numix-gtk-theme/gtk-3.20/scss/widgets/_button.scss

/*********
 ! Buttons
**********/

@include exports("button_extends") {
    // stuff for .needs-attention
    $_dot_color: if($variant=='light', $selected_bg_color, lighten($selected_bg_color, .15));

    @keyframes needs_attention {
        from {
            background-image: -gtk-gradient(radial, center center, 0, center center, .01, to($_dot_color), to(transparent));
        }

        to {
            background-image: -gtk-gradient(radial, center center, 0, center center, .5, to($selected_bg_color), to(transparent));
        }
    }

    %needs_attention {
        animation: needs_attention 150ms ease-in;
        $_dot_shadow: _text_shadow_color();
        $_dot_shadow_r: if($variant=='light', .5, .45);
        background-image: -gtk-gradient(radial, center center, 0, center center, .5, to($_dot_color), to(transparent)),
                          -gtk-gradient(radial, center center, 0, center center, $_dot_shadow_r, to($_dot_shadow), to(transparent));
        background-size: 6px 6px, 6px 6px;
        background-repeat: no-repeat;

        @if $variant == 'light' {
            background-position: right 3px, right 4px;
        } @else {
            background-position: right 3px, right 2px;
        }

        &:backdrop { background-size: 6px 6px, 0 0; }

        &:dir(rtl) {
            @if $variant == 'light' {
                background-position: left 3px, left 4px;
            } @else {
                background-position: left 3px, left 2px;
            }
        }
    }

    %button {
        min-height: 22px;
        min-width: 20px;
        padding: ($spacing - 3px) ($spacing + 1px);
        border-width: 1px;
        border-style: solid;
        border-radius: $roundness;
        transition: 150ms ease;
        outline-color: transparent;
    }

    %undecorated_button {
        border-color: transparent;
        background-color: transparent;
        background-image: none;
        box-shadow: none;
    }

    %linked_middle {
        border-radius: 0;
        border-left-style: none;
        border-right-style: solid;

        &:dir(rtl) {
            border-radius: 0; // needed when including %linked_middle:dir(rtl)
            border-right-style: none;
            border-left-style: solid;
        }
    }

    %linked_vertical_middle {
        border-radius: 0;
        border-top-style: none;
        border-bottom-style: solid;

        &:dir(rtl) {
            border-radius: 0; // needed when including %linked_vertical_middle:dir(rtl)
            border-top-style: none;
            border-bottom-style: solid;
        }
    }

    %linked_button {
        border-width: 1px;
        border-style: solid;
        border-radius: 0;
        border-right-style: none;
        border-left-style: none;

        &:first-child {
            border-width: 1px;
            border-radius: $roundness;
            border-left-style: solid;
            border-right-style: none;
            border-top-right-radius: 0;
            border-bottom-right-radius: 0;

            &:dir(rtl) {
                border-left-style: none;
                border-right-style: solid;
            }
        }

        &:last-child {
            border-width: 1px;
            border-radius: $roundness;
            border-left-style: none;
            border-right-style: solid;
            border-top-left-radius: 0;
            border-bottom-left-radius: 0;

            &:dir(rtl) {
                border-left-style: solid;
                border-right-style: none;
            }
        }

        &:only-child, &:first-child:only-child {
            border-width: 1px;
            border-style: solid;
        }

        &:only-child {
            border-radius: $roundness;
        }
    }

    %linked_vertical_button {
        border-width: 1px;
        border-style: solid;
        border-radius: 0;
        border-top-style: none;
        border-bottom-style: none;

        &:first-child {
            border-width: 1px;
            border-radius: $roundness;
            border-top-style: solid;
            border-bottom-style: none;
            border-bottom-left-radius: 0;
            border-bottom-right-radius: 0;

            &:dir(rtl) {
                border-top-style: none;
                border-bottom-style: solid;
            }
        }

        &:last-child {
            border-width: 1px;
            border-radius: $roundness;
            border-top-style: none;
            border-bottom-style: solid;
            border-top-left-radius: 0;
            border-top-right-radius: 0;

            &:dir(rtl) {
                border-top-style: solid;
                border-bottom-style: none;
            }
        }

        &:only-child, &:first-child:only-child {
            border-width: 1px;
            border-style: solid;
        }

        &:only-child {
            border-radius: $roundness;
        }
    }
}

@mixin linked_button($bg) {
    $border_strength: if(lightness($bg) > 50, 0, .1);
    $shadow_strength: if(lightness($bg) > 50, 0, .1);

    @extend %linked_button;

    box-shadow: inset -1px 0 border_normal(rgba(0, 0, 0, .12 + $border_strength)),
    0 1px 2px -1px alpha($dark_shadow, .12 + $shadow_strength);

    &:focus, &:hover {
        box-shadow: inset -1px 0 border_focus(rgba(0, 0, 0, .12 + $border_strength)),
        0 1px 2px -1px alpha($dark_shadow, .32 + $shadow_strength);
    }

    &:active, &:active:hover,
    &:active:focus, &:active:hover:focus,
    &:checked, &:checked:hover,
    &:checked:focus, &:checked:hover:focus {
        box-shadow: inset -1px 0 border_active(rgba(0, 0, 0, .12 + $border_strength)),
        inset 0 1px alpha($dark_shadow, .07),
        inset 0 -1px alpha($dark_shadow, .05);
    }

    &:disabled { box-shadow: inset -1px 0 shade($bg, .8); }

    &:last-child, &:only-child { box-shadow: 0 1px 2px -1px alpha($dark_shadow, .12 + $shadow_strength); }

    &:last-child:hover, &:only-child:hover { box-shadow: 0 1px 2px -1px alpha($dark_shadow, .32 + $shadow_strength); }

    &:disabled:last-child, &:disabled:only-child,
    &:active:disabled:last-child, &:active:disabled:only-child,
    &:checked:disabled:last-child, &:checked:disabled:only-child { box-shadow: none; }

    &:active:last-child, &:active:last-child:focus, &:active:last-child:hover, &:active:last-child:hover:focus,
    &:checked:last-child, &:checked:last-child:focus, &:checked:last-child:hover, &:checked:last-child:hover:focus {
        box-shadow: inset 0 1px alpha($dark_shadow, .07),
        inset -1px 0 alpha($dark_shadow, .06);
    }

    &:active:only-child, &:active:only-child:focus, &:active:only-child:hover, &:active:only-child:hover:focus,
    &:checked:only-child, &:checked:only-child:focus, &:checked:only-child:hover, &:checked:only-child:hover:focus {
        box-shadow: inset 1px 0 alpha($dark_shadow, .06),
        inset 0 1px alpha($dark_shadow, .07),
        inset -1px 0 alpha($dark_shadow, .06);
    }
}

@mixin linked_vertical_button($bg) {
    $border_strength: if(lightness($bg) > 50, 0, .1);
    $shadow_strength: if(lightness($bg) > 50, 0, .1);

    @extend %linked_vertical_button;

    box-shadow: inset 0 -1px border_normal(rgba(0, 0, 0, .12 + $border_strength)),
    0 1px 2px -1px alpha($dark_shadow, .12 + $shadow_strength);

    &:focus, &:hover {
        box-shadow: inset 0 -1px border_focus(rgba(0, 0, 0, .12 + $border_strength)),
        0 1px 2px -1px alpha($dark_shadow, .32 + $shadow_strength);
    }

    &:active, &:active:hover,
    &:active:focus, &:active:hover:focus,
    &:checked, &:checked:hover,
    &:checked:focus, &:checked:hover:focus {
        box-shadow: inset 0 -1px border_active(rgba(0, 0, 0, .12 + $border_strength)),
        inset 1px 0 alpha($dark_shadow, .07),
        inset -1px 0 alpha($dark_shadow, .05);
    }

    &:disabled { box-shadow: inset 0 -1px shade($bg, .8); }

    &:last-child, &:only-child { box-shadow: 0 1px 2px -1px alpha($dark_shadow, .12 + $shadow_strength); }

    &:last-child:hover, &:only-child:hover { box-shadow: 0 1px 2px -1px alpha($dark_shadow, .32 + $shadow_strength); }

    &:disabled:last-child, &:disabled:only-child,
    &:active:disabled:last-child, &:active:disabled:only-child,
    &:checked:disabled:last-child, &:checked:disabled:only-child { box-shadow: none; }

    &:active:last-child, &:active:last-child:focus, &:active:last-child:hover, &:active:last-child:hover:focus,
    &:checked:last-child, &:checked:last-child:focus, &:checked:last-child:hover, &:checked:last-child:hover:focus {
        box-shadow: inset 0 1px alpha($dark_shadow, .07),
        inset -1px 0 alpha($dark_shadow, .06);
    }

    &:active:only-child, &:active:only-child:focus, &:active:only-child:hover, &:active:only-child:hover:focus,
    &:checked:only-child, &:checked:only-child:focus, &:checked:only-child:hover, &:checked:only-child:hover:focus {
        box-shadow: inset 1px 0 alpha($dark_shadow, .06),
        inset 0 1px alpha($dark_shadow, .07),
        inset -1px 0 alpha($dark_shadow, .06);
    }
}

@mixin button($bg, $fg) {
    $border_strength: if(lightness($bg) > 50, 0, .1);
    $shadow_strength: if(lightness($bg) > 50, 0, .1);

    $button_bg: if(hue($bg) == 0deg, shade($bg, 1.2), $bg);

    @extend %button;
    @include linear-gradient($button_bg);
    @include border(rgba(0, 0, 0, .12 + $border_strength));

    color: $fg;
    box-shadow: 0 1px 2px -1px alpha($dark_shadow, .12 + $shadow_strength);

    &.flat {
        border-color: alpha($button_bg, 0);
        background-color: alpha($button_bg, 0);
        background-image: none;
        box-shadow: none;
    }

    &, &.flat {
        &:focus, &:hover {
            @include linear-gradient(shade($button_bg, 1.2));
            @include border(rgba(0, 0, 0, .2 + $border_strength));

            box-shadow: 0 1px 2px -1px alpha($dark_shadow, .32 + $shadow_strength);
        }

        &:checked, &:active {
            @include linear-gradient(shade($button_bg, .7), to top);

            color: $white;
            box-shadow: inset 1px 0 alpha($dark_shadow, .06),
            inset 0 1px alpha($dark_shadow, .07),
            inset -1px 0 alpha($dark_shadow, .06),
            inset 0 -1px alpha($dark_shadow, .05);

            &:focus, &:hover {
                @include linear-gradient(shade($button_bg, .65), to top);

                color: $white;
            }
        }

        &:focus, &:hover { color: $fg; }

        &:active:disabled, &:checked:disabled {
            @include linear-gradient(shade($button_bg, .9));

            color: $fg;
            box-shadow: none;
        }

        &:disabled:disabled {
            @if (lightness($button_bg) > 50) {
                @include linear-gradient(shade($button_bg, .95));
            } @else {
                @include linear-gradient(alpha($button_bg, .3));
            }

            color: mix($bg, $fg, .5);
            box-shadow: none;
        }
    }

    &.flat {
        &:disabled:disabled {
            background-color: transparent;
            background-image: none;
            color: mix($bg, $fg, .5);
            box-shadow: none;
        }
    }

    &.image-button {
        min-width: 24px;
        padding-left: $spacing;
        padding-right: $spacing;
    }

    &.text-button {
        padding-left: $spacing * 2;
        padding-right: $spacing * 2;
    }

    &.text-button.image-button {
        padding-left: $spacing;
        padding-right: $spacing;

        label {
            padding-left: $spacing;
            padding-right: $spacing;
        }
    }

    &.separator, .separator {
        border: 1px solid currentColor;
        color: shade($bg, ($contrast + .1));

        &:disabled { color: shade($button_bg, .85); }
    }
}

@include exports("button") {
    %close_button {
        min-height: 22px;
        min-width: 16px;
        border: 1px solid transparent;
        background-color: transparent;
        background-image: none;
        box-shadow: none;

        &:focus, &:hover {
            border: 1px solid alpha($black, .3);
            background-color: alpha($white, .2);
            background-image: none;
            box-shadow: none;
        }

        &:active, &:checked, &:active:hover, &:checked:hover {
            border: 1px solid alpha($black, .3);
            background-color: alpha($black, .1);
            background-image: none;
            box-shadow: none;
        }
    }

    button {
        @include button(shade($bg_color, 1.2), $fg_color);

        .inline-toolbar &,
        .linked > & { @include linked_button(shade($bg_color, 1.2)); }

        .linked.vertical > & { @include linked_vertical_button(shade($bg_color, 1.2)); }

        &.osd {
            @include button($osd_bg, $osd_fg);

            &.image-button {
                padding: 0;
                min-height: 36px;
                min-width: 36px;
            }
        }

        &.circular,
        &.circular-button { // FIXME: aggregate to buttons
            padding: 0;
            min-width: 26px;
            min-height: 26px;
            border-radius: 9999px; // Fixed: https://github.com/GNOME/gtk/commit/a6409458f0d50d673a4dc370b9251993b7835b6b
            -gtk-outline-radius: 9999px;

            label { padding: 0; }
        }
    }

    spinbutton {
        button {
            color: mix($text_color, $base_color, .4);

            &:active, &:checked, &:hover { color: $text_color; }

            &:disabled { color: alpha($insensitive_fg_color, .8); }

            &:backdrop { color: mix($backdrop_base_color, $backdrop_fg_color, .9); }

            &:backdrop:disabled { color: alpha($backdrop_insensitive_color, .8); }
        }

        &:not(.vertical) {
            @extend %entry;
            @include linear-gradient($base_color, to top);
            @include border($base_color);

            padding: 0;

            color: $text_color;
            caret-color: $text_color;

            &:focus, &:active { border-color: border_focus($borders_color); }

            &:disabled {
                @include linear-gradient(shade($base_color, .9), to top);

                color: mix($base_color, $text_color, .5);
            }

            entry {
                // reset all the other props since the spinbutton node is styled here
                border: 0;
                border-radius: 0;
                box-shadow: none;
            }

            button {
                border-radius: 0;
                border-color: alpha($borders_color, .8);
                border-style: none none none solid;
                background-image: none;
                box-shadow: none;

                &:dir(rtl) { border-style: none solid none none; }

                &:active { box-shadow: inset 0 2px 3px -1px transparentize($black, .8); }

                &:backdrop { border-color: alpha($backdrop_borders_color, .8); }

                &:backdrop:disabled {
                    border-style: none none none solid; // It is needed or it gets overridden

                    &:dir(rtl) { border-style: none solid none none; }
                }

                &:dir(rtl):first-child { border-radius: $roundness 0 0 $roundness; }

                &:dir(ltr):last-child { border-radius: 0 $roundness $roundness 0; }
            }
        }

        &.vertical {
            button, entry {
                min-width: 0;
                padding-left: $spacing - 1px;
                padding-right: $spacing - 1px;
            }

            entry {
                // reset all the other props since the spinbutton node is styled here
                border-radius: 0;
            }

            button {
                &.up {
                    border-style: solid solid none solid;
                    border-radius: $roundness $roundness 0 0;
                }

                &.down {
                    border-style: none solid solid solid;
                    border-radius: 0 0 $roundness $roundness;
                }
            }
        }
    }
}

/******************
! ComboBoxes *
*******************/

@include exports("combobox") {
    combobox {
        button.combo {
            // otherwise the arrow placement is not symmetric
            min-width: 0;
            padding-left: 8px;
            padding-right: 8px;
        }

        arrow {
            -gtk-icon-source: -gtk-icontheme('pan-down-symbolic');
            min-height: 16px;
            min-width: 16px;
        }

        box button, box entry {
            @extend %linked_button;
            padding: ($spacing - 3px) ($spacing + 1px);
        }

        .linked:not(.vertical) > & > box > button.combo {
            // the combo is a composite widget so the way we do button linked doesn't
            // work, special case needed. See
            // https://bugzilla.gnome.org/show_bug.cgi?id=733979
            &:dir(ltr) { @extend %linked_middle; }
            // specificity bump
            &:dir(rtl) { @extend %linked_middle:dir(rtl); }
        }

        .linked:not(.vertical) > &:first-child > box > button.combo { @extend %linked_button:first-child; }

        .linked:not(.vertical) > &:last-child > box > button.combo { @extend %linked_button:last-child; }

        .linked:not(.vertical) > &:only-child > box > button.combo { @extend %linked_button:only-child; }
    }
}