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xcb: Handle a wider range of glyph positions

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_can_composite_glyphs() checks that the position of each glyph can be
represented as a 16-bit offset from the destination origin.

Fixes https://bugs.freedesktop.org/show_bug.cgi?id=31897
This commit is contained in:
Andrea Canciani 2010-12-22 11:30:45 +01:00
parent 10bae9d9ce
commit 588dead005
1 changed files with 9 additions and 17 deletions
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26
src/cairo-xcb-surface-render.c
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@ -4447,25 +4447,8 @@ _composite_glyphs (void *closure,
glyph_cache[cache_index] = scaled_glyph;
}
/* Glyph skipping:
*
* 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.
* To ensure this, we'll make sure that (glyph2.x - glyph1.x) fits in
* a signed 15bit integer. The trivial option would be to allow
* coordinates -8192..8192, but that's kinda dull. It probably will
* take a decade or so to get monitors 8192x4096 or something. A
* negative value of -8192 on the other hand, is absolutely useless.
* Note that we do want to allow some negative positions. The glyph
* may start off the screen but part of it make it to the screen.
* Anyway, we will allow positions in the range -4096..122887. That
* will buy us a few more years before this stops working.
*/
this_x = _cairo_lround (info->glyphs[i].d.x) - dst_x;
this_y = _cairo_lround (info->glyphs[i].d.y) - dst_y;
assert (! (((this_x+4096) | (this_y+4096)) & ~0x3fffu));
this_glyphset_info = _cairo_xcb_scaled_glyph_get_glyphset_info (scaled_glyph);
if (glyphset_info == NULL)
@ -4492,8 +4475,17 @@ _composite_glyphs (void *closure,
* prefer the latter is the fact that Xserver ADDs all glyphs
* to the mask first, and then composes that to final surface,
* though it's not a big deal.
*
* If the glyph has a coordinate which cannot be represented
* as a 16-bit offset from the previous glyph, flush the
* current chunk. The current glyph will be the first one in
* the next chunk, thus its coordinates will be an offset from
* the destination origin. This offset is guaranteed to be
* representable as 16-bit offset in _can_composite_glyphs().
*/
if (request_size + width > max_request_size - _cairo_sz_x_glyph_elt_t ||
this_x - x > INT16_MAX || this_x - x < INT16_MIN ||
this_y - y > INT16_MAX || this_y - y < INT16_MIN ||
this_glyphset_info != glyphset_info)
{
status = _emit_glyphs_chunk (dst, op, src,