Hey there! Let's break down how to fix both of your issues with the wm overscan command.

一、解决部分应用（WhatsApp、启动器）的额外黑色边框问题 #

The extra black borders you're seeing in apps like WhatsApp and your launcher usually happen because these apps don't automatically adapt to the global overscan setting—they might have hardcoded layout constraints or rely on the system's default window bounds instead of respecting the overscan adjustment. Here are a few actionable fixes:

1. 为特定应用单独配置Overscan #

Instead of applying the overscan globally, target the problematic apps directly with a modified command. For example:

# 针对WhatsApp设置overscan
wm overscan --user 0 com.whatsapp 0,80,0,0
# 针对启动器（替换成你的启动器包名，比如Nova Launcher是com.teslacoilsw.launcher）
wm overscan --user 0 [你的启动器包名] 0,80,0,0

This forces the specific app to respect the overscan bounds instead of using its default layout.

2. 调整应用的显示比例设置 #

Most Android systems have a built-in setting to tweak how apps display:

• Go to Settings > Display > App Display Size (or similar wording like "Fullscreen Apps")
• Find WhatsApp and your launcher in the list
• Set their display mode to "Fullscreen" or "Adaptive" (options may vary by device)
  This tells the app to expand its layout to fill the entire adjusted screen area.

3. 检查应用内部设置 #

Some apps (including launchers) have their own fullscreen settings:

• For WhatsApp: Look for display-related toggles in the app's main settings (some versions have a "Fullscreen" option hidden under display preferences)
• For launchers: Long-press the home screen to open the launcher settings, then look for options like "Hide Status Bar" or "Fullscreen Mode" to force it to fill the overscan-adjusted screen.

二、将Overscan区域颜色改为黑色（而非状态栏颜色） #

By default, the overscan area inherits the system's window background color (which often matches the status bar or system theme). To set it to pure black, you'll need to adjust the system's window background settings. Here's how:

1. 使用Settings命令（需ADB或Root权限） #

If you're running commands via ADB or have a rooted device, use this command to set the system window background to black:

# 设置窗口背景为黑色（0xff000000是ARGB格式的纯黑色）
settings put system window_background_color 0xff000000

After running this, restart your device or restart the system UI (with adb shell am restart or su && killall system_server) to apply the change.

2. 针对Root设备：修改Framework资源（进阶） #

If the above command doesn't work, you can modify the system's framework resources (requires root and a tool like APK Editor):

• Locate framework-res.apk in /system/framework/
• Open it and navigate to res/values/colors.xml
• Find the window_background entry and change its value to #ff000000 (pure black)
• Recompile and push the modified APK back to the system, then reboot.

Note: This is an advanced method—make sure to back up the original framework-res.apk before making changes to avoid breaking your system.

内容的提问来源于stack exchange，提问作者CodeSharpMarvin