Update documentation (typos and minor corrections)

README.txt

@@ -164,10 +164,10 @@ Building FLTK under Microsoft Windows
     See README.Windows.txt and README.CMake.txt for more info.
 
 
-BUILDING HTML DOCUMENTATION
+Building HTML Documentation
 
     FLTK uses Doxygen for documentation, so you'll at least need doxygen
-    installed for creating html docs, and additionally LaTeX for creating
+    installed for creating HTML docs, and additionally LaTeX for creating
     PDF documentation.
 
     If you want to build the documentation, change directory to your build
@@ -185,7 +185,7 @@ BUILDING HTML DOCUMENTATION
     `ninja pdf`, respectively.
 
 
-INTERNET RESOURCES
+Internet Resources
 
     FLTK is available on the internet in a bunch of locations:
 
@@ -199,14 +199,14 @@ INTERNET RESOURCES
     the package manager of your (Linux, Unix, macOS) operating system.
 
 
-GENERAL QUESTIONS
+General Questions
 
     To join the FLTK mailing list, go to the following web page:
 
         https://groups.google.com/forum/#!forum/fltkgeneral
 
-    You can find detailed instructions on how you can register for the
-    mailing list (even w/o a Google account) at the bottom of this page:
+    Detailed instructions on how to register for the mailing list (even
+    without a Google account) can be found further down on this page:
 
         https://www.fltk.org/newsgroups.php
 
@@ -216,7 +216,7 @@ GENERAL QUESTIONS
         https://github.com/fltk/fltk/discussions/categories/q-a
 
 
-REPORTING BUGS
+Reporting Bugs
 
     If you are new to FLTK, or have general questions about how to use FLTK,
     or aren't sure if you found a bug, please ask first on the fltk.general
@@ -229,7 +229,7 @@ REPORTING BUGS
         https://github.com/fltk/fltk/discussions/categories/q-a
 
 
-    See also paragraph GENERAL QUESTIONS above for more info.
+    See also paragraph "General Questions" above for more info.
 
     If you are sure you found a bug, please see the following page for
     further information on how to report a bug:
@@ -237,15 +237,15 @@ REPORTING BUGS
         https://www.fltk.org/bugs.php
 
 
-TRADEMARKS
+Trademarks
 
-    Microsoft and Windows are registered trademarks of Microsoft Corporation.
-    UNIX is a registered trademark of the X/Open Group, Inc.
-    OpenGL is a registered trademark of Silicon Graphics, Inc.
-    macOS is a registered trademark of Apple Computers, Inc.
+    - Microsoft and Windows are registered trademarks of Microsoft Corporation.
+    - UNIX is a registered trademark of the X/Open Group, Inc.
+    - OpenGL is a registered trademark of Silicon Graphics, Inc.
+    - macOS is a registered trademark of Apple Computers, Inc.
 
 
-COPYRIGHT
+Copyright
 
     FLTK is copyright 1998-2025 by Bill Spitzak and others,
     see the CREDITS.txt file for more info.

src/Fl_add_idle.cxx

@@ -119,7 +119,7 @@ int Fl::has_idle(Fl_Idle_Handler cb, void* data) {
   The given idle callback is only removed if \p data matches the
   value used when the idle callback was installed. If the idle
   callback wants to remove itself, the value provided by the \p data
-  variable can (and should) be used.
+  argument can (and should) be used.
 
   Example for a "one-shot" idle callback, i.e. one that removes itself
   when it is called for the first time.
@@ -147,6 +147,8 @@ int Fl::has_idle(Fl_Idle_Handler cb, void* data) {
     }
   \endcode
 
+  \param[in]  cb    idle callback in question
+  \param[in]  data  optional data. Default: zero / nullptr.
 */
 void Fl::remove_idle(Fl_Idle_Handler cb, void* data) {
   idle_cb* p = first;