Add an advanced pref to use the "correct" algorithm for computing line height,...

Add an advanced pref to use the "correct" algorithm for computing line height, which involves magic incantations. It produces better results for Input Mono Condensed and seems to match what Terminal does. Issue 6159.

Also removed some unneeded baseline offset plumbing.

sources/FontSizeEstimator.h

@@ -36,7 +36,10 @@
 }
 @property (nonatomic, assign) NSSize size;
-@property (nonatomic, assign) double baseline;
+
+// Returns a text container and layout manager that are ready to measure a capital W.
++ (NSTextContainer *)newTextContainer;
++ (NSLayoutManager *)newLayoutManagerForFont:(NSFont *)aFont textContainer:(NSTextContainer *)textContainer;
 + (instancetype)fontSizeEstimatorForFont:(NSFont *)aFont;

sources/FontSizeEstimator.m

@@ -29,11 +29,11 @@
 #import "FontSizeEstimator.h"
 #import "DebugLogging.h"
+#import "iTermAdvancedSettingsModel.h"
 @implementation FontSizeEstimator
 @synthesize size;
-@synthesize baseline;
 - (instancetype)initWithSize:(NSSize)s baseline:(double)b {
     self = [super init];
@@ -44,6 +44,25 @@
     return self;
 }
++ (NSLayoutManager *)newLayoutManagerForFont:(NSFont *)aFont textContainer:(NSTextContainer *)textContainer {
+    NSString *myString = @"W";
+
+    NSTextStorage *textStorage = [[[NSTextStorage alloc] initWithString:myString] autorelease];
+    NSLayoutManager *layoutManager = [[[NSLayoutManager alloc] init] autorelease];
+    [layoutManager addTextContainer:textContainer];
+    [textStorage addLayoutManager:layoutManager];
+    [textStorage addAttribute:NSFontAttributeName
+                        value:aFont
+                        range:NSMakeRange(0, [textStorage length])];
+    [textContainer setLineFragmentPadding:0.0];
+    [layoutManager glyphRangeForTextContainer:textContainer];
+    return layoutManager;
+}
+
++ (NSTextContainer *)newTextContainer {
+    return [[[NSTextContainer alloc] initWithContainerSize:NSMakeSize(FLT_MAX, FLT_MAX)] autorelease];
+}
+
 + (id)fontSizeEstimatorForFont:(NSFont *)aFont
 {
     FontSizeEstimator* fse = [[[FontSizeEstimator alloc] init] autorelease];
@@ -82,10 +101,16 @@
         size.width = MAX(1, size.width);
         size.height = MAX(1, size.height);
-        double baseline = -(floorf([aFont leading]) - floorf([aFont descender]));
-        fse.size = size;
-        fse.baseline = baseline;
+        if ([iTermAdvancedSettingsModel useExperimentalFontMetrics]) {
+            NSTextContainer *textContainer = [self newTextContainer];
+            NSLayoutManager *layoutManager = [self newLayoutManagerForFont:aFont
+                                                             textContainer:textContainer];
+            NSRect usedRect = [layoutManager usedRectForTextContainer:textContainer];
+            fse.size = usedRect.size;
+        } else {
+            fse.size = size;
+        }
     }
     return fse;
 }

sources/PTYFontInfo.m

@@ -9,6 +9,8 @@
 #import "PTYFontInfo.h"
 #import "DebugLogging.h"
+#import "FontSizeEstimator.h"
+#import "iTermAdvancedSettingsModel.h"
 @implementation NSFont(PTYFontInfo)
@@ -106,7 +108,15 @@
 }
 - (CGFloat)computedBaselineOffset {
-    return -(floorf(font_.leading) - floorf(self.descender));
+    if ([iTermAdvancedSettingsModel useExperimentalFontMetrics]) {
+        NSTextContainer *textContainer = [FontSizeEstimator newTextContainer];
+        NSLayoutManager *layoutManager = [FontSizeEstimator newLayoutManagerForFont:font_ textContainer:textContainer];
+        CGFloat lineHeight = [layoutManager usedRectForTextContainer:textContainer].size.height;
+        CGFloat baselineOffsetFromTop = [layoutManager defaultBaselineOffsetForFont:font_];
+        return -floorf(lineHeight - baselineOffsetFromTop);
+    } else {
+        return -(floorf(font_.leading) - floorf(self.descender));
+    }
 }
 // From https://github.com/DrawKit/DrawKit/blob/master/framework/Code/NSBezierPath%2BText.m#L648

sources/PTYTextView.m

@@ -653,33 +653,22 @@ static const int kDragThreshold = 3;
 + (NSSize)charSizeForFont:(NSFont *)aFont
         horizontalSpacing:(double)hspace
-          verticalSpacing:(double)vspace
-                 baseline:(double *)baseline {
+          verticalSpacing:(double)vspace {
     FontSizeEstimator* fse = [FontSizeEstimator fontSizeEstimatorForFont:aFont];
     NSSize size = [fse size];
     size.width = ceil(size.width * hspace);
     size.height = ceil(vspace * ceil(size.height + [aFont leading]));
-    if (baseline) {
-        *baseline = [fse baseline];
-    }
     return size;
 }
-+ (NSSize)charSizeForFont:(NSFont*)aFont horizontalSpacing:(double)hspace verticalSpacing:(double)vspace
-{
-    return [PTYTextView charSizeForFont:aFont horizontalSpacing:hspace verticalSpacing:vspace baseline:nil];
-}
-
 - (void)setFont:(NSFont*)aFont
     nonAsciiFont:(NSFont *)nonAsciiFont
     horizontalSpacing:(double)horizontalSpacing
     verticalSpacing:(double)verticalSpacing
 {
-    double baseline;
     NSSize sz = [PTYTextView charSizeForFont:aFont
                            horizontalSpacing:1.0
-                             verticalSpacing:1.0
-                                    baseline:&baseline];
+                             verticalSpacing:1.0];
     _charWidthWithoutSpacing = sz.width;
     _charHeightWithoutSpacing = sz.height;

sources/iTermAdvancedSettingsModel.h

@@ -195,5 +195,6 @@
 + (BOOL)statusBarIcon;
 + (BOOL)sensitiveScrollWheel;
 + (BOOL)disableCustomBoxDrawing;
++ (BOOL)useExperimentalFontMetrics;
 @end

sources/iTermAdvancedSettingsModel.m

@@ -285,4 +285,6 @@ DEFINE_BOOL(killSessionsOnLogout, NO, @"Experimental Features: Kill sessions on
 // This causes problems like issue 6052, where repeats cause the IME to swallow subsequent keypresses.
 DEFINE_BOOL(experimentalKeyHandling, NO, @"General: Improved support for input method editors like AquaSKK.");
+DEFINE_BOOL(useExperimentalFontMetrics, NO, @"Experimental Features: Use a more theoretically correct technique to measure line height.\nYou must restart iTerm2 or adjust a session's font size for this change to take effect.");
+
 @end