Fix issue with font line spacing support and add option for it

Recent change to stateful renderer (#858) has inadvertantly changed how
MacVim handles line spacing. Previously, MacVim intentionally ignores
the line spacing of a font and creates a new dummy font that essentially
has line spacing of 1, but the new code uses the font as is. This means
font with non-standard line spacing (e.g. Input Mono) will look
different. This is technically the correct way to handle fonts but is
different from how MacVim has worked for years.

Also, see last time this regression (where MacVim didn't discard line
spacing) happened in #928 / #949 which was fixed in #957. Also see #977
where the bug was filed the other way requesting for using the font's
line spacing instead of discarding it.

This commit re-introduces the behavior to discard line spacing, but only
provides it as an option (can be set in the preference pane), while
defaulting to using the line spacing as that seems more correct.

Note that from a casual survey of other terminals and editors, this
behavior is quite inconsistent. Xcode does use the font's line spacing,
and was partially the motivation of switching to that as a default.

Close #1152.

Author: ychin

runtime/doc/gui_mac.txt

@@ -241,7 +241,7 @@ is sent back to the server application.
 
 Some settings are global to the MacVim application and would not make sense as
 Vim options.  These settings are stored in the user defaults database and can
-be accessed via the "MacVim.Preferences..." menu item.
+be accessed via the "MacVim.Preferences…" menu item.
 
 							*macvim-user-defaults*
 Not all entries in the user defaults database are exposed via the preference
@@ -265,6 +265,7 @@ KEY				VALUE ~
 *MMNativeFullScreen*		use native full screen mode [bool]
 *MMNoFontSubstitution*		disable automatic font substitution [bool]
 				(Deprecated: Non-CoreText renderer only)
+*MMFontPreserveLineSpacing*	use the line-spacing as specified by font [bool]
 *MMNoTitleBarWindow*		hide title bar [bool]
 *MMTitlebarAppearsTransparent*	enable a transparent titlebar [bool]
 *MMAppearanceModeSelection*	dark mode selection (|macvim-dark-mode|)[bool]

runtime/doc/tags

@@ -5015,6 +5015,7 @@ MMAppearanceModeSelection	gui_mac.txt	/*MMAppearanceModeSelection*
 MMCellWidthMultiplier	gui_mac.txt	/*MMCellWidthMultiplier*
 MMDialogsTrackPwd	gui_mac.txt	/*MMDialogsTrackPwd*
 MMDisableLaunchAnimation	gui_mac.txt	/*MMDisableLaunchAnimation*
+MMFontPreserveLineSpacing	gui_mac.txt	/*MMFontPreserveLineSpacing*
 MMFullScreenFadeTime	gui_mac.txt	/*MMFullScreenFadeTime*
 MMLoginShellArgument	gui_mac.txt	/*MMLoginShellArgument*
 MMLoginShellCommand	gui_mac.txt	/*MMLoginShellCommand*

src/MacVim/Base.lproj/Preferences.xib

@@ -59,6 +59,7 @@
 - (BOOL)openFiles:(NSArray *)filenames withArguments:(NSDictionary *)args;
 
 - (void)refreshAllAppearances;
+- (void)refreshAllFonts;
 
 - (IBAction)newWindow:(id)sender;
 - (IBAction)newWindowAndActivate:(id)sender;

src/MacVim/MMAppController.h

@@ -229,6 +229,7 @@ + (void)initialize
         [NSNumber numberWithBool:YES],    MMTranslateCtrlClickKey,
         [NSNumber numberWithInt:0],       MMOpenInCurrentWindowKey,
         [NSNumber numberWithBool:NO],     MMNoFontSubstitutionKey,
+        [NSNumber numberWithBool:YES],    MMFontPreserveLineSpacingKey,
         [NSNumber numberWithBool:YES],    MMLoginShellKey,
         [NSNumber numberWithInt:MMRendererCoreText],
                                           MMRendererKey,
@@ -1109,6 +1110,15 @@ - (void)refreshAllAppearances
     }
 }
 
+- (void)refreshAllFonts
+{
+    unsigned count = [vimControllers count];
+    for (unsigned i = 0; i < count; ++i) {
+        MMVimController *vc = [vimControllers objectAtIndex:i];
+        [vc.windowController refreshFonts];
+    }
+}
+
 - (IBAction)newWindow:(id)sender
 {
     ASLogDebug(@"Open new window");

src/MacVim/MMAppController.m

@@ -32,6 +32,8 @@
     BOOL                        ligatures;
     BOOL                        thinStrokes;
 
+    BOOL                        forceRefreshFont; // when true, don't early out of setFont calls.
+
     MMTextViewHelper            *helper;
 
     NSMutableDictionary<NSNumber *, NSFont *> *fontVariants;

src/MacVim/MMCoreTextView.h

@@ -221,6 +221,8 @@ - (id)initWithFrame:(NSRect)frame
 {
     if (!(self = [super initWithFrame:frame]))
         return nil;
+
+    forceRefreshFont = NO;
 
     self.wantsLayer = YES;
 
@@ -374,24 +376,57 @@ - (NSRect)rectForColumnsInRange:(NSRange)range
 
 - (void)setFont:(NSFont *)newFont
 {
-    if (!newFont || [font isEqual:newFont])
+    if (!newFont) {
         return;
+    }
+    if (!forceRefreshFont) {
+        if ([font isEqual:newFont])
+            return;
+    }
+    forceRefreshFont = NO;
 
-    double em = round(defaultAdvanceForFont(newFont));
+    const double em = round(defaultAdvanceForFont(newFont));
 
-    float cellWidthMultiplier = [[NSUserDefaults standardUserDefaults]
+    const float cellWidthMultiplier = [[NSUserDefaults standardUserDefaults]
             floatForKey:MMCellWidthMultiplierKey];
 
+    // Some fonts have non-standard line heights, and historically MacVim has
+    // chosen to ignore it. Provide the option for the user to choose whether to
+    // use the font's line height. If not preserving, will create a new font
+    // from scratch with just name and pt size, which will disard the line
+    // height information.
+    //
+    // Defaults to the new behavior (preserveLineHeight==true) because it's
+    // simpler and respects the font's design more.
+    //
+    // Note: this behavior is somewhat inconsistent across editors and
+    // terminals. Xcode, for example, seems to be equivalent to
+    // (preserveLineHeight==true), but other editors/terminals behave
+    // differently. Xcode respecting the line height is partially the motivation
+    // for setting that as the default.
+    const BOOL preserveLineHeight = [[NSUserDefaults standardUserDefaults]
+                                     boolForKey:MMFontPreserveLineSpacingKey];
+
+    [font release];
+    if (!preserveLineHeight) {
+        double pt = round([newFont pointSize]);
+
+        CTFontDescriptorRef desc = CTFontDescriptorCreateWithNameAndSize((CFStringRef)[newFont fontName], pt);
+        CTFontRef fontRef = CTFontCreateWithFontDescriptor(desc, pt, NULL);
+        CFRelease(desc);
+
+        font = (NSFont*)fontRef;
+    } else {
+        font = [newFont retain];
+    }
+    fontDescent = ceil(CTFontGetDescent((CTFontRef)font));
+
     // NOTE! Even though NSFontFixedAdvanceAttribute is a float, it will
     // only render at integer sizes.  Hence, we restrict the cell width to
     // an integer here, otherwise the window width and the actual text
     // width will not match.
     cellSize.width = columnspace + ceil(em * cellWidthMultiplier);
-    cellSize.height = linespace + defaultLineHeightForFont(newFont);
-    
-    [font release];
-    font = [newFont retain];
-    fontDescent = ceil(CTFontGetDescent((CTFontRef)font));
+    cellSize.height = linespace + defaultLineHeightForFont(font);
 
     [self clearAll];
     [fontVariants removeAllObjects];
@@ -414,7 +449,17 @@ - (void)setWideFont:(NSFont *)newFont
     [fontVariants removeAllObjects];
     [characterStrings removeAllObjects];
     [characterLines removeAllObjects];
+}
+
+- (void)refreshFonts
+{
+    // Mark force refresh, so that we won't try to use the cached font later.
+    forceRefreshFont = YES;
 
+    // Go through the standard path of updating fonts by passing the current
+    // font in. This lets Vim itself knows about the font change and initiates
+    // the resizing (depends on guioption-k) and redraws.
+    [self changeFont:NSFontManager.sharedFontManager];
 }
 
 - (NSFont *)font
@@ -893,6 +938,9 @@ - (NSSize)minSize
                       MMMinRows * cellSize.height + insetSize.height + bot);
 }
 
+// Called when font panel selection has been made. Send the selected font to
+// MMBackend so it would set guifont which will send a message back to MacVim to
+// call MMWindowController::setFont.
 - (void)changeFont:(id)sender
 {
     NSFont *newFont = [sender convertFont:font];

src/MacVim/MMCoreTextView.m

@@ -127,4 +127,10 @@ - (IBAction)appearanceChanged:(id)sender
     [[MMAppController sharedInstance] refreshAllAppearances];
 }
 
+- (IBAction)fontPropertiesChanged:(id)sender
+{
+    // Refresh all windows' fonts.
+    [[MMAppController sharedInstance] refreshAllFonts];
+}
+
 @end

src/MacVim/MMPreferenceController.m

@@ -47,6 +47,7 @@
 - (void)setFont:(NSFont *)newFont;
 - (NSFont *)fontWide;
 - (void)setWideFont:(NSFont *)newFont;
+- (void)refreshFonts;
 - (NSSize)cellSize;
 - (void)setLinespace:(float)newLinespace;
 - (void)setColumnspace:(float)newColumnspace;

src/MacVim/MMTextView.h

@@ -352,6 +352,11 @@ - (void)setWideFont:(NSFont *)newFont
     [(MMTextStorage*)[self textStorage] setWideFont:newFont];
 }
 
+- (void)refreshFonts
+{
+    // Doesn't do anything. CoreText renderer only.
+}
+
 - (NSSize)cellSize
 {
     return [(MMTextStorage*)[self textStorage] cellSize];