Add first methods in the new Minimap model

lib/minimap.coffee

@@ -1,3 +1,25 @@
+{CompositeDisposable} = require 'event-kit'
 
 module.exports =
 class Minimap
+  constructor: ({@textEditor}) ->
+    @subscriptions = new CompositeDisposable
+    @subscribeToConfig()
+
+  getTextEditor: -> @textEditor
+
+  getTextEditorHeight: -> @textEditor.getHeight() * @getScaleFactor()
+
+  getTextEditorScroll: -> @textEditor.getScrollTop() * @getScaleFactor()
+
+  getHeight: -> @textEditor.getLineCount() * @getLineHeight()
+
+  getScaleFactor: -> @getLineHeight() / @textEditor.getLineHeightInPixels()
+
+  getLineHeight: -> @charHeight + @interline
+
+  subscribeToConfig: ->
+    @subscriptions.add atom.config.observe 'minimap.charHeight', (@charHeight) =>
+    @subscriptions.add atom.config.observe 'minimap.charWidth', (@charWidth) =>
+
+    @subscriptions.add atom.config.observe 'minimap.interline', (@interline) =>

spec/minimap-spec.coffee

@@ -5,3 +5,38 @@ Minimap = require '../lib/minimap'
 describe 'Minimap', ->
   [editor, minimap, largeSample, smallSample] = []
 
+  beforeEach ->
+    atom.config.set 'minimap.charHeight', 4
+    atom.config.set 'minimap.charWidth', 2
+    atom.config.set 'minimap.interline', 1
+
+    editor = new TextEditor({})
+    editor.setLineHeightInPixels(10)
+    editor.setHeight(50)
+
+    minimap = new Minimap({textEditor: editor})
+    largeSample = fs.readFileSync(atom.project.resolve('large-file.coffee')).toString()
+    smallSample = fs.readFileSync(atom.project.resolve('sample.coffee')).toString()
+
+  it 'has an associated editor', ->
+    expect(minimap.getTextEditor()).toEqual(editor)
+
+  it 'measures the minimap size based on the current editor content', ->
+    editor.setText(smallSample)
+    expect(minimap.getHeight()).toEqual(20)
+
+    editor.setText(largeSample)
+    expect(minimap.getHeight()).toEqual(editor.getLineCount() * 5)
+
+  it 'measures the scaling factor between the editor and the minimap', ->
+    expect(minimap.getScaleFactor()).toEqual(0.5)
+
+  it 'measures the editor visible area size at minimap scale', ->
+    editor.setText(largeSample)
+    expect(minimap.getTextEditorHeight()).toEqual(25)
+
+  it 'scales the editor scroll based on the minimap scale factor', ->
+    editor.setText(largeSample)
+    editor.setScrollTop(1000)
+
+    expect(minimap.getTextEditorScroll()).toEqual(500)