Stateful, fast renderer for MMCoreTextView

This change replaces the current rendering paths in `MMCoreTextView`
with one which draws from an array of structs that represent the state
of each character cell. It applies draw commands to the array and marks
any touched cells as needing display instead of drawing to a view or
image buffer.

In my own tests, this renderer seems to be roughly twice as fast of the
current one. Because it seems to work for the use cases of all of the
current renderers and reused a lot of code, this PR replaces the other
paths instead of adding a preference.

Fixes macvim-dev#796.

Author: s4y

src/MacVim/MMAppController.m

@@ -247,8 +247,6 @@ + (void)initialize
         [NSNumber numberWithBool:NO],     MMSuppressTerminationAlertKey,
         [NSNumber numberWithBool:YES],    MMNativeFullScreenKey,
         [NSNumber numberWithDouble:0.25], MMFullScreenFadeTimeKey,
-        [NSNumber numberWithBool:NO],     MMUseCGLayerAlwaysKey,
-        @(shouldUseBufferedDrawing()),    MMBufferedDrawingKey,
         [NSNumber numberWithBool:YES],    MMShareFindPboardKey,
         nil];
 

src/MacVim/MMCoreTextView.h

@@ -31,41 +31,11 @@
     BOOL                        antialias;
     BOOL                        ligatures;
     BOOL                        thinStrokes;
-    BOOL                        drawPending;
-    NSMutableArray              *drawData;
 
     MMTextViewHelper            *helper;
 
-    unsigned                    maxlen;
-    CGGlyph                     *glyphs;
-    CGPoint                     *positions;
     NSMutableArray              *fontCache;
-
-    // Issue draws onto an CGImage that caches the drawn results instead of
-    // directly in drawRect:. This is the default behavior in cases where simply
-    // drawing incrementally in drawRect: doesn't work. Those cases are:
-    // 1. Non-native fullscreen
-    // 2. 10.14+ (views are always layer-backed which means the view buffer will
-    //    be cleared and we can't incrementally draw in drawRect:)
-    //    
-    // This can be configured by setting MMBufferedDrawingKey in user defaults.
-    BOOL                        cgBufferDrawEnabled;
-    BOOL                        cgBufferDrawNeedsUpdateContext;
-    CGContextRef                cgContext;
-    
-    // *Deprecated*
-    // Draw onto a CGLayer instead of lazily updating the view's buffer in
-    // drawRect: which is error-prone and relying on undocumented behaviors
-    // (that the OS will preserve the old buffer).
-    //
-    // This is deprecated. Use cgBufferDrawEnabled instead which is more
-    // efficient.
-    //    
-    // This can be configured by setting MMUseCGLayerAlwaysKey in user defaults.
-    BOOL                        cgLayerEnabled;
-    CGLayerRef                  cgLayer;
-    CGContextRef                cgLayerContext;
-    NSLock                      *cgLayerLock;
+    NSMutableDictionary<NSNumber*,NSFont*> *fontVariantCache;
 
     // These are used in MMCoreTextView+ToolTip.m
     id trackingRectOwner_;              // (not retained)
@@ -113,13 +83,10 @@
 - (BOOL)convertPoint:(NSPoint)point toRow:(int *)row column:(int *)column;
 - (NSRect)rectForRow:(int)row column:(int)column numRows:(int)nr
           numColumns:(int)nc;
-- (void)setCGLayerEnabled:(BOOL)enabled;
-- (BOOL)getCGLayerEnabled;
 
 //
 // NSTextView methods
 //
-- (void)setFrameSize:(NSSize)newSize;
 - (void)keyDown:(NSEvent *)event;
 - (void)insertText:(id)string;
 - (void)doCommandBySelector:(SEL)selector;