DWM Blur for Mica/Acrylic

[Patrice Terrier]

A compact demo of real DWM blur with an image overlay, gradient tint, and DPI-aware text rendering.
All packed in a stand-alone 24 KB /MT binary linked with TClib.lib.

Main Highlights

• True DWM blur toggle (Right-Click) with instant switch — no transition flash.
• Optional image overlay (Middle-Click), scaled and clipped to cover the client while preserving aspect.
• Mouse-wheel–driven alpha control with speed-sensitive step (base 8 → up to 64).
• DPI-aware (Per-Monitor-V2) rendering, sharp at any scaling.
• Seamless maximize/restore via off-viewport reposition — no white flash or DWM fade.
• Off-screen GDI+ compositing (double-buffered).
• Two-color linear gradient overlay via GradientPaintDC, variable opacity / angle.
• Private font collection with dynamic memory allocation (use-and-forget).
• Text orientation: horizontal, bottom-up, or top-down, perfectly centered and clipped.
• Black-theme caption bar with adaptive text color.
• Custom small rounded corners replacing Windows 11’s exaggerated defaults.
• Compatible with Windows 10 & 11 (Mica / Acrylic supported).

Controls
Mouse Right-Click Toggle DWM blur
Mouse Middle-Click Toggle overlay image
Mouse Wheel Adjust overlay alpha (speed-based)


Technical Notes

• Pure Win32 / GDI+ C++ (Visual Studio 2022).
• Static link /MT with TClib.lib → stand-alone 24 KB executable.
• Direct-linked DPI APIs (SetThreadDpiAwarenessContext, GetDpiForWindow, etc.).
• No external runtime or dependencies.
• GDI+ text pipeline: DrawStringFormatedEx + BlurTextPlus.
• Gradient painting handled by GradientPaintDC (two-color ARGB, any angle).
• Caption bar color auto-adapts to Windows theme.
• Custom region defines small uniform corner radius for balanced frame geometry.
• Works seamlessly with DWM blur, Mica, or Acrylic on Windows 11.

Developer Notes

Project goal
To recreate the original Vista-style blur aesthetic with a modern, DPI-aware GDI+ implementation, packaged in a self-contained 24 KB binary (no runtime dependencies).
The design emphasizes simplicity, instant response, and pixel-perfect rendering at any scale.

Rendering architecture

• All drawing is performed on an off-screen buffer created via GDI+ (Graphics object) to guarantee flicker-free updates.
• Final presentation uses BitBlt to the window DC in WM_PAINT.
• WM_ERASEBKGND always returns 1 to avoid background flashes.
• Composition order:
• DWM blur background (if enabled)
• Background image (aspect-preserving cover fit, clipped to client)
• Gradient overlay via GradientPaintDC (two-color linear fill with alpha)
• Text and caption rendering (horizontal or rotated)

Image handling

• Loaded once at WM_CREATE using GDI+ (GdipCreateBitmapFromFile).
• Auto-fit logic computes the largest uniform scale to cover the client area while preserving aspect ratio.
• Clipping handled with IntersectClipRect.
• The image alpha channel is applied dynamically with GdipApplyImageAlpha(img, imgAlpha).

Alpha control

• WM_MOUSEWHEEL adjusts imgAlpha with a base step of 8, automatically scaled for faster wheel spins (up to 64).
• Alpha change triggers a re-composite via InvalidateRect (no erase).

Gradient overlay

• Implemented by GradientPaintDC.
• Simple two-color linear gradient (ARGB start → end), angle-based, with full opacity control.
• Blended using SourceOver compositing on top of the image background.

Text engine

• Uses custom DrawStringFormatedEx and BlurTextPlus for precise GDI+ text layout.
• Supports three orientations: horizontal, bottom-up, and top-down.
• Centered rotation around the text bounding box, with automatic clipping and no duplication artifacts.
• Anti-aliased text rendering via TextRenderingHintAntiAlias.
• Optional soft shadow or blur behind text.

Font management

• Uses GDI+ Private Font Collection API (GdipPrivateAddFontFile / GdipPrivateAddMemoryFont).
• Fonts are loaded dynamically, kept in memory only while needed ("use-and-forget").
• Supports multiple concurrent fonts without leaks or persistent registry installs.

DPI awareness

• Fully Per-Monitor-V2 compliant; no manifest required.
• Enabled through direct calls to SetProcessDpiAwarenessContext and SetThreadDpiAwarenessContext.
• Scale factor (dpi_scale) computed from GetDpiForSystem or GetDpiForWindow as fallback.

Window behavior

• Maximize handling: the window is temporarily moved off-viewport (y = -5000) during SC_MAXIMIZE to suppress DWM transition flashes, then restored normally on SIZE_RESTORED.
• Rounded corners: replaced the default Windows 11 exaggeration with a small, uniform radius using a custom region.
• Caption bar: custom draw with adaptive color — black for dark theme, light for bright.
• Theme changes: WM_SETTINGCHANGE updates caption and text colors automatically.

Performance & build

• Compiled with Visual Studio 2022 /MT.
• Linked with TClib.lib for minimal runtime footprint.
• Final binary: approximately 24 KB stand-alone executable.
• No heap allocations during painting (only during initialization).
• Compatible with Windows 10 and 11, both light and dark modes.

• The full VS2022 C/C++ 64-bit project is attached to this post.