Method
GtkConstraintLayoutadd_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)]
This method is renamed to gtk_constraint_layout_add_constraints_from_description() in language bindings |
Parameters
lines |
An array of char* |
An array of Visual Format Language lines defining a set of constraints. |
|
The length of the array is specified in the n_lines argument. | |
The data is owned by the caller of the function. | |
Each element is a NUL terminated UTF-8 string. | |
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 |
|
The data is owned by the caller of the function. | |
error |
GError ** |
The return location for a GError* , or NULL . |
Return value
Returns: | A list of GtkConstraint* |
The list of
|
|
The caller of the method takes ownership of the data container, but not the data inside it. |