a few last missing minor bits of DB's refactored display code

git-svn-id: svn://svn.savannah.gnu.org/nano/trunk/nano@1561 35c25a1d-7b9e-4130-9fde-d3aeb78583b8

ChangeLog

@@ -46,12 +46,13 @@ CVS code -
 	  instead of several; and do some other minor refactoring of
 	  related display functions to simplify them.  New functions
 	  mark_order() and display_string(); changes to actual_x(),
-	  strnlenpt(), blank_bottombars(), edit_add(), update_line(),
-	  statusbar(), and do_replace_highlight(). (David Benbennick)
-	  DLR: Add minor cosmetic tweaks, add missing NANO_SMALL #ifdef
-	  around the text for a backwards search in the refactored code,
-	  and enclose dump_buffer() and dump_buffer_reverse() in one
-	  ENABLE_DEBUG #ifdef instead of two.
+	  strnlenpt(), blank_bottombars(), blank_edit(),
+	  get_page_start(), edit_add(), update_line(), statusbar(), and
+	  do_replace_highlight(). (David Benbennick)  DLR: Add minor
+	  cosmetic tweaks, add missing NANO_SMALL #ifdef around the text
+	  for a backwards search in the refactored code, and enclose
+	  dump_buffer() and dump_buffer_reverse() in one ENABLE_DEBUG
+	  #ifdef instead of two.
 	- Convert memmove() function calls to charmove() macro calls, as
 	  the former all work on char*'s. (DLR)
 - files.c:

src/proto.h

@@ -473,7 +473,7 @@ void onekey(const char *keystroke, const char *desc, int len);
 #ifndef NDEBUG
 int check_linenumbers(const filestruct *fileptr);
 #endif
-int get_page_start(int column);
+size_t get_page_start(size_t column);
 void reset_cursor(void);
 void add_marked_sameline(int begin, int end, filestruct *fileptr, int y,
 			 int virt_cur_x, int this_page);

src/winio.c

@@ -411,7 +411,7 @@ void blank_bottomwin(void)
 void blank_edit(void)
 {
     int i;
-    for (i = 0; i <= editwinrows - 1; i++)
+    for (i = 0; i < editwinrows; i++)
 	mvwaddstr(edit, i, 0, hblank);
 }
 
@@ -963,13 +963,22 @@ int check_linenumbers(const filestruct *fileptr)
 }
 #endif
 
- /* nano scrolls horizontally within a line in chunks.  This function
+/* nano scrolls horizontally within a line in chunks.  This function
  * returns the column number of the first character displayed in the
-  * window when the cursor is at the given column. */
-int get_page_start(int column)
+ * window when the cursor is at the given column.  Note that
+ * 0 <= column - get_page_start(column) < COLS. */
+size_t get_page_start(size_t column)
 {
-    assert(COLS > 9);
-    return column < COLS - 1 ? 0 : column - 7 - (column - 8) % (COLS - 9);
+    assert(COLS > 0);
+    if (column == 0 || column < COLS - 1)
+	return 0;
+    else if (COLS > 9)
+	return column - 7 - (column - 8) % (COLS - 9);
+    else if (COLS > 2)
+	return column - (COLS - 2);
+    else
+	return column - (COLS - 1);
+		/* The parentheses are necessary to avoid overflow. */
 }
 
 /* Resets current_y, based on the position of current, and puts the
@@ -1318,7 +1327,7 @@ void update_line(const filestruct *fileptr, size_t index)
 
     /* Next, convert variables that index the line to their equivalent
      * positions in the expanded line. */
-    index = fileptr == current ? strnlenpt(fileptr->data, index) : 0;
+    index = (fileptr == current) ? strnlenpt(fileptr->data, index) : 0;
     page_start = get_page_start(index);
 
     /* Expand the line, replacing Tab by spaces, and control characters