Fix up alpha buffer handling for Windows.

- add two new Pixel Format Descriptors that do not have alpha bits to
mirror the two that do.
- add logic to wglChoosePixelFormat to match PFD's with respect to alpha.
- Create/clear software alpha buffer as required.
Now a wgl or GLUT program can control the creation of a software alpha
buffer via the PFD or GLUT parms, respectively.

3 files changed, 53 insertions, 10 deletions

diff --git a/include/GL/wmesa.h b/include/GL/wmesa.h
index 94b61974c37..67ca17f7a4a 100644
--- a/include/GL/wmesa.h
+++ b/include/GL/wmesa.h
@@ -1,4 +1,4 @@
-/* $Id: wmesa.h,v 1.1 1999/08/19 00:55:40 jtg Exp $ */
+/* $Id: wmesa.h,v 1.2 2002/04/23 18:23:32 kschultz Exp $ */
 
 /*
  * Mesa 3-D graphics library
@@ -24,8 +24,17 @@
 
 /*
  * $Log: wmesa.h,v $
- * Revision 1.1  1999/08/19 00:55:40  jtg
- * Initial revision
+ * Revision 1.2  2002/04/23 18:23:32  kschultz
+ * Fix up alpha buffer handling for Windows.
+ * - add two new Pixel Format Descriptors that do not have alpha bits to
+ * mirror the two that do.
+ * - add logic to wglChoosePixelFormat to match PFD's with respect to alpha.
+ * - Create/clear software alpha buffer as required.
+ * Now a wgl or GLUT program can control the creation of a software alpha
+ * buffer via the PFD or GLUT parms, respectively.
+ *
+ * Revision 1.1.1.1  1999/08/19 00:55:40  jtg
+ * Imported sources
  *
  * Revision 3.2  1999/01/03 02:54:45  brianp
  * updated per Ted Jump
@@ -101,13 +110,17 @@ typedef struct wmesa_context *WMesaContext;
  *                    GL_FALSE = color index mode
  *         db_flag - GL_TRUE = double-buffered,
  *                   GL_FALSE = single buffered
+ *         alpha_flag - GL_TRUE = create software alpha buffer,
+ *                      GL_FALSE = no software alpha buffer
  *
  * Note: Indexed mode requires double buffering under Windows.
  *
  * Return:  a WMesa_context or NULL if error.
  */
 extern WMesaContext WMesaCreateContext(HWND hWnd,HPALETTE* pPal,
-                                       GLboolean rgb_flag,GLboolean db_flag);
+                                       GLboolean rgb_flag,
+                                       GLboolean db_flag,
+                                       GLboolean alpha_flag);
 
 
 /*
diff --git a/src/mesa/drivers/windows/wgl.c b/src/mesa/drivers/windows/wgl.c
index 0db57641fe1..62a4c1704ce 100644
--- a/src/mesa/drivers/windows/wgl.c
+++ b/src/mesa/drivers/windows/wgl.c
@@ -1,4 +1,4 @@
-/* $Id: wgl.c,v 1.9 2001/09/18 16:39:38 kschultz Exp $ */
+/* $Id: wgl.c,v 1.10 2002/04/23 18:23:33 kschultz Exp $ */
 
 /*
 * This library is free software; you can redistribute it and/or
@@ -100,6 +100,7 @@ int qt_ext = sizeof(ext) / sizeof(ext[0]);
 
 struct __pixelformat__	pix[] =
 {
+    /* Double Buffer, alpha */
     {	{	sizeof(PIXELFORMATDESCRIPTOR),	1,
         PFD_DRAW_TO_WINDOW|PFD_SUPPORT_OPENGL|PFD_GENERIC_FORMAT|PFD_DOUBLEBUFFER|PFD_SWAP_COPY,
         PFD_TYPE_RGBA,
@@ -107,6 +108,7 @@ struct __pixelformat__	pix[] =
         0,	0,	0,	0,	0,	16,	8,	0,	0,	0,	0,	0,	0 },
         GL_TRUE
     },
+    /* Single Buffer, alpha */
     {	{	sizeof(PIXELFORMATDESCRIPTOR),	1,
         PFD_DRAW_TO_WINDOW|PFD_SUPPORT_OPENGL|PFD_GENERIC_FORMAT,
         PFD_TYPE_RGBA,
@@ -114,6 +116,22 @@ struct __pixelformat__	pix[] =
         0,	0,	0,	0,	0,	16,	8,	0,	0,	0,	0,	0,	0 },
         GL_FALSE
     },
+    /* Double Buffer, no alpha */
+    {	{	sizeof(PIXELFORMATDESCRIPTOR),	1,
+        PFD_DRAW_TO_WINDOW|PFD_SUPPORT_OPENGL|PFD_GENERIC_FORMAT|PFD_DOUBLEBUFFER|PFD_SWAP_COPY,
+        PFD_TYPE_RGBA,
+        24,	8,	0,	8,	8,	8,	16,	0,	0,
+        0,	0,	0,	0,	0,	16,	8,	0,	0,	0,	0,	0,	0 },
+        GL_TRUE
+    },
+    /* Single Buffer, no alpha */
+    {	{	sizeof(PIXELFORMATDESCRIPTOR),	1,
+        PFD_DRAW_TO_WINDOW|PFD_SUPPORT_OPENGL|PFD_GENERIC_FORMAT,
+        PFD_TYPE_RGBA,
+        24,	8,	0,	8,	8,	8,	16,	0,	0,
+        0,	0,	0,	0,	0,	16,	8,	0,	0,	0,	0,	0,	0 },
+        GL_FALSE
+    },
 };
 
 int				qt_pix = sizeof(pix) / sizeof(pix[0]);
@@ -158,7 +176,8 @@ WGLAPI HGLRC GLAPIENTRY wglCreateContext(HDC hdc)
         if ( wgl_ctx[i].ctx == NULL )
         {
             wgl_ctx[i].ctx = WMesaCreateContext( hWnd, NULL, GL_TRUE,
-                pix[curPFD-1].doubleBuffered );
+                pix[curPFD-1].doubleBuffered, 
+                pix[curPFD-1].pfd.cAlphaBits ? GL_TRUE : GL_FALSE);
             if (wgl_ctx[i].ctx == NULL)
                 break;
             wgl_ctx[i].hdc = hdc;
@@ -559,6 +578,8 @@ WGLAPI int GLAPIENTRY wglChoosePixelFormat(HDC hdc,
             continue;
         if(ppfd->iPixelType != pix[i].pfd.iPixelType)
             delta++;
+        if(ppfd->cAlphaBits != pix[i].pfd.cAlphaBits)
+            delta++;
         if(delta < bestdelta)
         {
             best = i + 1;
diff --git a/src/mesa/drivers/windows/wmesa.c b/src/mesa/drivers/windows/wmesa.c
index 4f057bfad73..73037b7d05c 100644
--- a/src/mesa/drivers/windows/wmesa.c
+++ b/src/mesa/drivers/windows/wmesa.c
@@ -1,4 +1,4 @@
-/* $Id: wmesa.c,v 1.26 2002/03/16 00:53:15 brianp Exp $ */
+/* $Id: wmesa.c,v 1.27 2002/04/23 18:23:33 kschultz Exp $ */
 
 /*
  * Windows (Win32) device driver for Mesa 3.4
@@ -396,6 +396,13 @@ static clear(GLcontext* ctx, GLbitfield mask,
   /* sanity check - can't have right(stereo) buffers */ 
   assert((mask & (DD_FRONT_RIGHT_BIT | DD_BACK_RIGHT_BIT)) == 0); 
   
+  /* clear alpha */
+  if ((mask & (DD_FRONT_LEFT_BIT | DD_BACK_RIGHT_BIT)) &&
+      ctx->DrawBuffer->UseSoftwareAlphaBuffers &&
+      ctx->Color.ColorMask[ACOMP]) {
+      _mesa_clear_alpha_buffers( ctx );
+  }
+
   if (*colorMask == 0xffffffff && ctx->Color.IndexMask == 0xffffffff) { 
       if (mask & DD_BACK_LEFT_BIT) { 
 #if defined(USE_GDI_TO_CLEAR) 
@@ -1240,7 +1247,8 @@ static void GetPalette(HPALETTE Pal,RGBQUAD *aRGB)
 
 WMesaContext WMesaCreateContext( HWND hWnd, HPALETTE* Pal,
 				 GLboolean rgb_flag,
-				 GLboolean db_flag )
+				 GLboolean db_flag,
+                                 GLboolean alpha_flag )
 {
   RECT CR;
   WMesaContext c;
@@ -1318,7 +1326,8 @@ WMesaContext WMesaCreateContext( HWND hWnd, HPALETTE* Pal,
   c->gl_visual = _mesa_create_visual(rgb_flag,
 				     db_flag,    /* db_flag */
 				     GL_FALSE,   /* stereo */
-				     8,8,8,8,    /* r, g, b, a bits */
+				     8,8,8,      /* r, g, b bits */
+                                     alpha_flag ? 8 : 0, /* alpha bits */
 				     0,          /* index bits */
 				     16,         /* depth_bits */
 				     8,          /* stencil_bits */
@@ -1355,7 +1364,7 @@ WMesaContext WMesaCreateContext( HWND hWnd, HPALETTE* Pal,
 					   c->gl_visual->depthBits > 0,
 					   c->gl_visual->stencilBits > 0,
 					   c->gl_visual->accumRedBits > 0,
-					   GL_FALSE /* s/w alpha */ );
+					   alpha_flag /* s/w alpha */ );
   if (!c->gl_buffer) {
     _mesa_destroy_visual( c->gl_visual );
     _mesa_free_context_data( c->gl_ctx );