[cairo] Always keep text in foreground?

[Daniel Goldman]

Thanks for the replies. I ended up reading the data file twice, stroking  and 
filling the polygons first pass, and applying the labels the second  pass, as 
shown in a simplified form by Arjen. It was somewhat  inconvenient, but not a 
big deal. I already knew that was a possible  solution. 


It's a big data file, which I would rather not read twice. But  it's still fast 
enough. It would even be possible to split the  data file into two data files: 
one with the points, the other with the  labels. But I'll only do that if ever a 
speed problem. 


The reason I posted was to understand cairo better, to clarify if cairo has the 
luxury of  automatically keeping the text in the foreground. I appreciate 
Benjamin  explaining why this is not the case. I can live without the  luxury. 


Daniel

>
>If you code is like this:
>
>
>for (x = something with A and B)
>{
>    my_draw_polygon(x);
>    my_draw_label(x);
>}
>
>
>Change it to:
>
>
>for (x = something with A and B)
>{
>    my_draw_polygon(x);
>}
>
>
>for (x = something with A and B)
>{
>    my_draw_label(x);
>}
>
>
>Groeten, Arjen
>
>
>Hi,
>>
>>I make the path for polygon A, stroke it, fill with red, and apply "Long Label
>>A"  using pango. Next, I stroke polygon B, fill with blue, and apply "Label 
B".
>>Everything is  great, expect the polygon B fill overlaps and hides part of 
>"Long
>>Label A" text.
>>
>>
>>-----------------------
>>| Long Label A        |
>>|         |   Label B |
>>-----------------------
>>    A         B
>>
>>How do I always keep the text in the z-order foreground? I already know about
>>decreasing  font size and making the labels appear on multiple lines to 
prevent
>>overlaps. I'm looking for something to use when overlap cannot be prevented. I
>>tried using alpha channel, so the label can show through, but  I lose too much
>>intensity for both text and fill colors.
>>
>>
>>In other words, is there a way to tell cairo / pango "I want this text to 
>always
>>be  foreground", or "I want this fill to always be background".
>>
>>If not, is it possible (or advisable) to write the polygons to one context (I
>>guess), write the text to another context (or whatever), and then overlay the
>>text over the polygons? If this is feasible, could someone sketch out the key
>>functions to use.
>>
>>Perhaps I will end up doing all the polygons first, and then doing all the
>>labels. It's just  inconvenient, since I get all the data for one polygon, its
>>label and the label  positioning, then get all the data for the next polygon,
>>etc.
>>
>>
>>I'm not saying the default behavior (fill overlays previous text) is wrong. 
I'm
>>just hoping I can override it. I looked  through the cairo and pango docs and
>>past postings and couldn't find the answer.
>>
>>
>>Thanks,
>>Daniel
>>--
>>cairo mailing list
>>cairo at cairographics.org
>>http://lists.cairographics.org/mailman/listinfo/cairo
>>
>>
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