add slide shortcuts

[chaz/talk-introduction-to-psgi] / js / common.js

diff --git a/js/common.js b/js/common.js
new file mode 100644 (file)
index 0000000..3832adb
--- /dev/null
+++ b/js/common.js
@@ -0,0 +1,55 @@
+
+/*
+ * Create a shortcut on a number key to jump to a named slide.
+ *
+ * Using the hotkey on the target slide will go "back" to the slide that was active before jumping
+ * to the target slide.
+ *
+ * Example: Jump to the slide named "myslide" when the "1" key is pressed.
+ *   createHotkey(1, 'myslide');
+ */
+function createHotkey(key, slideName) {
+    var targetSlide = slideshow.getSlideByName(slideName);
+    var lastSlide   = -1;
+    document.addEventListener('keydown', function(e) {
+        if (e.which === key + 48) {
+            var currentNum  = slideshow.getCurrentSlideIndex() + 1;
+            var targetNum   = targetSlide.getSlideIndex() + 1;
+            if (currentNum !== targetNum) {
+                lastSlide = currentNum;
+                slideshow.gotoSlide(targetNum);
+            }
+            else {
+                slideshow.gotoSlide(lastSlide);
+            }
+        }
+    });
+};
+
+/*
+ * Set a hotkey "u" to navigate backwards in time.
+ *
+ * If you get on the wrong slide, this might be the easiest way to get back on track. This is what
+ * you might expect the browser's "Back" button to do if it worked.
+ */
+(function() {
+    var history = [];
+    var skip    = false;
+    slideshow.on('hideSlide', function(slide) {
+        if (skip) {
+            skip = false;
+            return;
+        }
+        history.push(slide.getSlideIndex() + 1);
+    });
+    document.addEventListener('keydown', function(e) {
+        if (e.which === 85 /* [u]ndo */) {
+            var lastNum = history.pop();
+            if (lastNum) {
+                skip = true;
+                slideshow.gotoSlide(lastNum);
+            }
+        }
+    });
+})();
+