From f0920bf63b7816ef4fb66cd3c5dc0d7f76f29faf Mon Sep 17 00:00:00 2001
From: Nathan Sobo <nathan@github.com>
Date: Mon, 19 Jan 2015 10:48:44 -0700
Subject: [PATCH] Start on TextEditorPresenter with lines state

---
 spec/text-editor-presenter-spec.coffee | 80 ++++++++++++++++++++++++++
 src/text-editor-presenter.coffee       | 20 +++++++
 2 files changed, 100 insertions(+)
 create mode 100644 spec/text-editor-presenter-spec.coffee
 create mode 100644 src/text-editor-presenter.coffee

diff --git a/spec/text-editor-presenter-spec.coffee b/spec/text-editor-presenter-spec.coffee
new file mode 100644
index 000000000..021548033
--- /dev/null
+++ b/spec/text-editor-presenter-spec.coffee
@@ -0,0 +1,80 @@
+TextBuffer = require 'text-buffer'
+TextEditor = require '../src/text-editor'
+TextEditorPresenter = require '../src/text-editor-presenter'
+
+describe "TextEditorPresenter", ->
+  [buffer, editor] = []
+
+  beforeEach ->
+    buffer = new TextBuffer(filePath: require.resolve('./fixtures/sample.js'))
+    editor = new TextEditor({buffer})
+    waitsForPromise -> buffer.load()
+
+  afterEach ->
+    editor.destroy()
+    buffer.destroy()
+
+  expectValues = (actual, expected) ->
+    for key, value of expected
+      expect(actual[key]).toBe value
+
+  describe "lines", ->
+    describe "on initialization", ->
+      it "contains the lines that are visible on screen, plus the overdraw margin", ->
+        presenter = new TextEditorPresenter(model: editor, clientHeight: 25, scrollTop: 0, lineHeight: 10, lineOverdrawMargin: 1)
+
+        line0 = editor.tokenizedLineForScreenRow(0)
+        expectValues presenter.state.lines[line0.id], {
+          screenRow: 0
+          tokens: line0.tokens
+          top: 10 * 0
+        }
+
+        line1 = editor.tokenizedLineForScreenRow(1)
+        expectValues presenter.state.lines[line1.id], {
+          screenRow: 1
+          tokens: line1.tokens
+          top: 10 * 1
+        }
+
+        line2 = editor.tokenizedLineForScreenRow(2)
+        expectValues presenter.state.lines[line2.id], {
+          screenRow: 2
+          tokens: line2.tokens
+          top: 10 * 2
+        }
+
+        # this row is rendered due to the overdraw margin
+        line3 = editor.tokenizedLineForScreenRow(3)
+        expectValues presenter.state.lines[line3.id], {
+          screenRow: 3
+          tokens: line3.tokens
+          top: 10 * 3
+        }
+
+      it "contains the lines that are visible on screen, minus the overdraw margin", ->
+        presenter = new TextEditorPresenter(model: editor, clientHeight: 25, scrollTop: 115, lineHeight: 10, lineOverdrawMargin: 1)
+
+        # this row is rendered due to the overdraw margin
+        line10 = editor.tokenizedLineForScreenRow(10)
+        expectValues presenter.state.lines[line10.id], {
+          screenRow: 10
+          tokens: line10.tokens
+          top: 10 * 10
+        }
+
+        line11 = editor.tokenizedLineForScreenRow(11)
+        expectValues presenter.state.lines[line11.id], {
+          screenRow: 11
+          tokens: line11.tokens
+          top: 10 * 11
+        }
+
+        line12 = editor.tokenizedLineForScreenRow(12)
+        expectValues presenter.state.lines[line12.id], {
+          screenRow: 12
+          tokens: line12.tokens
+          top: 10 * 12
+        }
+
+        # rows beyond the end of the content are not rendered
diff --git a/src/text-editor-presenter.coffee b/src/text-editor-presenter.coffee
new file mode 100644
index 000000000..3dcb6c657
--- /dev/null
+++ b/src/text-editor-presenter.coffee
@@ -0,0 +1,20 @@
+module.exports =
+class TextEditorPresenter
+  constructor: ({@model, @clientHeight, @scrollTop, @lineHeight, @lineOverdrawMargin}) ->
+    @state = {}
+    @buildLinesState()
+
+  buildLinesState: ->
+    @state.lines = {}
+    startRow = Math.floor(@scrollTop / @lineHeight) - @lineOverdrawMargin
+    startRow = Math.max(0, startRow)
+    endRow = startRow + Math.ceil(@clientHeight / @lineHeight) + @lineOverdrawMargin
+    endRow = Math.min(@model.getScreenLineCount(), endRow)
+
+    for line, i in @model.tokenizedLinesForScreenRows(startRow, endRow)
+      row = startRow + i
+      @state.lines[line.id] = {
+        screenRow: row
+        tokens: line.tokens
+        top: row * @lineHeight
+      }