Revert Firefox Proton to Photon compact

proton-compact-userchrome.css

/**
 * Moved to a new repository.
 * https://github.com/intrnl/firefox-revert-proton
 */

:root {
  --tab-min-height: 28px !important;
  --toolbarbutton-inner-padding: 6px !important;
  --toolbarbutton-outer-padding: 1px !important;
  --toolbar-start-end-padding: 1px !important;
  --panel-font-size: 1em !important;
  --panel-separator-margin: 8px 0px !important;
  --panel-subview-body-padding: 8px 0px !important;
  --arrowpanel-border-radius: 0px !important;
  --arrowpanel-menuitem-padding: 4px 16px !important;
  --arrowpanel-menuitem-margin: 0px !important;
  --arrowpanel-menuitem-border-radius: 0px !important;
}

/** Tab */
.tabbrowser-tab {
  --tab-line-color: #0A84FF;
  --tab-label-mask-size: 2em !important;
  padding-inline: 0 !important;
}

#tabbrowser-tabs[haspinnedtabs]:not([positionpinnedtabs]) .tabbrowser-tab[first-visible-unpinned-tab] {
  margin-inline-start: 0px !important;
}

.tab-label {
  line-height: 1.7em;
}

.tab-background {
  box-shadow: none !important;
  margin-block: 0 !important;
  border-block-start: 2px solid transparent !important;
  border-radius: 0 !important;
}

.tabbrowser-tab:hover:not([selected]) .tab-background {
  border-block-start-color: color-mix(in srgb, currentColor 33%, transparent) !important;
}

[selected] .tab-background {
  background-color: var(--toolbar-bgcolor) !important;
  background-image: var(--toolbar-bgimage) !important;
  border-block-start-color: var(--tab-line-color) !important;
}

/** Tab misc. */
.tab-context-line {
  background-color: transparent !important;
  background-image: linear-gradient(to right, transparent 10%, var(--identity-tab-color) 10%, var(--identity-tab-color) 90%, transparent 90%);
  margin: -2px !important;
  transform: translateY(26px);
}

.tab-icon-image {
  opacity: 1 !important;
}

.tab-icon-overlay {
  fill-opacity: 1 !important;
  opacity: 1 !important;
  transition: none !important;
  border-radius: 10px !important;
  top: -4.5px !important;
  inset-inline-end: -9px !important;
  z-index: 1 !important;
}

.tab-icon-overlay:hover {
  background-color: white !important;
  color: black !important;
}

.tab-secondary-label {
  display: none !important;
}

.tab-close-button {
  background-image: url(chrome://global/skin/icons/close.svg);
  background-size: 14px;
  background-position: center;
  background-repeat: no-repeat;
  list-style-image: unset !important;
  width: 20px !important;
  height: 20px !important;
  padding: 2px !important;
  margin-block-start: 1px !important;
  margin-inline-end: -2px !important;
}

#tabs-newtab-button {
 padding: 0 1px !important; 
}

/** Tab border */
:is(:root[sizemode='normal'], :root[gtktiledwindow='true']) .tabbrowser-tab:first-of-type {
  margin-inline-start: 1px !important;
}

.tabbrowser-tab::after,
.tabbrowser-tab::before {
  border-inline-start: 1px solid var(--toolbarbutton-active-background);
}
.tabbrowser-tab::before {
  margin-inline-start: -1px;
}

:root[tabsintitlebar]:not([extradragspace]) #toolbar-menubar[autohide=true] + #TabsToolbar .tabbrowser-tab::after,
.tabbrowser-tab:hover::after,
.tabbrowser-tab[multiselected]::after,
#tabbrowser-tabs:not([movingtab]) .tabbrowser-tab[beforehovered]::after,
#tabbrowser-tabs:not([movingtab]) .tabbrowser-tab[before-multiselected]::after {
  margin-block-start: var(--tabs-top-border-width);
  margin-block-end: 0;
}

#tabbrowser-tabs:not([movingtab]) .tabbrowser-tab[beforeselected-visible]::after,
#tabbrowser-tabs[movingtab] .tabbrowser-tab[visuallyselected]::before,
.tabbrowser-tab[visuallyselected]::after,
.tabbrowser-tab[visuallyselected]::before {
  border-color: var(--tabs-border-color);
  margin-block-start: 0;
  margin-block-end: var(--tabs-navbar-shadow-size);
}

.tabbrowser-tab::after,
.tabbrowser-tab[visuallyselected]::before,
.tabbrowser-tab:first-of-type::before,
#tabbrowser-tabs[movingtab] .tabbrowser-tab[visuallyselected]::before {
  content: '';
  display: block;
}

/** Mega bar, Search bar */
#search-container, #urlbar-container {
  --urlbar-container-height: 32px !important;
  padding-block: 2px !important;
}

#urlbar, #searchbar {
  --urlbar-height: 26px !important;
  --urlbar-min-height: 26px !important;
  --urlbar-toolbar-height: 32px !important;
}

#urlbar-input-container {
  --urlbar-icon-padding: 4px !important;
  border: 0 !important;
}

/* TODO: figure out why the width calculation isn't working as intended. */
.urlbar-icon {
  height: 24px !important;
  width: 24px !important;
}

:is(.chromeUI, .extensionPage, .notSecureText) #identity-icon-box {
  background-color: transparent !important;
}
:is(.chromeUI, .extensionPage, .notSecureText) #identity-icon-box:hover {
  background-color: hsla(0, 0%, 70%, 0.2) !important;;
}
:is(.chromeUI, .extensionPage, .notSecureText) :is(#identity-icon-box:active, #identity-icon-box[open]) {
  background-color: hsla(0, 0%, 70%, 0.3) !important;;
}


/** Panel */
#downloadsPanel,
#widget-overflow,
#appMenu-popup,
#customizationui-widget-panel,
#identity-popup,
#permission-popup,
#protections-popup {
  margin-block-start: -2px !important;
}

.panel-header {
  padding: 8px !important;
}

.panel-header + toolbarseparator {
  margin-block-start: 0px !important;
}

.panel-footer.panel-footer-menulike {
  margin: 0px !important;
  padding-block: 8px !important;
}

.panel-footer.panel-footer-menulike > button {
  padding: var(--arrowpanel-menuitem-padding) !important;
  margin: 0px !important;
  border-radius: var(--arrowpanel-menuitem-border-radius) !important;
}
.panel-footer.panel-footer-menulike > button:hover {
  color: inherit !important;
  outline: none !important;
}

.panel-footer.panel-footer-menulike > button label {
  margin-block: 0px !important;
}

[extension] toolbarseparator {
  margin-block-end: 0px !important;
}

.subviewbutton-back {
  transform: none !important;
  margin: 0px !important;
}

.subview-subheader {
  font-size: inherit !important;
}

.panel-subview-footer-button {
  margin-block-end: 8px !important;
}

.PanelUI-subView menuseparator {
  appearance: none !important;
}

/** Panel banner */
:is(.panel-banner-item, .addon-banner-item) {
  margin-bottom: 8px !important;
}

.addon-banner-item::after {
  margin-inline-end: 8px !important;
}

/** Main panel */
#appMenu-fxa-label2 {
  padding: var(--arrowpanel-menuitem-padding) !important;
}

#appMenu-fxa-label2 label {
  margin: 0px !important;
}

toolbarseparator.proton-zap {
  border-image: none !important;
}

#appMenu-zoom-controls2 {
  padding-inline-end: 12px !important;
}

.toolbaritem-combined-buttons:not([widget-type='button-and-view']),
.toolbaritem-menu-buttons {
  margin-inline-end: 0px !important;
}

/** Overflow panel */
#widget-overflow-mainView toolbarseparator {
  margin-block-start: 0 !important;
}

.PanelUI-subView .toolbaritem-combined-buttons > .subviewbutton {
  margin-inline-end: 0px !important;
}

/** Accounts panel */
.PanelUI-remotetabs-clientcontainer > label {
  font-size: inherit !important;
  padding-block-end: 2px !important;
  margin-inline-start: 16px !important;
}

/** Synced tabs panel */
#PanelUI-remotetabs .panel-subview-body {
  margin-block-end: 8px !important;
}

/** Downloads panel */
#downloadsPanel-blockedSubview, #downloadsPanel-mainView {
  padding: 0px !important;
}

#emptyDownloads {
  padding: var(--arrowpanel-menuitem-padding) !important;
  padding-block: 16px !important;
}

#downloadsListBox {
  margin: var(--panel-separator-margin) !important;
}

#downloadsListBox > richlistitem {
  height: 4.5em !important;
  padding: var(--arrowpanel-menuitem-padding) !important;
  padding-inline: 12px !important;
  margin: 0px !important;
  border-radius: 0px !important;
}

/** Identity security panel */
#identity-popup-securityView .identity-popup-security-content {
  border-block-end: 0px !important;
  padding-block-start: 8px !important;
  padding-block-end: 0px !important;
}

#identity-popup-securityView #identity-popup-securityView-body {
  padding-block-start: 0px !important;
  padding-block-end: 8px !important;
  margin-inline: calc(2em + 24px) 1em !important;
}

/** Tracking protection panel */
.protections-popup-footer-button, .protections-popup-category {
  height: auto !important;
  min-height: unset !important;
}

#protections-popup-content {
  margin: 8px 0 !important;
}

#protections-popup-blocking-section-header,
#protections-popup-not-blocking-section-header,
#protections-popup-not-found-section-header {
  height: 26px !important;
  padding: 4px 16px !important;
  margin: 0px !important;
}

#protections-popup-not-blocking-section-header,
#protections-popup-not-found-section-header {
  margin-block-start: 8px !important;
}

/** Dedicated search panel */
#PopupSearchAutoComplete .search-panel-current-engine {
  padding: 4px 12px !important;
}

#PopupSearchAutoComplete .autocomplete-richlistitem {
  padding: 4px 8px !important;
}

#PopupSearchAutoComplete .search-panel-one-offs-header {
  padding: 4px 8px !important;
}

#PopupSearchAutoComplete .search-panel-one-offs-container {
  padding: 4px 8px !important;
}

#PopupSearchAutoComplete .search-setting-button {
  min-height: unset !important;
  padding: var(--arrowpanel-menuitem-padding) !important;
  border-radius: var(--arrowpanel-menuitem-border-radius) !important;
}

#PopupSearchAutoComplete .search-setting-button .button-box {
  -moz-box-pack: start !important;
}


/** Notification bar (DRM etc) */
notification-message:not([style*='margin']) {
  margin: 0px !important;
}

.container.infobar {
  border-radius: 0px !important;
}

.container.infobar::before {
  content: unset !important;
}

.container.infobar .icon {
  margin-block: auto !important;
  margin-inline: calc(8px + 3px) !important;
}

.container.infobar .notification-content {
  display: flex !important;
  justify-content: space-between !important;
  width: -moz-available !important;
  margin-inline-start: 0px !important;
}

.container.infobar .notification-message {
  margin-inline-end: 8px !important;
}

.container.infobar .notification-button {
  border-radius: 2px !important;
  margin: 0px !important;
}

/** Dialogs */
@-moz-document url('chrome://global/content/commonDialog.xhtml'),
    url('chrome://mozapps/content/handling/permissionDialog.xhtml'),
    url('chrome://mozapps/content/handling/appChooser.xhtml'),
    url-prefix("chrome://global/content/print.html")
{
  :root, #commonDialog {
    --subdialog-font-size: 1em !important;
    --in-content-button-vertical-padding: 0px !important;
    --in-content-button-horizontal-padding: 8px !important;
    --in-content-primary-button-text-color: rgb(255, 255, 255) !important;
    --in-content-primary-button-background: var(--blue-60) !important;
    --in-content-primary-button-background-hover: var(--blue-70) !important;
    --in-content-primary-button-background-active: var(--blue-80) !important;
    --checkbox-checked-color: rgb(255, 255, 255) !important;
    --checkbox-checked-bgcolor: var(--blue-60) !important;
    --checkbox-checked-hover-bgcolor: var(--blue-70) !important;
    --checkbox-checked-active-bgcolor var(--blue-80) !important;
  }
  
  dialog[subdialog] {
    padding: 16px 10px !important;
  }
  
  button {
    min-width: 6.3em !important;
  }
}

Photon Dark color scheme (alternative)
Photon Light color scheme (alternative)