Fix: Overlay-Next: Grid is occluded by scene geometry in wireframe mode

It was still using the depth buffer from Workbench.

Use the dummy texture and point sampling to avoid
more invasive changes.

source/blender/draw/engines/overlay/overlay_next_grid.hh

@@ -15,6 +15,7 @@
 
 #include "ED_image.hh"
 #include "ED_view3d.hh"
+#include "GPU_texture.hh"
 
 #include "draw_shader_shared.hh"
 #include "overlay_next_private.hh"
@@ -47,6 +48,9 @@ class Grid {
 
     data_.push_update();
 
+    /* Use dummy depth texture in xray mode to avoid occluding the grid with the scene geometry. */
+    GPUTexture **depth_tx = state.xray_enabled ? &res.dummy_depth_tx : &res.depth_tx;
+
     grid_ps_.init();
     grid_ps_.state_set(DRW_STATE_WRITE_COLOR | DRW_STATE_BLEND_ALPHA);
     if (state.space_type == SPACE_IMAGE) {
@@ -57,7 +61,7 @@ class Grid {
           res.theme_settings.color_background, res.theme_settings.color_grid, 0.5);
       sub.push_constant("ucolor", color_back);
       sub.push_constant("tile_scale", float3(data_.size));
-      sub.bind_texture("depthBuffer", &res.depth_tx);
+      sub.bind_texture("depthBuffer", depth_tx);
       sub.draw(shapes.quad_solid.get());
     }
     {
@@ -65,7 +69,7 @@ class Grid {
       sub.shader_set(res.shaders.grid.get());
       sub.bind_ubo("grid_buf", &data_);
       sub.bind_ubo("globalsBlock", &res.globals_buf);
-      sub.bind_texture("depth_tx", &res.depth_tx);
+      sub.bind_texture("depth_tx", depth_tx, GPUSamplerState::default_sampler());
       if (zneg_flag_ & SHOW_AXIS_Z) {
         sub.push_constant("grid_flag", zneg_flag_);
         sub.push_constant("plane_axes", zplane_axes_);

source/blender/draw/engines/overlay/shaders/overlay_grid_frag.glsl

@@ -203,7 +203,7 @@ void main()
     }
   }
 
-  float scene_depth = texelFetch(depth_tx, ivec2(gl_FragCoord.xy), 0).r;
+  float scene_depth = texture(depth_tx, gl_FragCoord.xy / vec2(textureSize(depth_tx, 0)), 0).r;
   if (flag_test(grid_flag, GRID_BACK)) {
     fade *= (scene_depth == 1.0) ? 1.0 : 0.0;
   }