master 237f4f9295: Fix dimensions of console window of restarted Emacs on MS-Windows

[Eli Zaretskii]

branch: master
commit 237f4f9295d17d15c58ffce9728b72aa1e529172
Author: Eli Zaretskii <eliz@gnu.org>
Commit: Eli Zaretskii <eliz@gnu.org>

    Fix dimensions of console window of restarted Emacs on MS-Windows
    
    * src/w32.c (get_console_font_size): New function.
    (w32_reexec_emacs): Call 'get_console_font_size' to set up the
    dimensions of the restarted Emacs's console window to the same
    values as that of the original Emacs.
---
 src/w32.c | 72 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++----
 1 file changed, 68 insertions(+), 4 deletions(-)

diff --git a/src/w32.c b/src/w32.c
index 74923ffece..a8f69565d6 100644
--- a/src/w32.c
+++ b/src/w32.c
@@ -348,6 +348,7 @@ static BOOL g_b_init_reg_open_key_ex_w;
 static BOOL g_b_init_reg_query_value_ex_w;
 static BOOL g_b_init_expand_environment_strings_w;
 static BOOL g_b_init_get_user_default_ui_language;
+static BOOL g_b_init_get_console_font_size;
 
 BOOL g_b_init_compare_string_w;
 BOOL g_b_init_debug_break_process;
@@ -537,6 +538,18 @@ typedef LONG (WINAPI *RegQueryValueExW_Proc) 
(HKEY,LPCWSTR,LPDWORD,LPDWORD,LPBYT
 typedef DWORD (WINAPI *ExpandEnvironmentStringsW_Proc) (LPCWSTR,LPWSTR,DWORD);
 typedef LANGID (WINAPI *GetUserDefaultUILanguage_Proc) (void);
 
+typedef COORD (WINAPI *GetConsoleFontSize_Proc) (HANDLE, DWORD);
+typedef struct
+{
+  DWORD nFont;
+  COORD dwFontSize;
+} CONSOLE_FONT_INFO;
+typedef BOOL (WINAPI *GetCurrentConsoleFont_Proc) (
+    HANDLE,
+    BOOL,
+    CONSOLE_FONT_INFO *);
+
+
   /* ** A utility function ** */
 static BOOL
 is_windows_9x (void)
@@ -10618,6 +10631,47 @@ realpath (const char *file_name, char *resolved_name)
   return xstrdup (tgt);
 }
 
+static void
+get_console_font_size (HANDLE hscreen, int *font_width, int *font_height)
+{
+  static GetCurrentConsoleFont_Proc s_pfn_Get_Current_Console_Font = NULL;
+  static GetConsoleFontSize_Proc s_pfn_Get_Console_Font_Size = NULL;
+
+  /* Default guessed values, for when we cannot obtain the actual ones.  */
+  *font_width = 8;
+  *font_height = 12;
+
+  if (!is_windows_9x ())
+    {
+      if (g_b_init_get_console_font_size == 0)
+       {
+         HMODULE hm_kernel32 = LoadLibrary ("Kernel32.dll");
+         if (hm_kernel32)
+           {
+             s_pfn_Get_Current_Console_Font = (GetCurrentConsoleFont_Proc)
+               get_proc_addr (hm_kernel32, "GetCurrentConsoleFont");
+             s_pfn_Get_Console_Font_Size = (GetConsoleFontSize_Proc)
+               get_proc_addr (hm_kernel32, "GetConsoleFontSize");
+           }
+         g_b_init_get_console_font_size = 1;
+       }
+    }
+  if (s_pfn_Get_Current_Console_Font && s_pfn_Get_Console_Font_Size)
+    {
+      CONSOLE_FONT_INFO font_info;
+
+      if (s_pfn_Get_Current_Console_Font (hscreen, FALSE, &font_info))
+       {
+         COORD font_size = s_pfn_Get_Console_Font_Size (hscreen,
+                                                        font_info.nFont);
+         if (font_size.X > 0)
+           *font_width = font_size.X;
+         if (font_size.Y > 0)
+           *font_height = font_size.Y;
+       }
+    }
+}
+
 /* A replacement for Posix execvp, used to restart Emacs.  This is
    needed because the low-level Windows API to start processes accepts
    the command-line arguments as a single string, so we cannot safely
@@ -10642,18 +10696,27 @@ w32_reexec_emacs (char *cmd_line, const char *wdir)
       if (screen_handle != INVALID_HANDLE_VALUE
          && GetConsoleScreenBufferInfo (screen_handle, &screen_info))
        {
+         int font_width, font_height;
+
          /* Make the restarted Emacs's console window the same
-            dimensions as ours.  FIXME: for some reason this doesn't
-            seem to work!  */
-         si.dwFlags |= STARTF_USECOUNTCHARS;
+            dimensions as ours.  */
          si.dwXCountChars = screen_info.dwSize.X;
          si.dwYCountChars = screen_info.dwSize.Y;
+         get_console_font_size (screen_handle, &font_width, &font_height);
+         si.dwXSize =
+           (screen_info.srWindow.Right - screen_info.srWindow.Left + 1)
+           * font_width;
+         si.dwYSize =
+           (screen_info.srWindow.Bottom - screen_info.srWindow.Top + 1)
+           * font_height;
+         si.dwFlags |= STARTF_USESIZE | STARTF_USECOUNTCHARS;
        }
       /* This is a kludge: it causes the restarted "emacs -nw" to have
         a new console window created for it, and that new window
         might have different (default) properties, not the ones of
         the parent process's console window.  But without this,
-        restarting Emacs in the -nw mode simply doesn't work.
+        restarting Emacs in the -nw mode simply doesn't work,
+        probably because the parent's console is still in use.
         FIXME!  */
       dwCreationFlags = CREATE_NEW_CONSOLE;
     }
@@ -10742,6 +10805,7 @@ globals_of_w32 (void)
   g_b_init_compare_string_w = 0;
   g_b_init_debug_break_process = 0;
   g_b_init_get_user_default_ui_language = 0;
+  g_b_init_get_console_font_size = 0;
   num_of_processors = 0;
   /* The following sets a handler for shutdown notifications for
      console apps. This actually applies to Emacs in both console and