blank out alpha channel

panda/src/tinydisplay/tinyXGraphicsWindow.cxx

@@ -234,14 +234,12 @@ begin_flip() {
                        _reduced_frame_buffer->xsize, _reduced_frame_buffer->ysize);
   }
 
-  if (_bytes_per_pixel == 4 && _pitch == _full_frame_buffer->linesize) {
-    // If we match the expected bpp, we don't need an intervening copy
-    // operation.  Just point the XImage directly at the framebuffer
-    // data.
-    _ximage->data = (char *)_full_frame_buffer->pbuf;
-  } else {
-    ZB_copyFrameBuffer(_full_frame_buffer, _ximage->data, _pitch);
-  }
+  // We can't just point the XPutImage directly at our own framebuffer
+  // data, even if the bytes_per_pixel matches, because some X
+  // displays will respect the alpha channel and make the window
+  // transparent there.  We don't want transparent windows where the
+  // alpha data happens to less than 1.0.
+  ZB_copyFrameBufferNoAlpha(_full_frame_buffer, _ximage->data, _pitch);
 
   XPutImage(_display, _xwindow, _gc, _ximage, 0, 0, 0, 0,
             _full_frame_buffer->xsize, _full_frame_buffer->ysize);
@@ -1830,19 +1828,14 @@ create_reduced_frame_buffer() {
 void TinyXGraphicsWindow::
 create_ximage() {
   if (_ximage != NULL) {
-    if (_bytes_per_pixel != 4) {
-      PANDA_FREE_ARRAY(_ximage->data);
-    }
+    PANDA_FREE_ARRAY(_ximage->data);
     _ximage->data = NULL;
     XDestroyImage(_ximage);
     _ximage = NULL;
   }
 
   int image_size = _full_frame_buffer->ysize * _pitch;
-  char *data = NULL;
-  if (_bytes_per_pixel != 4) {
-    data = (char *)PANDA_MALLOC_ARRAY(image_size);
-  }
+  char *data = (char *)PANDA_MALLOC_ARRAY(image_size);
 
   _ximage = XCreateImage(_display, _visual, _depth, ZPixmap, 0, data,
                          _full_frame_buffer->xsize, _full_frame_buffer->ysize,

panda/src/tinydisplay/zbuffer.cxx

@@ -148,6 +148,30 @@ static void ZB_copyBuffer(const ZBuffer * zb,
     }
 }
 
+static void
+ZB_copyBufferNoAlpha(const ZBuffer * zb, void *buf, int linesize) {
+  const PIXEL *q = zb->pbuf;
+  PIXEL *p = (PIXEL *)buf;
+  int xsize = zb->xsize;
+  for (int y = 0; y < zb->ysize; ++y) {
+    const PIXEL *q1 = q;
+    PIXEL *p1 = p;
+    PIXEL *p2 = p1 + xsize;
+    while (p1 < p2) {
+      // Make sure the alpha bits are set to 0xff.
+#ifdef WORDS_BIGENDIAN        
+      *p1 = *q1 | 0x000000ff;
+#else
+      *p1 = *q1 | 0xff000000;
+#endif
+      ++p1;
+      ++q1;
+    }
+    p = (PIXEL *) ((char *) p + linesize);
+    q = (const PIXEL *) ((const char *) q + zb->linesize);
+  }
+}
+
 #define RGB32_TO_RGB16(v) \
   (((v >> 8) & 0xf800) | (((v) >> 5) & 0x07e0) | (((v) & 0xff) >> 3))
 
@@ -228,6 +252,30 @@ void ZB_copyFrameBuffer(const ZBuffer * zb, void *buf,
     }
 }
 
+void ZB_copyFrameBufferNoAlpha(const ZBuffer * zb, void *buf,
+                               int linesize)
+{
+    switch (zb->mode) {
+#ifdef TGL_FEATURE_16_BITS
+    case ZB_MODE_5R6G5B:
+	ZB_copyFrameBuffer5R6G5B(zb, buf, linesize);
+	break;
+#endif
+#ifdef TGL_FEATURE_24_BITS
+    case ZB_MODE_RGB24:
+	ZB_copyFrameBufferRGB24(zb, buf, linesize);
+	break;
+#endif
+#ifdef TGL_FEATURE_32_BITS
+    case ZB_MODE_RGBA:
+	ZB_copyBufferNoAlpha(zb, buf, linesize);
+	break;
+#endif
+    default:
+	assert(0);
+    }
+}
+
 // Copy from (source_xmin,source_ymin)+(source_xsize,source_ysize) to 
 //  (dest_xmin,dest_ymin)+(dest_xsize,dest_ysize).
 void ZB_zoomFrameBuffer(ZBuffer *dest, int dest_xmin, int dest_ymin, int dest_xsize, int dest_ysize,

panda/src/tinydisplay/zbuffer.h

@@ -230,6 +230,7 @@ int texcoord_mirror_once(int coord, int max_coord);
 
 /* linesize is in BYTES */
 void ZB_copyFrameBuffer(const ZBuffer *zb,void *buf,int linesize);
+void ZB_copyFrameBufferNoAlpha(const ZBuffer *zb,void *buf,int linesize);
 void ZB_zoomFrameBuffer(ZBuffer *dest, int dest_xmin, int dest_ymin, 
                         int dest_xsize, int dest_ysize,
                         const ZBuffer *source, int source_xmin, int source_ymin,