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Controls automatic resizing and repositioning of objects in a static layout.




set-object-automatic-resize object &key x-align y-align x-offset y-offset x-ratio y-ratio width-ratio height-ratio aspect-ratio aspect-ratio-y-weight pinboard



A pinboard-object or a simple-pane.


nil, :left, :center or :right.


nil, :top, :center or :bottom.


A real number, default value 0.


A real number, default value 0.


A positive real number or nil.


A positive real number or nil.


A positive real number or nil.


A positive real number or nil.


A positive real number, t or nil.


A real number, default value 0.5.


A static-layout, if supplied. This argument is deprecated, and can always be omitted.


The function set-object-automatic-resize arranges for object to be resized and/or re-positioned automatically when pinboard is resized, or removes such a setting.

The value of aspect-ratio can be t, which means use the current aspect ratio of object (that is, its height divided by its width).

object should be either a pinboard-object or a simple-pane which is (or will be) displayed in a static-layout. This object will be added to the description of the layout by one of its :description initarg, (setf capi:layout-description) or manipulate-pinboard.

pinboard is the layout for object . If pinboard is already displayed with object in its description , the argument pinboard can be omitted.

When pinboard is resized, object is resized if either height-ratio or width-ratio are set.

The new width of object is calculated as follows:

The new height of object is calculated as follows:

If all of width-ratio , height-ratio and aspect-ratio are set, the new width and height of object are calculated as follows:

  1. Compute calculated-width as the width of pinboard multiplied by width-ratio , and calculated-height as the height of pinboard multiplied by height-ratio .
  2. Compute aspect-ratio-ratio as
  3. (/ (/ calculated-height calculated-width ) aspect-ratio )
  4. Compute correction as
  5. ( expt aspect-ratio-ratio aspect-ratio-y-weight )
  6. Compute the new width as calculated-width multiplied by correction , and the new height as the new width multiplied by aspect-ratio .

The result is that if aspect-ratio-y-weight is 0, correction is 1 and height-ratio is effectively ignored, while if aspect-ratio-y-weight is 1, correction cancels the effect of width-ratio . With the default value of 0.5, the resulting position is in the (geometric) middle, and object takes a fixed fraction of the area of the pinboard.

After resizing (if needed), object is also positioned horizontally if x-align is non-nil, and vertically if y-align is non-nil.

The new x coordinate of object is calculated as follows:

The new y coordinate of object is calculated similarly, using y-ratio and y-offset , with an adjustment such that the top, center or bottom of object aligns with the new coordinate according to y-align .

If all of width-ratio , height-ratio , x-align and y-align are nil, automatic resizing/re-positioning of object is removed.

set-object-automatic-resize can be called before object is actually displayed, and its effect persists over calls adding and removing object to/from static-layouts. The effect of set-object-automatic-resize also persists if object is removed and added again, either to the same layout or another layout.

Repeated calls to set-object-automatic-resize set only the values that are passed to set-object-automatic-resize. Keys that are not passed are left with their previous value. A call that removes the automatic resizing (because width-ratio , height-ratio , x-align and y-align are all nil) erases all the values.

set-object-automatic-resize returns t if the object is set up for automatic resizing, or nil if the object is set up for no automatic resizing.

  1. The initarg :automatic-resize can be used to set up automatic resizing in the call to make-instance.
  2. The name set-object-automatic-resize is slightly inaccurate, because this function can alter an object's position without actually changing its size.
Compatibility note

In LispWorks 6.0 the effect of set-object-automatic-resize does not persist if the object is removed and then added, to any layout.

In LispWorks 6.0 each call to set-object-automatic-resize sets all the values.


Put an object of fixed size at the top right corner:

(set-object-automatic-resize object 
                             :x-ratio 1 :x-align :right)

Put an object in the bottom-right quadrant:

 :x-ratio 0.5 :y-ratio 0.5
 :width-ratio 0.5 :height-ratio 0.5)

Put an object with a fixed aspect ratio and object width linear with the width of the layout in the center:

 :x-align :center :y-align :center
 :x-ratio 0.5 :y-ratio 0.5
 :aspect-ratio 0.6 :width-ratio 0.1)

There is a further example in

(example-edit-file "capi/layouts/automatic-resize")
See also


CAPI User Guide and Reference Manual (Unix version) - 25 Feb 2015