fenix-fox/chrome/window_control_placeholder_support.css

/* Source file https://github.com/MrOtherGuy/firefox-csshacks/tree/master/chrome/window_control_placeholder_support.css made available under Mozilla Public License v. 2.0
See the above repository for updates as well as full license text. */

/* Creates placeholders for window controls */
/* This is a supporting file used by other stylesheets */

/* This stylesheet is pretty much unnecessary if window titlebar is enabled */

/* This file should preferably be imported before other stylesheets */

/* Defaults for window controls on RIGHT side of the window */
/* Modify these values to match your preferences */
:root:is([tabsintitlebar], [sizemode="fullscreen"]) {
  --uc-window-control-width: 138px; /* Space reserved for window controls (Win10) */
  /* Extra space reserved on both sides of the nav-bar to be able to drag the window */
  --uc-window-drag-space-pre: 30px; /* left side*/
  --uc-window-drag-space-post: 30px; /* right side*/
}

:root:is([tabsintitlebar][sizemode="maximized"], [sizemode="fullscreen"]) {
  --uc-window-drag-space-pre: 0px; /* Remove pre space */
}

@media  (-moz-platform: windows-win7),
        (-moz-platform: windows-win8),
        (-moz-os-version: windows-win7),
        (-moz-os-version: windows-win8){
  :root:is([tabsintitlebar], [sizemode="fullscreen"]) {
    --uc-window-control-width: 105px;
  }
}

@media (-moz-gtk-csd-available) {
  :root:is([tabsintitlebar],[sizemode="fullscreen"]) {
    --uc-window-control-width: 84px;
  }
}
@media (-moz-platform: macos){
  :root:is([tabsintitlebar],[sizemode="fullscreen"]) {
    --uc-window-control-width: 72px;
  }
}

.titlebar-buttonbox, #window-controls{ color: var(--toolbar-color) }
:root[sizemode="fullscreen"] .titlebar-buttonbox-container{ display: none }
:root[sizemode="fullscreen"] #navigator-toolbox { position: relative; }

:root[sizemode="fullscreen"] #TabsToolbar > .titlebar-buttonbox-container:last-child,
:root[sizemode="fullscreen"] #window-controls{
  position: absolute;
  display: flex;
  top: 0;
  right:0;
  height: 40px;
}

:root[sizemode="fullscreen"] #TabsToolbar > .titlebar-buttonbox-container:last-child,
:root[uidensity="compact"][sizemode="fullscreen"] #window-controls{ height: 32px }

#nav-bar{
  border-inline: var(--uc-window-drag-space-pre,0px) solid var(--toolbar-bgcolor);
  border-inline-style: solid !important;
  border-right-width: calc(var(--uc-window-control-width,0px) + var(--uc-window-drag-space-post,0px));
}

/* Rules for window controls on left layout */
@media (-moz-gtk-csd-reversed-placement),
       (-moz-platform: macos){
  :root[tabsintitlebar="true"] #nav-bar{
    border-inline-width: calc(var(--uc-window-control-width,0px) + var(--uc-window-drag-space-post,0px)) var(--uc-window-drag-space-pre,0px)
  }
  :root[sizemode="fullscreen"] #TabsToolbar > .titlebar-buttonbox-container:last-child,
  :root[sizemode="fullscreen"] #window-controls{ right: unset }
}

/* This pref can be used to force window controls on left even if that is not normal behavior on your OS */
@supports -moz-bool-pref("userchrome.force-window-controls-on-left.enabled"){
  :root[tabsintitlebar="true"] #nav-bar{
    border-inline-width: calc(var(--uc-window-control-width,0px) + var(--uc-window-drag-space-post,0px)) var(--uc-window-drag-space-pre,0px)
  }
  :root[sizemode="fullscreen"] #TabsToolbar > .titlebar-buttonbox-container:last-child,
  :root[sizemode="fullscreen"] #window-controls{ right: unset; }
  .titlebar-buttonbox-container{ -moz-box-ordinal-group: 0 !important; }
  .titlebar-buttonbox{ -moz-box-direction: reverse }
}