Don't use next-line and previous-line in non-interactive ways.

- it messes up in visual-line-mode

Fixes #10

features/edit-lines.feature

@@ -0,0 +1,32 @@
+Feature: Switching from a multiline region to multiple cursors
+
+  Scenario: Single line region
+    When I insert "hello there"
+    And I select "there"
+    And I press "C-S-c C-S-c"
+    Then I should have one cursor
+
+  Scenario: Edit lines
+    When I insert:
+    """
+    hello
+    there
+    """
+    And I go to the front of the word "hello"
+    And I set the mark
+    And I go to the front of the word "there"
+    And I press "C-S-c C-S-c"
+    Then I should have 2 cursors
+
+  Scenario: Edit only real lines, even in visual-line-mode
+    Given I turn on visual-line-mode
+    And I insert:
+    """
+    some very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very
+    long text
+    """
+    And I go to the front of the word "some"
+    And I set the mark
+    And I go to the front of the word "long"
+    And I press "C-S-c C-S-c"
+    Then I should have 2 cursors

features/support/env.el

@@ -21,6 +21,7 @@
  (global-set-key (kbd "C-<") 'mc/mark-previous-like-this)
  (global-set-key (kbd "M-!") 'mc/mark-all-like-this)
  (global-set-key (kbd "M-#") 'mc/mark-all-in-region)
+ (global-set-key (kbd "C-S-c C-S-c") 'mc/edit-lines)
  (global-set-key (kbd "H-SPC") 'set-rectangular-region-anchor)
  (switch-to-buffer
   (get-buffer-create "*multiple-cursors*"))

mc-edit-lines.el

@@ -40,11 +40,11 @@ line point is on."
   (mc/remove-fake-cursors)
   (let* ((point-line (line-number-at-pos))
          (mark-line (progn (exchange-point-and-mark) (line-number-at-pos)))
-         (navigation-func (if (< point-line mark-line) 'previous-line 'next-line)))
+         (direction (if (< point-line mark-line) :up :down)))
     (deactivate-mark)
     (while (not (eq (line-number-at-pos) point-line))
       (mc/create-fake-cursor-at-point)
-      (funcall navigation-func))
+      (if (eq direction :up) (forward-line -1) (forward-line 1)))
     (multiple-cursors-mode)))
 
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