path: root/src/_responsive.scss

////
/// responsive properties.
///
/// The mixins and functions in this file allow you to scale any px- or rem-based value depending on
/// the available viewport width. One popular use case is the dynamic scaling of fonts.
///
/// The code in this file is based on an article by Niklas Postulart:
/// http://niklaspostulart.de/2015/10/sass-responsive-type-mixin
/// 
/// The following adjustments were made:
/// - Support any property passed by the user, not just font-size
/// - Allow multiple target viewports / values
/// - Provide a variant of the mixin which integrates include-media for media queries
///
/// @group Responsive
///
/// @access public
////

@use './functions';
@use './contexts';

///
/// Context ID used for responsive environment-related mixins.
///
/// @type string
///
$context-id: 'responsive' !default;

///
/// Context ID used for responsive environment-related mixins.
///
/// @type list
///
$named-viewports: () !default;

/// 
/// Scale a property uniformly between a specific set of target viewports / values.
///
/// @param {string | list} $props            - Property or list of properties to set
/// @param {number}        $responsive-map   - A map with keys = viewports and values = target value
/// @param {bool}          $fluid    [true]  - If enabled, property values will smoothly transition from one viewport to the next
/// @param {bool}          $vertical [false] - If enabled, property viewport height will be used instead of viewport width
///
/// @example scss - Responsive font-size between 2 viewports
///   .something {
///     @include property(font-size, ( 320px: 20px, 720px: 30px ));
///   }
///   
///   // Generates:
///   
///   @media (min-width: 320px) and (max-width: 720px) {
///     .something {
///       font-size: calc(20px + 10 * ((100vw - 20px) / 400));
///     }
///   }
///   
///   @media (max-width: 320px) {
///     .something {
///       font-size: 20px;
///     }
///   }
///   
///   @media (min-width: 720px) {
///     .something {
///       font-size: 30px;
///     }
///   }
///
/// @example scss - Responsive font-size between 3 viewports
///   .something {
///     @include property(font-size, ( 320px: 20px, 720px: 30px, 1280px: 40px ));
///   }
///   
///   // Generates:
///   
///   @media (min-width: 320px) and (max-width: 720px) {
///     .something {
///       font-size: calc(20px + 10 * ((100vw - 20px) / 400));
///     }
///   }
///   
///   @media (min-width: 720px) and (max-width: 1280px) {
///     .something {
///       font-size: calc(30px + 10 * ((100vw - 30px) / 400));
///     }
///   }
///   
///   @media (max-width: 320px) {
///     .something {
///       font-size: 20px;
///     }
///   }
///   
///   @media (min-width: 720px) {
///     .something {
///       font-size: 30px;
///     }
///   }
///
@mixin property($props, $responsive-map, $fluid: true, $vertical: false) {
    @include env(map-keys($responsive-map), $fluid, $vertical) {
        @if type-of($props) == list {
            @each $prop in $props {
                #{$prop}: set(map-values($responsive-map));
            }
        } @else {
            #{$props}: set(map-values($responsive-map));
        }
    }
}

/// 
/// Create a new responsive environment by specifying a set of viewports.
/// Inside a responsive environment, use the set function to make a property scale automatically.
///
/// @param {list} $viewports        - Viewports sorted in ascending order
/// @param {bool} $fluid [true]     - If enabled, property values will smoothly transition from one viewport to the next
/// @param {bool} $vertical [false] - If enabled, property viewport height will be used instead of viewport width
///
/// @content
///
/// @see {function} set
///
/// @example scss - Responsive font-size between 2 viewports
///   .something {
///     @include env((320px, 720px)) {
///       font-size: set(20px, 30px);
///     }
///   }
///   
///   // Generates:
///   
///   @media (min-width: 320px) and (max-width: 720px) {
///     .something {
///       font-size: calc(20px + 10 * ((100vw - 20px) / 400));
///     }
///   }
///   
///   @media (max-width: 320px) {
///     .something {
///       font-size: 20px;
///     }
///   }
///   
///   @media (min-width: 720px) {
///     .something {
///       font-size: 30px;
///     }
///   }
///
@mixin env($viewports, $fluid: true, $vertical: false) {
    @if length($viewports) <= 1 {
        @error '$viewports must contain at least two viewports.';
    }

    $new-viewports: ();

    @each $viewport in $viewports {
        @if map-has-key($named-viewports, $viewport) {
            $viewport: map-get($named-viewports, $viewport);
        }

        @if (type-of($viewport) != number) or unitless($viewport) {
            @error '$viewports contains invalid viewports.';
        }

        $new-viewports: append($new-viewports, $viewport);
    }

    $viewports: functions.quicksort($new-viewports);

    @if $new-viewports != $viewports {
        @error '$viewports was not sorted in ascending order.';
    }

    @if $fluid {
        $first-vp: nth($viewports, 1);
        $last-vp:  nth($viewports, length($viewports));

        @include contexts.push($context-id, 'env', (
            'viewports': $viewports,
            'mode':      set,
            'index':     1,
            'fluid':     $fluid,
            'vertical':  $vertical,
        ));

        @content;

        @include contexts.pop($context-id);

        @for $i from 1 to length($viewports) {
            $prev-vp: nth($viewports, $i);
            $next-vp: nth($viewports, $i + 1);

            @if not $vertical {
                @media (min-width: $prev-vp) and (max-width: $next-vp) {
                    @include contexts.push($context-id, 'env', (
                        'viewports': $viewports,
                        'mode':      transition,
                        'index':     $i,
                        'fluid':     $fluid,
                        'vertical':  $vertical,
                    ));

                    @content;

                    @include contexts.pop($context-id);
                }
            } @else {
                @media (min-height: $prev-vp) and (max-height: $next-vp) {
                    @include contexts.push($context-id, 'env', (
                        'viewports': $viewports,
                        'mode':      transition,
                        'index':     $i,
                        'fluid':     $fluid,
                        'vertical':  $vertical,
                    ));

                    @content;

                    @include contexts.pop($context-id);
                }
            }
        }

        @if not $vertical {
            @media (min-width: $last-vp) {
                @include contexts.push($context-id, 'env', (
                    'viewports': $viewports,
                    'mode':      set,
                    'index':     length($viewports),
                    'fluid':     $fluid,
                    'vertical':  $vertical,
                ));

                @content;

                @include contexts.pop($context-id);
            }
        } @else {
            @media (min-height: $last-vp) {
                @include contexts.push($context-id, 'env', (
                    'viewports': $viewports,
                    'mode':      set,
                    'index':     length($viewports),
                    'fluid':     $fluid,
                    'vertical':  $vertical,
                ));

                @content;

                @include contexts.pop($context-id);
            }
        }
    } @else {
        @include contexts.push($context-id, 'env', (
            'viewports': $viewports,
            'mode':      set,
            'index':     1,
            'fluid':     $fluid,
            'vertical':  $vertical,
        ));

        @content;

        @include contexts.pop($context-id);

        @for $i from 2 through length($viewports) {
            $vp: nth($viewports, $i);

            @if not $vertical {
                @media (min-width: $vp) {
                    @include contexts.push($context-id, 'env', (
                        'viewports': $viewports,
                        'mode':      set,
                        'index':     $i
                    ));

                    @content;

                    @include contexts.pop($context-id);
                }
            } @else {
                @media (min-height: $vp) {
                    @include contexts.push($context-id, 'env', (
                        'viewports': $viewports,
                        'mode':      set,
                        'index':     $i
                    ));

                    @content;

                    @include contexts.pop($context-id);
                }
            }
        }
    }
}

///
/// Make a property scale automatically inside a responsive environment.
///
/// @param {list} $values - Value for each viewport in the responsive environment. The first value will be used for the first viewport, the second value for the second viewport, and so on.
/// 
/// @return {number|string}
///
@function set($values, $without-calc: false) {
    $noop: contexts.assert-stack-must-contain($context-id, 'env');

    $data:      nth(contexts.get($context-id, 'env'), 2);
    $viewports: map-get($data, 'viewports');
    $mode:      map-get($data, 'mode');
    $fluid:     map-get($data, 'fluid');
    $vertical:  map-get($data, 'vertical');

    @if length($values) != length($viewports) {
        @error '$values must contain the same number of items as the responsive environment\'s $viewports.';
    }

    @if $mode == set {
        @return nth($values, map-get($data, 'index'));
    } @else {
        $index:      map-get($data, 'index');
        $prev-vp:    nth($viewports, $index);
        $next-vp:    nth($viewports, $index + 1);
        $prev-value: nth($values, $index);
        $next-value: nth($values, $index + 1);

        @return fluid-calc($prev-value, $next-value, $prev-vp, $next-vp, $vertical, $without-calc);
    }
}

/// 
/// Generate the calc() function that uniformly scales a value from $min-value to $max-value depending
/// on the viewport width.
///
/// @param {number} $min-value        - Minimum value
/// @param {number} $max-value        - Maximum value
/// @param {number} $min-viewport     - Minimum viewport size
/// @param {number} $max-viewport     - Maximum viewport size
/// @param {bool}   $vertical [false] - If enabled, property viewport height will be used instead of viewport width
///
/// @access private
///
@function fluid-calc($min-value, $max-value, $min-viewport, $max-viewport, $vertical: false, $without-calc: false) {
    $value-unit:        unit($min-value);
    $max-value-unit:    unit($max-value);
    $viewport-unit:     unit($min-viewport);
    $max-viewport-unit: unit($max-viewport);

    @if $min-value == 0 {
        $value-unit: $max-value-unit;
    }
    @if $max-value == 0 {
        $max-value-unit: $value-unit;
    }
    @if $min-viewport == 0 {
        $viewport-unit: $max-viewport-unit;
    }
    @if $max-viewport == 0 {
        $max-viewport-unit: $viewport-unit;
    }

    @if ($value-unit != $max-value-unit) or ($viewport-unit != $max-viewport-unit) {
        @error 'Units of $min-value and $max-value, $min-viewport and $max-viewport must match.';
    }

    @if ($value-unit == rem) and ($viewport-unit == px) {
        $min-viewport:  functions.px-to-rem($min-viewport);
        $max-viewport:  functions.px-to-rem($max-viewport);
        $viewport-unit: rem;
    } @else if ($value-unit == px) and ($viewport-unit == rem) {
        $min-value:  functions.px-to-rem($min-value);
        $max-value:  functions.px-to-rem($max-value);
        $value-unit: rem;
    }

    @if $value-unit != $viewport-unit {
        @error 'This combination of units is not supported.';
    }

    $value-diff:    functions.strip-unit($max-value - $min-value);
    $viewport-diff: functions.strip-unit($max-viewport - $min-viewport);

    $calc: '';

    @if $min-value != 0 {
        $calc: '#{$min-value} + ';
    }

    @if not $vertical {
        $calc: unquote('#{$calc}#{$value-diff} * (100vw - #{$min-viewport}) / #{$viewport-diff}');
    } @else {
        $calc: unquote('#{$calc}#{$value-diff} * (100vh - #{$min-viewport}) / #{$viewport-diff}');
    }

    @if $without-calc {
        @return $calc;
    } @else {
        @return calc(#{$calc});
    }
}

@include contexts.create($context-id);