Hacks to set up another attempt at transparency

sources/Metal/Renderers/iTermBackgroundColorRenderer.m

@@ -45,7 +45,7 @@
         _cellRenderer = [[iTermMetalCellRenderer alloc] initWithDevice:device
                                                     vertexFunctionName:@"iTermBackgroundColorVertexShader"
                                                   fragmentFunctionName:@"iTermBackgroundColorFragmentShader"
-                                                              blending:YES
+                                                              blending:NO
                                                         piuElementSize:sizeof(iTermBackgroundColorPIU)
                                                    transientStateClass:[iTermBackgroundColorRendererTransientState class]];
     }

sources/SessionView.m

@@ -135,6 +135,7 @@ static NSDate* lastResizeDate_;
         if (@available(macOS 10.11, *)) {
             _metalView = [[MTKView alloc] initWithFrame:_scrollview.contentView.frame
                                                  device:MTLCreateSystemDefaultDevice()];
+            _metalView.layer.opaque = NO;
             [self addSubview:_metalView];
             _metalView.paused = YES;
             _metalView.enableSetNeedsDisplay = YES;

sources/TextViewWrapper.m

@@ -37,9 +37,11 @@
 - (void)drawRect:(NSRect)rect
 {
-    [child_.delegate textViewDrawBackgroundImageInView:self
-                                              viewRect:rect
-                                blendDefaultBackground:YES];
+//    [child_.delegate textViewDrawBackgroundImageInView:self
+//                                              viewRect:rect
+//                                blendDefaultBackground:YES];
+    [[NSColor clearColor] set];
+    NSRectFill(rect);
 }
 - (void)addSubview:(NSView *)child

sources/iTermMetalGlue.m

@@ -167,6 +167,7 @@ static BOOL iTermTextDrawingHelperIsCharacterDrawable(screen_char_t *c,
     assert([NSThread isMainThread]);
     self = [super init];
     if (self) {
+        textView.hidden = YES;
         _havePreviousCharacterAttributes = NO;
         _isFrontTextView = (textView == [[iTermController sharedInstance] frontTextView]);
         _unfocusedSelectionColor = VectorForColor([[_colorMap colorForKey:kColorMapSelection] colorDimmedBy:2.0/3.0