[Xcb] xcb_image_text_8 Transparent Background

Cinolt cinolt.yk at gmail.com
Sun Jan 2 01:05:45 PST 2011

After trying to use xcb_poly_text_8, I seem to be facing a similar problem
as is described here:

I define a structure:

    char *chars;
    int nchars;
    int delta;
    xcb_font_t font;
  } item;

  item.chars = "Test";
  item.nchars = 4;
  item.delta = 0;
  item.font = 0;

and I call xcb_poly_text_8_checked:

cookie_text = xcb_poly_text_8_checked(c, w, gc, 16, 16, 1, (const
error = xcb_request_check(c, cookie_text);
printf("%d\n", (*error).error_code);

and get the output 16, which in X11/X.h is defined as BadLength. Are there
any examples at all of a working implementation of this function?

On Sun, Jan 2, 2011 at 3:40 AM, Aaron Plattner <aplattner at nvidia.com> wrote:

> On Sat, Jan 01, 2011 at 07:35:30PM -0800, Cinolt wrote:
> > Hello, the xcb_image_text_8 function seems to fill the area of the text
> > with the background color, and in my case it is black if not specified.
> > Is there any way to prevent it from filling in a background color, and
> > only draw the text? Here is a minimal example illustrating my problem, as
> > this only displays a black box when I want to draw black text. Setting
> > XCB_GC_FUNCTION to XCB_GX_CLEAR seems to have no effect.
> I don't think ImageText8 is what you want, then (emphasis mine):
> ImageText8
>           drawable: DRAWABLE
>           gc: GCONTEXT
>           x, y: INT16
>           string: STRING8
>           Errors: Drawable, GContext, Match
>           The x and y coordinates are relative to drawable's origin,
>           and specify the baseline starting position (the initial
> ====>      character origin). The effect is to first fill a
> ====>      destination rectangle with the background pixel defined in
> ====>      gc, and then paint the text with the foreground pixel.
>           The upper left corner of the filled rectangle is at
>                   [x + overall-left, y - font-ascent]
>           the width is
>                   overall-right - overall-left
>           and the height is
>                   font-ascent + font-descent
>           where overall-left, overall-right, font-ascent, and
>           as font-descent are would be returned by a QueryTextExtents
>           call using gc and string.
> ====>      The alu-function and fill-style defined in gc are ignored for
> ====>      this request; the effective alu-function is Copy and the
> ====>      effective fill-style Solid.
>           For fonts defined with two-byte matrix indexing, each STRING8
>           byte is interpreted as a byte2 value of a CHAR2B with a byte1
>           value of zero.
>           GC components: plane-mask, foreground, background, font,
>           subwindow-mode, clip-x-origin, clip-y-origin, clip-mask
> I think what you want is PolyText8.
> -- Aaron
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