Mercurial > sdl-ios-xcode
view docs/man3/SDL_JoystickGetAxis.3 @ 1544:ab1e4c41ab71
Fixed bug #33
Mike Frysinger wrote:
> with libsdl-1.2.9, some games (like bomberclone) started
> segfaulting in Gentoo
[...snip...]
> the last change in the last hunk:
[...snip...]
> if i change the statement to read:
> (table[which].blit_features & GetBlitFeatures()) == GetBlitFeatures()
> bomberclone no longer segfaults on my box
Alex Volkov wrote:
> The test "(table[which].blit_features & GetBlitFeatures()) ==
> table[which].blit_features)" is correct, and the previous
> "(table[which].cpu_mmx == SDL_HasMMX())" was actually broken.
I think there is potentially a slightly different cause of the above problem.
During the introduction of the Altivec code, the blit_table struct field
'alpha' got changed from a straightforward enum to a bitmask, which makes
perfect sense by itself. However, now the table driven blitter selection code
in SDL_CalculateBlitN() can choose the wrong blitters when searching for a
NO_ALPHA blitter because of the following code:
int a_need = 0;
...
(a_need & table[which].alpha) == a_need &&
When searching through the normal_blit_2[] table, a SET_ALPHA blitter (like
Blit_RGB565_ARGB8888) can now be selected instead of a NO_ALPHA one, causing
alpha channel bits to appear in a non-alpha destination surface. I suppose this
could theoretically be an indirect cause of the segfault mentioned above.
I *think* this can be fixed by changing to
int a_need = NO_ALPHA;
author | Sam Lantinga <slouken@libsdl.org> |
---|---|
date | Wed, 15 Mar 2006 15:47:49 +0000 |
parents | e5bc29de3f0a |
children | 546f7c1eb755 |
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.TH "SDL_JoystickGetAxis" "3" "Tue 11 Sep 2001, 23:00" "SDL" "SDL API Reference" .SH "NAME" SDL_JoystickGetAxis\- Get the current state of an axis .SH "SYNOPSIS" .PP \fB#include "SDL\&.h" .sp \fBSint16 \fBSDL_JoystickGetAxis\fP\fR(\fBSDL_Joystick *joystick, int axis\fR); .SH "DESCRIPTION" .PP \fBSDL_JoystickGetAxis\fP returns the current state of the given \fBaxis\fR on the given \fBjoystick\fR\&. .PP On most modern joysticks the X axis is usually represented by \fBaxis\fR 0 and the Y axis by \fBaxis\fR 1\&. The value returned by \fBSDL_JoystickGetAxis\fP is a signed integer (-32768 to 32768) representing the current position of the \fBaxis\fR, it maybe necessary to impose certain tolerances on these values to account for jitter\&. It is worth noting that some joysticks use axes 2 and 3 for extra buttons\&. .SH "RETURN VALUE" .PP Returns a 16-bit signed integer representing the current position of the \fBaxis\fR\&. .SH "EXAMPLES" .PP .PP .nf \f(CWSint16 x_move, y_move; SDL_Joystick *joy1; \&. \&. x_move=SDL_JoystickGetAxis(joy1, 0); y_move=SDL_JoystickGetAxis(joy1, 1);\fR .fi .PP .SH "SEE ALSO" .PP \fI\fBSDL_JoystickNumAxes\fP\fR ...\" created by instant / docbook-to-man, Tue 11 Sep 2001, 23:00