Fix non-native full screen bad interaction with window delegate

This issue was detected when adding new tests for non-native full
screen. When setting 'fuoptions' to empty and going full screen, the
code would fail but also crash, due to a number of issues:

1. `enterFullScreen`'s setting of presentationOptions somehow triggers a
   window resize on the normal window, which leads to `windowDidResize`
   delegate being called. This is a degenerate situation as the window
   controller thinks we are already in full screen even though we
   haven't finished setting up yet, and in particular `nonFuVimViewSize`
   is still 0. This leads to the desired desired frame size being set
   incorrectly to 0.
2. `constrainRows:columns:toSize` does not sanity check the results when
   we have such degenerate small sizes, and end up calculating a desired
   rows to -1, which makes no sense. This leads to various wrong
   calculations.
3. MMCoreTextView loops through the grid using a size_t even though
   grid.rows is an int. This is a poor code practice in general and
   results in a crash as the loop comparison cast the -1 to size_t and
   the loop didn't correctly terminate.

Fix 1 (the root cause) by making sure we detact the window delegate
immediately when entering full screen to prevent any stray window
messages from causing issues. Also safeguard `windowDidResize` so it
only handles the full screen path if we have `fullScreenEnabled` set.

For 2 and 3, add the sanity checks and also fix the size_t to use int
when looping.

For some reason this issue only showed up in CI but not in local
testing, probably due to different screen environments.

Author: ychin

src/MacVim/MMCoreTextView.m

@@ -831,7 +831,7 @@ - (void)drawRect:(NSRect)rect
 
     // Function to draw all rows
     void (^drawAllRows)(void (^)(CGContextRef,CGRect,int)) = ^(void (^drawFunc)(CGContextRef,CGRect,int)){
-        for (size_t r = 0; r < grid.rows; r++) {
+        for (int r = 0; r < grid.rows; r++) {
             const CGRect rowRect = [self rectForRow:(int)r
                                              column:0
                                             numRows:1
@@ -1276,6 +1276,9 @@ - (NSSize)constrainRows:(int *)rows columns:(int *)cols toSize:(NSSize)size
         if (fh < 1.0f) fh = 1.0f;
 
         desiredRows = floor((size.height - ih)/fh);
+        // Sanity checking in case unusual window sizes lead to degenerate results
+        if (desiredRows < 1)
+            desiredRows = 1;
         desiredSize.height = fh*desiredRows + ih;
     }
 
@@ -1285,6 +1288,9 @@ - (NSSize)constrainRows:(int *)rows columns:(int *)cols toSize:(NSSize)size
         if (fw < 1.0f) fw = 1.0f;
 
         desiredCols = floor((size.width - iw)/fw);
+        // Sanity checking in case unusual window sizes lead to degenerate results
+        if (desiredCols < 1)
+            desiredCols = 1;
         desiredSize.width = fw*desiredCols + iw;
     }
 

src/MacVim/MMFullScreenWindow.m

@@ -136,6 +136,15 @@ - (void)enterFullScreen
 {
     ASLogDebug(@"Enter full-screen now");
 
+    // Detach the window delegate right now to prevent any stray window
+    // messages (e.g. it may get resized when setting presentationOptions
+    // below) being sent to the window controller while we are in the middle of
+    // setting up the full screen window.
+    NSWindowController *winController = [target windowController];
+    id delegate = [target delegate];
+    [winController setWindow:nil];
+    [target setDelegate:nil];
+
     // Hide Dock and menu bar when going to full screen. Only do so if the current screen
     // has a menu bar and dock.
     if ([self screenHasDockAndMenu]) {
@@ -162,13 +171,6 @@ - (void)enterFullScreen
     // this call so set the frame again just in case.
     [self setFrame:[[target screen] frame] display:NO];
 
-    // fool delegate
-    id delegate = [target delegate];
-    [target setDelegate:nil];
-    
-    // make target's window controller believe that it's now controlling us
-    [[target windowController] setWindow:self];
-
     oldTabBarStyle = [[view tabBarControl] styleName];
 
     NSString *style =
@@ -181,7 +183,7 @@ - (void)enterFullScreen
     [view removeFromSuperviewWithoutNeedingDisplay];
     [[self contentView] addSubview:view];
     [self setInitialFirstResponder:[view textView]];
-    
+
     // NOTE: Calling setTitle:nil causes an exception to be raised (and it is
     // possible that 'target' has no title when we get here).
     if ([target title]) {
@@ -196,8 +198,10 @@ - (void)enterFullScreen
 
     [self setOpaque:[target isOpaque]];
 
+    // reassign target's window controller to believe that it's now controlling us
     // don't set this sooner, so we don't get an additional
-    // focus gained message  
+    // focus gained message
+    [winController setWindow:self];
     [self setDelegate:delegate];
 
     // Store view dimension used before entering full-screen, then resize the

src/MacVim/MMTextStorage.m

@@ -895,6 +895,9 @@ - (NSSize)fitToSize:(NSSize)size rows:(int *)rows columns:(int *)columns
         if (fh < 1.0f) fh = 1.0f;
 
         fitRows = floor(size.height/fh);
+        // Sanity checking in case unusual window sizes lead to degenerate results
+        if (fitRows < 1)
+            fitRows = 1;
         fitSize.height = fh*fitRows;
     }
 
@@ -903,6 +906,9 @@ - (NSSize)fitToSize:(NSSize)size rows:(int *)rows columns:(int *)columns
         if (fw < 1.0f) fw = 1.0f;
 
         fitCols = floor(size.width/fw);
+        // Sanity checking in case unusual window sizes lead to degenerate results
+        if (fitCols < 1)
+            fitCols = 1;
         fitSize.width = fw*fitCols;
     }
 

src/MacVim/MMWindowController.m

@@ -1307,9 +1307,7 @@ - (void)windowDidResize:(id)sender
     // Calling setFrameSizeKeepGUISize: instead of setFrameSize: prevents a
     // degenerate case where frameSizeMayHaveChanged: ends up resizing the window
     // *again* causing windowDidResize: to be called.
-    if (fullScreenWindow == nil) {
-        [vimView setFrameSizeKeepGUISize:[self contentSize]];
-    } else {
+    if (fullScreenEnabled && fullScreenWindow != nil) {
         // Non-native full screen mode is more complicated and needs to
         // re-layout the Vim view to properly account for the menu bar / notch,
         // and misc fuopt configuration.
@@ -1318,6 +1316,9 @@ - (void)windowDidResize:(id)sender
         [vimView setFrameOrigin:desiredFrame.origin];
         [vimView setFrameSizeKeepGUISize:desiredFrame.size];
     }
+    else {
+        [vimView setFrameSizeKeepGUISize:[self contentSize]];
+    }
 }
 
 - (void)windowDidChangeBackingProperties:(NSNotification *)notification