hterm: fix typo in blink preference handling

Commit cce97c4 (hterm: add a helper for
setting CSS variables) added a typo with the blink preference.  Fix that
and rework the code a bit to support tests.

Change-Id: I134b375f6548f9e0a838962de173827d3a43950e
Reviewed-on: https://chromium-review.googlesource.com/845479
Reviewed-by: David Schneider <[email protected]>
Reviewed-by: Brandon Gilmore <[email protected]>
Tested-by: Mike Frysinger <[email protected]>

Author: vapier

hterm/js/hterm_terminal.js

@@ -390,7 +390,7 @@ hterm.Terminal.prototype.setProfile = function(profileId, opt_callback) {
     },
 
     'enable-blink': function(v) {
-      terminal.syncBlinkState();
+      terminal.setTextBlink(!!v);
     },
 
     'enable-clipboard-write': function(v) {
@@ -771,6 +771,20 @@ hterm.Terminal.prototype.setCssVar = function(name, value,
       `${opt_prefix}${name}`, value);
 };
 
+/**
+ * Get a CSS variable.
+ *
+ * Normally this is used to get variables in the hterm namespace.
+ *
+ * @param {string} name The variable to read.
+ * @param {string?} opt_prefix The variable namespace/prefix to use.
+ * @return {string} The current setting for this variable.
+ */
+hterm.Terminal.prototype.getCssVar = function(name, opt_prefix='--hterm-') {
+  return this.document_.documentElement.style.getPropertyValue(
+      `${opt_prefix}${name}`);
+};
+
 /**
  * Set the font size for this terminal.
  *
@@ -862,11 +876,14 @@ hterm.Terminal.prototype.syncBoldSafeState = function() {
 };
 
 /**
- * Enable or disable blink based on the enable-blink pref.
+ * Control text blinking behavior.
+ *
+ * @param {boolean=} state Whether to enable support for blinking text.
  */
-hterm.Terminal.prototype.syncBlinkState = function() {
-  this.setCssVar('node-duration',
-                 this.prefs_.get('enable-blink') ? '0.7s' : '0');
+hterm.Terminal.prototype.setTextBlink = function(state) {
+  if (state === undefined)
+    state = this.prefs_.get('enable-blink');
+  this.setCssVar('blink-node-duration', state ? '0.7s' : '0');
 };
 
 /**

hterm/js/hterm_terminal_tests.js

@@ -477,3 +477,25 @@ hterm.Terminal.Tests.addTest('display-img-invalid', function(result, cx) {
 
   result.requestTime(200);
 });
+
+/**
+ * Verify turning text blink on/off works.
+ *
+ * This test isn't great.  Since we use CSS animations for everything, we
+ * assume that part is working, so we just check the stored timing values.
+ */
+hterm.Terminal.Tests.addTest('text-blink', function(result, cx) {
+  // Default blink state is enabled.
+  this.terminal.setTextBlink();
+  result.assert('0' != this.terminal.getCssVar('blink-node-duration'));
+
+  // Explicitly turn it off.
+  this.terminal.setTextBlink(false);
+  result.assertEQ('0', this.terminal.getCssVar('blink-node-duration'));
+
+  // Explicitly turn it back on.
+  this.terminal.setTextBlink(true);
+  result.assert('0' != this.terminal.getCssVar('blink-node-duration'));
+
+  result.pass();
+});