPFN_SetProcessDpiAwareness; begin @lpSetProcessDpiAwarenessContext := GetProcAddress(LoadLibrary('User32.dll'), 'SetProcessDpiAwarenessContext'); if Assigned(lpSetProcessDpiAwarenessContext) then begin lpSetProcessDpiAwarenessContext(DPI_AWARENESS_CONTEXT_UNAWARE); end else begin @lpSetProcessDpiAwareness := GetProcAddress(LoadLibrary('Shcore.dll'), 'SetProcessDpiAwareness'); if Assigned(lpSetProcessDpiAwareness) then lpSetProcessDpiAwareness(PROCESS_DPI_UNAWARE); end; Application.Initialize; Application.MainFormOnTaskbar := True; Application.CreateForm(TMyMainForm, MyMainForm); Application.Run; end.

See Setting the default DPI awareness for a process on MSDN for more details.

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