Add information about default font

Signed-off-by: Konstantin Aladyshev <aladyshev22@gmail.com>

1 files changed, 25 insertions, 0 deletions

diff --git a/Lessons/Lesson_52/README.md b/Lessons/Lesson_52/README.md
index 2ab4d34..93376ad 100644
--- a/Lessons/Lesson_52/README.md
+++ b/Lessons/Lesson_52/README.md
@@ -168,6 +168,31 @@ For example wide `A` can be something like this:
     },
 ```
 
+# Default font glyphs
+
+In case you wonder where default font is defined look at the https://github.com/tianocore/edk2/blob/master/MdeModulePkg/Universal/Console/GraphicsConsoleDxe/LaffStd.c:
+```
+EFI_NARROW_GLYPH  gUsStdNarrowGlyphData[] = {
+  { 0x0020, 0x00, {0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00}},
+  { 0x0021, 0x00, {0x00,0x00,0x00,0x18,0x3C,0x3C,0x3C,0x18,0x18,0x18,0x18,0x18,0x00,0x18,0x18,0x00,0x00,0x00,0x00}},
+  { 0x0022, 0x00, {0x00,0x00,0x00,0x6C,0x6C,0x6C,0x28,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00}},
+  ...
+  { 0x0000, 0x00, {0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00}} //EOL
+};
+
+// Get available Unicode glyphs narrow fonts(8*19 pixels) size.
+UINT32 mNarrowFontSize =  sizeof (gUsStdNarrowGlyphData);
+```
+
+This `gUsStdNarrowGlyphData` array is used to create a font package and register it in the HII database. For the actual code look at the `RegisterFontPackage` function in the file https://github.com/tianocore/edk2/blob/master/MdeModulePkg/Universal/Console/GraphicsConsoleDxe/GraphicsConsole.c
+
+When we investigated package lists in the HII database this was the one responsible for this font:
+```
+PackageList[10]: GUID=F5F219D3-7006-4648-AC8D-D61DFB7BC6AD; size=0x14EC  // mFontPackageListGuid
+        Package[0]: type=SIMPLE_FONTS; size=0x14D4
+        Package[1]: type=END; size=0x4
+```
+
 # Get Glyph data for the Russian font
 
 Honestly getting the Glyph data is a hardest part for adding a font.