I downloaded the JavaFx source code from http://hg.openjdk.java.net/openjfx/2.2/master/rt/summary.
The name of the folder in the zip file is re-e71070b0e0c0.
I unzipped this and added the folder under Project Structure - Global Libraries in Idea, however it doesn't work. When I try to open a class it just shows field names and /* compiled code */. I couldn't find anything in the manual.
Much of the information in this answer is now outdated.
More up-to-date information on using JavaFX with Java 11+ in IntelliJ Idea, is available at:
Though, the above-linked article is more focused on using JavaFX in IntelliJ rather than viewing JavaFX library source code in IntelliJ.
These instructions are only necessary for the JavaFX 2.x branch and will be obsoleted once JDK 8 is released.
After you have downloaded the source zip and extracted it, open Idea and follow these instructions:
Modify the source structure for your 1.7 SDK:
File | Project Structure | SDKs | Sourcepath
For each sub-project in the extracted zip, type Alt+Insert and add the respective source directory. For example rt-e71070b0e0c0\javafx-ui-charts\src, rt-e71070b0e0c0\javafx-ui-common\src, etc. Not all JavaFX 2.x source code is currently open sourced, so this will only add the open sourced portions.
Set the documentation lookup path:
File | Project Structure | SDKs | Documentation Paths
Specify a url Alt+S for the documentation: http://docs.oracle.com/javafx/2/api/
In your JavaFX application source, place your cursor over a JavaFX class usage, for instance LineChart:
Press Ctrl+B to open the source code file LineChart.java from your downloaded zip.
Press Shift+F1 to open documentation on the LineChart in a browser.
Press Ctrl+Q to get quick access to documentation from in the IDE.
Update Oct 16 2013
JDK 8 now includes JavaFX source files.
To tell Idea where JavaFX sources are:
Modify the source structure for your 1.8 SDK:
File | Project Structure | SDKs | Sourcepath
Press Alt+S to add the file javafx-src.zip, which is located in the root directory of the JDK 8 distribution.
Set the documentation lookup path:
File | Project Structure | SDKs | Documentation Paths
Specify a url Alt+S for the documentation: http://download.java.net/jdk8/jfxdocs.
The JDK 8 JavaFX documentation url will likely change when JDK 8 reaches General Availability release stage.
Step 3 above provides keyboard shortcuts to quickly access the JavaFX sources and documentation from your project.
(Since this is one of the Google hits for "javafx source code", I'll dump this anwer here too):
Quoting from this answer: For Java 8, the source of the public parts of JavaFX are actually laying right along in the JDK installation as a sibling of src.zip: javafx-src.zip - on the root of your normal JDK Java 8 installation.
Eclipse doesn't by default link them up when you add the JRE (or it finds it itself) - obviously a bug - so you'll have to do that yourself, by hitting Preferences -> Installed JREs. Find your JDK 8, hit Edit button. On the list JRE system libraries, expand the jfxrt.jar node, and link in the javafx-src.zip file.
I've faced this problem on Ubuntu 16.04 with JavaFX 8 (open-jfx package). The fix was to install the missing source package:
sudo apt install openjfx-source
IntellJ started showing JavaFX source code the second after the command finished executing.
