From 114c64765d4b9076101b111c1afa41ceac4ea39c Mon Sep 17 00:00:00 2001
From: Matthew Flatt <mflatt@racket-lang.org>
Date: Fri, 8 Apr 2011 11:39:41 -0600
Subject: [PATCH] racket/draw: fix baseline on font substitution in "combine"
 mode

---
 collects/racket/draw/private/dc.rkt | 51 +++++++++++++++++------------
 1 file changed, 30 insertions(+), 21 deletions(-)

diff --git a/collects/racket/draw/private/dc.rkt b/collects/racket/draw/private/dc.rkt
index 5f9c71defe..af7a2ae3e6 100644
--- a/collects/racket/draw/private/dc.rkt
+++ b/collects/racket/draw/private/dc.rkt
@@ -1244,7 +1244,7 @@
               ;; This is combine mode. It has to be a little complicated, after all,
               ;; because we may need to implement font substitution ourselves, which
               ;; breaks the string into multiple layouts.
-              (let loop ([s s] [w 0.0] [h 0.0] [d 0.0] [a 0.0])
+              (let loop ([s s] [draw? draw?] [measured? #f] [w 0.0] [h 0.0] [d 0.0] [a 0.0])
                 (cond
                  [(not s)
                   (when rotate? (cairo_restore cr))
@@ -1280,28 +1280,37 @@
                                    ;; find a face that works for the long character:
                                    (install-alternate-face (string-ref s 0) layout font desc attrs context))
                                  (substring s (max 1 ok-count))))])
-                      (let ([logical (make-PangoRectangle 0 0 0 0)])
-                        (pango_layout_get_extents layout #f logical)
-                        (when draw?
-                          (let ([bl (/ (pango_layout_get_baseline layout) (exact->inexact PANGO_SCALE))])
-                            (pango_layout_get_extents layout #f logical)
-                            (cairo_move_to cr (text-align-x/delta (+ x w) 0) (text-align-y/delta (+ y bl) 0))
-                            ;; Draw the text:
-                            (pango_cairo_show_layout_line cr (pango_layout_get_line_readonly layout 0))))
-                        (cond
-                         [(and draw? (not next-s))
-                          (g_object_unref layout)
-                          (when rotate? (cairo_restore cr))]
-                         [else
-                          (let ([nw (if blank?
-                                        0.0
-                                        (integral (/ (PangoRectangle-width logical) (exact->inexact PANGO_SCALE))))]
-                                [nh (/ (PangoRectangle-height logical) (exact->inexact PANGO_SCALE))]
+                      (cond
+                       [(and draw? next-s (not measured?))
+                        ;; It's going to take multiple layouts, so first gather measurements.
+                        (let-values ([(w2 h d a) (loop s #f #f w h d a)])
+                          ;; draw again, supplying `h', `d', and `a' for the whole line
+                          (loop s #t #t w h d a))]
+                       [else
+                        (let ([logical (make-PangoRectangle 0 0 0 0)])
+                          (pango_layout_get_extents layout #f logical)
+                          (let ([nh (/ (PangoRectangle-height logical) (exact->inexact PANGO_SCALE))]
                                 [nd (/ (- (PangoRectangle-height logical)
                                           (pango_layout_get_baseline layout))
-                                       (exact->inexact PANGO_SCALE))]
-                                [na 0.0])
-                            (loop next-s (+ w nw) (max h nh) (max d nd) (max a na)))]))))]))
+                                       (exact->inexact PANGO_SCALE))])
+                            (when draw?
+                              (let ([bl (if measured? (- h d) (- nh nd))])
+                                (pango_layout_get_extents layout #f logical)
+                                (cairo_move_to cr 
+                                               (text-align-x/delta (+ x w) 0) 
+                                               (text-align-y/delta (+ y bl) 0))
+                                ;; Draw the text:
+                                (pango_cairo_show_layout_line cr (pango_layout_get_line_readonly layout 0))))
+                            (cond
+                             [(and draw? (not next-s))
+                              (g_object_unref layout)
+                              (when rotate? (cairo_restore cr))]
+                             [else
+                              (let ([nw (if blank?
+                                            0.0
+                                            (integral (/ (PangoRectangle-width logical) (exact->inexact PANGO_SCALE))))]
+                                    [na 0.0])
+                                (loop next-s measured? draw? (+ w nw) (max h nh) (max d nd) (max a na)))])))])))]))
               ;; This is character-by-character mode. It uses a cached per-character+font layout
               ;;  object.
               (let ([cache (if (or combine?