Text bounding box

Hi,

Sometimes, the bounding box returned by gp:get-string-extent doesn't match the actual size of the drawn text. Is this expected behavior? (Could be due to kerning or other font stuff that I don't know enough about)

Otherwise, is it a bug in GP/CAPI or in the underlying rendering system?

I've only tested this on OS X so far, so I don't know yet if the problem is present on other platforms as well.

Below is example code to reproduce the problem.

Thanks
Erik


(defun display-output-pane (display-callback &rest args &key (visible-min-width 200) (visible-min-height 100) &allow-other-keys)
  (capi:contain (apply 'make-instance
                       'capi:output-pane
                       :display-callback display-callback
                       :input-model (list (list '(:button-1 :press) #'(lambda (pane x y)
                                                                        (declare (ignore x y))
                                                                        (gp:invalidate-rectangle pane))))
                       args)))

(defmacro with-output-pane ((sym &rest args) &body display-callback)
  `(display-output-pane (lambda (,sym &rest r) ,@display-callback) ,@args))

(with-output-pane (port)
  (loop for font-desc in (list (gp:make-font-description :family "Arial" :size 14 :weight :normal)
                               (gp:make-font-description :family "Arial Narrow" :size 14 :weight :normal)
                               (gp:make-font-description :family "Source Sans Pro" :size 12 :weight :light)
                               (gp:make-font-description :family "Times New Roman" :size 14 :weight :normal :slant :italic))
        with y = 10 do
        (let ((font (gp:find-best-font port font-desc))
              (text "Synchronize now"))
          (multiple-value-bind (left top right bottom)
              (gp:get-string-extent port text font)
            (gp:draw-rectangle port (- 10 left) y (- right left) (- bottom top) :filled t :foreground :yellow)
            (gp:draw-string port text (- 10 left) (- y top) :font font)
            (incf y (+ (- bottom top) 10))))))



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