Added some comments regarding font height

CONTRIBUTORS

@@ -3374,6 +3374,7 @@ Thomas Reufer <thomas@reufer.ch>
  font drawing in high level OSDs
  for fixing regenerating the index of audio recordings
  for implementing the SVDRP commands 'LSTD' and 'PRIM'
+ for adding some comments regarding font height
 
 Eike Sauer <EikeSauer@t-online.de>
  for reporting a problem with channels that need more than 5 TS packets for detecting

HISTORY

@@ -9198,3 +9198,4 @@ Video Disk Recorder Revision History
   removed), but rather by the main program loop reacting to changes in Setup.PrimaryDVB.
 - The new SVDRP commands 'LSTD' and 'PRIM' can be used to list all available devices
   and to switch the primary device (thanks to Thomas Reufer).
+- Added some comments regarding font height (thanks to Thomas Reufer).

font.h

@@ -4,7 +4,7 @@
  * See the main source file 'vdr.c' for copyright information and
  * how to reach the author.
  *
- * $Id: font.h 4.2 2016/12/22 12:43:24 kls Exp $
+ * $Id: font.h 4.3 2017/11/11 14:05:07 kls Exp $
  */
 
 #ifndef __FONT_H
@@ -54,6 +54,8 @@ public:
           ///< Returns the width of the given string in pixel.
   virtual int Height(void) const = 0;
           ///< Returns the height of this font in pixel (all characters have the same height).
+          ///< If the font contains descenders, its total height may be higher than the character
+          ///< height specified during creation.
   int Height(const char *s) const { return Height(); }
           ///< Returns the height of this font in pixel (obsolete, just for backwards compatibility).
   virtual void DrawText(cBitmap *Bitmap, int x, int y, const char *s, tColor ColorFg, tColor ColorBg, int Width) const = 0;
@@ -75,10 +77,12 @@ public:
           ///< function that called GetFont() has returned.
   static cFont *CreateFont(const char *Name, int CharHeight, int CharWidth = 0);
           ///< Creates a new font object with the given Name and makes its characters
-          ///< CharHeight pixels high. If CharWidth is given, it overwrites the font's
-          ///< default width. Name is of the form "Family:Style", for instance
-          ///< "Verdana:Bold Italic" or "Times New Roman". See GetAvailableFontNames()
-          ///< for how to get a list of all available font names.
+          ///< CharHeight pixels high. The actual height of the required drawing area
+          ///< might be higher than CharHeight if the font contains descenders.
+          ///< If CharWidth is given, it overwrites the font's default width.
+          ///< Name is of the form "Family:Style", for instance "Verdana:Bold Italic" or
+          ///< "Times New Roman". See GetAvailableFontNames() for how to get a list of
+          ///< all available font names.
           ///< If the requested font can't be created, a dummy font is returned.
           ///< The caller must delete the font when it is no longer needed.
   static bool GetAvailableFontNames(cStringList *FontNames, bool Monospaced = false);