Improve scrolling by performing styling in methods called before drawing instead of inside drawing

which then caused the drawing to be abandoned, and black blocks to appear on-screen.
Discard responsive scrolling overdraw when that overdrawn content is invalid.
Style just the visible area instead of the whole document when styling changes run beyond
painting area.

3 files changed, 85 insertions, 0 deletions

diff --git a/cocoa/ScintillaCocoa.h b/cocoa/ScintillaCocoa.h
index 9098d2000..415094c35 100644
--- a/cocoa/ScintillaCocoa.h
+++ b/cocoa/ScintillaCocoa.h
@@ -113,8 +113,10 @@ private:
 protected:
   Point GetVisibleOriginInMain();
   PRectangle GetClientRectangle();
+  virtual PRectangle GetClientDrawingRectangle();
   Point ConvertPoint(NSPoint point);
   virtual void RedrawRect(PRectangle rc);
+  virtual void DiscardOverdraw();
   virtual void Redraw();
 
   virtual void Initialise();
@@ -144,6 +146,7 @@ public:
   bool SetIdle(bool on);
   void SetMouseCapture(bool on);
   bool HaveMouseCapture();
+  void WillDraw(NSRect rect);
   void ScrollText(int linesToMove);
   void SetVerticalScrollPos();
   void SetHorizontalScrollPos();
diff --git a/cocoa/ScintillaCocoa.mm b/cocoa/ScintillaCocoa.mm
index f9e67f7b4..c5f24fcd6 100644
--- a/cocoa/ScintillaCocoa.mm
+++ b/cocoa/ScintillaCocoa.mm
@@ -714,6 +714,22 @@ PRectangle ScintillaCocoa::GetClientRectangle()
 //--------------------------------------------------------------------------------------------------
 
 /**
+ * Allow for prepared rectangle
+ */
+PRectangle ScintillaCocoa::GetClientDrawingRectangle() {
+  SCIContentView *content = ContentView();
+  if ([content respondsToSelector: @selector(setPreparedContentRect:)]) {
+    NSRect rcPrepared = [content preparedContentRect];
+    if (!NSIsEmptyRect(rcPrepared))
+      return PRectangle(rcPrepared.origin.x, rcPrepared.origin.y,
+                        rcPrepared.origin.x+rcPrepared.size.width, rcPrepared.origin.y + rcPrepared.size.height);
+  }
+  return ScintillaCocoa::GetClientRectangle();
+}
+
+//--------------------------------------------------------------------------------------------------
+
+/**
  * Converts the given point from base coordinates to local coordinates and at the same time into
  * a native Point structure. Base coordinates are used for the top window used in the view hierarchy.
  * Returned value is in view coordinates.
@@ -739,12 +755,24 @@ void ScintillaCocoa::RedrawRect(PRectangle rc)
 
 //--------------------------------------------------------------------------------------------------
 
+void ScintillaCocoa::DiscardOverdraw()
+{
+  // If running on 10.9, reset prepared area to visible area
+  SCIContentView *content = ContentView();
+  if ([content respondsToSelector: @selector(setPreparedContentRect:)]) {
+    content.preparedContentRect = [content visibleRect];
+  }
+}
+
+//--------------------------------------------------------------------------------------------------
+
 /**
  * Ensure all of prepared content is also redrawn.
  */
 void ScintillaCocoa::Redraw()
 {
   wMargin.InvalidateAll();
+  DiscardOverdraw();
   wMain.InvalidateAll();
 }
 
@@ -1563,6 +1591,29 @@ void ScintillaCocoa::PaintMargin(NSRect aRect)
 //--------------------------------------------------------------------------------------------------
 
 /**
+ * Prepare for drawing.
+ *
+ * @param rect The area that will be drawn, given in the sender's coordinate system.
+ */
+void ScintillaCocoa::WillDraw(NSRect rect)
+{
+  RefreshStyleData();
+  PRectangle rcWillDraw = NSRectToPRectangle(rect);
+  int positionAfterRect = PositionAfterArea(rcWillDraw);
+  pdoc->EnsureStyledTo(positionAfterRect);
+  NotifyUpdateUI();
+  if (WrapLines(wsVisible)) {
+    // Wrap may have reduced number of lines so more lines may need to be styled
+    positionAfterRect = PositionAfterArea(rcWillDraw);
+    pdoc->EnsureStyledTo(positionAfterRect);
+    // The wrapping process has changed the height of some lines so redraw all.
+    Redraw();
+  }
+}
+
+//--------------------------------------------------------------------------------------------------
+
+/**
  * ScrollText is empty because scrolling is handled by the NSScrollView.
  */
 void ScintillaCocoa::ScrollText(int linesToMove)
diff --git a/cocoa/ScintillaView.mm b/cocoa/ScintillaView.mm
index 7769d87ef..222fcdc8f 100644
--- a/cocoa/ScintillaView.mm
+++ b/cocoa/ScintillaView.mm
@@ -228,6 +228,37 @@ static NSCursor *cursorFromEnum(Window::Cursor cursor)
 //--------------------------------------------------------------------------------------------------
 
 /**
+ * Called before repainting.
+ */
+- (void) viewWillDraw
+{
+  const NSRect *rects;
+  NSInteger nRects = 0;
+  [self getRectsBeingDrawn:&rects count:&nRects];
+  if (nRects > 0) {
+    NSRect rectUnion = rects[0];
+    for (int i=0;i<nRects;i++) {
+      rectUnion = NSUnionRect(rectUnion, rects[i]);
+    }
+    mOwner.backend->WillDraw(rectUnion);
+  }
+  [super viewWillDraw];
+}
+
+//--------------------------------------------------------------------------------------------------
+
+/**
+ * Called before responsive scrolling overdraw.
+ */
+- (void) prepareContentInRect: (NSRect) rect
+{
+  mOwner.backend->WillDraw(rect);
+  [super prepareContentInRect: rect];
+}
+
+//--------------------------------------------------------------------------------------------------
+
+/**
  * Gets called by the runtime when the view needs repainting.
  */
 - (void) drawRect: (NSRect) rect