QT | set part size sizehint, minimumsizehint, sizepolicy, stretch factor

Environmental Science ：Qt Creator5.5.1

- sizeHint: Size hint

sizeHint Attribute saves the recommended size of the part , For different parts , Default to have different sizeHint; Of the same part sizeHint It could be different , The size changes with the content of the part .

- minimumSizeHint: Minimum size hint

minimumSizeHint Saved a suggested minimum size prompt , Generally, it plays a role in the layout .

- sizePolicy: Size strategy

sizePolicy The default layout behavior of the assembly is saved , Works in both horizontal and vertical directions , Controls the size change behavior of components in the layout manager . Explain the scaling method of components in layout management . Values are ：

• Fixed： fixed ; Parts cannot be retracted , Its size can only be sizeHint() Value .

• Minimum：sizeHint() Set a minimum value for the part , The minimum component cannot be less than this value , But parts can be stretched .

• Maximum：sizeHint() Set a maximum value for the part , The maximum value of components cannot be greater than this , But parts can be compressed .

• Preferred： Priority ;sizeHint() Provide an optimal size for components , But it can change , Can stretch or compress .

• Expanding： Enlarged ;sizeHint() Provide a suitable size for the part , Parts can be compressed , But parts tend to be stretched to get larger sizes .

• MinimumExpanding：sizeHint() The size provided to the part is the minimum , Parts tend to be stretched to get larger sizes .

• Ignord：sizeHint() The value of is ignored , The part will be stretched as much as possible to obtain a larger size .

sizePolicy( Size strategy ) And sizeHint( Size hint ) The value of is related .

give an example ：

stay Qt Desiner One of them Spacer come out , Set up Spacer Of sizeHint The width is 200, But on the interface Spacer The width of does not reach 200. You can see its sizeType Property is set to Expanding.

If you change it to Fixed, This interface Spacer It widened immediately , Now its actual height is sizeHint Height .

- stretch factor: The scaling factor

stretch factor It is used to set the proportion between parts . In the figure widget_title It is a horizontal layout QWidget, There are four parts ：

So in its property bar layoutStretch There are four numbers in the attribute ,“0,0,0,0”

These four numbers represent the width ratio of the four parts is 1:1:1:1, We can modify the proportional relationship between components , Select the proportional value , Change the value to ：“2,1,1,1”, At this time , The first component is the other three components 2 Double the width .