OpenEuphoria

Re: [WIN32] 2-D Graphics Engine for Win32

• Posted by Ray Smith <smithr at IX.NET.AU> Nov 16, 2000
• 394 views

Hi,

An Update on the retrace problem with eu3buf.exw:

>The retrace message you receive in eu3buf.exw means your video card
>can't handle something.  I get the same message on my work and 2 home PC's.
>At this stage I haven't even look at what it means, the demo still works
>though, but obviously without "some" effects.

Note: The C demo programs that come with Allegro (ie the ones I have
converted to Euphoria) are for all platforms that Allegro supports.
*Some* features aren't available in all platforms and the functions
request_scroll() and poll_scroll() aren't [fully?] supported under Windows.

I'll leave it in there for now, as it *might* be applicable in a Linux port.

Obviously if you are writing a program for Win9x uses only you wouldn't use
this feature / or you wouldn't show the message since many uses won't have
support for these functions.

See below for the doco from the manual.

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int request_scroll(int x, int y);

This function is used for triple buffering. It requests a hardware scroll
to the specified position, but returns immediately rather than waiting for
a retrace. The scroll will then take place during the next vertical
retrace, but you can carry on running other code in the meantime and use
the poll_scroll() routine to detect when the flip has actually taken place
(see examples/ex3buf.c). Triple buffering is only possible on certain
hardware: it will work in any mode-X resolution if the timer retrace
simulator is active (but this doesn't work correctly under win95), plus it
is supported by the VBE 3.0 and VBE/AF drivers for a limited number of high-
end graphics cards. You can look at the GFX_CAN_TRIPLE_BUFFER bit in the
gfx_capabilities flag to see if it will work with the current driver.

------------

Ray Smith