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coretext: use alternate approach to calcaulate cell height and ascent

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Fixes #174
This commit is contained in:
Mitchell Hashimoto
2023-07-03 14:26:06 -07:00
parent 0e802b6118
commit 369a7dda4c
2 changed files with 10 additions and 86 deletions
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95
src/font/face/coretext.zig
View File

@ -270,7 +270,7 @@ pub const Face = struct {
break :offset_y @intFromFloat(@ceil(baseline_with_offset)); break :offset_y @intFromFloat(@ceil(baseline_with_offset));
}; };
// log.warn("renderGlyph rect={} width={} height={} render_x={} render_y={} offset_y={} ascent={} cell_height={} cell_baseline={}", .{ // std.log.warn("renderGlyph rect={} width={} height={} render_x={} render_y={} offset_y={} ascent={} cell_height={} cell_baseline={}", .{
// rect, // rect,
// width, // width,
// height, // height,
@ -331,95 +331,20 @@ pub const Face = struct {
break :cell_width @floatCast(@ceil(max)); break :cell_width @floatCast(@ceil(max));
}; };
// Calculate the cell height by using CoreText's layout engine // Calculate the layout metrics for height/ascent by just asking
// to tell us after laying out some text. This is inspired by Kitty's // the font. I also tried Kitty's approach at one point which is to
// approach. Previously we were using descent/ascent math and it wasn't // use the CoreText layout engine but this led to some glyphs being
// quite the same with CoreText and I never figured out why. // set incorrectly.
const layout_metrics: struct { const layout_metrics: struct {
height: f32, height: f32,
ascent: f32, ascent: f32,
} = metrics: { } = metrics: {
const unit = "AQWMH_gyl " ** 100; const ascent = @round(ct_font.getAscent());
const descent = @round(ct_font.getDescent());
// Setup our string we'll layout. We just stylize a string of const leading = @round(ct_font.getLeading());
// ASCII characters to setup the letters.
const string = try macos.foundation.MutableAttributedString.create(unit.len);
defer string.release();
const rep = try macos.foundation.String.createWithBytes(unit, .utf8, false);
defer rep.release();
string.replaceString(macos.foundation.Range.init(0, 0), rep);
string.setAttribute(
macos.foundation.Range.init(0, unit.len),
macos.text.StringAttribute.font,
ct_font,
);
// Create our framesetter with our string. This is used to
// emit "frames" for the layout.
const fs = try macos.text.Framesetter.createWithAttributedString(@ptrCast(string));
defer fs.release();
// Create a rectangle to fit all of this and create a frame of it.
// The rectangle needs to fit all of our text so we use some
// heuristics based on cell_width to calculate it. We are
// VERY generous with our rect here because the text must fit.
const path_rect = rect: {
// The cell width at this point is valid, so let's make it
// fit 50 characters wide.
const width = cell_width * 50;
// We are trying to calculate height so we don't know how
// high to make our frame. Well-behaved fonts will probably
// not have a height greater than 4x the width, so let's just
// generously use that metric to ensure we fit the frame.
const big_cell_height = cell_width * 4;
// If we are fitting about ~50 characters per row, we need
// unit.len / 50 rows to fit all of our text.
const rows = (unit.len / 50) * 2;
// Our final height is the number of rows times our generous height.
const height = rows * big_cell_height;
break :rect macos.graphics.Rect.init(10, 10, width, height);
};
const path = try macos.graphics.MutablePath.create();
path.addRect(null, path_rect);
defer path.release();
const frame = try fs.createFrame(
macos.foundation.Range.init(0, 0),
@ptrCast(path),
null,
);
defer frame.release();
// Use our text layout from earlier to measure the difference
// between the lines.
var points: [2]macos.graphics.Point = undefined;
frame.getLineOrigins(macos.foundation.Range.init(0, 1), points[0..]);
frame.getLineOrigins(macos.foundation.Range.init(1, 1), points[1..]);
const lines = frame.getLines();
const line = lines.getValueAtIndex(macos.text.Line, 0);
// Get the bounds of the line to determine the ascent.
const bounds = line.getBoundsWithOptions(.{ .exclude_leading = true });
const bounds_ascent = bounds.size.height + bounds.origin.y;
const baseline = @floor(bounds_ascent + 0.5);
// This is an alternate approach to the above to calculate the
// baseline by simply using the ascender. Using this approach led
// to less accurate results, but I'm leaving it here for reference.
// var ascent: f64 = 0;
// var descent: f64 = 0;
// var leading: f64 = 0;
// _ = line.getTypographicBounds(&ascent, &descent, &leading);
//std.log.warn("ascent={} descent={} leading={}", .{ ascent, descent, leading });
break :metrics .{ break :metrics .{
.height = @floatCast(points[0].y - points[1].y), .height = @floatCast(ascent + descent + leading),
.ascent = @floatCast(baseline), .ascent = @floatCast(ascent),
}; };
}; };

1
src/font/face/freetype.zig
View File

@ -485,7 +485,6 @@ pub const Face = struct {
.strikethrough_thickness = @intFromFloat(strikethrough.thickness), .strikethrough_thickness = @intFromFloat(strikethrough.thickness),
}; };
// std.log.warn("font size size={d}", .{ct_font.getSize()});
// std.log.warn("font metrics={}", .{result}); // std.log.warn("font metrics={}", .{result});
return result; return result;