Fixed double-clicking on border resulting in bad resize

Fix issue where if the user double-clicks on the window border or corner
to resize MacVim (the macOS behavior is to resize the window all the way
to the screen's border), it results in an incomplete resize and also
takes a long time.

The code was spamming the Vim instance with live resize messages,
leading to slowdown and dropped messages. Fix it by rate limiting the
messages to one at a time, which speeds things up, and clean up when
live resize finishes to make sure things look right.

Author: ychin

src/MacVim/MMVimView.h

@@ -27,6 +27,8 @@
     NSMutableArray      *scrollbars;
 }
 
+@property BOOL pendingLiveResize;
+
 - (MMVimView *)initWithFrame:(NSRect)frame vimController:(MMVimController *)c;
 
 - (MMTextView *)textView;

src/MacVim/MMVimView.m

@@ -920,7 +920,19 @@ - (void)frameSizeMayHaveChanged:(BOOL)keepGUISize
                    "%dx%d (%s)", cols, rows, constrained[1], constrained[0],
                    MessageStrings[msgid]);
 
-        [vimController sendMessageNow:msgid data:data timeout:1];
+        if (msgid != LiveResizeMsgID || !self.pendingLiveResize) {
+            // Live resize messages can be sent really rapidly, especailly if
+            // it's from double clicking the window border (to indicate filling
+            // all the way to that side to the window manager). We want to rate
+            // limit sending live resize one at a time, or the IPC will get
+            // swamped which causes slowdowns and some messages will also be dropped.
+            // As a result we basically discard all live resize messages if one
+            // is already going on. liveResizeDidEnd: will perform a final clean
+            // up resizing.
+            self.pendingLiveResize = (msgid == LiveResizeMsgID);
+
+            [vimController sendMessageNow:msgid data:data timeout:1];
+        }
 
         // We only want to set the window title if this resize came from
         // a live-resize, not (for example) setting 'columns' or 'lines'.

src/MacVim/MMWindowController.m

@@ -398,6 +398,7 @@ - (void)setTextDimensionsWithRows:(int)rows columns:(int)cols isLive:(BOOL)live
     // user drags to resize the window.
 
     [vimView setDesiredRows:rows columns:cols];
+    vimView.pendingLiveResize = NO;
 
     if (setupDone && !live && !keepGUISize) {
         shouldResizeVimView = YES;
@@ -712,6 +713,13 @@ - (void)liveResizeDidEnd
         [lastSetTitle release];
         lastSetTitle = nil;
     }
+
+    // If we are in the middle of rapid resize (e.g. double-clicking on the border/corner
+    // of window), we would fire off a lot of LiveResizeMsgID messages where some will be
+    // intentionally omitted to avoid swamping IPC. If that happens this will perform a
+    // final clean up that makes sure the Vim view is sized correctly within the window.
+    // See frameSizeMayHaveChanged: for where the omission/rate limiting happens.
+    [self resizeView];
 }
 
 - (void)setBlurRadius:(int)radius