summaryrefslogtreecommitdiffstats
path: root/src/mesa/swrast
diff options
context:
space:
mode:
Diffstat (limited to 'src/mesa/swrast')
-rw-r--r--src/mesa/swrast/s_alphabuf.c16
-rw-r--r--src/mesa/swrast/s_auxbuffer.c121
-rw-r--r--src/mesa/swrast/s_auxbuffer.h41
-rw-r--r--src/mesa/swrast/s_buffers.c109
-rw-r--r--src/mesa/swrast/s_context.c9
-rw-r--r--src/mesa/swrast/s_context.h3
-rw-r--r--src/mesa/swrast/s_span.c4
-rw-r--r--src/mesa/swrast/swrast.h16
8 files changed, 256 insertions, 63 deletions
diff --git a/src/mesa/swrast/s_alphabuf.c b/src/mesa/swrast/s_alphabuf.c
index e0468a4c91f..b563baf39a0 100644
--- a/src/mesa/swrast/s_alphabuf.c
+++ b/src/mesa/swrast/s_alphabuf.c
@@ -114,13 +114,13 @@ _swrast_clear_alpha_buffers( GLcontext *ctx )
for (bufferBit = 1; bufferBit <= 8; bufferBit = bufferBit << 1) {
if (bufferBit & ctx->Color._DrawDestMask) {
GLchan *buffer;
- if (bufferBit == FRONT_LEFT_BIT) {
+ if (bufferBit == DD_FRONT_LEFT_BIT) {
buffer = ctx->DrawBuffer->FrontLeftAlpha;
}
- else if (bufferBit == FRONT_RIGHT_BIT) {
+ else if (bufferBit == DD_FRONT_RIGHT_BIT) {
buffer = ctx->DrawBuffer->FrontRightAlpha;
}
- else if (bufferBit == BACK_LEFT_BIT) {
+ else if (bufferBit == DD_BACK_LEFT_BIT) {
buffer = ctx->DrawBuffer->BackLeftAlpha;
}
else {
@@ -175,17 +175,17 @@ GLchan *get_alpha_buffer( GLcontext *ctx )
{
SWcontext *swrast = SWRAST_CONTEXT(ctx);
- switch (swrast->CurrentBuffer) {
- case FRONT_LEFT_BIT:
+ switch (swrast->CurrentBufferBit) {
+ case DD_FRONT_LEFT_BIT:
return ctx->DrawBuffer->FrontLeftAlpha;
break;
- case BACK_LEFT_BIT:
+ case DD_BACK_LEFT_BIT:
return ctx->DrawBuffer->BackLeftAlpha;
break;
- case FRONT_RIGHT_BIT:
+ case DD_FRONT_RIGHT_BIT:
return ctx->DrawBuffer->FrontRightAlpha;
break;
- case BACK_RIGHT_BIT:
+ case DD_BACK_RIGHT_BIT:
return ctx->DrawBuffer->BackRightAlpha;
break;
default:
diff --git a/src/mesa/swrast/s_auxbuffer.c b/src/mesa/swrast/s_auxbuffer.c
new file mode 100644
index 00000000000..ca36d90ded8
--- /dev/null
+++ b/src/mesa/swrast/s_auxbuffer.c
@@ -0,0 +1,121 @@
+/*
+ * Mesa 3-D graphics library
+ * Version: 6.1
+ *
+ * Copyright (C) 1999-2004 Brian Paul All Rights Reserved.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included
+ * in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
+ * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
+ * BRIAN PAUL BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
+ * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+
+
+#include "glheader.h"
+#include "imports.h"
+
+#include "s_auxbuffer.h"
+#include "s_context.h"
+
+
+
+void
+_swrast_alloc_aux_buffers( GLframebuffer *buffer )
+{
+ GLuint i;
+
+ for (i = 0; i < buffer->Visual.numAuxBuffers; i++) {
+ if (buffer->AuxBuffers[i]) {
+ _mesa_free(buffer->AuxBuffers[i]);
+ buffer->AuxBuffers[i] = NULL;
+ }
+
+ buffer->AuxBuffers[i] = _mesa_malloc(buffer->Width * buffer->Height
+ * 4 * sizeof(GLchan));
+ }
+}
+
+
+
+/* RGBA */
+#define NAME(PREFIX) PREFIX##_aux
+#define SPAN_VARS \
+ const SWcontext *swrast = SWRAST_CONTEXT(ctx);
+#define INIT_PIXEL_PTR(P, X, Y) \
+ GLchan *P = swrast->CurAuxBuffer + ((Y) * ctx->DrawBuffer->Width + (X)) * 4; \
+ assert(swrast->CurAuxBuffer);
+
+#define INC_PIXEL_PTR(P) P += 4
+#if CHAN_TYPE == GL_FLOAT
+#define STORE_RGB_PIXEL(P, X, Y, R, G, B) \
+ P[0] = MAX2((R), 0.0F); \
+ P[1] = MAX2((G), 0.0F); \
+ P[2] = MAX2((B), 0.0F); \
+ P[3] = CHAN_MAXF
+#define STORE_RGBA_PIXEL(P, X, Y, R, G, B, A) \
+ P[0] = MAX2((R), 0.0F); \
+ P[1] = MAX2((G), 0.0F); \
+ P[2] = MAX2((B), 0.0F); \
+ P[3] = CLAMP((A), 0.0F, CHAN_MAXF)
+#else
+#define STORE_RGB_PIXEL(P, X, Y, R, G, B) \
+ P[0] = R; P[1] = G; P[2] = B; P[3] = CHAN_MAX
+#define STORE_RGBA_PIXEL(P, X, Y, R, G, B, A) \
+ P[0] = R; P[1] = G; P[2] = B; P[3] = A
+#endif
+#define FETCH_RGBA_PIXEL(R, G, B, A, P) \
+ R = P[0]; G = P[1]; B = P[2]; A = P[3]
+#include "swrast/s_spantemp.h"
+
+
+
+/**
+ * Called from driver's SetBuffer() function to choose an aux buffer.
+ */
+void
+_swrast_use_aux_buffer(GLcontext *ctx, GLframebuffer *buffer, GLuint bufferBit)
+{
+ SWcontext *swrast = SWRAST_CONTEXT(ctx);
+
+ switch (bufferBit) {
+ case DD_AUX0_BIT:
+ ASSERT(buffer->Visual.numAuxBuffers >= 1);
+ swrast->CurAuxBuffer = ctx->DrawBuffer->AuxBuffers[0];
+ break;
+ case DD_AUX1_BIT:
+ ASSERT(buffer->Visual.numAuxBuffers >= 2);
+ swrast->CurAuxBuffer = ctx->DrawBuffer->AuxBuffers[1];
+ break;
+ case DD_AUX2_BIT:
+ ASSERT(buffer->Visual.numAuxBuffers >= 3);
+ swrast->CurAuxBuffer = ctx->DrawBuffer->AuxBuffers[2];
+ break;
+ case DD_AUX3_BIT:
+ ASSERT(buffer->Visual.numAuxBuffers >= 4);
+ swrast->CurAuxBuffer = ctx->DrawBuffer->AuxBuffers[3];
+ break;
+ default:
+ swrast->CurAuxBuffer = NULL;
+ }
+
+ swrast->Driver.WriteRGBASpan = write_rgba_span_aux;
+ swrast->Driver.WriteRGBSpan = write_rgb_span_aux;
+ swrast->Driver.WriteMonoRGBASpan = write_monorgba_span_aux;
+ swrast->Driver.WriteRGBAPixels = write_rgba_pixels_aux;
+ swrast->Driver.WriteMonoRGBAPixels = write_monorgba_pixels_aux;
+ swrast->Driver.ReadRGBASpan = read_rgba_span_aux;
+ swrast->Driver.ReadRGBAPixels = read_rgba_pixels_aux;
+}
+
diff --git a/src/mesa/swrast/s_auxbuffer.h b/src/mesa/swrast/s_auxbuffer.h
new file mode 100644
index 00000000000..48fb6951a18
--- /dev/null
+++ b/src/mesa/swrast/s_auxbuffer.h
@@ -0,0 +1,41 @@
+/*
+ * Mesa 3-D graphics library
+ * Version: 6.1
+ *
+ * Copyright (C) 1999-2004 Brian Paul All Rights Reserved.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included
+ * in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
+ * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
+ * BRIAN PAUL BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
+ * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+
+
+#ifndef S_AUXBUFFER_H
+#define S_AUXBUFFER_H
+
+
+#include "context.h"
+
+
+extern void
+_swrast_alloc_aux_buffers( GLframebuffer *buffer );
+
+
+extern void
+_swrast_use_aux_buffer(GLcontext *ctx, GLframebuffer *buffr, GLuint bufferBit);
+
+
+#endif /* S_AUXBUFFER_H */
diff --git a/src/mesa/swrast/s_buffers.c b/src/mesa/swrast/s_buffers.c
index 894cc4060f0..7888bb618f7 100644
--- a/src/mesa/swrast/s_buffers.c
+++ b/src/mesa/swrast/s_buffers.c
@@ -1,6 +1,6 @@
/*
* Mesa 3-D graphics library
- * Version: 6.0.1
+ * Version: 6.1
*
* Copyright (C) 1999-2004 Brian Paul All Rights Reserved.
*
@@ -30,16 +30,17 @@
#include "s_accum.h"
#include "s_alphabuf.h"
+#include "s_auxbuffer.h"
#include "s_context.h"
#include "s_depth.h"
#include "s_masking.h"
#include "s_stencil.h"
-
-
-/*
+/**
* Clear the color buffer when glColorMask or glIndexMask is in effect.
+ * We'll have specified which color buffer to clear by previously
+ * calling Driver.SetBuffer().
*/
static void
clear_color_buffer_with_masking( GLcontext *ctx )
@@ -86,9 +87,10 @@ clear_color_buffer_with_masking( GLcontext *ctx )
}
-
-/*
+/**
* Clear a color buffer without index/channel masking.
+ * We'll have specified which color buffer to clear by previously
+ * calling Driver.SetBuffer().
*/
static void
clear_color_buffer(GLcontext *ctx)
@@ -131,11 +133,10 @@ clear_color_buffer(GLcontext *ctx)
}
-
-/*
- * Clear the front/back/left/right color buffers.
- * This function is usually only called if we need to clear the
- * buffers with masking.
+/**
+ * Clear the front/back/left/right/aux color buffers.
+ * This function is usually only called if the device driver can't
+ * clear its own color buffers for some reason (such as with masking).
*/
static void
clear_color_buffers(GLcontext *ctx)
@@ -145,7 +146,7 @@ clear_color_buffers(GLcontext *ctx)
GLuint bufferBit;
/* loop over four possible dest color buffers */
- for (bufferBit = 1; bufferBit <= 8; bufferBit = bufferBit << 1) {
+ for (bufferBit = 1; bufferBit <= DD_AUX3_BIT; bufferBit <<= 1) {
if (bufferBit & ctx->Color._DrawDestMask) {
(*swrast->Driver.SetBuffer)(ctx, ctx->DrawBuffer, bufferBit);
@@ -163,7 +164,12 @@ clear_color_buffers(GLcontext *ctx)
}
-
+/**
+ * Called via the device driver's ctx->Driver.Clear() function if the
+ * device driver can't clear one or more of the buffers itself.
+ * \param mask bitwise-OR of DD_*_BIT flags.
+ * \param all if GL_TRUE, clear whole buffer, else clear specified region.
+ */
void
_swrast_Clear( GLcontext *ctx, GLbitfield mask,
GLboolean all,
@@ -172,13 +178,18 @@ _swrast_Clear( GLcontext *ctx, GLbitfield mask,
SWcontext *swrast = SWRAST_CONTEXT(ctx);
#ifdef DEBUG
{
- GLbitfield legalBits = DD_FRONT_LEFT_BIT |
+ const GLbitfield legalBits =
+ DD_FRONT_LEFT_BIT |
DD_FRONT_RIGHT_BIT |
DD_BACK_LEFT_BIT |
DD_BACK_RIGHT_BIT |
DD_DEPTH_BIT |
DD_STENCIL_BIT |
- DD_ACCUM_BIT;
+ DD_ACCUM_BIT |
+ DD_AUX0_BIT |
+ DD_AUX1_BIT |
+ DD_AUX2_BIT |
+ DD_AUX3_BIT;
assert((mask & (~legalBits)) == 0);
}
#endif
@@ -187,23 +198,34 @@ _swrast_Clear( GLcontext *ctx, GLbitfield mask,
/* do software clearing here */
if (mask) {
- if (mask & ctx->Color._DrawDestMask) clear_color_buffers(ctx);
- if (mask & GL_DEPTH_BUFFER_BIT) _swrast_clear_depth_buffer(ctx);
- if (mask & GL_ACCUM_BUFFER_BIT) _swrast_clear_accum_buffer(ctx);
- if (mask & GL_STENCIL_BUFFER_BIT) _swrast_clear_stencil_buffer(ctx);
- }
-
- /* clear software-based alpha buffer(s) */
- if ( (mask & GL_COLOR_BUFFER_BIT)
- && ctx->DrawBuffer->UseSoftwareAlphaBuffers
- && ctx->Color.ColorMask[ACOMP]) {
- _swrast_clear_alpha_buffers( ctx );
+ if (mask & ctx->Color._DrawDestMask) {
+ clear_color_buffers(ctx);
+ /* clear software-based alpha buffer(s) */
+ if (ctx->DrawBuffer->UseSoftwareAlphaBuffers
+ && ctx->Color.ColorMask[ACOMP]) {
+ _swrast_clear_alpha_buffers( ctx );
+ }
+ }
+ if (mask & DD_DEPTH_BIT) {
+ _swrast_clear_depth_buffer(ctx);
+ }
+ if (mask & DD_ACCUM_BIT) {
+ _swrast_clear_accum_buffer(ctx);
+ }
+ if (mask & DD_STENCIL_BIT) {
+ _swrast_clear_stencil_buffer(ctx);
+ }
}
RENDER_FINISH(swrast,ctx);
}
+/**
+ * Typically called via ctx->Driver.ResizeBuffers().
+ * Reallocate all software-based depth/stencil/accum/etc buffers
+ * to match current window dimensions.
+ */
void
_swrast_alloc_buffers( GLframebuffer *buffer )
{
@@ -220,6 +242,9 @@ _swrast_alloc_buffers( GLframebuffer *buffer )
if (buffer->UseSoftwareAlphaBuffers) {
_swrast_alloc_alpha_buffers( buffer );
}
+ if (buffer->UseSoftwareAuxBuffers) {
+ _swrast_alloc_aux_buffers( buffer );
+ }
}
@@ -244,9 +269,9 @@ _swrast_use_read_buffer( GLcontext *ctx )
SWcontext *swrast = SWRAST_CONTEXT(ctx);
/* Do this so the software-emulated alpha plane span functions work! */
- swrast->CurrentBuffer = ctx->Pixel._ReadSrcMask;
+ swrast->CurrentBufferBit = ctx->Pixel._ReadSrcMask;
/* Tell the device driver where to read/write spans */
- (*swrast->Driver.SetBuffer)( ctx, ctx->ReadBuffer, swrast->CurrentBuffer );
+ swrast->Driver.SetBuffer(ctx, ctx->ReadBuffer, swrast->CurrentBufferBit);
}
@@ -270,17 +295,25 @@ _swrast_use_draw_buffer( GLcontext *ctx )
* we loop over multiple color buffers when needed.
*/
- if (ctx->Color._DrawDestMask & FRONT_LEFT_BIT)
- swrast->CurrentBuffer = FRONT_LEFT_BIT;
- else if (ctx->Color._DrawDestMask & BACK_LEFT_BIT)
- swrast->CurrentBuffer = BACK_LEFT_BIT;
- else if (ctx->Color._DrawDestMask & FRONT_RIGHT_BIT)
- swrast->CurrentBuffer = FRONT_RIGHT_BIT;
- else if (ctx->Color._DrawDestMask & BACK_RIGHT_BIT)
- swrast->CurrentBuffer = BACK_RIGHT_BIT;
+ if (ctx->Color._DrawDestMask & DD_FRONT_LEFT_BIT)
+ swrast->CurrentBufferBit = DD_FRONT_LEFT_BIT;
+ else if (ctx->Color._DrawDestMask & DD_BACK_LEFT_BIT)
+ swrast->CurrentBufferBit = DD_BACK_LEFT_BIT;
+ else if (ctx->Color._DrawDestMask & DD_FRONT_RIGHT_BIT)
+ swrast->CurrentBufferBit = DD_FRONT_RIGHT_BIT;
+ else if (ctx->Color._DrawDestMask & DD_BACK_RIGHT_BIT)
+ swrast->CurrentBufferBit = DD_BACK_RIGHT_BIT;
+ else if (ctx->Color._DrawDestMask & DD_AUX0_BIT)
+ swrast->CurrentBufferBit = DD_AUX0_BIT;
+ else if (ctx->Color._DrawDestMask & DD_AUX1_BIT)
+ swrast->CurrentBufferBit = DD_AUX1_BIT;
+ else if (ctx->Color._DrawDestMask & DD_AUX2_BIT)
+ swrast->CurrentBufferBit = DD_AUX2_BIT;
+ else if (ctx->Color._DrawDestMask & DD_AUX3_BIT)
+ swrast->CurrentBufferBit = DD_AUX3_BIT;
else
/* glDrawBuffer(GL_NONE) */
- swrast->CurrentBuffer = FRONT_LEFT_BIT; /* we always have this buffer */
+ swrast->CurrentBufferBit = DD_FRONT_LEFT_BIT; /* we always have this buffer */
- (*swrast->Driver.SetBuffer)( ctx, ctx->DrawBuffer, swrast->CurrentBuffer );
+ swrast->Driver.SetBuffer(ctx, ctx->DrawBuffer, swrast->CurrentBufferBit);
}
diff --git a/src/mesa/swrast/s_context.c b/src/mesa/swrast/s_context.c
index be800d4d594..94b57e4bbfd 100644
--- a/src/mesa/swrast/s_context.c
+++ b/src/mesa/swrast/s_context.c
@@ -91,10 +91,7 @@ _swrast_update_rasterflags( GLcontext *ctx )
* MULTI_DRAW_BIT flag. Also set it if we're drawing to no
* buffers or the RGBA or CI mask disables all writes.
*/
- if (ctx->Color._DrawDestMask != FRONT_LEFT_BIT &&
- ctx->Color._DrawDestMask != BACK_LEFT_BIT &&
- ctx->Color._DrawDestMask != FRONT_RIGHT_BIT &&
- ctx->Color._DrawDestMask != BACK_RIGHT_BIT) {
+ if (_mesa_bitcount(ctx->Color._DrawDestMask) != 1) {
/* more than one color buffer designated for writing (or zero buffers) */
RasterMask |= MULTI_DRAW_BIT;
}
@@ -582,9 +579,9 @@ _swrast_CreateContext( GLcontext *ctx )
swrast->AllowPixelFog = GL_TRUE;
if (ctx->Visual.doubleBufferMode)
- swrast->CurrentBuffer = BACK_LEFT_BIT;
+ swrast->CurrentBufferBit = DD_BACK_LEFT_BIT;
else
- swrast->CurrentBuffer = FRONT_LEFT_BIT;
+ swrast->CurrentBufferBit = DD_FRONT_LEFT_BIT;
/* Optimized Accum buffer */
swrast->_IntegerAccumMode = GL_TRUE;
diff --git a/src/mesa/swrast/s_context.h b/src/mesa/swrast/s_context.h
index 081d2557ad5..d6a14e6b4a0 100644
--- a/src/mesa/swrast/s_context.h
+++ b/src/mesa/swrast/s_context.h
@@ -281,6 +281,7 @@ typedef struct
GLboolean _IntegerAccumMode; /**< Storing unscaled integers? */
GLfloat _IntegerAccumScaler; /**< Implicit scale factor */
+ GLchan *CurAuxBuffer;
/* Working values:
*/
@@ -288,7 +289,7 @@ typedef struct
GLuint NewState;
GLuint StateChanges;
GLenum Primitive; /* current primitive being drawn (ala glBegin) */
- GLuint CurrentBuffer; /* exactly one of FRONT_LEFT_BIT, BACK_LEFT_BIT, etc*/
+ GLbitfield CurrentBufferBit; /* exactly one the of DD_*_BIT buffer bits */
/** Mechanism to allow driver (like X11) to register further
* software rasterization routines.
diff --git a/src/mesa/swrast/s_span.c b/src/mesa/swrast/s_span.c
index 801595d970c..13248fdc7cd 100644
--- a/src/mesa/swrast/s_span.c
+++ b/src/mesa/swrast/s_span.c
@@ -653,7 +653,7 @@ multi_write_index_span( GLcontext *ctx, struct sw_span *span )
ASSERT(span->end < MAX_WIDTH);
/* Set the current read/draw buffer */
- swrast->CurrentBuffer = bufferBit;
+ swrast->CurrentBufferBit = bufferBit;
(*swrast->Driver.SetBuffer)(ctx, ctx->DrawBuffer, bufferBit);
/* make copy of incoming indexes */
@@ -710,7 +710,7 @@ multi_write_rgba_span( GLcontext *ctx, struct sw_span *span )
ASSERT(span->end < MAX_WIDTH);
/* Set the current read/draw buffer */
- swrast->CurrentBuffer = bufferBit;
+ swrast->CurrentBufferBit = bufferBit;
(*swrast->Driver.SetBuffer)(ctx, ctx->DrawBuffer, bufferBit);
/* make copy of incoming colors */
diff --git a/src/mesa/swrast/swrast.h b/src/mesa/swrast/swrast.h
index e1220cff4e1..9447e998808 100644
--- a/src/mesa/swrast/swrast.h
+++ b/src/mesa/swrast/swrast.h
@@ -262,18 +262,18 @@ _swrast_copy_texsubimage3d(GLcontext *ctx,
*/
struct swrast_device_driver {
- void (*SetBuffer)( GLcontext *ctx, GLframebuffer *buffer, GLuint bufferBit);
+ void (*SetBuffer)(GLcontext *ctx, GLframebuffer *buffer, GLuint bufferBit);
/*
- * Specifies the current buffer for span/pixel writing/reading.
+ * Specifies the current color buffer for span/pixel writing/reading.
* buffer indicates which window to write to / read from. Normally,
* this'll be the buffer currently bound to the context, but it doesn't
* have to be!
- * bufferBit indicates which color buffer, one of:
- * FRONT_LEFT_BIT - this buffer always exists
- * BACK_LEFT_BIT - when double buffering
- * FRONT_RIGHT_BIT - when using stereo
- * BACK_RIGHT_BIT - when using stereo and double buffering
- * AUXn_BIT - if aux buffers are implemented
+ * bufferBit indicates which color buffer, exactly one of:
+ * DD_FRONT_LEFT_BIT - this buffer always exists
+ * DD_BACK_LEFT_BIT - when double buffering
+ * DD_FRONT_RIGHT_BIT - when using stereo
+ * DD_BACK_RIGHT_BIT - when using stereo and double buffering
+ * DD_AUXn_BIT - if aux buffers are implemented
*/