How do I draw a single line of text in a SwiftUI Canvas, scaled to fill a given rectangle?
Example:
Canvas { context, size in
let r = CGRect(origin: CGPointZero, size: size); // Whole canvas
let t = Text("Hello World");
context.draw(t, in: r);
}
Outside of Canvas I'd add .minimumScaleFactor(0) .lineLimit(1), and I guess set a large default font size, and I'd get the result I want.
But inside Canvas, .minimumScaleFactor and .lineLimit don't seem to be available; they return some View, not Text, which can't be used in context.draw. (Is there a trick to make that work?)
I have written the following to do this, but I think there must be an easier way to achieve this! Suggestions?
extension GraphicsContext {
mutating func draw_text_in_rect(string: String, rect: CGRect)
{
let text = Text(string) .font(.system(size: 25));
// The font size used here does matter, because e.g. letter spacing
// varies with the font size.
let resolved = resolve(text);
let text_size = resolved.measure(in: CGSize(width: CGFloat.infinity, height: CGFloat.infinity));
let text_aspect = text_size.width / text_size.height;
let fit_size = CGSize(width: min(rect.size.width, rect.size.height*text_aspect),
height: min(rect.size.height, rect.size.width/text_aspect));
let fit_rect = CGRect(x: rect.origin.x + (rect.size.width-fit_size.width)/2,
y: rect.origin.y + (rect.size.height-fit_size.height)/2,
width: fit_size.width,
height: fit_size.height);
let scale = fit_size.width / text_size.width;
// For debug:
// var p = Path();
// p.addRect(fit_rect);
// stroke(p, with: GraphicsContext.Shading.color(.red), lineWidth: 1);
translateBy(x: fit_rect.minX, y: fit_rect.minY);
scaleBy(x:scale, y:scale);
draw(resolved, at: CGPointZero, anchor: UnitPoint.topLeading);
transform = CGAffineTransformIdentity;
}
};
