Method
Gtk.ConstraintLayout.add_constraints_from_descriptionv
Declaration [src]
GList*
gtk_constraint_layout_add_constraints_from_descriptionv (
GtkConstraintLayout* layout,
const char* const* lines,
gsize n_lines,
int hspacing,
int vspacing,
GHashTable* views,
GError** error
)
Description [src]
Creates a list of constraints from a VFL description.
The Visual Format Language, VFL, is based on Apple’s AutoLayout VFL.
The views
dictionary is used to match GtkConstraintTarget
instances to the symbolic view name inside the VFL.
The VFL grammar is:
<visualFormatString> = (<orientation>)?
(<superview><connection>)?
<view>(<connection><view>)*
(<connection><superview>)?
<orientation> = 'H' | 'V'
<superview> = '|'
<connection> = '' | '-' <predicateList> '-' | '-'
<predicateList> = <simplePredicate> | <predicateListWithParens>
<simplePredicate> = <metricName> | <positiveNumber>
<predicateListWithParens> = '(' <predicate> (',' <predicate>)* ')'
<predicate> = (<relation>)? <objectOfPredicate> (<operatorList>)? ('@' <priority>)?
<relation> = '==' | '<=' | '>='
<objectOfPredicate> = <constant> | <viewName> | ('.' <attributeName>)?
<priority> = <positiveNumber> | 'required' | 'strong' | 'medium' | 'weak'
<constant> = <number>
<operatorList> = (<multiplyOperator>)? (<addOperator>)?
<multiplyOperator> = [ '*' | '/' ] <positiveNumber>
<addOperator> = [ '+' | '-' ] <positiveNumber>
<viewName> = [A-Za-z_]([A-Za-z0-9_]*) // A C identifier
<metricName> = [A-Za-z_]([A-Za-z0-9_]*) // A C identifier
<attributeName> = 'top' | 'bottom' | 'left' | 'right' | 'width' | 'height' |
'start' | 'end' | 'centerX' | 'centerY' | 'baseline'
<positiveNumber> // A positive real number parseable by `g_ascii_strtod()`
<number> // A real number parseable by `g_ascii_strtod()`
Note: The VFL grammar used by GTK is slightly different than the one defined by Apple, as it can use symbolic values for the constraint’s strength instead of numeric values; additionally, GTK allows adding simple arithmetic operations inside predicates.
Examples of VFL descriptions are:
// Default spacing
[button]-[textField]
// Width constraint
[button(>=50)]
// Connection to super view
|-50-[purpleBox]-50-|
// Vertical layout
V:[topField]-10-[bottomField]
// Flush views
[maroonView][blueView]
// Priority
[button(100@strong)]
// Equal widths
[button1(==button2)]
// Multiple predicates
[flexibleButton(>=70,<=100)]
// A complete line of layout
|-[find]-[findNext]-[findField(>=20)]-|
// Operators
[button1(button2 / 3 + 50)]
// Named attributes
[button1(==button2.height)]
Parameters
lines |
An array of char* |
an array of Visual Format Language lines defining a set of constraints |
|
The length of the array is in the n_lines argument | |
Ownership is not transferred to the callee | |
n_lines |
gsize |
the number of lines |
|
hspacing |
int |
default horizontal spacing value, or -1 for the fallback value |
|
vspacing |
int |
default vertical spacing value, or -1 for the fallback value |
|
views |
GHashTable* |
a dictionary of |
|
Ownership is not transferred to the callee |
Return value
Returns: A list of GtkConstraint |
|
the list of
|
|
Ownership of the container type is transferred to the caller |