From ea79af728c2ac9c8ca8536010bb2b92cf366ab70 Mon Sep 17 00:00:00 2001
From: Chris Wilson <chris@chris-wilson.co.uk>
Date: Thu, 8 May 2008 17:23:44 +0100
Subject: [PATCH] [cairo-xlib] Scan for a glyphset to match a pending free
 glyph.

In order to avoid re-rasterising a glyph that is pending an
XRenderFreeGlyph, we first scan all glyphsets and their arrays of
pending_free_glyphs for a matching glyph. The additional cost of
scanning the extra arrays should be negligble as most fonts will only
have the single array (which we would scan anyway) but we potentially
save an expensive rasterisation and short-lived image surface.

(As suggested by Behdad Esfahbod.)
---
 src/cairo-xlib-surface.c | 90 ++++++++++++++++++++++++++++++++--------
 1 file changed, 72 insertions(+), 18 deletions(-)

diff --git a/src/cairo-xlib-surface.c b/src/cairo-xlib-surface.c
index 0c2996833..562703e40 100644
--- a/src/cairo-xlib-surface.c
+++ b/src/cairo-xlib-surface.c
@@ -2990,6 +2990,71 @@ _cairo_xlib_scaled_font_get_glyphset_info_for_format (cairo_scaled_font_t *scale
     return glyphset_info;
 }
 
+static cairo_bool_t
+_cairo_xlib_glyphset_info_has_pending_free_glyph (
+				cairo_xlib_font_glyphset_info_t *glyphset_info,
+				unsigned long glyph_index)
+{
+    if (glyphset_info->pending_free_glyphs != NULL) {
+	cairo_xlib_font_glyphset_free_glyphs_t *to_free;
+	int i;
+
+	to_free = glyphset_info->pending_free_glyphs;
+	for (i = 0; i < to_free->glyph_count; i++) {
+	    if (to_free->glyph_indices[i] == glyph_index) {
+		to_free->glyph_count--;
+		memmove (&to_free->glyph_indices[i],
+			 &to_free->glyph_indices[i+1],
+			 (to_free->glyph_count - i) * sizeof (to_free->glyph_indices[0]));
+		return TRUE;
+	    }
+	}
+    }
+
+    return FALSE;
+}
+
+static cairo_xlib_font_glyphset_info_t *
+_cairo_xlib_scaled_font_get_glyphset_info_for_pending_free_glyph (
+					       cairo_scaled_font_t *scaled_font,
+					       unsigned long glyph_index,
+					       cairo_image_surface_t *surface)
+{
+    cairo_xlib_surface_font_private_t *font_private;
+    int i;
+
+    font_private = scaled_font->surface_private;
+    if (font_private == NULL)
+	return NULL;
+
+    if (surface != NULL) {
+	switch (surface->format) {
+	default:
+	case CAIRO_FORMAT_RGB24:
+	case CAIRO_FORMAT_ARGB32: i = GLYPHSET_INDEX_ARGB32; break;
+	case CAIRO_FORMAT_A8:     i = GLYPHSET_INDEX_A8;     break;
+	case CAIRO_FORMAT_A1:     i = GLYPHSET_INDEX_A1;     break;
+	}
+	if (_cairo_xlib_glyphset_info_has_pending_free_glyph (
+						&font_private->glyphset_info[i],
+						glyph_index))
+	{
+	    return &font_private->glyphset_info[i];
+	}
+    } else {
+	for (i = 0; i < NUM_GLYPHSETS; i++) {
+	    if (_cairo_xlib_glyphset_info_has_pending_free_glyph (
+						&font_private->glyphset_info[i],
+						glyph_index))
+	    {
+		return &font_private->glyphset_info[i];
+	    }
+	}
+    }
+
+    return NULL;
+}
+
 static cairo_status_t
 _cairo_xlib_surface_add_glyph (Display *dpy,
 			       cairo_scaled_font_t   *scaled_font,
@@ -3006,6 +3071,13 @@ _cairo_xlib_surface_add_glyph (Display *dpy,
 
     glyph_index = _cairo_scaled_glyph_index (scaled_glyph);
 
+    /* check to see if we have a pending XRenderFreeGlyph for this glyph */
+    glyphset_info = _cairo_xlib_scaled_font_get_glyphset_info_for_pending_free_glyph (scaled_font, glyph_index, glyph_surface);
+    if (glyphset_info != NULL) {
+	_cairo_xlib_scaled_glyph_set_glyphset_info (scaled_glyph, glyphset_info);
+	return CAIRO_STATUS_SUCCESS;
+    }
+
     if (!glyph_surface) {
 	status = _cairo_scaled_glyph_lookup (scaled_font,
 					     glyph_index,
@@ -3042,23 +3114,6 @@ _cairo_xlib_surface_add_glyph (Display *dpy,
 	    return CAIRO_INT_STATUS_UNSUPPORTED;
     }
 
-    /* check to see if we have a pending XRenderFreeGlyph for this glyph */
-    if (glyphset_info->pending_free_glyphs != NULL) {
-	cairo_xlib_font_glyphset_free_glyphs_t *to_free;
-	int i;
-
-	to_free = glyphset_info->pending_free_glyphs;
-	for (i = 0; i < to_free->glyph_count; i++) {
-	    if (to_free->glyph_indices[i] == glyph_index) {
-		to_free->glyph_count--;
-		memmove (&to_free->glyph_indices[i],
-			 &to_free->glyph_indices[i+1],
-			 (to_free->glyph_count - i) * sizeof (to_free->glyph_indices[0]));
-		goto DONE;
-	    }
-	}
-    }
-
     /* If the glyph surface has zero height or width, we create
      * a clear 1x1 surface, to avoid various X server bugs.
      */
@@ -3195,7 +3250,6 @@ _cairo_xlib_surface_add_glyph (Display *dpy,
     if (data != glyph_surface->data)
 	free (data);
 
- DONE:
     _cairo_xlib_scaled_glyph_set_glyphset_info (scaled_glyph, glyphset_info);
 
  BAIL: