v13-rc1 (2025-Dec-09)

New features

Separate the "geometry" animation trigger into "size" and "position" to allow finer-grained control. "geometry" is kept as an alias for setting both "size" and "position".
Add a "urgent" target that can be used in rules to match urgent (according to ICCCM) windows. (#1445)
New "shadow-color" per-window option can now be used in rules to give each window a different shadow color. (#257)
Added new animation trigger color, which can now be used to transition window shadow-color changes. (#257)
Add support for using custom shaders when rendering the desktop background. (#1440)
New variables "window-blur-opacity-before", and "window-blur-opacity" are now available in animation scripts. (#919)
New per-window option blur-opacity can now be used in rules. (#919)
Macro definitions can now be specified when setting shader in window rules. (#1066)

--legacy-backends is now deprecated. Setting it no longer has an effect.
resize-damage, glx-no-stencil and glx-no-rebind-pixmap are now deprecated, because they only works on legacy backends.
Removed several options that have been deprecated for a long time, this includes:
- glx-fshader-win
- glx-swap-method
- glx-use-gpushader4
- menu-opacity
- vsync-aggressive
- respect-prop-shadow
- sw-opti
- clear-shadow

The desktop background image is no longer smeared to fill the screen. If it's too small, it will be too small. (#1464)

Fix sometimes window property changes aren't reflected in picom.
Fix shadow-opacity being applied twice. You may need to adjust your shadow-opacity settings.
Properly fix the longstanding "request too big" problem when uploading shadow images. (Previous workaround: 69b3eee) (#257)
Fix window frames not being blended correctly when using frame-opacity with saved-image-blend.
Fix shadow not being correctly masked when scaled. (#1389)
Fix misaligned shadow and window when they are scaled. (#1389)
Fix unexpected relative movement between shadow and window when they are scaled. (#1389)
background blur does not cover the entire background if the window has rounded corner and is scaled.
Fix shaders in window-shader-fg-rule being erroneously reported as failed to load.
Fix --blur-background-fixed having no effect. (#1402)
Fix assertion failure when running with some window managers (e.g. qtile) and no window is focused (#1384)

Breaking change to backend API, to allow better image creation, and applying tints to windows.
Refactor shadow rendering, preparing for dynamic shadow colors.
Backend API 2.0 breaking change, backend_mask_image.origin is now a vec2.
Backend API 2.0 breaking change, backend_blur_args now has source_mask_scale.
Backend API 2.0 breaking change, backend_blit_args.shader is now shader_handle instead of void *.