From c17d6ba48748126b07e57fdf2b1cd4d9e6d9ceae Mon Sep 17 00:00:00 2001
From: Nathan Sobo <nathan@github.com>
Date: Wed, 8 May 2013 14:18:51 -0600
Subject: [PATCH] Adjust multiple mappings if needed when applying screen
 deltas

If there are multiple mappings following the start row of the delta
that span fewer screen rows than the delta, we collapse mappings to 0
screen rows until we have removed the number of rows specified by the
delta.

Expanding positive deltas expands the first mapping following the
start row as it did previously.
---
 spec/app/row-map-spec.coffee | 23 +++++++++++++++++++++++
 src/app/row-map.coffee       | 15 ++++++++++++---
 2 files changed, 35 insertions(+), 3 deletions(-)

diff --git a/spec/app/row-map-spec.coffee b/spec/app/row-map-spec.coffee
index d1b99fdc8..5442be663 100644
--- a/spec/app/row-map-spec.coffee
+++ b/spec/app/row-map-spec.coffee
@@ -156,3 +156,26 @@ describe "RowMap", ->
         expect(map.bufferRowRangeForScreenRow(11)).toEqual [15, 20]
         expect(map.bufferRowRangeForScreenRow(5)).toEqual [5, 10]
         expect(map.bufferRowRangeForScreenRow(21)).toEqual [25, 30]
+
+  describe ".applyScreenDelta(startScreenRow, delta)", ->
+    describe "when applying a positive delta", ->
+      it "can enlarge the screen side of existing mappings", ->
+        map.mapBufferRowRange(5, 6, 3) # wrapped line
+        map.applyScreenDelta(5, 2) # wrap it twice more
+        expect(map.screenRowRangeForBufferRow(5)).toEqual [5, 10]
+
+    describe "when applying a negative delta", ->
+      it "can collapse the screen side of multiple mappings to 0 until the entire delta has been applied", ->
+        map.mapBufferRowRange(5, 10, 1)  # inner fold 1
+        map.mapBufferRowRange(11, 13, 1)  # inner fold 2
+        map.mapBufferRowRange(15, 20, 1) # inner fold 3
+        map.mapBufferRowRange(22, 27, 1) # following fold
+
+        map.applyScreenDelta(6, -5)
+
+        expect(map.screenRowRangeForBufferRow(5)).toEqual [5, 6]
+        expect(map.screenRowRangeForBufferRow(9)).toEqual [5, 6]
+        expect(map.screenRowRangeForBufferRow(10)).toEqual [6, 6]
+        expect(map.screenRowRangeForBufferRow(19)).toEqual [6, 6]
+        expect(map.screenRowRangeForBufferRow(22)).toEqual [8, 9]
+        expect(map.screenRowRangeForBufferRow(26)).toEqual [8, 9]
diff --git a/src/app/row-map.coffee b/src/app/row-map.coffee
index 4e8fb8267..485f2a6b6 100644
--- a/src/app/row-map.coffee
+++ b/src/app/row-map.coffee
@@ -50,9 +50,18 @@ class RowMap
     { mapping } = @traverseToBufferRow(startBufferRow)
     mapping?.bufferRows += delta
 
-  applyScreenDelta: (startBufferRow, delta) ->
-    { mapping } = @traverseToScreenRow(startBufferRow)
-    mapping?.screenRows += delta
+  applyScreenDelta: (startScreenRow, delta) ->
+    { index } = @traverseToScreenRow(startScreenRow)
+    until delta == 0
+      { bufferRows, screenRows } = @mappings[index]
+      screenRows += delta
+      if screenRows < 0
+        delta = screenRows
+        screenRows = 0
+      else
+        delta = 0
+      @mappings[index] = { bufferRows, screenRows }
+      index++
 
   traverseToBufferRow: (targetBufferRow) ->
     bufferRow = 0