Fix rendering issues with the 10.14 SDK.

Before this commit, the Core Text renderer relied on a legacy behavior
of NSView to keep its content across draws. setNeedsDisplayInRect: drew
over parts of the existing content as drawing commands were received,
without ever redrawing old content.

Layer backed views don't preserve content between draws and may be asked
to redraw at any time, and layer backing is default on in the 10.14 SDK.

This change adds a way to draw to a CGBitmapContext and then display
that in the view's layer. It's similar to the CGLayer path, but I wasn't
able to get the CGLayer path to work without hanging or crashing when I
scrolled. My best guess from looking at stack traces is that using
CGContextDrawLayerInRect to draw a layer into itself doesn't actually
copy pixels, but adds the self-draw as an action to be performed when
the CGLayer is drawn into a bitmap context. Scrolling stacks these
actions, which either hangs or overflows the stack when drawn.

The new code is controlled by the MMBufferedDrawing user default, which
is on by default on macOS >= 10.14 with this change. Fixes #751.

Author: s4y

src/MacVim/MMAppController.m

@@ -248,6 +248,7 @@ + (void)initialize
         [NSNumber numberWithBool:YES],    MMNativeFullScreenKey,
         [NSNumber numberWithDouble:0.25], MMFullScreenFadeTimeKey,
         [NSNumber numberWithBool:NO],     MMUseCGLayerAlwaysKey,
+        @(shouldUseBufferedDrawing()),    MMBufferedDrawingKey,
         [NSNumber numberWithBool:YES],    MMShareFindPboardKey,
         nil];
 

src/MacVim/MMCoreTextView.h

@@ -46,6 +46,8 @@
     CGContextRef                cgLayerContext;
     NSLock                      *cgLayerLock;
 
+    CGContextRef                cgContext;
+
     // These are used in MMCoreTextView+ToolTip.m
     id trackingRectOwner_;              // (not retained)
     void *trackingRectUserData_;

src/MacVim/MMCoreTextView.m

@@ -168,6 +168,8 @@ - (void)dealloc
     [drawData release];  drawData = nil;
     [fontCache release];  fontCache = nil;
 
+    CGContextRelease(cgContext);  cgContext = nil;
+
     [helper setTextView:nil];
     [helper release];  helper = nil;
 
@@ -215,6 +217,7 @@ - (void)setDefaultColorsBackground:(NSColor *)bgColor
         [defaultForegroundColor release];
         defaultForegroundColor = fgColor ? [fgColor retain] : nil;
     }
+    [self setNeedsDisplay:YES];
 }
 
 - (NSColor *)defaultBackgroundColor
@@ -444,11 +447,18 @@ - (BOOL)_wantsKeyDownForEvent:(id)event
 }
 
 - (void)setFrameSize:(NSSize)newSize {
-    if (!drawPending && !NSEqualSizes(newSize, self.frame.size) && drawData.count == 0) {
+    if (NSEqualSizes(newSize, self.bounds.size))
+        return;
+    if (!drawPending) {
         [NSAnimationContext beginGrouping];
         drawPending = YES;
     }
     [super setFrameSize:newSize];
+    [self updateCGContext];
+}
+
+- (void)viewDidChangeBackingProperties {
+    [self updateCGContext];
 }
 
 - (void)keyDown:(NSEvent *)event
@@ -606,6 +616,26 @@ - (BOOL)isFlipped
     return NO;
 }
 
+- (void)updateCGContext {
+    if (cgContext || [[NSUserDefaults standardUserDefaults]
+                      boolForKey:MMBufferedDrawingKey]) {
+        CGContextRelease(cgContext);
+        NSRect backingRect = [self convertRectToBacking:self.bounds];
+        cgContext = CGBitmapContextCreate(NULL, NSWidth(backingRect), NSHeight(backingRect), 8, 0, self.window.colorSpace.CGColorSpace, kCGImageAlphaPremultipliedFirst | kCGBitmapByteOrder32Host);
+        CGContextScaleCTM(cgContext, self.window.backingScaleFactor, self.window.backingScaleFactor);
+    }
+}
+
+- (BOOL)wantsUpdateLayer {
+    return cgContext != nil;
+}
+
+- (void)updateLayer {
+    CGImageRef contentsImage = CGBitmapContextCreateImage(cgContext);
+    self.layer.contents = (id)contentsImage;
+    CGImageRelease(contentsImage);
+}
+
 - (void)drawRect:(NSRect)rect
 {
     NSGraphicsContext *context = [NSGraphicsContext currentContext];
@@ -653,7 +683,12 @@ - (void)drawRect:(NSRect)rect
 
 - (void)performBatchDrawWithData:(NSData *)data
 {
-    if (cgLayerEnabled && drawData.count == 0 && [self getCGContext]) {
+    if (cgContext) {
+        [NSGraphicsContext saveGraphicsState];
+        NSGraphicsContext.currentContext = [NSGraphicsContext graphicsContextWithCGContext:cgContext flipped:self.flipped];
+        [self batchDrawData:data];
+        [NSGraphicsContext restoreGraphicsState];
+    } else if (cgLayerEnabled && drawData.count == 0 && [self getCGContext]) {
         [cgLayerLock lock];
         [self batchDrawData:data];
         [cgLayerLock unlock];
@@ -669,6 +704,9 @@ - (void)performBatchDrawWithData:(NSData *)data
 
 - (void)setCGLayerEnabled:(BOOL)enabled
 {
+    if (cgContext)
+        return;
+
     cgLayerEnabled = enabled;
 
     if (!cgLayerEnabled)
@@ -710,13 +748,13 @@ - (CGContextRef)getCGContext
 
 - (void)setNeedsDisplayCGLayerInRect:(CGRect)rect
 {
-    if (cgLayerEnabled)
+    if (cgLayerEnabled || cgContext)
        [self setNeedsDisplayInRect:rect];
 }
 
 - (void)setNeedsDisplayCGLayer:(BOOL)flag
 {
-    if (cgLayerEnabled)
+    if (cgLayerEnabled || cgContext)
        [self setNeedsDisplay:flag];
 }
 
@@ -1491,7 +1529,18 @@ - (void)drawString:(const UniChar *)chars length:(UniCharCount)length
 
 - (void)scrollRect:(NSRect)rect lineCount:(int)count
 {
-    if (cgLayerEnabled) {
+    if (cgContext) {
+        NSRect fromRect = NSOffsetRect(self.bounds, 0, -count * cellSize.height);
+        NSRect toRect = NSOffsetRect(rect, 0, -count * cellSize.height);
+        CGContextSaveGState(cgContext);
+        CGContextClipToRect(cgContext, toRect);
+        CGContextSetBlendMode(cgContext, kCGBlendModeCopy);
+        CGImageRef contentsImage = CGBitmapContextCreateImage(cgContext);
+        CGContextDrawImage(cgContext, fromRect, contentsImage);
+        CGImageRelease(contentsImage);
+        CGContextRestoreGState(cgContext);
+        [self setNeedsDisplayCGLayerInRect:toRect];
+    } else if (cgLayerEnabled) {
         CGContextRef context = [self getCGContext];
         int yOffset = count * cellSize.height;
         NSRect clipRect = rect;

src/MacVim/MMVimView.m

@@ -189,7 +189,7 @@ - (void)dealloc
 
 - (BOOL)isOpaque
 {
-    return YES;
+    return textView.defaultBackgroundColor.alphaComponent == 1;
 }
 
 - (void)drawRect:(NSRect)rect
@@ -511,6 +511,7 @@ - (void)setDefaultColorsBackground:(NSColor *)back foreground:(NSColor *)fore
         MMScroller *sb = [scrollbars objectAtIndex:i];
         [sb setNeedsDisplay:YES];
     }
+    [self setNeedsDisplay:YES];
 }
 
 

src/MacVim/MMWindowController.m

@@ -543,6 +543,7 @@ - (void)setDefaultColorsBackground:(NSColor *)back foreground:(NSColor *)fore
     [decoratedWindow setOpaque:isOpaque];
     if (fullScreenWindow)
         [fullScreenWindow setOpaque:isOpaque];
+    [decoratedWindow setBackgroundColor:back];
 
     [vimView setDefaultColorsBackground:back foreground:fore];
 }

src/MacVim/Miscellaneous.h

@@ -53,6 +53,7 @@ extern NSString *MMNativeFullScreenKey;
 extern NSString *MMUseMouseTimeKey;
 extern NSString *MMFullScreenFadeTimeKey;
 extern NSString *MMUseCGLayerAlwaysKey;
+extern NSString *MMBufferedDrawingKey;
 
 
 // Enum for MMUntitledWindowKey
@@ -156,3 +157,4 @@ NSArray *normalizeFilenames(NSArray *filenames);
 
 BOOL shouldUseYosemiteTabBarStyle();
 BOOL shouldUseMojaveTabBarStyle();
+BOOL shouldUseBufferedDrawing();

src/MacVim/Miscellaneous.m

@@ -49,6 +49,7 @@
 NSString *MMUseMouseTimeKey             = @"MMUseMouseTime";
 NSString *MMFullScreenFadeTimeKey       = @"MMFullScreenFadeTime";
 NSString *MMUseCGLayerAlwaysKey         = @"MMUseCGLayerAlways";
+NSString *MMBufferedDrawingKey          = @"MMBufferedDrawing";
 
 
 
@@ -316,3 +317,14 @@ - (NSInteger)tag
 #endif
     return false;
 }
+
+BOOL
+shouldUseBufferedDrawing()
+{
+#if MAC_OS_X_VERSION_MAX_ALLOWED >= MAC_OS_X_VERSION_10_14
+    if (@available(macos 10.14, *)) {
+        return YES;
+    }
+#endif
+    return NO;
+}