Issue with WizardForm.Color := clNone Transparency in Inno Setup (Win11 Style)

[super big mouth]

Dear Support,

I’ve been highly impressed with Inno Setup – it’s one of the most robust installation tools I’ve ever used. However, I’m currently stuck on an issue that neither Google searches nor AI assistants could resolve. I’d sincerely appreciate your help!

Problem:

• Trying to achieve a modern Windows 11-style window (rounded corners + drop shadow).
• Using Inno Setup 5.6+ with a 32-bit transparent PNG (attached).
• Set WizardForm.Color := clNone (documented as "transparent"), but shadow edges turn black instead of blending.

What I’ve Tried:
✔ Confirmed PNG has alpha channel (tested in Photoshop).
✔ Tested multiple versions (5.6.0+).

Could you advise how to properly implement transparency? Thank you for your expertise!

[Eivind Bakkestuen]

Did your multiple versions test include the latest v6.x?

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[super big mouth]

Yes, including v6.4.3 (see attached).

clNone is black.

[Martijn Laan]

Op 17-5-2025 om 17:18 schreef super big mouth:

Trying to achieve a modern Windows 11-style window (rounded corners + drop shadow).

Are you talking about getting this on older versions of Windows? Because on Windows 11 the corners of the wizard should be rounded already.

This transparency and shadow is handled by Windows' Desktop Window Manager (DWM) and your current approach is never going to work. You will need to call DWM functions instead to make such changes but I don't know which ones (if any) would get you rounded corners on older version of Windows. Also don't think it's a good idea to begin with: on an older version like Windows 10 the wizard should look like a Windows 10 window and not a Windows 11 window.

Many DWM functions are undocumented BTW, and risky to call, especially from an installer which is supposed to always work.

Greetings,
Martijn