bug#32932: 27.0.50; render bugs on macOS Mojave

[Alan Third <alan@idiocy.org>]

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On Sun, Feb 02, 2020 at 08:49:44AM -0800, Aaron Jensen wrote:
> On Sun, Feb 2, 2020 at 5:42 AM Alan Third <alan@idiocy.org> wrote:
> >
> > Out of interest, is the mac port fast under the same conditions? Here
> > their performance seems to be almost identical with the mac port only
> > fractionally faster, and their performance scales similarly with frame
> > size.
> 
> For scrolling/full repaints the mac port is significantly faster,
> similar to repaint speed of cursor moves. With the patch, Emacs 28's
> full repaint when taking about 3/5s of my screen takes about 400ms
> whereas it's about 16.7ms (60fps) with mac port. Emacs 27 seems to
> paint even faster than that.

Amazingly the attached patch is faster than the mac port on my machine
(13" retina macbook pro) in the scroll test.

I can’t see that holding for your screen, though.

> On Sun, Feb 2, 2020 at 5:46 AM Alan Third <alan@idiocy.org> wrote:
> >
> > > Cures the speed problems for me, but the text became fuzzy (MacBook Pro Retina).
> > > Two Emacs instances, without and with the patch:
> >
> > Thanks for testing it. I think the fuzzyness is just the pre‐mojave
> > anti‐aliasing coming back. I don’t know why.
> 
> Ah, good eye. Mine is blurry too. Could it be creating a layer that is
> the size of hidpi scaled window but not the actual pixel size of the
> window? That would explain the blur if it was then drawn to a larger
> pixel-wise window.

So turns out you need to do some fancy‐pants manoeuvres to scale
CGLayers correctly. They also appear to draw faster when correctly
scaled, presumably because it’s not having to scale everything while
drawing to the screen.

> > I think that second URL is wrong, but I’ve read that quote before.
> > Normal double buffering is simply drawing like we do on Emacs 27.
> > There are plenty of places in the documentation that push you towards
> > just drawing when you want to recreate part of the screen, however as
> > we know Emacs redisplay isn’t really amenable to that approach.
> 
> Do you know the cause of the glitching? Or is that still unclear? I
> wonder if we could take some time to walk through it together, maybe
> something will stand out?

I know exactly what’s causing the glitching, but I’ll come back to
this tomorrow.
-- 
Alan Third

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From 90e329cb6956bd40e927d74576ca8b5f48e5a72e Mon Sep 17 00:00:00 2001
From: Alan Third <alan@idiocy.org>
Date: Sat, 1 Feb 2020 21:17:29 +0000
Subject: [PATCH v2] Use CGLayer instead of NSBitmapImageRep (bug#32932)

---
 src/nsterm.h |  4 +--
 src/nsterm.m | 89 +++++++++++++++++++++++++++-------------------------
 2 files changed, 48 insertions(+), 45 deletions(-)

diff --git a/src/nsterm.h b/src/nsterm.h
index 980ca534cf..eefa4d706d 100644
--- a/src/nsterm.h
+++ b/src/nsterm.h
@@ -418,7 +418,7 @@ #define NSTRACE_UNSILENCE()
    NSWindow *nonfs_window;
    BOOL fs_is_native;
 #ifdef NS_IMPL_COCOA
-   NSBitmapImageRep *drawingBuffer;
+   CGLayerRef drawingBuffer;
 #endif
 @public
    struct frame *emacsframe;
@@ -464,7 +464,7 @@ #define NSTRACE_UNSILENCE()
 - (void)focusOnDrawingBuffer;
 #endif
 - (void)copyRect:(NSRect)srcRect to:(NSRect)dstRect;
-- (void)createDrawingBufferWithRect:(NSRect)rect;
+- (void)createDrawingBuffer;
 
 /* Non-notification versions of NSView methods. Used for direct calls.  */
 - (void)windowWillEnterFullScreen;
diff --git a/src/nsterm.m b/src/nsterm.m
index 9d427b9b38..3576b851a5 100644
--- a/src/nsterm.m
+++ b/src/nsterm.m
@@ -1141,7 +1141,6 @@ static NSRect constrain_frame_rect(NSRect frameRect, bool isFullscreen)
 
 #ifdef NS_IMPL_COCOA
   [NSGraphicsContext setCurrentContext:nil];
-  [view display];
 #else
   block_input ();
 
@@ -2853,7 +2852,9 @@ so some key presses (TAB) are swallowed by the system.  */
   ns_unfocus (f);
 
   /* as of 2006/11 or so this is now needed */
-  ns_redraw_scroll_bars (f);
+  /* FIXME: I don't see any reason for this and removing it makes no
+     difference here.  Do we need it for GNUstep?  */
+  //ns_redraw_scroll_bars (f);
   unblock_input ();
 }
 
@@ -3169,18 +3170,6 @@ so some key presses (TAB) are swallowed by the system.  */
 
       NSTRACE_RECT ("fromRect", fromRect);
 
-      /* Because we're drawing into an offscreen buffer which isn't
-         flipped, the images come out upside down.  To work around it
-         we need to do some fancy transforms.  */
-      {
-        NSAffineTransform *transform = [NSAffineTransform transform];
-        [transform translateXBy:0 yBy:NSMaxY(imageRect)];
-        [transform scaleXBy:1 yBy:-1];
-        [transform concat];
-
-        imageRect.origin.y = 0;
-      }
-
       [img drawInRect: imageRect
              fromRect: fromRect
             operation: NSCompositingOperationSourceOver
@@ -3938,11 +3927,6 @@ Function modeled after x_draw_glyph_string_box ().
 
       NSAffineTransform *doTransform = [NSAffineTransform transform];
 
-      /* We have to flip the image around the X axis as the offscreen
-         bitmap we're drawing to is flipped.  */
-      [doTransform scaleXBy:1 yBy:-1];
-      [doTransform translateXBy:0 yBy:-[img size].height];
-
       /* ImageMagick images don't have transforms.  */
       if (img->transform)
         [doTransform appendTransform:img->transform];
@@ -4838,7 +4822,7 @@ in certain situations (rapid incoming events).
   if (NILP (window->vertical_scroll_bar))
     {
       if (width > 0 && height > 0)
-	ns_clear_frame_area (f, left, top, width, height);
+        ns_clear_frame_area (f, left, top, width, height);
 
       bar = [[EmacsScroller alloc] initFrame: r window: win];
       wset_vertical_scroll_bar (window, make_mint_ptr (bar));
@@ -7104,7 +7088,7 @@ - (void) updateFrameSize: (BOOL) delay
          from non-native fullscreen, in other circumstances it appears
          to be a noop.  (bug#28872) */
       wr = NSMakeRect (0, 0, neww, newh);
-      [self createDrawingBufferWithRect:wr];
+      [self createDrawingBuffer];
       [view setFrame: wr];
 
       // To do: consider using [NSNotificationCenter postNotificationName:].
@@ -7444,7 +7428,7 @@ - (instancetype) initFrameFromEmacs: (struct frame *)f
   maximizing_resize = NO;
 #endif
 
-  [self createDrawingBufferWithRect:r];
+  [self createDrawingBuffer];
 
   win = [[EmacsWindow alloc]
             initWithContentRect: r
@@ -8229,7 +8213,7 @@ - (instancetype)toggleToolbar: (id)sender
 }
 
 
-- (void)createDrawingBufferWithRect:(NSRect)rect
+- (void)createDrawingBuffer
   /* Create and store a new NSBitmapImageRep for Emacs to draw
      into.
 
@@ -8239,10 +8223,24 @@ - (void)createDrawingBufferWithRect:(NSRect)rect
      retain the old method of drawing direct to the EmacsView.  */
 {
 #ifdef NS_IMPL_COCOA
+  NSGraphicsContext *screen;
+  CGFloat scale = [[self window] backingScaleFactor];
+  NSRect frame = [self frame];
+  NSSize size = frame.size;
+
   if (drawingBuffer != nil)
-    [drawingBuffer release];
+    CGLayerRelease (drawingBuffer);
+
+  size.width *= scale;
+  size.height *= scale;
+
+  screen = [NSGraphicsContext graphicsContextWithBitmapImageRep:
+                    [self bitmapImageRepForCachingDisplayInRect:frame]];
+
+  drawingBuffer = CGLayerCreateWithContext ([screen CGContext], size, nil);
+  CGContextRef cgctx = CGLayerGetContext (drawingBuffer);
+  CGContextScaleCTM(cgctx, scale, scale);
 
-  drawingBuffer = [[self bitmapImageRepForCachingDisplayInRect:rect] retain];
 #endif
 }
 
@@ -8250,11 +8248,15 @@ - (void)createDrawingBufferWithRect:(NSRect)rect
 #ifdef NS_IMPL_COCOA
 - (void)focusOnDrawingBuffer
 {
-  /* Creating the graphics context each time is very slow, but it
-     doesn't seem possible to cache and reuse it.  */
-  [NSGraphicsContext
-    setCurrentContext:
-      [NSGraphicsContext graphicsContextWithBitmapImageRep:drawingBuffer]];
+  NSGraphicsContext *buf;
+  CGContextRef cgctx = CGLayerGetContext (drawingBuffer);
+  CGFloat scale = [[self window] backingScaleFactor];
+
+  buf =
+    [NSGraphicsContext
+        graphicsContextWithCGContext:cgctx flipped:YES];
+
+  [NSGraphicsContext setCurrentContext:buf];
 }
 
 
@@ -8269,7 +8271,7 @@ - (void)windowDidChangeBackingProperties:(NSNotification *)notification
    if (old != new)
      {
        NSRect frame = [self frame];
-       [self createDrawingBufferWithRect:frame];
+       [self createDrawingBuffer];
        ns_clear_frame (emacsframe);
        expose_frame (emacsframe, 0, 0, NSWidth (frame), NSHeight (frame));
      }
@@ -8284,13 +8286,18 @@ - (void)copyRect:(NSRect)srcRect to:(NSRect)dstRect
   NSTRACE_RECT ("Destination", dstRect);
 
 #ifdef NS_IMPL_COCOA
-  [drawingBuffer drawInRect:dstRect
-                   fromRect:srcRect
-                  operation:NSCompositingOperationCopy
-                   fraction:1.0
-             respectFlipped:NO
-                      hints:nil];
+  CGRect offsetRect = CGRectMake (NSMinX (dstRect) - NSMinX (srcRect),
+                                  NSMinY (dstRect) - NSMinY (srcRect),
+                                  NSWidth ([self frame]),
+                                  NSHeight ([self frame]));
+  [[NSGraphicsContext currentContext] saveGraphicsState];
+
+  NSRectClip (dstRect);
 
+  CGContextDrawLayerInRect ([[NSGraphicsContext currentContext] CGContext],
+                             offsetRect, drawingBuffer);
+
+  [[NSGraphicsContext currentContext] restoreGraphicsState];
   [self setNeedsDisplayInRect:dstRect];
 #else
   hide_bell();              // Ensure the bell image isn't scrolled.
@@ -8313,12 +8320,8 @@ - (void)drawRect: (NSRect)rect
     return;
 
 #ifdef NS_IMPL_COCOA
-  [drawingBuffer drawInRect:rect
-                   fromRect:rect
-                  operation:NSCompositingOperationSourceOver
-                   fraction:1
-             respectFlipped:NO
-                      hints:nil];
+  CGContextRef ctx = [[NSGraphicsContext currentContext] CGContext];
+  CGContextDrawLayerInRect (ctx, [self frame], drawingBuffer);
 #else
   int x = NSMinX (rect), y = NSMinY (rect);
   int width = NSWidth (rect), height = NSHeight (rect);
-- 
2.24.0