Compatibility: refactor user agent detection

This patch moves the user agent checks to the top of the file to reduce
duplication and to provide a clear overview of which user agent we are
detecting.

Moreover, we extract inline user agent checks as well and use existing
checks in more places. Finally, we fix the indenting in one place for
consistency.

web/compatibility.js

@@ -17,6 +17,19 @@
 (function compatibilityWrapper() {
   'use strict';
 
+var userAgent = navigator.userAgent;
+
+var isAndroid = /Android/.test(userAgent);
+var isAndroidPre3 = /Android\s[0-2][^\d]/.test(userAgent);
+var isAndroidPre5 = /Android\s[0-4][^\d]/.test(userAgent);
+var isChrome = userAgent.indexOf('Chrom') >= 0;
+var isChromeWithRangeBug = /Chrome\/(39|40)\./.test(userAgent);
+var isIE = userAgent.indexOf('Trident') >= 0;
+var isIOS = /\b(iPad|iPhone|iPod)(?=;)/.test(userAgent);
+var isOpera = userAgent.indexOf('Opera') >= 0;
+var isSafari = /Safari\//.test(userAgent) &&
+               !/(Chrome\/|Android\s)/.test(userAgent);
+
 // Initializing PDFJS global object here, it case if we need to change/disable
 // some PDF.js features, e.g. range requests
 if (typeof PDFJS === 'undefined') {
@@ -29,12 +42,12 @@ if (typeof PDFJS === 'undefined') {
   if (typeof Uint8Array !== 'undefined') {
     // Support: iOS<6.0
     if (typeof Uint8Array.prototype.subarray === 'undefined') {
-        Uint8Array.prototype.subarray = function subarray(start, end) {
+      Uint8Array.prototype.subarray = function subarray(start, end) {
-          return new Uint8Array(this.slice(start, end));
+        return new Uint8Array(this.slice(start, end));
-        };
+      };
-        Float32Array.prototype.subarray = function subarray(start, end) {
+      Float32Array.prototype.subarray = function subarray(start, end) {
-          return new Float32Array(this.slice(start, end));
+        return new Float32Array(this.slice(start, end));
-        };
+      };
     }
 
     // Support: Android<4.1
@@ -429,7 +442,7 @@ if (typeof PDFJS === 'undefined') {
   function isDisabled(node) {
     return node.disabled || (node.parentNode && isDisabled(node.parentNode));
   }
-  if (navigator.userAgent.indexOf('Opera') !== -1) {
+  if (isOpera) {
     // use browser detection since we cannot feature-check this bug
     document.addEventListener('click', ignoreIfTargetDisabled, true);
   }
@@ -439,7 +452,7 @@ if (typeof PDFJS === 'undefined') {
 // Support: IE
 (function checkOnBlobSupport() {
   // sometimes IE loosing the data created with createObjectURL(), see #3977
-  if (navigator.userAgent.indexOf('Trident') >= 0) {
+  if (isIE) {
     PDFJS.disableCreateObjectURL = true;
   }
 })();
@@ -452,28 +465,19 @@ if (typeof PDFJS === 'undefined') {
   PDFJS.locale = navigator.userLanguage || 'en-US';
 })();
 
+// Support: Safari 6.0+, Android<3.0, Chrome 39/40, iOS
 (function checkRangeRequests() {
   // Safari has issues with cached range requests see:
   // https://github.com/mozilla/pdf.js/issues/3260
   // Last tested with version 6.0.4.
-  // Support: Safari 6.0+
-  var isSafari = /Safari\//.test(navigator.userAgent) &&
-                 !/(Chrome\/|Android\s)/.test(navigator.userAgent);
 
   // Older versions of Android (pre 3.0) has issues with range requests, see:
   // https://github.com/mozilla/pdf.js/issues/3381.
   // Make sure that we only match webkit-based Android browsers,
   // since Firefox/Fennec works as expected.
-  // Support: Android<3.0
-  var isOldAndroid = /Android\s[0-2][^\d]/.test(navigator.userAgent);
 
   // Range requests are broken in Chrome 39 and 40, https://crbug.com/442318
-  var isChromeWithRangeBug = /Chrome\/(39|40)\./.test(navigator.userAgent);
+  if (isSafari || isAndroidPre3 || isChromeWithRangeBug || isIOS) {
-
-  // Range requests are broken in iOS 10, but likely also in prior versions.
-  var isIOS = /\b(iPad|iPhone|iPod)(?=;)/.test(navigator.userAgent);
-
-  if (isSafari || isOldAndroid || isChromeWithRangeBug || isIOS) {
     PDFJS.disableRange = true;
     PDFJS.disableStream = true;
   }
@@ -485,7 +489,7 @@ if (typeof PDFJS === 'undefined') {
   // Android 2.x has so buggy pushState support that it was removed in
   // Android 3.0 and restored as late as in Android 4.2.
   // Support: Android 2.x
-  if (!history.pushState || navigator.userAgent.indexOf('Android 2.') >= 0) {
+  if (!history.pushState || isAndroidPre3) {
     PDFJS.disableHistory = true;
   }
 })();
@@ -505,17 +509,17 @@ if (typeof PDFJS === 'undefined') {
     // Old Chrome and Android use an inaccessible CanvasPixelArray prototype.
     // Because we cannot feature detect it, we rely on user agent parsing.
     var polyfill = false, versionMatch;
-    if (navigator.userAgent.indexOf('Chrom') >= 0) {
+    if (isChrome) {
-      versionMatch = navigator.userAgent.match(/Chrom(e|ium)\/([0-9]+)\./);
+      versionMatch = userAgent.match(/Chrom(e|ium)\/([0-9]+)\./);
       // Chrome < 21 lacks the set function.
       polyfill = versionMatch && parseInt(versionMatch[2]) < 21;
-    } else if (navigator.userAgent.indexOf('Android') >= 0) {
+    } else if (isAndroid) {
       // Android < 4.4 lacks the set function.
       // Android >= 4.4 will contain Chrome in the user agent,
       // thus pass the Chrome check above and not reach this block.
-      polyfill = /Android\s[0-4][^\d]/g.test(navigator.userAgent);
+      polyfill = isAndroidPre5;
-    } else if (navigator.userAgent.indexOf('Safari') >= 0) {
+    } else if (isSafari) {
-      versionMatch = navigator.userAgent.
+      versionMatch = userAgent.
         match(/Version\/([0-9]+)\.([0-9]+)\.([0-9]+) Safari\//);
       // Safari < 6 lacks the set function.
       polyfill = versionMatch && parseInt(versionMatch[1]) < 6;
@@ -545,7 +549,6 @@ if (typeof PDFJS === 'undefined') {
     window.setTimeout(callback, 20);
   }
 
-  var isIOS = /\b(iPad|iPhone|iPod)(?=;)/.test(navigator.userAgent);
   if (isIOS) {
     // requestAnimationFrame on iOS is broken, replacing with fake one.
     window.requestAnimationFrame = fakeRequestAnimationFrame;
@@ -560,9 +563,8 @@ if (typeof PDFJS === 'undefined') {
     fakeRequestAnimationFrame;
 })();
 
+// Support: Android, iOS
 (function checkCanvasSizeLimitation() {
-  var isIOS = /\b(iPad|iPhone|iPod)(?=;)/.test(navigator.userAgent);
-  var isAndroid = /Android/g.test(navigator.userAgent);
   if (isIOS || isAndroid) {
     // 5MP
     PDFJS.maxCanvasPixels = 5242880;
@@ -572,9 +574,7 @@ if (typeof PDFJS === 'undefined') {
 // Disable fullscreen support for certain problematic configurations.
 // Support: IE11+ (when embedded).
 (function checkFullscreenSupport() {
-  var isEmbeddedIE = (navigator.userAgent.indexOf('Trident') >= 0 &&
+  if (isIE && window.parent !== window) {
-                      window.parent !== window);
-  if (isEmbeddedIE) {
     PDFJS.disableFullscreen = true;
   }
 })();