一、简介
NSVisualEffectView 是 macOS 10.10 后开放的一个类，继承自 UIView
提供一个模糊效果的视图
二、相关属性
blendingMode
NSVisualEffectBlendingMode 枚举
typedef NS_ENUM(NSInteger, NSVisualEffectBlendingMode) {
/// Blend with the area behind the window (such as the Desktop or other windows).
NSVisualEffectBlendingModeBehindWindow,
/// Blend with the area behind the view in the window.
NSVisualEffectBlendingModeWithinWindow,
} NS_AVAILABLE_MAC(10_10);
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Behind-window blending uses the content behind the window as the background for your visual effect view. Behind-window blending makes your entire window stand out above other windows and apps on the desktop. Sheets and popovers use behind-window blending.
In-window blending uses the window’s content as the background for your visual effect view. Typically, you use in-window blending with scrolling content, so that the scrolled content remains partially visible under other parts of your window chrome. Toolbars always use in-window blending.
Behind-window 会将窗口背后的内容，作为模糊效果的背景视图；弹窗和表单一般使用 Behind-Window 模式;
In-Window 会将窗体内容作为模糊的背景视图。当滚动窗口时，滚动的内容会在 visualView 下面模糊展示。工具栏 Toolbars 一般使用 In-Window 模式。
设置blendingMode 为 behindwindow，在当前窗口不显示半透明效果；
state
typedef NS_ENUM(NSInteger, NSVisualEffectState) {
/// Use the active look only when the containing window is active.
NSVisualEffectStateFollowsWindowActiveState,
/// Use the active look always.
NSVisualEffectStateActive,
/// Use the inactive look always.
NSVisualEffectStateInactive,
} NS_AVAILABLE_MAC(10_10);
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NSVisualEffectStateActive
激活状态，可以显示半透明模糊；
NSVisualEffectStateInactive
非激活状态，显示不透明
NSVisualEffectStateFollowsWindowActiveState
窗口是激活状态，就是激活。
设置颜色
既然继承自 NSView，那么设置layer color 看看；
设置后，就没有模糊效果了。
allowsVibrancy
当前这个类不会自动添加 vibrancy 到内容；
如果需要 vibrancy，需要创建类继承自 NSVisualEffectView，重写 allowsVibrancy 方法：
-(BOOL)allowsVibrancy{
return YES;
}
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Appkit 会给适当的视图添加 vibrancy。比如 NSTextField, 会增加文字和背景的对比效果。
一般不要去修改标准视图和控件的 vibrancy 属性。
material
模糊的材料，不同的场景使用不同的材料；
简单测试看不出区别，用的时候可以多留意细节。
NSVisualEffectMaterial 枚举
typedef NS_ENUM(NSInteger, NSVisualEffectMaterial) {
/// The material used by window titlebars.
NSVisualEffectMaterialTitlebar = 3,
/// The material used in some table views, menus, etc., to indicate selection.
NSVisualEffectMaterialSelection = 4,
/// The material used by menus.
NSVisualEffectMaterialMenu NS_ENUM_AVAILABLE_MAC(10_11) = 5,
/// The material used in the background of NSPopover windows.
NSVisualEffectMaterialPopover NS_ENUM_AVAILABLE_MAC(10_11) = 6,
/// The material used in the background of window sidebars.
NSVisualEffectMaterialSidebar NS_ENUM_AVAILABLE_MAC(10_11) = 7,
/// The material used in various in-line header or footer views (e.g., by NSTableView).
NSVisualEffectMaterialHeaderView NS_ENUM_AVAILABLE_MAC(10_14) = 10,
/// The material used as the background of sheet windows.
NSVisualEffectMaterialSheet NS_ENUM_AVAILABLE_MAC(10_14) = 11,
/// The material used by opaque window backgrounds.
NSVisualEffectMaterialWindowBackground NS_ENUM_AVAILABLE_MAC(10_14) = 12,
/// The material used as the background of heads-up display (HUD) windows.
NSVisualEffectMaterialHUDWindow NS_ENUM_AVAILABLE_MAC(10_14) = 13,
/// The material used as the background of full-screen modal UI.
NSVisualEffectMaterialFullScreenUI NS_ENUM_AVAILABLE_MAC(10_14) = 15,
/// The material used as the background of tool tips.
NSVisualEffectMaterialToolTip NS_ENUM_AVAILABLE_MAC(10_14) = 17,
/// The material used as the opaque background of content (e.g., by NSScrollView, NSTableView, NSCollectionView, etc.).
NSVisualEffectMaterialContentBackground NS_ENUM_AVAILABLE_MAC(10_14) = 18,
/// The material used under window backgrounds.
NSVisualEffectMaterialUnderWindowBackground NS_ENUM_AVAILABLE_MAC(10_14) = 21,
/// The material used as the background behind document pages.
NSVisualEffectMaterialUnderPageBackground NS_ENUM_AVAILABLE_MAC(10_14) = 22,
/// A default material appropriate for the view's effectiveAppearance. You should instead choose an appropriate semantic material.
NSVisualEffectMaterialAppearanceBased NS_ENUM_DEPRECATED_MAC(10_10, API_TO_BE_DEPRECATED, "Use a specific semantic material instead.") = 0,
// Materials with specific looks. You should instead choose an appropriate semantic material.
NSVisualEffectMaterialLight NS_ENUM_DEPRECATED_MAC(10_10, API_TO_BE_DEPRECATED, "Use a semantic material instead. To force the appearance of a view hierarchy, set the `appearance` property to an appropriate NSAppearance value.") = 1,
NSVisualEffectMaterialDark NS_ENUM_DEPRECATED_MAC(10_10, API_TO_BE_DEPRECATED, "Use a semantic material instead. To force the appearance of a view hierarchy, set the `appearance` property to an appropriate NSAppearance value.") = 2,
NSVisualEffectMaterialMediumLight NS_ENUM_DEPRECATED_MAC(10_11, API_TO_BE_DEPRECATED, "Use a semantic material instead. To force the appearance of a view hierarchy, set the `appearance` property to an appropriate NSAppearance value.") = 8,
NSVisualEffectMaterialUltraDark NS_ENUM_DEPRECATED_MAC(10_11, API_TO_BE_DEPRECATED, "Use a semantic material instead. To force the appearance of a view hierarchy, set the `appearance` property to an appropriate NSAppearance value.") = 9,
} NS_AVAILABLE_MAC(10_10);
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interiorBackgroundStyle（只读）
NSBackgroundStyle 枚举
typedef NS_ENUM(NSInteger, NSBackgroundStyle) {
/* The background reflects the predominant color scheme of the view's appearance. */
NSBackgroundStyleNormal = 0,
/* The background is indicating emphasis (e.g. selection state) using an alternate color or visual effect. Content may alter its appearance to reflect this emphasis. */
NSBackgroundStyleEmphasized,
/* The background is intended to appear higher than the content drawn on it. Content might need to be inset. */
NSBackgroundStyleRaised,
/* The background is intended to appear lower than the content drawn on it. Content might need to be embossed. */
NSBackgroundStyleLowered,
}
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原文：https://blog.csdn.net/lovechris00/article/details/83273998