FLUID: Add support for lambda callbacks.

Starting the callback text with a '[' assumes that
the rest of the callback is a lambda and generates
inlined code for it.

1 files changed, 10 insertions, 5 deletions

diff --git a/fluid/documentation/src/page_widget_panel.dox b/fluid/documentation/src/page_widget_panel.dox
index 7a1261d62..d897037e4 100644
--- a/fluid/documentation/src/page_widget_panel.dox
+++ b/fluid/documentation/src/page_widget_panel.dox
@@ -369,13 +369,18 @@
  \image html wp_cpp_callback.png
  \image latex wp_cpp_callback.png "" width=7cm
 
- The callback field can be interpreted in two ways. If the callback text is only
- a single word, FLUID assumes that this is the name of an external callback
- function and declares it in the header as
+ The callback field can be interpreted in three ways. If the callback text is
+ only a single word, FLUID assumes that this is the name of an external
+ callback function and declares it in the header as
  `extern void my_button_action(Fl_Button*, void*);`.
 
- Otherwise, FLUID assumes that the text is the body of a C++ callback function
- and instead creates a local static callback function. The name of the callback
+ If the first letter of the callback text is a '[', FLUID expects a lambda
+ function which will be inlined into the widget creation code. The lambda
+ signature must be `[](Fl_Widget*, void*)->void { ... }`. The widget pointer
+ can be casted to another type inside the lambda.
+
+ Otherwise, FLUID assumes that the text is the body of a C++ function,
+ and a local static callback function is created. The name of the callback
  function is generated by FLUID and guaranteed to be unique within the file.
  ```
  static void cb_input(Fl_Input *o, void *v) {