[evince] libview: Fix moving the caret cursor between lines in multicolumn documents

[Carlos Garcia Campos <carlosgc src gnome org>]

commit 415ab079ea4baf2e406c43a30cb90c06d6793c88
Author: Carlos Garcia Campos <carlosgc gnome org>
Date:   Tue Jul 2 21:05:04 2013 +0200

    libview: Fix moving the caret cursor between lines in multicolumn documents
    
    And also the caret cursor location when positioned with the mouse when
    clicking on areas with no text, like margins or even the space between
    columns.

 libview/ev-view.c |   77 ++++++++++++++++++++++++++++++++--------------------
 1 files changed, 47 insertions(+), 30 deletions(-)
---
diff --git a/libview/ev-view.c b/libview/ev-view.c
index e49532f..8990831 100644
--- a/libview/ev-view.c
+++ b/libview/ev-view.c
@@ -4023,9 +4023,11 @@ position_caret_cursor_at_location (EvView *view,
        guint        n_areas = 0;
        gint         page;
        gint         offset = -1 ;
+       gint         first_line_offset;
+       gint         last_line_offset = -1;
        gint         doc_x, doc_y;
        EvRectangle *rect;
-       guint        i, j;
+       guint        i;
 
        if (!view->caret_enabled || view->rotation != 0)
                return FALSE;
@@ -4041,29 +4043,38 @@ position_caret_cursor_at_location (EvView *view,
        if (!areas)
                return FALSE;
 
-       /* First look for the line of text at location */
-       for (i = 0; i < n_areas; i++) {
+       i = 0;
+       while (i < n_areas && offset == -1) {
                rect = areas + i;
 
-               if (doc_y >= rect->y1 && doc_y <= rect->y2)
-                       break;
-       }
-
-       if (i == n_areas)
-               return FALSE;
-
-       if (doc_x <= rect->x1) {
-               /* Location is before the start of the line */
-               offset = i;
-       } else {
-               for (j = i; j < n_areas; j++) {
-                       rect = areas + j;
+               first_line_offset = -1;
+               while (doc_y >= rect->y1 && doc_y <= rect->y2) {
+                       if (first_line_offset == -1) {
+                               if (doc_x <= rect->x1) {
+                                       /* Location is before the start of the line */
+                                       if (last_line_offset != -1) {
+                                               EvRectangle *last = areas + last_line_offset;
+                                               gint         dx1, dx2;
+
+                                               /* If there's a previous line, check distances */
+
+                                               dx1 = doc_x - last->x2;
+                                               dx2 = rect->x1 - doc_x;
+
+                                               if (dx1 < dx2)
+                                                       offset = last_line_offset;
+                                               else
+                                                       offset = i;
+                                       } else {
+                                               offset = i;
+                                       }
 
-                       if (doc_y < rect->y1) {
-                               /* Location is after the end of the line */
-                               offset = j;
-                               break;
+                                       last_line_offset = i + 1;
+                                       break;
+                               }
+                               first_line_offset = i;
                        }
+                       last_line_offset = i + 1;
 
                        if (doc_x >= rect->x1 && doc_x <= rect->x2) {
                                /* Location is inside the line. Position the caret before
@@ -4071,20 +4082,26 @@ position_caret_cursor_at_location (EvView *view,
                                 * falls within the left or right half of the bounding box.
                                 */
                                if (doc_x <= rect->x1 + (rect->x2 - rect->x1) / 2)
-                                       offset = j;
+                                       offset = i;
                                else
-                                       offset = j + 1;
+                                       offset = i + 1;
                                break;
                        }
 
+                       i++;
+                       rect = areas + i;
                }
-       }
 
-       if (offset == -1) {
-               /* This is the last line and loocation is after the end of the line */
-               offset = n_areas;
+               if (first_line_offset == -1)
+                       i++;
        }
 
+       if (last_line_offset == -1)
+               return FALSE;
+
+       if (offset == -1)
+               offset = last_line_offset;
+
        if (view->cursor_offset != offset || view->cursor_page != page) {
                view->cursor_offset = offset;
                view->cursor_page = page;
@@ -4938,7 +4955,6 @@ cursor_backward_line (EvView *view)
        PangoLogAttr *log_attrs = NULL;
        gulong        n_attrs;
 
-       /* FIXME: Keep the line offset when moving between lines */
        if (!cursor_go_to_line_start (view))
                return FALSE;
 
@@ -4949,7 +4965,8 @@ cursor_backward_line (EvView *view)
 
        do {
                view->cursor_offset--;
-       } while (view->cursor_offset >= 0 && !log_attrs[view->cursor_offset].is_cursor_position);
+       } while (view->cursor_offset >= 0 && !log_attrs[view->cursor_offset].is_mandatory_break);
+       view->cursor_offset = MAX (0, view->cursor_offset);
 
        return TRUE;
 }
@@ -4987,7 +5004,6 @@ cursor_forward_line (EvView *view)
        PangoLogAttr *log_attrs = NULL;
        gulong        n_attrs;
 
-       /* FIXME: Keep the line offset when moving between lines */
        if (!cursor_go_to_line_end (view))
                return FALSE;
 
@@ -5092,7 +5108,8 @@ ev_view_move_cursor (EvView         *view,
                return TRUE;
 
        if (step == GTK_MOVEMENT_DISPLAY_LINES) {
-               position_caret_cursor_at_location (view, view->cursor_line_offset,
+               position_caret_cursor_at_location (view,
+                                                  MAX (rect.x, view->cursor_line_offset),
                                                   rect.y + (rect.height / 2));
        } else {
                view->cursor_line_offset = rect.x;