Use the regular preprocess-function for the CSS files as well

An old shortcoming of the `preprocessCSS`-function is its complete lack of support for our "normal" defines, which makes it very difficult to have build-specific CSS rules. Recently we've started using specially crafted comments to remove CSS rules from the MOZCENTRAL build, but (ab)using the `preprocessCSS`-function in this way really doesn't feel great.
However, it turns out to be surprisingly simple to instead use the "regular" `preprocess`-function for the CSS files as well. The only special-handling that's still necessary is the helper-function for dealing with CSS-imports, but apart from that everything seems to just work.

One reason, as far as I can tell, for having a separate `preprocessCSS`-function was likely that we originally used *lots* of vendor-prefixed CSS rules in our CSS files. With improvements over the years, especially thanks to Autoprefixer and PostCSS, we've been able to remove *almost* all non-standard CSS rules and the need for special-casing the CSS parsing has mostly vanished.

*Please note:* As part of testing this patch I've diffed the output of `gulp generic`, `gulp mozcentral`, and `gulp chromium` against the `master`-branch to check that there was no obvious breakage.

external/builder/builder.js

@@ -38,9 +38,25 @@ function preprocess(inFilename, outFilename, defines) {
     return fs.realpathSync(inFilename) + ":" + lineNumber;
   }
 
+  function expandCssImports(content, baseUrl) {
+    return content.replace(
+      /^\s*@import\s+url\(([^)]+)\);\s*$/gm,
+      function (all, url) {
+        const file = path.join(path.dirname(baseUrl), url);
+        const imported = fs.readFileSync(file, "utf8").toString();
+        return expandCssImports(imported, file);
+      }
+    );
+  }
+
   // TODO make this really read line by line.
-  const lines = fs.readFileSync(inFilename).toString().split("\n");
+  let content = fs.readFileSync(inFilename, "utf8").toString();
-  const totalLines = lines.length;
+  // Handle CSS-imports first, when necessary.
+  if (/\.css$/i.test(inFilename)) {
+    content = expandCssImports(content, inFilename);
+  }
+  const lines = content.split("\n"),
+    totalLines = lines.length;
   let out = "";
   let i = 0;
   function readLine() {
@@ -123,7 +139,7 @@ function preprocess(inFilename, outFilename, defines) {
   let state = STATE_NONE;
   const stack = [];
   const control =
-    /^(?:\/\/|<!--)\s*#(if|elif|else|endif|expand|include|error)\b(?:\s+(.*?)(?:-->)?$)?/;
+    /^(?:\/\/|\s*\/\*|<!--)\s*#(if|elif|else|endif|expand|include|error)\b(?:\s+(.*?)(?:\*\/|-->)?$)?/;
 
   while ((line = readLine()) !== null) {
     ++lineNumber;
@@ -199,82 +215,6 @@ function preprocess(inFilename, outFilename, defines) {
 }
 exports.preprocess = preprocess;
 
-function preprocessCSS(inFilename, outFilename, defines) {
-  function hasPrefixedMozcentral(line) {
-    return /(^|\W)-(ms|o|webkit)-\w/.test(line);
-  }
-
-  function expandImports(content, baseUrl) {
-    return content.replace(
-      /^\s*@import\s+url\(([^)]+)\);\s*$/gm,
-      function (all, url) {
-        const file = path.join(path.dirname(baseUrl), url);
-        const imported = fs.readFileSync(file, "utf8").toString();
-        return expandImports(imported, file);
-      }
-    );
-  }
-
-  function removePrefixed(content, hasPrefixedFilter) {
-    const lines = content.split(/\r?\n/g);
-    let i = 0;
-    while (i < lines.length) {
-      const line = lines[i];
-      if (!hasPrefixedFilter(line)) {
-        i++;
-        continue;
-      }
-      if (/\{\s*$/.test(line)) {
-        let bracketLevel = 1;
-        let j = i + 1;
-        while (j < lines.length && bracketLevel > 0) {
-          const checkBracket = /([{}])\s*$/.exec(lines[j]);
-          if (checkBracket) {
-            if (checkBracket[1] === "{") {
-              bracketLevel++;
-            } else if (!lines[j].includes("{")) {
-              bracketLevel--;
-            }
-          }
-          j++;
-        }
-        lines.splice(i, j - i);
-      } else if (/[};]\s*$/.test(line)) {
-        lines.splice(i, 1);
-      } else {
-        // multiline? skipping until next directive or bracket
-        do {
-          lines.splice(i, 1);
-        } while (
-          i < lines.length &&
-          !/\}\s*$/.test(lines[i]) &&
-          !lines[i].includes(":")
-        );
-        if (i < lines.length && /\S\s*}\s*$/.test(lines[i])) {
-          lines[i] = lines[i].substring(lines[i].indexOf("}"));
-        }
-      }
-      // collapse whitespaces
-      while (lines[i] === "" && lines[i - 1] === "") {
-        lines.splice(i, 1);
-      }
-    }
-    return lines.join("\n");
-  }
-
-  if (!defines) {
-    throw new Error("Missing CSS preprocessor defines.");
-  }
-
-  let content = fs.readFileSync(inFilename, "utf8").toString();
-  content = expandImports(content, inFilename);
-  if (defines.MOZCENTRAL) {
-    content = removePrefixed(content, hasPrefixedMozcentral);
-  }
-  fs.writeFileSync(outFilename, content);
-}
-exports.preprocessCSS = preprocessCSS;
-
 /**
  * Merge two defines arrays. Values in the second param will override values in
  * the first.

external/builder/fixtures/if-nested-expected.css

@@ -0,0 +1,3 @@
+div {
+  margin: 0;
+}

external/builder/fixtures/if-nested.css

@@ -0,0 +1,14 @@
+/*#if TRUE*/
+div {
+  margin: 0;
+  /*#if FALSE*/
+  padding: 0;
+  /*#endif*/
+}
+/*#endif*/
+
+/*#if FALSE*/
+p {
+  margin: 0;
+}
+/*#endif*/

gulpfile.js

@@ -816,7 +816,7 @@ gulp.task("cmaps", function (done) {
 
 function preprocessCSS(source, defines) {
   const outName = getTempFile("~preprocess", ".css");
-  builder.preprocessCSS(source, outName, defines);
+  builder.preprocess(source, outName, defines);
   let out = fs.readFileSync(outName).toString();
   fs.unlinkSync(outName);
 

web/viewer.css

@@ -29,7 +29,9 @@
 
   --main-color: rgba(12, 12, 13, 1);
   --body-bg-color: rgba(237, 237, 240, 1);
-  --errorWrapper-bg-color: rgba(255, 110, 110, 1); /* -webkit-non-mozcentral */
+  /*#if !MOZCENTRAL*/
+  --errorWrapper-bg-color: rgba(255, 110, 110, 1);
+  /*#endif*/
   --progressBar-color: rgba(10, 132, 255, 1);
   --progressBar-indeterminate-bg-color: rgba(221, 221, 222, 1);
   --progressBar-indeterminate-blend-color: rgba(116, 177, 239, 1);
@@ -77,7 +79,9 @@
   --toolbarButton-zoomIn-icon: url(images/toolbarButton-zoomIn.svg);
   --toolbarButton-presentationMode-icon: url(images/toolbarButton-presentationMode.svg);
   --toolbarButton-print-icon: url(images/toolbarButton-print.svg);
-  --toolbarButton-openFile-icon: url(images/toolbarButton-openFile.svg); /* -webkit-non-mozcentral */
+  /*#if GENERIC*/
+  --toolbarButton-openFile-icon: url(images/toolbarButton-openFile.svg);
+  /*#endif*/
   --toolbarButton-download-icon: url(images/toolbarButton-download.svg);
   --toolbarButton-bookmark-icon: url(images/toolbarButton-bookmark.svg);
   --toolbarButton-viewThumbnail-icon: url(images/toolbarButton-viewThumbnail.svg);
@@ -112,7 +116,9 @@
   :root {
     --main-color: rgba(249, 249, 250, 1);
     --body-bg-color: rgba(42, 42, 46, 1);
-    --errorWrapper-bg-color: rgba(169, 14, 14, 1); /* -webkit-non-mozcentral */
+    /*#if !MOZCENTRAL*/
+    --errorWrapper-bg-color: rgba(169, 14, 14, 1);
+    /*#endif*/
     --progressBar-color: rgba(0, 96, 223, 1);
     --progressBar-indeterminate-bg-color: rgba(40, 40, 43, 1);
     --progressBar-indeterminate-blend-color: rgba(20, 68, 133, 1);
@@ -457,9 +463,11 @@ select {
 #findInput {
   width: 200px;
 }
+/*#if !MOZCENTRAL*/
 #findInput::-webkit-input-placeholder {
   color: rgba(191, 191, 191, 1);
 }
+/*#endif*/
 #findInput::placeholder {
   font-style: normal;
 }
@@ -817,10 +825,12 @@ select {
   mask-image: var(--toolbarButton-print-icon);
 }
 
-#openFile::before, /* -webkit-non-mozcentral */
+/*#if GENERIC*/
-#secondaryOpenFile::before /* -webkit-non-mozcentral */ {
+#openFile::before,
+#secondaryOpenFile::before {
   mask-image: var(--toolbarButton-openFile-icon);
 }
+/*#endif*/
 
 #download::before,
 #secondaryDownload::before {
@@ -1002,10 +1012,11 @@ a.secondaryToolbarButton[href="#"] {
   background-repeat: no-repeat;
   background-position: 3px;
 }
-
+/*#if !MOZCENTRAL*/
 #pageNumber::-webkit-inner-spin-button {
   -webkit-appearance: none;
 }
+/*#endif*/
 
 .toolbarField:focus {
   border-color: #0a84ff;
@@ -1174,7 +1185,8 @@ a:focus > .thumbnail > .thumbnailSelectionRing,
   background: rgba(0, 0, 255, 0.3);
 }
 
-#errorWrapper /* -webkit-non-mozcentral */ {
+/*#if !MOZCENTRAL*/
+#errorWrapper {
   background-color: var(--errorWrapper-bg-color);
   color: var(--main-color);
   left: 0;
@@ -1184,17 +1196,17 @@ a:focus > .thumbnail > .thumbnailSelectionRing,
   padding: 3px 6px;
 }
 
-#errorMessageLeft /* -webkit-non-mozcentral */ {
+#errorMessageLeft {
   float: left;
 }
-#errorMessageRight /* -webkit-non-mozcentral */ {
+#errorMessageRight {
   float: right;
 }
 
-#errorSpacer /* -webkit-non-mozcentral */ {
+#errorSpacer {
   clear: both;
 }
-#errorMoreInfo /* -webkit-non-mozcentral */ {
+#errorMoreInfo {
   background-color: var(--field-bg-color);
   color: var(--field-color);
   border: 1px solid var(--field-border-color);
@@ -1202,6 +1214,7 @@ a:focus > .thumbnail > .thumbnailSelectionRing,
   margin: 3px;
   width: 98%;
 }
+/*#endif*/
 
 .dialogButton {
   width: auto;