paper: make all source lines have the same minimum height

Empty source lines in paper and coal themes used to have smaller height than
every other line (because of the way line numbers are shown and because they
are using smaller font). This wasn't very noticeable before the follow lines
functionality was added, but after that just using the follow-lines button to
select a block of code with empty lines would demonstrate the fact that empty
lines didn't have enough height - there were white "gaps" in the selection
block.

Since this problem occurs when lines don't have any content inside, let's
create a pseudo-element (it's unselectable because of that) which still doesn't
have any content, but fills up empty lines to 100% of their height because of
display: inline-block. This is the most natural way to solve this annoyance
that I've found so far.

Hardcoding height isn't useful because we can have wrapped lines, in which case
multiple lines of text need to fit into a single <span>.

Setting min-height or line-height doesn't remove the gaps when viewed in
Chromium.

mercurial/templates/static/style-paper.css

@@ -1,542 +1,547 b''
 body {
   margin: 0;
   padding: 0;
   background: white;
   color: black;
   font-family: sans-serif;
 }
 
 .container {
   padding-left: 115px;
 }
 
 .main {
   position: relative;
   background: white;
   padding: 2em 2em 2em 0;
 }
 
 #.main {
   width: 98%;
 }
 
 .overflow {
   width: 100%;
   overflow: auto;
 }
 
 .menu {
   width: 90px;
   margin: 0;
   font-size: 80%;
   text-align: left;
   position: absolute;
   top: 20px;
   left: 20px;
   right: auto;
 }
 
 .menu ul {
   list-style: none;
   padding: 0;
   margin: 10px 0 0 0;
   border-left: 2px solid #999;
 }
 
 .menu li {
   margin-bottom: 3px;
   padding: 2px 4px;
   background: white;
   color: black;
   font-weight: normal;
 }
 
 .menu li.active {
   font-weight: bold;
 }
 
 .menu img {
   width: 75px;
   height: 90px;
   border: 0;
 }
 
 div.atom-logo {
   margin-top: 10px;
 }
 
 .atom-logo img{
   width: 14px;
   height: 14px;
   border: 0;
 }
 
 .menu a { color: black; display: block; }
 
 .search {
   position: absolute;
   top: .7em;
   right: 2em;
 }
 
 form.search div#hint {
   display: none;
   position: absolute;
   top: 40px;
   right: 0px;
   width: 190px;
   padding: 5px;
   background: #ffc;
   font-size: 70%;
   border: 1px solid yellow;
   border-radius: 5px;
 }
 
 form.search:hover div#hint { display: block; }
 
 a { text-decoration:none; }
 .age { white-space:nowrap; }
 .date { white-space:nowrap; }
 .indexlinks { white-space:nowrap; }
 .parity0,
 .stripes4 > :nth-child(4n+1),
 .stripes2 > :nth-child(2n+1) { background-color: #f0f0f0; }
 .parity1,
 .stripes4 > :nth-child(4n+3),
 .stripes2 > :nth-child(2n+2) { background-color: white; }
 .plusline { color: green; }
 .minusline { color: #dc143c; } /* crimson */
 .atline { color: purple; }
 
 .diffstat-table {
   margin-top: 1em;
 }
 .diffstat-file {
   white-space: nowrap;
   font-size: 90%;
 }
 .diffstat-total {
   white-space: nowrap;
   font-size: 90%;
 }
 .diffstat-graph {
   width: 100%;
 }
 .diffstat-add {
   background-color: green;
   float: left;
 }
 .diffstat-remove {
   background-color: red;
   float: left;
 }
 
 .navigate {
   text-align: right;
   font-size: 60%;
   margin: 1em 0;
 }
 
 .phase {
   color: #999;
   font-size: 70%;
   border-bottom: 1px dotted #999;
   font-weight: normal;
   margin-left: .5em;
   vertical-align: baseline;
 }
 
 .obsolete {
   color: #999;
   font-size: 70%;
   border-bottom: 1px dashed #999;
   font-weight: normal;
   margin-left: .5em;
   vertical-align: baseline;
 }
 
 .instability {
   color: #000;
   font-size: 70%;
   border-bottom: 1px solid #000;
   font-weight: normal;
   margin-left: .5em;
   vertical-align: baseline;
 }
 
 .tag {
   color: #999;
   font-size: 70%;
   font-weight: normal;
   margin-left: .5em;
   vertical-align: baseline;
 }
 
 .branchhead {
   color: #000;
   font-size: 80%;
   font-weight: normal;
   margin-left: .5em;
   vertical-align: baseline;
 }
 
 ul#graphnodes .branchhead {
   font-size: 75%;
 }
 
 .branchname {
   color: #000;
   font-size: 60%;
   font-weight: normal;
   margin-left: .5em;
   vertical-align: baseline;
 }
 
 /* Common */
 pre { margin: 0; }
 
 h2 { font-size: 120%; border-bottom: 1px solid #999; }
 h2 a { color: #000; }
 h3 {
   margin-top: +.7em;
   font-size: 100%;
 }
 
 /* log and tags tables */
 .bigtable {
   border-bottom: 1px solid #999;
   border-collapse: collapse;
   font-size: 90%;
   width: 100%;
   font-weight: normal;
   text-align: left;
 }
 
 .bigtable td {
   padding: 1px 4px;
   vertical-align: top;
 }
 
 .bigtable th {
   padding: 1px 4px;
   border-bottom: 1px solid #999;
 }
 .bigtable tr { border: none; }
 .bigtable .age { width: 7em; }
 .bigtable .author { width: 15em; }
 .bigtable .description { }
 .bigtable .description .base { font-size: 70%; float: right; line-height: 1.66; }
 .bigtable .node { width: 5em; font-family: monospace;}
 .bigtable .permissions { width: 8em; text-align: left;}
 .bigtable .size { width: 5em; text-align: right; }
 .bigtable .annotate { text-align: right; }
 .bigtable td.annotate { font-size: smaller; }
 .bigtable td.source { font-size: inherit; }
 tr.thisrev a { color:#999999; text-decoration: none; }
 tr.thisrev td.source { color:#009900; }
 td.annotate {
   white-space: nowrap;
 }
 div.annotate-info {
   z-index: 5;
   display: none;
   position: absolute;
   background-color: #FFFFFF;
   border: 1px solid #999;
   text-align: left;
   color: #000000;
   padding: 5px;
 }
 div.annotate-info a { color: #0000FF; }
 td.annotate:hover div.annotate-info { display: inline; }
 
 #diffopts-form {
   font-size: smaller;
   color: #424242;
   padding-bottom: 10px;
   display: none;
 }
 
 .source, .sourcefirst {
   font-family: monospace;
   white-space: pre;
   padding: 1px 4px;
   font-size: 90%;
 }
 .sourcefirst { border-bottom: 1px solid #999; font-weight: bold; }
 .source a { color: #999; font-size: smaller; font-family: monospace;}
 .bottomline { border-bottom: 1px solid #999; }
 
 .sourcelines {
   font-size: 90%;
   position: relative;
   counter-reset: lineno;
 }
 
 .wrap > span {
     white-space: pre-wrap;
 }
 
 .linewraptoggle {
     float: right;
 }
 
 .diffblocks { counter-reset: lineno; }
 .diffblocks > div { counter-increment: lineno; }
 
 .sourcelines > span {
   display: inline-block;
   box-sizing: border-box;
   width: 100%;
   padding: 1px 0px 1px 5em;
   counter-increment: lineno;
 }
 
 .sourcelines > span:before {
   -moz-user-select: -moz-none;
   -khtml-user-select: none;
   -webkit-user-select: none;
   -ms-user-select: none;
   user-select: none;
   display: inline-block;
   margin-left: -6em;
   width: 4em;
   font-size: smaller;
   color: #999;
   text-align: right;
   content: counters(lineno, ".");
   float: left;
 }
 
+.sourcelines > span:after {
+  content: '';
+  display: inline-block;
+}
+
 .sourcelines > span:target, tr:target td {
   background-color: #bfdfff;
 }
 
 /* Followlines */
 tbody.sourcelines > tr.followlines-selected,
 pre.sourcelines > span.followlines-selected {
   background-color: #99C7E9;
 }
 
 div#followlines {
   background-color: #FFF;
   border: 1px solid #999;
   padding: 5px;
   position: fixed;
 }
 
 div.followlines-cancel {
   text-align: right;
 }
 
 div.followlines-cancel > button {
   line-height: 80%;
   padding: 0;
   border: 0;
   border-radius: 2px;
   background-color: inherit;
   font-weight: bold;
 }
 
 div.followlines-cancel > button:hover {
   color: #FFFFFF;
   background-color: #CF1F1F;
 }
 
 div.followlines-link {
   margin: 2px;
   margin-top: 4px;
   font-family: sans-serif;
 }
 
 .btn-followlines {
   position: absolute;
   display: none;
   cursor: pointer;
   box-sizing: content-box;
   font-size: 12px;
   width: 13px;
   height: 13px;
   border-radius: 3px;
   margin: 0px;
   margin-top: -2px;
   padding: 0px;
   background-color: #E5FDE5;
   border: 1px solid #9BC19B;
   font-family: monospace;
   text-align: center;
   line-height: 5px;
 }
 
 span.followlines-select .btn-followlines {
   margin-left: -1.5em;
 }
 
 .btn-followlines:hover {
   transform: scale(1.2, 1.2);
 }
 
 .btn-followlines .followlines-plus {
   color: green;
 }
 
 .btn-followlines .followlines-minus {
   color: red;
 }
 
 .btn-followlines-end {
   background-color: #ffdcdc;
 }
 
 .sourcelines tr:hover .btn-followlines,
 .sourcelines span.followlines-select:hover > .btn-followlines {
   display: inline;
 }
 
 .btn-followlines-hidden,
 .sourcelines tr:hover .btn-followlines-hidden {
   display: none;
 }
 
 .sourcelines > a {
     display: inline-block;
     position: absolute;
     left: 0px;
     width: 4em;
     height: 1em;
 }
 
 .fileline { font-family: monospace; }
 .fileline img { border: 0; }
 
 .tagEntry .closed { color: #99f; }
 
 /* Changeset entry */
 #changesetEntry {
   border-collapse: collapse;
   font-size: 90%;
   width: 100%;
   margin-bottom: 1em;
 }
 
 #changesetEntry th {
   padding: 1px 4px;
   width: 4em;
   text-align: right;
   font-weight: normal;
   color: #999;
   vertical-align: top;
 }
 
 div.description {
   border-left: 2px solid #999;
   margin: 1em 0 1em 0;
   padding: .3em;
   white-space: pre;
   font-family: monospace;
 }
 
 /* Graph */
 div#wrapper {
 	position: relative;
 	border-top: 1px solid black;
 	border-bottom: 1px solid black;
 	margin: 0;
 	padding: 0;
 }
 
 canvas {
 	position: absolute;
 	z-index: 5;
 	top: -0.7em;
 	margin: 0;
 }
 
 ul#graphnodes {
 	list-style: none inside none;
 	padding: 0;
 	margin: 0;
 }
 
 ul#graphnodes li {
 	height: 39px;
 	overflow: visible;
 }
 
 ul#graphnodes li .fg {
 	position: absolute;
 	z-index: 10;
 }
 
 ul#graphnodes li .info {
 	font-size: 70%;
 }
 
 /* Comparison */
 .legend {
     padding: 1.5% 0 1.5% 0;
 }
 
 .legendinfo {
     border: 1px solid #999;
     font-size: 80%;
     text-align: center;
     padding: 0.5%;
 }
 
 .equal {
     background-color: #ffffff;
 }
 
 .delete {
     background-color: #faa;
     color: #333;
 }
 
 .insert {
     background-color: #ffa;
 }
 
 .replace {
     background-color: #e8e8e8;
 }
 
 .header {
     text-align: center;
 }
 
 .block {
     border-top: 1px solid #999;
 }
 
 .breadcrumb {
     color: gray;
 }
 
 .breadcrumb a {
     color: blue;
 }
 
 .scroll-loading {
   -webkit-animation: change_color 1s linear 0s infinite alternate;
   -moz-animation: change_color 1s linear 0s infinite alternate;
   -o-animation: change_color 1s linear 0s infinite alternate;
   animation: change_color 1s linear 0s infinite alternate;
 }
 
 @-webkit-keyframes change_color {
   from { background-color: #A0CEFF; } to {  }
 }
 @-moz-keyframes change_color {
   from { background-color: #A0CEFF; } to {  }
 }
 @-o-keyframes change_color {
   from { background-color: #A0CEFF; } to {  }
 }
 @keyframes change_color {
   from { background-color: #A0CEFF; } to {  }
 }
 
 .scroll-loading-error {
     background-color: #FFCCCC !important;
 }