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On 12/31/21 2:21 PM, Albrecht Schlosser
wrote:
On 12/31/21 8:54 PM Greg Ercolano
wrote:
Trying to just draw a simple "X" to all four corners of the
Fl_Cairo_Window.
Having trouble getting this working.
My understanding is the default coordinate space of cairo is:
(0.0, 0.0) = top/left
(1.0, 1.0) = bottom/right
..and to use FLTK's coordinate space, you'd use cairo_scale(cr,
w(), h())
to convert to the window's integer coordinate space.
Here's what I have (it doesn't work - weird behavior).
Am I missing something?
I don't know how the coordinate systems are (or should be)
translated, but if I change only your two drawing code lines to
cairo_move_to(cr, 0.0, 0.0); cairo_line_to(cr, 1.0, 1.0); // draw diagonal "\" cairo_move_to(cr, 0.0, 1.0); cairo_line_to(cr, 1.0, 0.0); // draw diagonal "/"
the "green X" works for me.
If you look at test/cairo_test.cxx you can see that all the
"buttons" are drawn inside the (0.0 ... 1.0) coordinate space,
using the same cairo_scale instruction as you do.
Thanks, I get that too.
Though still not sure how to achieve FLTK drawing coordinates.
One would think if setting the scale to (w,h) gets you a
(0,0,1,1) coord system,
then a scale of (1.0/w, 1.0/h) would achieve a (0,0,w,h) coord
system,
but that doesn't seem to work. Or at least I'm not seeing
anything.
Maybe the scale is affecting the line width coordinate space, but
doing
the above and setting the line width to 1.0 doesn't work.. hmm.
Anyway, that's what I'm struggling with.
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