在图形用户界面中，Window Manager 用于控制窗口系统内窗口的位置和外观的系统软件。大多数窗口管理器旨在帮助提供一个桌面环境。简而言之，窗口管理器就是一个专门控制应用程序窗口在屏幕上如何放置、如何移动、如何改变大小、如何装饰以及如何切换的程序。
下图中标注的就是一个 Window Manager 的组成部分，但是图中 Window Content 的内容是由 Client 或软件绘制的，它不属于 Window Manager；
功能
类型：Compositing WM、Stacking WM、Tiling WM、Dynamic WM
创建应用程序窗口
DeepSeek / Window Manager 与 GTK 的关系
功能：窗口的装饰（边框、标题栏）、位置、大小、堆叠顺序、虚拟桌面、焦点策略、快捷键、……
当我们打开用 GTK 编写的应用（例如 gedit 文本编辑器）时：
所以，我们最终看到的 gedit 窗口是两者合作的产物：窗口内部的UI（内容）由 GTK 绘制。包裹着内容的窗口框架（外壳）由 Window Manager 绘制和管理。
Compositing Window Manager
Wikipedia/Compositing window manager
Compositing window managers let all windows be created and drawn separately and then put together and displayed in various 2D and 3D environments. The most advanced compositing window managers allow for a great deal of variety in interface look and feel, and for the presence of advanced 2D and 3D visual effects.
第一次接触「合成窗口管理器」是因为 ScreenKey 这个工具的背景无法透明。ScreenKey 支持背景透明（Opacity），但是需要安装并运行“合成窗口管理器”（例如，compton、“unagi、xcompmgr、……）。
第二次接触“合乘窗口管理器”是因为 Kazma 截图时，桌面背景无法透明。自然而然的想到了它，然后运行 xcompmgr，然后 Kazma 截图时，桌面背景可以透明显示。
例如：“compton”、“unagi”、“xcompmgr”、Sway
Stacking Window Manager
All window managers that have overlapping windows and are not compositing window managers are stacking window managers, although it is possible that not all use the same methods. Stacking window managers allow windows to overlap by drawing background windows first, which is referred to as the painter’s algorithm. Changes sometimes require that all windows be re-stacked or repainted, which usually involves redrawing every window. However, to bring a background window to the front usually only requires that one window be redrawn, since background windows may have bits of other windows painted over them, effectively erasing the areas that are covered.
例如：the Weston, KWin, and Mutter compositing window managers（Mutter 是 GNOME 3 的窗口管理器）
Tiling Window Manager
Tiling Window Management and i3wm config additions
Tiling window managers paint all windows on-screen by placing them side by side or above and below each other, so that no window ever covers another. Microsoft Windows 1.0 used tiling, and a variety of tiling window managers for X are available.
例如：XMonad、i3wm、Sway
Dynamic window manager
Dynamic window managers can dynamically switch between tiling or floating window layout. A variety of dynamic window managers for X are available.
针对窗口的绘制：Stacking WM vs. Compositing WM
The window manager sends each window a message to repaint itself when needed. Windows may overlap. When a window in front is moved, it can reveal an area of a window behind that was previously concealed. Window managers are broadly categorised by their strategy for causing that newly revealed area to be displayed to the user.
With a stacking manager, the repainting process can become corrupted when a program that is slow, unresponsive or buggy does not respond to messages in a timely manner. A malicious program can cause the system to appear unstable by simply neglecting to repaint its window.
With a compositing manager, if a window stops repainting itself when requested by the window manager, its last repaint will remain displayed and the window might be dimmed. Often, the title changes to reflect the status of the window as unresponsive. A program may prevent its window from being moved or unmapped, but generally will not cause repainting problems.
根据我们的理解，两者主要区别在与绘制窗口的时机。Stacking WM 是按需绘制，而 Compositing WM 则是更早的绘制并维护。
实现
PaperWM | Tiled scrollable window management for GNOME Shell
FVWM
Emacs X Window Manager
ch11ng/exwm: Emacs X Window Manager
EXWM – ArchWiki
for GNOME Desktop Environment
Metacity was the default window manager used by the GNOME 2 desktop environment.
Metacity was replaced by Mutter in GNOME 3. It is still used by GNOME Flashback.
GNOME Flashback 是为了在 GNOME 3 中提供类似 GNOME 2 用户体验。
Mutter
Compiz
https://en.wikipedia.org/wiki/Compiz
Compiz (/kɒmpɪz/) is a compositing window manager for the X Window System, using 3D graphics hardware to create fast compositing desktop effects for window management.