view docs/html/sdlcreatergbsurface.html @ 1212:7663bb0f52c7

To: sdl@libsdl.org From: Christian Walther <cwalther@gmx.ch> Date: Thu, 15 Dec 2005 21:19:53 +0100 Subject: [SDL] More mouse enhancements for Mac OS X The attached patch brings two more enhancements to mouse handling on Mac OS X (Quartz): 1. Currently, after launching an SDL application, SDL's notion of the mouse position is stuck in the top left corner (0,0) until the first time the mouse is moved. That's because the UpdateMouse() function isn't implemented in the Quartz driver. This patch adds it. 2. When grabbing input while the mouse cursor is hidden, the function CGAssociateMouseAndMouseCursorPosition(0) is called, which prevents the system's notion of the mouse location from moving (and therefore leaving the SDL window) even when the mouse is moved. However, apparently the Wacom tablet driver (and maybe other special pointing device drivers) doesn't care about that setting and still allows the mouse location to go outside of the window. Interestingly, the system cursor, which is made visible by the existing code in SDL in that case, does not follow the mouse location, but appears in the middle of the SDL window. The mouse location being outside of the window however means that mouse button events go to background applications (or the dock or whatever is there), which is very confusing to the user who sees no cursor outside of the SDL window. I have not found any way of intercepting these events (and that's probably by design, as "normal" applications shouldn't prevent the user from bringing other applications' windows to the front by clicking on them). An idea would be placing a fully transparent, screen-filling window in front of everything, but I fear that this might affect rendering performance (by doing unnecessary compositing, using up memory, or whatever). The deluxe solution to the problem would be talking to the tablet driver using AppleEvents to tell it to constrain its mapped area to the window (see Wacom's "TabletEventDemo" sample app, http://www.wacomeng.com/devsupport/mac/downloads.html), but I think that the bloat that solution would add to SDL would outweigh its usefulness. What I did instead in my patch is reassociating mouse and cursor when the mouse leaves the window while an invisible grab is in effect, and restoring the grab when the window is entered. That way, the grab can still be effectively broken by a tablet, but at least it's obvious to the user that it is broken. That change is minimal - it doesn't affect operation with a mouse (or a trackpad), and the code that it adds is not executed on every PumpEvents() call, only when entering and leaving the window. Unless there are any concerns about the patch, please apply. Feel free to shorten the lengthy comment in SDL_QuartzEvents.m if you think it's too verbose. Thanks -Christian
author Ryan C. Gordon <icculus@icculus.org>
date Mon, 02 Jan 2006 00:31:00 +0000
parents 355632dca928
children
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><H1
><A
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>SDL_CreateRGBSurface</H1
><DIV
CLASS="REFNAMEDIV"
><A
NAME="AEN1773"
></A
><H2
>Name</H2
>SDL_CreateRGBSurface&nbsp;--&nbsp;Create an empty SDL_Surface</DIV
><DIV
CLASS="REFSYNOPSISDIV"
><A
NAME="AEN1776"
></A
><H2
>Synopsis</H2
><DIV
CLASS="FUNCSYNOPSIS"
><A
NAME="AEN1777"
></A
><P
></P
><PRE
CLASS="FUNCSYNOPSISINFO"
>#include "SDL.h"</PRE
><P
><CODE
><CODE
CLASS="FUNCDEF"
>SDL_Surface *<B
CLASS="FSFUNC"
>SDL_CreateRGBSurface</B
></CODE
>(Uint32 flags, int width, int height, int depth, Uint32 Rmask, Uint32 Gmask, Uint32 Bmask, Uint32 Amask);</CODE
></P
><P
></P
></DIV
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN1783"
></A
><H2
>Description</H2
><P
>Allocate an empty surface (must be called after <A
HREF="sdlsetvideomode.html"
>SDL_SetVideoMode</A
>)</P
><P
>If <TT
CLASS="PARAMETER"
><I
>depth</I
></TT
> is 8 bits an empty palette is allocated for the surface, otherwise a 'packed-pixel' <A
HREF="sdlpixelformat.html"
><SPAN
CLASS="STRUCTNAME"
>SDL_PixelFormat</SPAN
></A
> is created using the <TT
CLASS="PARAMETER"
><I
>[RGBA]mask</I
></TT
>'s provided (see <A
HREF="sdlpixelformat.html"
><SPAN
CLASS="STRUCTNAME"
>SDL_PixelFormat</SPAN
></A
>). The <TT
CLASS="PARAMETER"
><I
>flags</I
></TT
> specifies the type of surface that should be created, it is an OR'd combination of the following possible values.</P
><DIV
CLASS="INFORMALTABLE"
><A
NAME="AEN1795"
></A
><P
></P
><TABLE
BORDER="1"
CLASS="CALSTABLE"
><TBODY
><TR
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="LITERAL"
>SDL_SWSURFACE</TT
></TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
>SDL will create the surface in system memory. This improves the performance of pixel level access, however you may not be able to take advantage of some types of hardware blitting.</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="LITERAL"
>SDL_HWSURFACE</TT
></TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
>SDL will attempt to create the surface in video memory. This will allow SDL to take advantage of Video-&#62;Video blits (which are often accelerated).</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="LITERAL"
>SDL_SRCCOLORKEY</TT
></TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
>This flag turns on colourkeying for blits from this surface. If
<TT
CLASS="LITERAL"
>SDL_HWSURFACE</TT
> is also specified and colourkeyed blits
are hardware-accelerated, then SDL will attempt to place the surface in
video memory.
Use <A
HREF="sdlsetcolorkey.html"
><TT
CLASS="FUNCTION"
>SDL_SetColorKey</TT
></A
>
to set or clear this flag after surface creation.</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="LITERAL"
>SDL_SRCALPHA</TT
></TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
>This flag turns on alpha-blending for blits from this surface. If
<TT
CLASS="LITERAL"
>SDL_HWSURFACE</TT
> is also specified and alpha-blending blits
are hardware-accelerated, then the surface will be placed in video memory if
possible.
Use <A
HREF="sdlsetalpha.html"
><TT
CLASS="FUNCTION"
>SDL_SetAlpha</TT
></A
> to
set or clear this flag after surface creation.</TD
></TR
></TBODY
></TABLE
><P
></P
></DIV
><DIV
CLASS="NOTE"
><BLOCKQUOTE
CLASS="NOTE"
><P
><B
>Note: </B
>If an alpha-channel is specified (that is, if <TT
CLASS="PARAMETER"
><I
>Amask</I
></TT
> is
nonzero), then the <TT
CLASS="LITERAL"
>SDL_SRCALPHA</TT
> flag is automatically
set. You may remove this flag by calling 
<A
HREF="sdlsetalpha.html"
><TT
CLASS="FUNCTION"
>SDL_SetAlpha</TT
></A
>
after surface creation.</P
></BLOCKQUOTE
></DIV
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN1826"
></A
><H2
>Return Value</H2
><P
>Returns the created surface, or <SPAN
CLASS="RETURNVALUE"
>NULL</SPAN
> upon error.</P
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN1830"
></A
><H2
>Example</H2
><PRE
CLASS="PROGRAMLISTING"
>    /* Create a 32-bit surface with the bytes of each pixel in R,G,B,A order,
       as expected by OpenGL for textures */
    SDL_Surface *surface;
    Uint32 rmask, gmask, bmask, amask;

    /* SDL interprets each pixel as a 32-bit number, so our masks must depend
       on the endianness (byte order) of the machine */
#if SDL_BYTEORDER == SDL_BIG_ENDIAN
    rmask = 0xff000000;
    gmask = 0x00ff0000;
    bmask = 0x0000ff00;
    amask = 0x000000ff;
#else
    rmask = 0x000000ff;
    gmask = 0x0000ff00;
    bmask = 0x00ff0000;
    amask = 0xff000000;
#endif

    surface = SDL_CreateRGBSurface(SDL_SWSURFACE, width, height, 32,
                                   rmask, gmask, bmask, amask);
    if(surface == NULL) {
        fprintf(stderr, "CreateRGBSurface failed: %s\n", SDL_GetError());
        exit(1);
    }</PRE
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN1833"
></A
><H2
>See Also</H2
><P
><A
HREF="sdlcreatergbsurfacefrom.html"
><TT
CLASS="FUNCTION"
>SDL_CreateRGBSurfaceFrom</TT
></A
>,
<A
HREF="sdlfreesurface.html"
><TT
CLASS="FUNCTION"
>SDL_FreeSurface</TT
></A
>,
<A
HREF="sdlsetvideomode.html"
><TT
CLASS="FUNCTION"
>SDL_SetVideoMode</TT
></A
>,
<A
HREF="sdllocksurface.html"
><TT
CLASS="FUNCTION"
>SDL_LockSurface</TT
></A
>,
<A
HREF="sdlpixelformat.html"
><SPAN
CLASS="STRUCTNAME"
>SDL_PixelFormat</SPAN
></A
>,
<A
HREF="sdlsurface.html"
><SPAN
CLASS="STRUCTNAME"
>SDL_Surface</SPAN
></A
>
<A
HREF="sdlsetalpha.html"
><TT
CLASS="FUNCTION"
>SDL_SetAlpha</TT
></A
>
<A
HREF="sdlsetcolorkey.html"
><TT
CLASS="FUNCTION"
>SDL_SetColorKey</TT
></A
></P
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