#36 create sub-bitmap of sub-bitmap

In Windows (MinGW, WinME) and allegro 3.9.40, creating
a sub-bitmap of a sub-bitmap doesn't work the same as
DOS (djgpp), the new bitmap is offset. Please see
example program below - the output should be a cross
in the centre of a box.

Peter

[Anonymous]

Example C++ program

[Robert J Ohannessian]

Logged In: YES
user_id=41801

It seems that the bug only affects the screen under Windows, and that hline and vline are working corectly. Here's another test code, which displays the problem in a better light. The light blue line and the circles should be drawn at the center of the screen (inside the sub-sub-bitmap) but they are not.

<pre>

include <allegro.h>

int main()
{
BITMAP m, s;

allegro_init();
install_keyboard();
set_gfx_mode(GFX_AUTODETECT, 640, 480, 0, 0);

m = create_sub_bitmap(screen, 160,120, 320, 240);
s = create_sub_bitmap(m,       80, 60, 160, 120);

rect(screen, 160,120, 160+320-1, 120+240-1, makecol(0, 255, 0));
rect(screen, 160+80,120+60, 160+80+160-1, 120+60+120-1, makecol(0, 255, 0));

rect(m, 0, 0, 319, 239, makecol(255, 0, 0));
rect(s, 0, 0, 159, 119, makecol(255, 0, 0));

line(s, 0, 0, 159, 119, makecol(255, 255, 255));
line(s, 0, 0, 159, 119, makecol(0, 255, 255));

circle(s, 80, 60, 30, makecol(255, 255, 0));
circlefill(s, 80, 60, 20, makecol(255, 255, 0));

hline(s, 1, 60, 158, makecol(128, 128, 255));

readkey();

set_gfx_mode(GFX_TEXT,0,0,0,0);
return 0;

} END_OF_MAIN();
</pre>

[Eric Botcazou]

Logged In: YES
user_id=113920

The fix is in the CVS tree, thanks to both of you for the
report and the exegesis ;-)
hline() and vline() were correctly working if the driver
was hw-accelerated because they are hw-accelerated
primitives, contrary to oblique lines and circles.

[Eric Botcazou]

Logged In: YES
user_id=113920

The fix is in the CVS tree, thanks to both of you for the
report and the exegesis ;-)
hline() and vline() were correctly working if the driver
was hw-accelerated because they are hw-accelerated
primitives, contrary to oblique lines and circles.