Custom Firefox userChrome.css File

userChrome.css

/*** Proton Tabs Tweaks ***/

/* Adjust tab corner shape, optionally remove space below tabs */

#tabbrowser-tabs {
    --user-tab-rounding: 0px;
}

.tab-background {
    border-radius: var(--user-tab-rounding) var(--user-tab-rounding) 0px 0px !important;
    margin-block: 1px 0 !important;
}
#scrollbutton-up, #scrollbutton-down { /* 6/10/2021 */
    border-top-width: 1px !important;
    border-bottom-width: 0 !important;
}
/* Container color bar visibility */
.tabbrowser-tab[usercontextid] > .tab-stack > .tab-background > .tab-context-line {
    margin: 0px max(calc(var(--user-tab-rounding) - 3px), 0px) !important;
}

/* Inactive tabs: Separator line style */

.tabbrowser-tab:not([selected=true]):not([multiselected=true]):not([beforeselected-visible="true"]) .tab-background {
    border-right: 1px solid var(--lwt-background-tab-separator-color, rgba(0, 0, 0, .20)) !important;
}
/* For dark backgrounds */
[brighttext="true"] .tabbrowser-tab:not([selected=true]):not([multiselected=true]):not([beforeselected-visible="true"]) .tab-background {
    border-right: 1px solid var(--lwt-background-tab-separator-color, var(--lwt-selected-tab-background-color, rgba(255, 255, 255, .20))) !important;
}
.tabbrowser-tab:not([selected=true]):not([multiselected=true]) .tab-background {
    border-radius: 0 !important;
}
/* Remove padding between tabs */
.tabbrowser-tab {
    padding-left: 0 !important;
    padding-right: 0 !important;
    font-size: 14px !important;
}

/* Tweak Options as of 8/11/2021; Generated Wed Aug 11 2021 14:16:12 GMT-0600 (Mountain Daylight Time) */


/*** Tighten up drop-down/context/popup menu spacing ***/

menupopup > menuitem, menupopup > menu {
  padding-block: 4px !important;
}

:root {
  --arrowpanel-menuitem-padding: 4px 8px !important;
}

/*** Audio Playing / Mute Button side-by-side when sound is playing ***/

#TabsToolbar {
    --user-mute-button-height: 20px;  /* default size is 12px, site icon is 16px */
}

/* Move the mute/unmute button to the right and enlarge it */
.tab-icon-overlay:not([pinned], [sharing], [crashed]):is([soundplaying], [muted]) {
    width: var(--user-mute-button-height) !important;
    height: var(--user-mute-button-height) !important;
    margin-left: calc(var(--user-mute-button-height) / 2 + 2px) !important; /* pushes icon to the right */
    margin-right: 2px !important; /* closes up some space before the text */
    padding: 0 !important; /* allows icon to expand to full size */
}

/* Move the site icon to the left a bit and adjust position */
.tab-icon-stack:not([pinned], [sharing], [crashed]):is([soundplaying], [muted]) > :not(.tab-icon-overlay) {
    margin-left: -4px !important; /* pushes icon to the left */
    margin-top: calc((var(--user-mute-button-height) - 16px) / 2) !important;  /* keep site icon reasonably positioned */
}

/* Override the rules for hover/not hover visibility */
   /* for mute button */
.tabbrowser-tab:not(:hover) .tab-icon-overlay:not([pinned], [sharing], [crashed]):is([soundplaying], [muted]), 
   /* for site icon */
.tabbrowser-tab:hover .tab-icon-stack:not([pinned], [sharing], [crashed]):is([soundplaying], [muted]) > :not(.tab-icon-overlay), 
   /* for site icon with Compact density */
:root[uidensity="compact"] .tab-icon-stack:not([pinned], [sharing], [crashed]):is([soundplaying], [muted]) > :not(.tab-icon-overlay) {
    opacity: 1 !important; /* overrides full transparency with full opacity */
}

/* Color the icon on hover for confirmation or avoidance */
.tab-icon-overlay:not([pinned], [sharing], [crashed]):is([soundplaying], [muted]):hover {
    fill: green !important;
}
[lwthemetextcolor="bright"] .tab-icon-overlay:not([pinned], [sharing], [crashed]):is([soundplaying], [muted]):hover {
    fill: lightgreen !important; /* for dark themes */
}

/* Tweaked Audio playing/Mute button rules for pinned tabs */
.tab-icon-overlay:not([crashed]):is([pinned], [sharing]):is([soundplaying], [muted]) {
    width: var(--user-mute-button-height) !important;
    height: var(--user-mute-button-height) !important;
    margin-left: 2px !important; /* allow some overlap to reduce expanded width */
    margin-right: -2px !important; /* reduce empty space on the right */
    padding: 0 !important; /* allows icon to expand to full size */
    top: 0 !important; /* align button with site icon */
}
.tab-icon-stack:not([crashed]):is([pinned], [sharing]):is([soundplaying], [muted]) > :not(.tab-icon-overlay) {
    margin-left: -6px !important; /* reduce empty space on the left */
    margin-top: calc((var(--user-mute-button-height) - 16px) / 2) !important;  /* keep site icon reasonably positioned */
}
.tabbrowser-tab:not(:hover) .tab-icon-overlay:not([crashed]):is([pinned], [sharing]):is([soundplaying], [muted]), 
   /* for site icon */
.tabbrowser-tab:hover .tab-icon-stack:not([crashed]):is([pinned], [sharing]):is([soundplaying], [muted]) > :not(.tab-icon-overlay), 
   /* for site icon with Compact density */
:root[uidensity="compact"] .tab-icon-stack:not([crashed]):is([pinned], [sharing]):is([soundplaying], [muted]) > :not(.tab-icon-overlay) {
    opacity: 1 !important; /* overrides full transparency with full opacity */
}
.tab-icon-overlay:not([crashed]):is([pinned], [sharing]):is([soundplaying], [muted]):hover {
    fill: green !important;
}
[lwthemetextcolor="bright"] .tab-icon-overlay:not([crashed]):is([pinned], [sharing]):is([soundplaying], [muted]):hover {
    fill: lightgreen !important; /* for dark themes */
}