Allow glTexImage1/2/3D to specify width/height/depth = 0.

This allows texture state to be resettable to default state.
Not allowed according to the spec, but allowed by all other OpenGL libs.

src/mesa/main/teximage.c

@@ -105,7 +105,7 @@ static void PrintTexture(GLcontext *ctx, const struct gl_texture_image *img)
 
 /*
  * Compute floor(log_base_2(n)).
- * If n <= 0 return -1.
+ * If n < 0 return -1.
  */
 static int
 logbase2( int n )
@@ -113,9 +113,11 @@ logbase2( int n )
    GLint i = 1;
    GLint log2 = 0;
 
-   if (n <= 0) {
+   if (n < 0)
       return -1;
-   }
+
+   if (n == 0)
+      return 0;
 
    while ( n > i ) {
       i *= 2;
@@ -1094,10 +1096,10 @@ texture_error_check( GLcontext *ctx, GLenum target,
       return GL_TRUE;
    }
 
-   if (width < 1 || height < 1 || depth < 1) {
+   if (width < 0 || height < 0 || depth < 0) {
       if (!isProxy) {
          _mesa_error(ctx, GL_INVALID_VALUE,
-                     "glTexImage%dD(width, height or depth < 1)", dimensions);
+                     "glTexImage%dD(width, height or depth < 0)", dimensions);
       }
       return GL_TRUE;
    }

src/mesa/main/texobj.c

@@ -310,6 +310,15 @@ _mesa_test_texobj_completeness( const GLcontext *ctx,
       return;
    }
 
+   /* Check width/height/depth for zero */
+   if (t->Image[baseLevel]->Width == 0 ||
+       t->Image[baseLevel]->Height == 0 ||
+       t->Image[baseLevel]->Depth == 0) {
+      incomplete(t, "texture width = 0");
+      t->Complete = GL_FALSE;
+      return;
+   }
+
    /* Compute _MaxLevel */
    if (t->Target == GL_TEXTURE_1D) {
       maxLog2 = t->Image[baseLevel]->WidthLog2;
@@ -559,7 +568,6 @@ _mesa_test_texobj_completeness( const GLcontext *ctx,
       }
       else if (t->Target == GL_TEXTURE_RECTANGLE_NV) {
          /* XXX special checking? */
-
       }
       else {
          /* Target = ??? */

src/mesa/main/texstate.c

@@ -2716,6 +2716,7 @@ update_texture_state( GLcontext *ctx )
       struct gl_texture_unit *texUnit = &ctx->Texture.Unit[unit];
       GLuint enableBits;
 
+      texUnit->_Current = NULL;
       texUnit->_ReallyEnabled = 0;
       texUnit->_GenFlags = 0;
 
@@ -2789,8 +2790,7 @@ update_texture_state( GLcontext *ctx )
       }
 
       if (!texUnit->_ReallyEnabled) {
-	 texUnit->_Current = NULL;
-	 continue;
+         continue;
       }
 
       if (texUnit->_ReallyEnabled)

src/mesa/main/texstore.c

@@ -195,9 +195,9 @@ transfer_teximage(GLcontext *ctx, GLuint dimensions,
           texDestFormat == GL_COLOR_INDEX ||
           texDestFormat == GL_DEPTH_COMPONENT);
    ASSERT(texDestAddr);
-   ASSERT(srcWidth >= 1);
-   ASSERT(srcHeight >= 1);
-   ASSERT(srcDepth >= 1);
+   ASSERT(srcWidth >= 0);
+   ASSERT(srcHeight >= 0);
+   ASSERT(srcDepth >= 0);
    ASSERT(dstXoffset >= 0);
    ASSERT(dstYoffset >= 0);
    ASSERT(dstZoffset >= 0);