[meld] Fix linkmap painting when offset from its TextViews

[Kai Willadsen <kaiw src gnome org>]

commit 0e036d6163d0fe36b541a84a936d7a2abdc05d6e
Author: Kai Willadsen <kai willadsen gmail com>
Date:   Tue Jul 14 17:55:02 2009 +1000

    Fix linkmap painting when offset from its TextViews
    
    The linkmap drawing code assumes that the linkmap has the same y-coords
    as both of its TextViews. While this is currently true, it doesn't hold
    when per-pane MsgAreas are used. This commit adds an offset correction
    so that linkmaps starting below their textviews will do the right thing.

 meld/filediff.py |    9 +++++++--
 1 files changed, 7 insertions(+), 2 deletions(-)
---
diff --git a/meld/filediff.py b/meld/filediff.py
index f33545a..de3fd10 100644
--- a/meld/filediff.py
+++ b/meld/filediff.py
@@ -1155,6 +1155,7 @@ class FileDiff(melddoc.MeldDoc, gnomeglade.Component):
         #
     def on_linkmap_expose_event(self, widget, event):
         wtotal, htotal = widget.allocation.width, widget.allocation.height
+        yoffset = widget.allocation.y
         context = widget.window.cairo_create()
         context.rectangle(event.area.x, event.area.y, event.area.width, event.area.height)
         context.clip()
@@ -1175,6 +1176,10 @@ class FileDiff(melddoc.MeldDoc, gnomeglade.Component):
         pix_start[which  ] = self.textview[which  ].get_visible_rect().y
         pix_start[which+1] = self.textview[which+1].get_visible_rect().y
 
+        rel_offset = [None] * self.num_panes
+        rel_offset[which] = self.textview[which].allocation.y - yoffset
+        rel_offset[which + 1] = self.textview[which + 1].allocation.y - yoffset
+
         def bounds(idx):
             return [self._pixel_to_line(idx, pix_start[idx]), self._pixel_to_line(idx, pix_start[idx]+htotal)]
         visible = [None] + bounds(which) + bounds(which+1)
@@ -1196,8 +1201,8 @@ class FileDiff(melddoc.MeldDoc, gnomeglade.Component):
                 break
 
             # f and t are short for "from" and "to"
-            f0,f1 = [self._line_to_pixel(which,   l) - pix_start[which  ] for l in c[1:3] ]
-            t0,t1 = [self._line_to_pixel(which+1, l) - pix_start[which+1] for l in c[3:5] ]
+            f0, f1 = [self._line_to_pixel(which, l) - pix_start[which] + rel_offset[which] for l in c[1:3]]
+            t0, t1 = [self._line_to_pixel(which + 1, l) - pix_start[which + 1] + rel_offset[which + 1] for l in c[3:5]]
 
             context.move_to(x_steps[0], f0 - 0.5)
             context.curve_to(x_steps[1], f0 - 0.5,