How to draw text in a non-flipped view ?

25/02/04 09:52
To draw text in a NSView view of my own, the view has to return YES from its isFlipped method. But if I really need to draw text in a non-flipped view, how ?
(If you don't see what we refer to, open the Sketch example in your Developer folder and comment out the isFlipped method of the SKGraphicView...).
This is a classical problem in any sketch board-like view, if you don't want a flipped view, the text will be drawn mirrored if you use the NSLayoutManager 's method drawGlyphsForGlyphRange without any precaution.
Here is a solution:
1. add a method to your NSView subclass to turn on/off the flipped state on the fly:
- (void)setFlipped:(BOOL)inFlipped
{
fFlipped = inFlipped ;
}

- (BOOL)isFlipped
{
return fFlipped;
}
fFlipped being of course an instance BOOL of your NSView sub-class.

2. in your drawing code, apply the following steps:
a. call your new setFlipped method with argument YES;

b. create a new NSAffineTransform *transform with the following matrix:
 1 0 0
0 -1 0
0 H 1
where H is the height of the bounding box of the text to be drawn;

c. save the current graphic state with [[NSGraphicsContext currentContext] saveGraphicsState];

d. apply the newly created affine transform with [transform concat];

e. draw your text mostly as usual: (example)
[myTextContainer setContainerSize:myBounds.size];
[myContents addLayoutManager:myLayoutManager];
[myLayoutManager drawBackgroundForGlyphRange:glyphRange atPoint:NSMakePoint(myBounds.origin.x, -myBounds.origin.y)];
[myLayoutManager drawGlyphsForGlyphRange:glyphRange atPoint:NSMakePoint(myBounds.origin.x, -myBounds.origin.y)];
BUT note the important reversing of the y value of the origin for the atPoint parameter !

f. restore the graphic state [[NSGraphicsContext currentContext] restoreGraphicsState];

g. restore the non flipped state of your view: [myView setFlipped:NO].