Cocoa Autolayout content hugging vs content compression resistance priority

Question

I can t find a clear answer on Apple documentation regarding Cocoa Autolayout about the difference between content hugging and compression resistance    Can somebody explain their usages and difference

User · Accepted Answer

A quick summary of the concepts    Hugging    content does not want to grow Compression Resistance    content does not want to shrink   Example   Say you ve got a button like this           Click Me          and you ve pinned the edges to a larger superview with priority 500   Then  if Hugging priority   500 it ll look like this    Click Me    If Hugging priority  lt  500 it ll look like this           Click Me          If the superview now shrinks then  if the Compression Resistance priority   500  it ll look like this   Click Me    Else if Compression Resistance priority  lt  500   it could look like this    Cli      If it doesn t work like this then you ve probably got some other constraints going on that are messing up your good work   E g  you could have it pinned to the superview with priority 1000  Or you could have a width priority  If so  this can be helpful   Editor   Size to Fit Content

User · Answer

source   mokagio  Intrinsic Content Size - Pretty self-explanatory  but views with variable content are aware of how big their content is and describe their content s size through this property  Some obvious examples of views that have intrinsic content sizes are UIImageViews  UILabels  UIButtons   Content Hugging Priority - The higher this priority is  the more a view resists growing larger than its intrinsic content size   Content Compression Resistance Priority - The higher this priority is  the more a view resists shrinking smaller than its intrinsic content size   Check here for more explanation  AUTO LAYOUT MAGIC  CONTENT SIZING PRIORITIES

User · Answer

Content Hugging and Content Compression Resistence Priorities work for elements which can calculate their size intrinsically depending upon the contents which are coming in   From Apple docs

User · Answer

Take a look at this video tutorial about Autolayout  they explain it carefully

User · Answer

contentCompressionResistancePriority     The view with the lowest value gets truncated when there is not enough space to fit everything   s intrinsicContentSize  contentHuggingPriority     The view with the lowest value gets expanded beyond its intrinsicContentSize when there is leftover space to fill

User · Answer

Let s say you have a button with the text   Click Me   What width should that button be   First  you definitely don t want the button to be smaller than the text  Otherwise  the text would be clipped  This is the horizontal compression resistance priority   Second  you don t want the button to be bigger than it needs to be  A button that looked like this                       Click  Me                       is obviously too big  You want the button to  hug  its contents without too much padding  This is the horizontal content hugging priority  For a button  it isn t as strong as the horizontal compression resistance priority

User · Answer

If view intrinsicContentSize width    NSViewNoIntrinsicMetric  then auto layout creates a special constraint of type NSContentSizeLayoutConstraint  This constraint acts like two normal constraints    a constraint requiring view width  lt   view intrinsicContentSize width with the horizontal hugging priority  and a constraint requiring view width  gt   view intrinsicContentSize width with the horizontal compression resistance priority    In Swift  with iOS 9 s new layout anchors  you could set up equivalent constraints like this   let horizontalHugging   view widthAnchor constraint      lessThanOrEqualToConstant  view intrinsicContentSize width  horizontalHugging priority   view contentHuggingPriority for   horizontal   let horizontalCompression   view widthAnchor constraint      greaterThanOrEqualToConstant  view intrinsicContentSize width  horizontalCompression priority   view contentCompressionResistancePriority for   horizontal    Similarly  if view intrinsicContentSize height    NSViewNoIntrinsicMetric  then auto layout creates an NSContentSizeLayoutConstraint that acts like two constraints on the view s height  In code  they would look like this   let verticalHugging   view heightAnchor constraint      lessThanOrEqualToConstant  view intrinsicContentSize height  verticalHugging priority   view contentHuggingPriority for   vertical   let verticalCompression   view heightAnchor constraint      greaterThanOrEqualToConstant  view intrinsicContentSize height  verticalCompression priority   view contentCompressionResistancePriority for   vertical    You can see these special NSContentSizeLayoutConstraint instances  if they exist  by printing view constraints after layout has run  Example   label constraints forEach   print  0        Output   lt NSContentSizeLayoutConstraint 0x7fd82982af90 H  UILabel 0x7fd82980e5e0 Hello  39   Hug 250 CompressionResistance 750 gt   lt NSContentSizeLayoutConstraint 0x7fd82982b4f0 V  UILabel 0x7fd82980e5e0 Hello  21   Hug 250 CompressionResistance 750 gt

User · Answer

The Content hugging priority is like a Rubber band that is placed around a view   The higher the priority value  the stronger the rubber band and the more it wants to hug to its content size  The priority value can be imagined like the  strength  of the rubber band  And the Content Compression Resistance is  how much a view  resists  getting smaller  The View with higher resistance priority value is the one that will resist compression

[cocoa] Cocoa Autolayout: content hugging vs content compression resistance priority

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