mouse: only type clicked chars if Ctrl pressed

People click with mouse occasionally, and typing gets them by
surprise. With Ctrl it can't be unintentional.

README.md

@@ -35,7 +35,7 @@ area outside of a cursor row, and another activates when you click
 inside the cursor row.
 
 Left button:
-  - types clicked char
+  - if Ctrl pressed: type clicked char; otherwise do nothing
   - moves the cursor to the clicked location
 
 Middle button:

src/command.c

@@ -578,22 +578,17 @@ static void advance_cmd_arg(void)
   return;
   }
 
-static unsigned short keyb_shift_states;
 static unsigned short keyb_get_rawcode(void)
 {
   unsigned short c = getch();
 
   if (c == 0x00/* || c == 0xE0*/)
     c = getch()<<8;
-
-  if (c == KEY_INSERT)
-    keyb_shift_states ^= KEYB_FLAG_INSERT;
-
   return c;
 }
-static unsigned short keyb_get_shift_states(void)
+unsigned short keyb_get_shift_states(void)
 {
-  return keyb_shift_states;
+  return bioskey(2);
 }
 
 static void prompt_for_and_get_cmd(void)

src/command.h

@@ -42,7 +42,16 @@
  */
 #define GET_ENHANCED_KEYSTROKE                0x10
 #define GET_EXTENDED_SHIFT_STATES             0x12
+
+#define KEYB_FLAG_RSHIFT    0x0001
+#define KEYB_FLAG_LSHIFT    0x0002
+#define KEYB_FLAG_CTRL      0x0004
+#define KEYB_FLAG_ALT       0x0008
+#define KEYB_FLAG_SCROLLOCK 0x0010
+#define KEYB_FLAG_NUMLOCK   0x0020
+#define KEYB_FLAG_CAPSLOCK  0x0040
 #define KEYB_FLAG_INSERT    0x0080
+
 #define KEY_ASCII(k)    (k & 0x00FF)
 #define KEY_SCANCODE(k) (k >> 0x08 )
 #define KEY_EXTM(k)     (k & 0xFF1F)
@@ -467,4 +476,6 @@ struct built_in_cmd
 extern struct built_in_cmd cmd_table[];
 extern const int CMD_TABLE_COUNT;
 
+unsigned short keyb_get_shift_states(void);
+
 #endif

src/mouse.c

@@ -23,6 +23,7 @@
 #include <sys/farptr.h>
 #include <go32.h>
 #include "asm.h"
+#include "command.h"
 #include "mouse.h"
 
 #define CF 1
@@ -78,6 +79,7 @@ static void mlb(int alt_fn, int x, int y)
 {
     __dpmi_regs r = { };
     short c;
+    int shift = keyb_get_shift_states();
 
     if (alt_fn) {
 	int cx = wherex();
@@ -89,6 +91,8 @@ static void mlb(int alt_fn, int x, int y)
 	    mvxr(x - cx);
 	return;
     }
+    if (!(shift & KEYB_FLAG_CTRL))
+	return;
 
     _conio_gettext(x, y, x, y, &c);