[cairo-xlib] Release glyph surfaces if we made them to be generated

The reasoning is that right now, applications render glyphs to images,
upload it to the X server, and keep a local copy in the cache.  The X
server works hard to reuse glyph renderings, by hashing glyph images and
reusing them.  So we are wasting memory in cairo apps that don't use the
glyph surface after uploading to the server, which is the case if you
don't use the glyph in an image surface.  The patch does not release the
glyph surface if it already existed in the cache, so, worst case
scenario is that we render the glyph twice, if you first use it with
xlib, then with image surface.  That effect should be negligible.
(cherry picked from commit 76e3b3cdc3dda986d420637cfc2445aca481a863)

1 files changed, 63 insertions, 20 deletions

diff --git a/src/cairo-xlib-surface.c b/src/cairo-xlib-surface.c
index 4fe62ed56..399417c97 100644
--- a/src/cairo-xlib-surface.c
+++ b/src/cairo-xlib-surface.c
@@ -2557,15 +2557,34 @@ _native_byte_order_lsb (void)
 
 static cairo_status_t
 _cairo_xlib_surface_add_glyph (Display *dpy,
-			       cairo_scaled_font_t  *scaled_font,
-			       cairo_scaled_glyph_t *scaled_glyph)
+			       cairo_scaled_font_t   *scaled_font,
+			       cairo_scaled_glyph_t **pscaled_glyph)
 {
     XGlyphInfo glyph_info;
     unsigned long glyph_index;
     unsigned char *data;
     cairo_status_t status = CAIRO_STATUS_SUCCESS;
     cairo_xlib_surface_font_private_t *font_private;
+    cairo_scaled_glyph_t *scaled_glyph = *pscaled_glyph;
     cairo_image_surface_t *glyph_surface = scaled_glyph->surface;
+    cairo_bool_t already_had_glyph_surface;
+
+    if (!glyph_surface) {
+
+	status = _cairo_scaled_glyph_lookup (scaled_font,
+					     _cairo_scaled_glyph_index (scaled_glyph),
+					     CAIRO_SCALED_GLYPH_INFO_METRICS |
+					     CAIRO_SCALED_GLYPH_INFO_SURFACE,
+					     pscaled_glyph);
+	if (status != CAIRO_STATUS_SUCCESS)
+	    return status;
+
+	scaled_glyph = *pscaled_glyph;
+	glyph_surface = scaled_glyph->surface;
+	already_had_glyph_surface = FALSE;
+    } else {
+	already_had_glyph_surface = TRUE;
+    }
 
     if (scaled_font->surface_private == NULL) {
 	status = _cairo_xlib_surface_font_init (dpy, scaled_font,
@@ -2575,6 +2594,31 @@ _cairo_xlib_surface_add_glyph (Display *dpy,
     }
     font_private = scaled_font->surface_private;
 
+    /* If the glyph surface has zero height or width, we create
+     * a clear 1x1 surface, to avoid various X server bugs.
+     */
+    if ((glyph_surface->width == 0) || (glyph_surface->height == 0)) {
+	cairo_t *cr;
+	cairo_surface_t *tmp_surface;
+
+	tmp_surface = cairo_image_surface_create (font_private->format, 1, 1);
+	cr = cairo_create (tmp_surface);
+	cairo_set_operator (cr, CAIRO_OPERATOR_CLEAR);
+	cairo_paint (cr);
+
+	status = cairo_status (cr);
+
+	cairo_destroy (cr);
+
+	tmp_surface->device_transform = glyph_surface->base.device_transform;
+	tmp_surface->device_transform_inverse = glyph_surface->base.device_transform_inverse;
+
+	glyph_surface = (cairo_image_surface_t *) tmp_surface;
+
+	if (status)
+	    goto BAIL;
+    }
+
     /* If the glyph format does not match the font format, then we
      * create a temporary surface for the glyph image with the font's
      * format.
@@ -2582,14 +2626,16 @@ _cairo_xlib_surface_add_glyph (Display *dpy,
     if (glyph_surface->format != font_private->format) {
 	cairo_t *cr;
 	cairo_surface_t *tmp_surface;
-	double x_offset, y_offset;
 
 	tmp_surface = cairo_image_surface_create (font_private->format,
 						  glyph_surface->width,
 						  glyph_surface->height);
+	tmp_surface->device_transform = glyph_surface->base.device_transform;
+	tmp_surface->device_transform_inverse = glyph_surface->base.device_transform_inverse;
+
 	cr = cairo_create (tmp_surface);
-	cairo_surface_get_device_offset (&glyph_surface->base, &x_offset, &y_offset);
-	cairo_set_source_surface (cr, &glyph_surface->base, x_offset, y_offset);
+
+	cairo_set_source_surface (cr, &glyph_surface->base, 0, 0);
 	cairo_set_operator (cr, CAIRO_OPERATOR_SOURCE);
 	cairo_paint (cr);
 
@@ -2597,9 +2643,6 @@ _cairo_xlib_surface_add_glyph (Display *dpy,
 
 	cairo_destroy (cr);
 
-	tmp_surface->device_transform = glyph_surface->base.device_transform;
-	tmp_surface->device_transform_inverse = glyph_surface->base.device_transform_inverse;
-
 	glyph_surface = (cairo_image_surface_t *) tmp_surface;
 
 	if (status)
@@ -2728,6 +2771,15 @@ _cairo_xlib_surface_add_glyph (Display *dpy,
     if (glyph_surface != scaled_glyph->surface)
 	cairo_surface_destroy (&glyph_surface->base);
 
+    /* if the scaled glyph didn't already have a surface attached
+     * to it, release the created surface now that we have it
+     * uploaded to the X server.  If the surface has already been
+     * there (eg. because image backend requested it), leave it in
+     * the cache
+     */
+    if (!already_had_glyph_surface)
+	_cairo_scaled_glyph_set_surface (scaled_glyph, scaled_font, NULL);
+
     return status;
 }
 
@@ -2913,7 +2965,6 @@ _cairo_xlib_surface_emit_glyphs (cairo_xlib_surface_t *dst,
 
 	status = _cairo_scaled_glyph_lookup (scaled_font,
 					     glyphs[i].index,
-					     CAIRO_SCALED_GLYPH_INFO_SURFACE |
 					     CAIRO_SCALED_GLYPH_INFO_METRICS,
 					     &scaled_glyph);
 	if (status != CAIRO_STATUS_SUCCESS)
@@ -2924,14 +2975,7 @@ _cairo_xlib_surface_emit_glyphs (cairo_xlib_surface_t *dst,
 
 	/* Glyph skipping:
 	 *
-	 * We skip any initial size-zero glyphs to avoid an X server bug (present
-	 * in at least Xorg 7.1 without EXA) which stops rendering glyphs after
-	 * the first zero-size glyph.  However, we don't skip all size-zero
-	 * glyphs, since that will force a new element at every space.  We
-	 * skip initial size-zero glyphs and hope that it's enough.  Since
-	 * Xft never exposed that bug, this assumption should be correct.
-	 *
-	 * We also skip any glyphs that have troublesome coordinates.  We want
+	 * We skip any glyphs that have troublesome coordinates.  We want
 	 * to make sure that (glyph2.x - (glyph1.x + glyph1.width)) fits in
 	 * a signed 16bit integer, otherwise it will overflow in the render
 	 * protocol.
@@ -2945,8 +2989,7 @@ _cairo_xlib_surface_emit_glyphs (cairo_xlib_surface_t *dst,
 	 * Anyway, we will allow positions in the range -1024..15359.  That
 	 * will buy us a few more years before this stops working.
 	 */
-	if ((!num_out_glyphs && !(scaled_glyph->surface->width && scaled_glyph->surface->height)) ||
-	    (((this_x+1024)|(this_y+1024))&~0x3fffu)) {
+	if (((this_x+1024)|(this_y+1024))&~0x3fffu) {
 	    glyphs[i].index = GLYPH_INDEX_SKIP;
 	    continue;
 	}
@@ -3002,7 +3045,7 @@ _cairo_xlib_surface_emit_glyphs (cairo_xlib_surface_t *dst,
 	if (scaled_glyph->surface_private == NULL) {
 	    status = _cairo_xlib_surface_add_glyph (dst->dpy,
 		                                    scaled_font,
-						    scaled_glyph);
+						    &scaled_glyph);
 	    if (status)
 		return status;
 	    scaled_glyph->surface_private = (void *) 1;