[win32] Add cairo_win32_font_face_create_for_logfontw_hfont

Patch from: Robert O'Callahan <roc@ocallahans.org>

Add cairo_win32_font_face_create_for_logfontw_hfont, allow win32
scaled_fonts to rescale themselves properly to the required CTM and
only use the font_face's hfont if we're sure it's appropriate.

2 files changed, 88 insertions, 22 deletions

diff --git a/src/cairo-win32-font.c b/src/cairo-win32-font.c
index 681dba77..64df7e2f 100644
--- a/src/cairo-win32-font.c
+++ b/src/cairo-win32-font.c
@@ -1,3 +1,4 @@
+/* -*- Mode: c; tab-width: 8; c-basic-offset: 4; indent-tabs-mode: t; -*- */
 /* cairo - a vector graphics library with display and print output
  *
  * Copyright © 2005 Red Hat, Inc
@@ -226,9 +227,15 @@ _get_system_quality (void)
     }
 }
 
+/* If face_hfont is non-NULL then font_matrix must be a simple scale by some
+ * factor S, ctm must be the identity, logfont->lfHeight must be -S,
+ * logfont->lfWidth, logfont->lfEscapement, logfont->lfOrientation must
+ * all be 0, and face_hfont is the result of calling CreateFontIndirectW on
+ * logfont.
+ */
 static cairo_scaled_font_t *
 _win32_scaled_font_create (LOGFONTW                   *logfont,
-			   HFONT                      hfont,
+			   HFONT                      face_hfont,
 			   cairo_font_face_t	      *font_face,
 			   const cairo_matrix_t       *font_matrix,
 			   const cairo_matrix_t       *ctm,
@@ -274,11 +281,21 @@ _win32_scaled_font_create (LOGFONTW                   *logfont,
     }
 
     f->em_square = 0;
-    f->scaled_hfont = hfont;
+    f->scaled_hfont = NULL;
     f->unscaled_hfont = NULL;
 
-    /* don't delete the hfont if it was passed in to us */
-    f->delete_scaled_hfont = !hfont;
+    if (f->quality == logfont->lfQuality ||
+        (logfont->lfQuality == DEFAULT_QUALITY &&
+         options->antialias == CAIRO_ANTIALIAS_DEFAULT)) {
+        /* If face_hfont is non-NULL, then we can use it to avoid creating our
+         * own --- because the constraints on face_hfont mentioned above
+         * guarantee it was created in exactly the same way that
+         * _win32_scaled_font_get_scaled_hfont would create it.
+         */
+        f->scaled_hfont = face_hfont;
+    }
+    /* don't delete the hfont if we're using the one passed in to us */
+    f->delete_scaled_hfont = !f->scaled_hfont;
 
     cairo_matrix_multiply (&scale, font_matrix, ctm);
     _compute_transform (f, &scale);
@@ -1483,6 +1500,11 @@ const cairo_scaled_font_backend_t cairo_win32_scaled_font_backend = {
 
 typedef struct _cairo_win32_font_face cairo_win32_font_face_t;
 
+/* If hfont is non-NULL then logfont->lfHeight must be -S for some S,
+ * logfont->lfWidth, logfont->lfEscapement, logfont->lfOrientation must
+ * all be 0, and hfont is the result of calling CreateFontIndirectW on
+ * logfont.
+ */
 struct _cairo_win32_font_face {
     cairo_font_face_t base;
     LOGFONTW logfont;
@@ -1496,6 +1518,14 @@ _cairo_win32_font_face_destroy (void *abstract_face)
 {
 }
 
+static cairo_bool_t
+_is_scale (const cairo_matrix_t *matrix, double scale)
+{
+    return matrix->xx == scale && matrix->yy == scale &&
+           matrix->xy == 0. && matrix->yx == 0. &&
+           matrix->x0 == 0. && matrix->y0 == 0.;
+}
+
 static cairo_status_t
 _cairo_win32_font_face_scaled_font_create (void			*abstract_face,
 					   const cairo_matrix_t	*font_matrix,
@@ -1503,10 +1533,20 @@ _cairo_win32_font_face_scaled_font_create (void			*abstract_face,
 					   const cairo_font_options_t *options,
 					   cairo_scaled_font_t **font)
 {
+    HFONT hfont = NULL;
+
     cairo_win32_font_face_t *font_face = abstract_face;
 
+    if (font_face->hfont) {
+        /* Check whether it's OK to go ahead and use the font-face's HFONT. */
+        if (_is_scale (ctm, 1.) &&
+            _is_scale (font_matrix, -font_face->logfont.lfHeight)) {
+            hfont = font_face->hfont;
+        }
+    }
+
     *font = _win32_scaled_font_create (&font_face->logfont,
-				       font_face->hfont,
+				       hfont,
 				       &font_face->base,
 				       font_matrix, ctm, options);
     if (*font)
@@ -1522,10 +1562,13 @@ static const cairo_font_face_backend_t _cairo_win32_font_face_backend = {
 };
 
 /**
- * cairo_win32_font_face_create_for_logfontw:
+ * cairo_win32_font_face_create_for_logfontw_hfont:
  * @logfont: A #LOGFONTW structure specifying the font to use.
- *   The lfHeight, lfWidth, lfOrientation and lfEscapement
- *   fields of this structure are ignored.
+ *   If hfont is null then the lfHeight, lfWidth, lfOrientation and lfEscapement
+ *   fields of this structure are ignored. Otherwise lfWidth, lfOrientation and
+ *   lfEscapement must be zero.
+ * @font: An #HFONT that can be used when the font matrix is a scale by
+ *   -lfHeight and the CTM is identity.
  *
  * Creates a new font for the Win32 font backend based on a
  * #LOGFONT. This font can then be used with
@@ -1538,18 +1581,18 @@ static const cairo_font_face_backend_t _cairo_win32_font_face_backend = {
  *  cairo_font_face_destroy() when you are done using it.
  **/
 cairo_font_face_t *
-cairo_win32_font_face_create_for_logfontw (LOGFONTW *logfont)
+cairo_win32_font_face_create_for_logfontw_hfont (LOGFONTW *logfont, HFONT font)
 {
     cairo_win32_font_face_t *font_face;
 
     font_face = malloc (sizeof (cairo_win32_font_face_t));
     if (!font_face) {
-	_cairo_error (CAIRO_STATUS_NO_MEMORY);
-	return (cairo_font_face_t *)&_cairo_font_face_nil;
+        _cairo_error (CAIRO_STATUS_NO_MEMORY);
+        return (cairo_font_face_t *)&_cairo_font_face_nil;
     }
 
     font_face->logfont = *logfont;
-    font_face->hfont = NULL;
+    font_face->hfont = font;
 
     _cairo_font_face_init (&font_face->base, &_cairo_win32_font_face_backend);
 
@@ -1557,6 +1600,28 @@ cairo_win32_font_face_create_for_logfontw (LOGFONTW *logfont)
 }
 
 /**
+ * cairo_win32_font_face_create_for_logfontw:
+ * @logfont: A #LOGFONTW structure specifying the font to use.
+ *   The lfHeight, lfWidth, lfOrientation and lfEscapement
+ *   fields of this structure are ignored.
+ *
+ * Creates a new font for the Win32 font backend based on a
+ * #LOGFONT. This font can then be used with
+ * cairo_set_font_face() or cairo_scaled_font_create().
+ * The #cairo_scaled_font_t
+ * returned from cairo_scaled_font_create() is also for the Win32 backend
+ * and can be used with functions such as cairo_win32_scaled_font_select_font().
+ *
+ * Return value: a newly created #cairo_font_face_t. Free with
+ *  cairo_font_face_destroy() when you are done using it.
+ **/
+cairo_font_face_t *
+cairo_win32_font_face_create_for_logfontw (LOGFONTW *logfont)
+{
+    return cairo_win32_font_face_create_for_logfontw_hfont (logfont, NULL);
+}
+
+/**
  * cairo_win32_font_face_create_for_hfont:
  * @font: An #HFONT structure specifying the font to use.
  *
@@ -1573,19 +1638,17 @@ cairo_win32_font_face_create_for_logfontw (LOGFONTW *logfont)
 cairo_font_face_t *
 cairo_win32_font_face_create_for_hfont (HFONT font)
 {
-    cairo_win32_font_face_t *font_face;
+    LOGFONTW logfont;
+    GetObject (font, sizeof(logfont), &logfont);
 
-    font_face = malloc (sizeof (cairo_win32_font_face_t));
-    if (!font_face) {
-	_cairo_error (CAIRO_STATUS_NO_MEMORY);
-	return (cairo_font_face_t *)&_cairo_font_face_nil;
+    if (logfont.lfEscapement != 0 || logfont.lfOrientation != 0 ||
+        logfont.lfWidth != 0) {
+        /* We can't use this font because that optimization requires that
+         * lfEscapement, lfOrientation and lfWidth be zero. */
+        font = NULL;
     }
 
-    font_face->hfont = font;
-
-    _cairo_font_face_init (&font_face->base, &_cairo_win32_font_face_backend);
-
-    return &font_face->base;
+    return cairo_win32_font_face_create_for_logfontw_hfont (&logfont, font);
 }
 
 /**
diff --git a/src/cairo-win32.h b/src/cairo-win32.h
index 8719d338..56643868 100644
--- a/src/cairo-win32.h
+++ b/src/cairo-win32.h
@@ -70,6 +70,9 @@ cairo_win32_font_face_create_for_logfontw (LOGFONTW *logfont);
 cairo_public cairo_font_face_t *
 cairo_win32_font_face_create_for_hfont (HFONT font);
 
+cairo_public cairo_font_face_t *
+cairo_win32_font_face_create_for_logfontw_hfont (LOGFONTW *logfont, HFONT font);
+
 cairo_public cairo_status_t
 cairo_win32_scaled_font_select_font (cairo_scaled_font_t *scaled_font,
 				     HDC                  hdc);